Title:
CARBON-SILICON COMPOSITE STRUCTURES AND METHODS OF FABRICATING THEREOF
Document Type and Number:
WIPO Patent Application WO/2024/086584
Kind Code:
A1
Abstract:
Described herein are carbon-silicon composite structures and methods of producing such structures. A carbon-silicon composite structure comprises one or more carbon-containing structures that have pores at least partially filled with silicon-containing structures. Specifically, the silicon-containing structures are attached to the pore walls while maintaining void spaces within these pores. These void spaces can accommodate silicon expansion during lithiation. Carbon-silicon composite structures can be produced by submerging carbon-containing structures into a precursor liquid solution (comprising a silicon-containing precursor) and driving this solution into the pores. The silicon-containing structures are then formed (from the silicon-containing precursor) within the pores either electrochemically (e.g., by applying a voltage to the solution and structures) or chemically (e.g., by introducing the structures into a reducing liquid solution). In some examples, these void spaces are sealed from the environment by additional structures, e.g., separate silicon-containing structures and/or carbon structures.
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Inventors:
LIU XIAOHUA (US)
YAO XIAHUI (US)
ZHOU SA (US)
HAN SONG (US)
YAO XIAHUI (US)
ZHOU SA (US)
HAN SONG (US)
Application Number:
PCT/US2023/077097
Publication Date:
April 25, 2024
Filing Date:
October 17, 2023
Export Citation:
Assignee:
GRU ENERGY LAB INC (US)
International Classes:
C01B32/00; C01B33/021; H01M4/02; H01M4/36; H01M4/38; H01M4/583
Domestic Patent References:
WO2019039856A1 | 2019-02-28 | |||
WO2021194149A1 | 2021-09-30 |
Foreign References:
CN110600719A | 2019-12-20 | |||
US20200020935A1 | 2020-01-16 | |||
KR20160033638A | 2016-03-28 |
Attorney, Agent or Firm:
GUSEV, Vladimir Y. (US)
Download PDF:
Claims:
Docket No. GRUEP026WO CLAIMS 1. A method of producing carbon‐silicon composite structures, the method comprising: submerging carbon‐containing structures into a precursor liquid solution comprising a precursor, wherein the carbon‐containing structures comprise pores and an exterior surface extending among the pores; reducing a gas pressure over a surface of the precursor liquid solution thereby driving the precursor liquid solution into the pores of the carbon‐containing structures; and forming silicon‐containing structures from the precursor within the pores and on the exterior surface of the carbon‐containing structures thereby producing the carbon‐silicon composite structures. 2. The method of claim 1, wherein, prior to forming the silicon‐containing structures, the carbon‐containing structures have a porosity of at least 1 m2/g. 3. The method of claim 1, wherein the carbon‐containing structures comprise at least one of graphite, hard carbon, glassy carbon, carbon foam, carbon paper, carbon molecular sieve, carbon black, activated carbon, carbon fibers, carbon nanotubes, graphene and graphene derivatives, and zero‐dimensional fullerene and fullerene derivatives. 4. The method of claim 1, wherein the silicon‐containing structures comprise a layer coating interior surfaces of the pores, coating the exterior surface of the carbon‐ containing structures, or coating both the interior surfaces of the pores and the exterior surface of the carbon‐containing structures. 5. The method of claim 4, wherein an average thickness (T) of the layer formed by the silicon‐containing structures is between 1 nanometer and 50 micrometers. 6. The method of claim 1, wherein the precursor is one or more of silicon tetrafluoride (SiF4), silicon tetrachloride (SiCl4), silicon tetrabromide (SiBr4), silicon tetraiodide (SiI4), HSiF3, H2SiF2, H3SiF, HSiCl3, H2SiCl3, H3SiCl, HSiBr3, H2SiBr2, H3SiBr, HSiI3, H2SiI2, H3SiI, germanium tetrachloride (GeCl4), germanium tetrabromide (GeBr4), germanium tetraiodide (GeI4), tin tetrachloride (SnCl4), tin tetrabromide (SnBr4) tin nitrate (Sn(NO3)4), tin (II) chloride (SnCl2), aluminum chloride (AlCl3), phosphorous chloride Page 29 of 33 Docket No. GRUEP026WO (PCl3), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium Bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium nitrate (LiNO3), lithium chlrode (LiCl), lithium bromide (LiBr), lithium iodode (LiI), cholorobenzene (C6H5Cl), dicholorbenze (C6H4Cl2), trichlorobenze (C6H3Cl3), hexacholorbenzene (C6Cl6), dibromobenzene (C6H4Br2), chloromethane (CH3Cl), dicholoromethane (CH2Cl2), trichloromethane (CHCl3), tetrachloro carbon (CCl4), and tetrabromo carbon (CBr4), pitch, acetylene (C2H2), methane (CH4), propylene (C3H6), methanol (CH3OH), ethanol (C2H5OH), isopropanol (C3H8O), acetonitrile (CH3CN), benzene (C6H6), toluene (C6H5CH3), propylene carbonate, glucose, dopamine, polyethylene glycol (PEG), melamine, phenol formaldehyde resin, polyimide resin, epoxy resin, cane sugar, and graphite powder. 7. The method of claim 1, wherein the precursor liquid solution comprising a precursor, wherein the carbon‐containing structures comprise pores and an exterior surface extending among the pores; reducing a gas pressure over a surface of the precursor liquid solution thereby driving the precursor liquid solution into the pores of the carbon‐containing structures; and forming silicon‐containing structures from the precursor within the pores and on the exterior surface of the carbon‐containing structures thereby producing the carbon‐silicon composite structures. 8. The method of claim 1, wherein forming the silicon‐containing structures comprises: removing the carbon‐containing structures from a bulk of the precursor liquid solution such that a portion of the precursor liquid solution remains within the pores of the carbon‐containing structures and on the exterior surface; and submerging the carbon‐containing structures, with the portion of the precursor liquid solution remaining within the pores and on the exterior surface of the carbon‐containing structures, into a reducing liquid solution comprising a reducing reagent that reacts with the precursor in the portion of the precursor liquid solution remaining within the pores and on the exterior surface forms the silicon‐containing structures at least within the pores. 9. The method of claim 8, wherein the reducing reagent is one or more of sodium borohydride (NaBH4), lithium aluminum hydride (LiAlH4), sodium hydride (NaH), silicon Page 30 of 33 Docket No. GRUEP026WO hydride (SiHx), sodium biphenyl, lithium biphenyl, potassium biphenyl, sodium naphthalene, lithium naphthalene, potassium naphthalene, and potassium crown ether. 10. The method of claim 1, wherein: the carbon‐containing structures are supported on a working electrode; a reference electrode is further submerged into the precursor liquid solution; and forming the silicon‐containing structures comprises applying a potential between the working electrode and the reference electrode thereby electrochemically forming the silicon‐containing structures. 11. The method of claim 1, further comprising: submerging the carbon‐silicon composite structures, comprising the silicon‐ containing structures at least with the pores of the carbon‐containing structures, into an additional precursor liquid solution such that the pores remain substantially free from the additional precursor liquid solution; and forming additional structures at openings of the pores thereby sealing the pores from environment. 12. The method of claim 11, wherein a porosity of the carbon‐silicon composite structures, after forming the additional structures at the openings of the pores, is at least 30%. 13. Carbon‐silicon composite structures comprising: carbon‐containing structures, wherein: the carbon‐containing structures comprise pores and an exterior surface extending among the pores, and the carbon‐containing structures are formed from at least one of graphite, hard carbon, glassy carbon, carbon foam, carbon paper, carbon molecular sieve, carbon black, activated carbon, carbon fibers, carbon nanotubes, graphene, a graphene derivative, zero‐dimensional fullerene, and a fullerene derivative; and silicon‐containing structures forming a layer coating the carbon‐containing structures, wherein: Page 31 of 33 Docket No. GRUEP026WO the layer of the silicon‐containing structures extends into at least some of the pores of the carbon‐containing structures and forms one or more of silicon‐structure pores and silicon plugs with the pores the carbon‐containing structures, and the layer of the silicon‐containing structures further extends over the exterior surface of the carbon‐containing structures among the pores. 14. The carbon‐silicon composite structures of claim 13, wherein the silicon‐containing structures comprise one or more non‐silicon materials selected from the group consisting of carbon, lithium, oxygen, titanium, nitrogen, magnesium, calcium, boron, phosphorous, fluorine, chlorine, bromine, iodine, hydrogen, iron, aluminum, copper, nickel, tin, and germanium. 15. The carbon‐silicon composite structures of claim 14, wherein the silicon‐containing structures comprise the one or more non‐silicon materials selected from the group consisting of carbon and lithium. 16. The carbon‐silicon composite structures of claim 14, wherein a weight ratio of the one or more non‐silicon materials in the silicon‐containing structures 0.1%‐50%. 17. The carbon‐silicon composite structures of claim 13, wherein an average thickness (T) of the layer formed by the silicon‐containing structures is between 1 nanometer and 50 micrometers. 18. The carbon‐silicon composite structures of claim 13, further comprising additional structures, positioned at openings of the silicon‐structure pores thereby sealing the silicon‐structure pores from environment. 19. The carbon‐silicon composite structures of claim 13, wherein the silicon‐containing structures are amorphous or partially in a crystalline state. 20. The carbon‐silicon composite structures of claim 13, wherein a weight ratio of silicon in the carbon‐silicon composite structures is between 5% ‐95%. Page 32 of 33 |
Description:
Docket No. GRUEP026WO PCT Patent Application CARBON‐SILICON COMPOSITE STRUCTURES AND METHODS OF FABRICATING THEREOF CROSS‐REFERENCE TO RELATED APPLICATIONS [0001] This application claims the benefit under 35 U.S.C. § 119(e) of US Provisi
onal Patent Application 63/379,810, filed on 2022‐10‐17, which is incorporated herein by reference in its entirety for all purposes. BACKGROUND [0002] High‐capacity materials, such as silicon, are very
desirable for various battery applications because of their high gravimetric (3579
mAh/g) and volumetric capacities. However, many high‐capacity materials undergo signifi
cant volume changes during charge‐discharge cycling (e.g., incorporation‐removal
of lithium ions). The repeated cycling and corresponding volume changes can cause pu
lverization of these materials and/or loss of electrical connections between these m
aterials and other electrode components. Conventional integration of high‐capacity
materials into electrodes typically results in high irreversible capacity losses
, excessive solid electrolyte interphase (SEI) formation, and losses of electrical
contacts within electrodes formed from these materials, all of which are highly undesi
rable. These issues have limited the application of high‐capacity active materials in bat
teries. As a result, graphite with a capacity of only 372 mAh/g remains the most common
negative active material in lithium‐ion batteries. [0003] Different solutions have been proposed to address the
se high‐capacity material integration issues. One example involves usin
g silicon nanostructures with controlled porosity to buffer the volume expansion. A
nother example uses composites with a conductive matrix including various carbon str
uctures. For example, chemical vapor deposition (CVD) has been proposed for depositi
ng silicon structures (from gas‐ phase Si‐containing precursors such as silane (SiH 4 ) and silicon tetrachloride (SiCl 4 )) and onto various matrix materials. Unfortunately, gas‐pha
se precursors are flammable (or even explosive) and are difficult to transport over
long distances. Furthermore, a gas phase precursor occupies a much larger space in comp
arison to liquid or solid Page 1 of 33 Docket No. GRUEP026WO precursors needed to produce the same amount of sili
con. Yet another example relies on nano‐silicon domains dispersed in bulky silicate
matrices (e.g., MgSiO 3 , Li 2 SiO 3 ). However, all of the solutions have various drawbacks
such as the low packing density of porous materials, the high production cost of dep
ositing silicon onto the carbon structures using gas‐phase reactions, and the instab
ility caused by aggregation and pulverization of silicon nanodomains inside silicate m
atrices. [0004] What is needed are carbon‐silicon composite structur
es comprising carbon‐ containing structures with pores partially filled by
silicon structures or, more generally, silicon‐containing structures and methods of forming
such composite structures. SUMMARY [0005] Described herein are carbon‐silicon composite structu
res and methods of producing such structures. A carbon‐silicon composite
structure comprises one or more carbon‐containing structures that have pores at
least partially filled with silicon‐ containing structures. Specifically, the silicon‐conta
ining structures are attached to the pore walls while maintaining void spaces within these
pores. These void spaces can accommodate silicon expansion during lithiation. Carbon
‐silicon composite structures can be produced by submerging carbon‐containing stru
ctures into a precursor liquid solution (comprising a precursor) and driving this so
lution into the pores. The silicon‐ containing structures are then formed (from the precu
rsor) within the pores either electrochemically (e.g., by applying a voltage to the
solution and structures) or chemically (e.g., by introducing the structures into
a reducing liquid solution). In some examples, these void spaces are sealed from the envi
ronment by additional structures, e.g., separate silicon‐containing structures and/or c
arbon structures. [0006] Clause 1. Carbon‐silicon composite structures compris
ing: carbon‐containing structures, wherein: the carbon‐containing structures
comprise pores and an exterior surface extending among the pores, and the carbon‐c
ontaining structures are formed from at least one of graphite, hard carbon, glassy
carbon, carbon foam, carbon paper, carbon molecular sieve, carbon black, activated carbon
, carbon fibers, carbon nanotubes, graphene, a graphene derivative, zero‐dime
nsional fullerene, and a fullerene derivative; and silicon‐containing structure
s forming a layer coating the carbon‐containing structures, wherein: the layer of
the silicon‐containing structures extends into at least some of the pores of the car
bon‐containing structures and forms Page 2 of 33 Docket No. GRUEP026WO one or more of silicon‐structure pores and silicon
plugs with the pores the carbon‐ containing structures, and the layer of the silicon
containing structures further extends over the exterior surface of the carbon‐containing
structures among the pores. [0007] Clause 2a. The carbon‐silicon composite structures o
f clause 1, wherein the carbon‐containing structures have a porosity of at
least 1 m2/g, not accounting for the silicon‐containing structures. [0008] Clause 2b. The carbon‐silicon composite structures o
f clause 1, wherein the silicon‐containing structures comprise one or more n
on‐silicon materials selected from the group consisting of carbon, lithium, oxygen, tita
nium, nitrogen, magnesium, calcium, boron, phosphorous, fluorine, chlorine, bromin
e, iodine, hydrogen, iron, aluminum, copper, nickel, tin, and germanium. [0009] Clause 2c. The carbon‐silicon composite structures o
f clause 2a, wherein the silicon‐containing structures comprise the one or mo
re non‐silicon materials selected from the group consisting of carbon and lithium. [0010] Clause 2d. The carbon‐silicon composite structures o
f clause 2a, wherein a weight ratio of the one or more non‐silicon materi
als in the silicon‐containing structures 0.1%‐50%. [0011] Clause 3. The carbon‐silicon composite structures of
clause 1, wherein the pores of the carbon‐containing structures have a po
re size of between 5 nanometers and 200 nanometers, not accounting for the silicon‐
containing structures. [0012] Clause 4. The carbon‐silicon composite structures of
clause 1, wherein an average thickness (T) of the layer formed by the si
licon‐containing structures is between 1 nanometer and 50 micrometers. [0013] Clause 5. The carbon‐silicon composite structures of
clause 1, wherein an average cross‐sectional dimension (D1) of the carbon
‐silicon composite structures is between 1 nanometer and 100 micrometers. [0014] Clause 6. The carbon‐silicon composite structures of
clause 1, further comprising additional structures, positioned at opening
s of the silicon‐structure pores thereby sealing the silicon‐structure pores from the
environment. [0015] Clause 7. The carbon‐silicon composite structures of
clause 6, wherein an exposed surface area of the carbon‐silicon composite
structures is reduced by at least two times with the additional structures at the open
ings of the pores. Page 3 of 33 Docket No. GRUEP026WO [0016] Clause 8. The carbon‐silicon composite structures of
clause 6, wherein the porosity of the carbon‐silicon composite structures
is at least 30% with the additional structures at the openings of the pores. [0017] Clause 9. The carbon‐silicon composite structures of
clause 6, wherein the additional structures comprise silicon. [0018] Clause 10. The carbon‐silicon composite structures o
f clause 1, wherein the silicon‐containing structures are amorphous or partia
lly in a crystalline state. [0019] Clause 11. The carbon‐silicon composite structures o
f clause 1, wherein a weight ratio of silicon in the carbon‐silicon compo
site structures is between 5% ‐95%. [0020] Clause 12. The carbon‐silicon composite structures o
f clause 1, wherein a weight ratio of silicon in the carbon‐silicon compo
site structures is between 0.1% ‐ 5%. [0021] Clause 13. A method of producing carbon‐silicon com
posite structures, the method comprising: submerging carbon‐containing struct
ures into a precursor liquid solution comprising a precursor, wherein the carbon‐
containing structures comprise pores and an exterior surface extending among the po
res; reducing a gas pressure over a surface of the precursor liquid solution thereby d
riving the precursor liquid solution into the pores of the carbon‐containing structures;
and forming silicon‐containing structures from the precursor within the pores and o
n the exterior surface of the carbon‐containing structures thereby producing the ca
rbon‐silicon composite structures. [0022] Clause 14. The method of clause 13, wherein, prior
to forming the silicon‐ containing structures, the carbon‐containing structure
s have a porosity of at least 1 m2/g. [0023] Clause 15. The method of clause 13, wherein the car
bon‐containing structures comprise at least one of graphite, hard carbon, glas
sy carbon, carbon foam, carbon paper, carbon molecular sieve, carbon black, activated
carbon, carbon fibers, carbon nanotubes, graphene and graphene derivatives, and zero
‐dimensional fullerene and fullerene derivatives. [0024] Clause 16. The method of clause 13, wherein the sil
icon‐containing structures comprise a layer coating the interior surfaces of th
e pores, coating the exterior surface of the carbon‐containing structures, or coating both
the interior surfaces of the pores and the exterior surface of the carbon‐containing s
tructures. Page 4 of 33 Docket No. GRUEP026WO [0025] Clause 17. The method of clause 16, wherein an aver
age thickness (T) of the layer formed by the silicon‐containing structures is
between 1 nanometer and 50 micrometers. [0026] Clause 18. The method of clause 13, wherein an aver
age cross‐sectional dimension (D1) of the carbon‐silicon composite struc
tures is between 1 nanometer and 100 micrometers. [0027] Clause 19. The method of clause 13, wherein the pre
cursor is one or more of SiCl 4 , SiHCl 3 , SiH 2 Cl 2 , (SiHCl 2 ) 2 , and SiCl 2 [Si(CH 3 ) 3 ] 2 , SiF 4 , SiBr 4 , and SiI 4 . [0028] Clause 20. The method of clause 13, wherein forming
the silicon‐containing structures comprises: removing the carbon‐containing
structures from a bulk of the precursor liquid solution such that a portion of the
precursor liquid solution remains within the pores of the carbon‐containing structures
and on the exterior surface; and submerging the carbon‐containing structures, with the
portion of the precursor liquid solution remaining within the pores and on the exter
ior surface of the carbon‐ containing structures, into a reducing liquid solution
comprising a reducing reagent that reacts with the precursor in the portion of th
e precursor liquid solution remaining within the pores and on the exterior surface forms
the silicon‐containing structures at least within the pores. [0029] Clause 21. The method of clause 20, wherein the red
ucing reagent is one or more of sodium borohydride (NaBH 4 ) and lithium aluminum hydride (LiAlH 4 ), sodium hydride (NaH), silicon hydride (SiHx), sodium biphenyl
, lithium biphenyl, potassium biphenyl, sodium naphthalene, lithium naphthalene, pota
ssium naphthalene, and potassium crown ether. [0030] Clause 22. The method of clause 20, wherein removing
the carbon‐containing structures from the bulk of the precursor liquid sol
ution comprises one of centrifuged and filtering. [0031] Clause 23. The method of clause 20, wherein a weigh
t ratio of the portion of the precursor liquid solution remaining within the po
res and on the exterior surface of the carbon‐containing structures is between 0.01 and
10000. [0032] Clause 24. The method of clause 13, wherein: the ca
rbon‐containing structures are supported on a working electrode; a reference el
ectrode is further submerged into the precursor liquid solution; and forming the silico
n‐containing structures comprises Page 5 of 33 Docket No. GRUEP026WO applying a potential between the working electrode an
d the reference electrode thereby electrochemically forming the silicon‐containi
ng structures. [0033] Clause 25. The method of clause 24, wherein the pot
ential applied between the working electrode and the reference electrode is
between 0.5V to 10V such that the working electrode is operable as a cathode. [0034] Clause 26. The method of clause 13, further comprisi
ng: submerging the carbon‐silicon composite structures, comprising the s
ilicon‐containing structures at least with the pores of the carbon‐containing struc
tures, into an additional precursor liquid solution such that the pores remain substantia
lly free from the additional precursor liquid solution; and forming additional stru
ctures at openings of the pores thereby sealing the pores from environment. [0035] Clause 27. The method of clause 26, wherein the add
itional precursor liquid solution and the precursor liquid solution differ in
one or more of viscosity, surface tension, and temperature. [0036] Clause 28. The method of clause 26, wherein an expo
sed surface area of the carbon‐silicon composite structures is reduced by at
least two times after forming the additional structures at the openings of the pores.
[0037] Clause 29. The method of clause 26, wherein the por
osity of the carbon‐silicon composite structures, after forming the additional str
uctures at the openings of the pores, is at least 30%. [0038] Clause 30. The method of clause 26, wherein the pre
cursor is one or more of silicon tetrafluoride (SiF 4 ), silicon tetrachloride (SiCl 4 ), silicon tetrabromide (SiBr 4 ), silicon tetraiodide (SiI 4 ), HSiF 3 , H 2 SiF 2 , H 3 SiF, HSiCl 3 , H 2 SiCl 3 , H 3 SiCl, HSiBr 3 , H 2 SiBr 2, H 3 SiBr, HSiI 3 , H 2 SiI 2 , H 3 SiI, germanium tetrachloride (GeCl 4 ), germanium tetrabromide (GeBr 4 ), germanium tetraiodide (GeI 4 ), tin tetrachloride (SnCl 4 ), tin tetrabromide (SnBr 4 ) tin nitrate (Sn(NO 3 ) 4 ), tin (II) chloride (SnCl 2 ), aluminum chloride (AlCl 3 ), phosphorous chloride (PCl 3 ), lithium hexafluorophosphate (LiPF 6 ), lithium perchlorate (LiClO 4 ), lithium Bis(fluorosulfonyl)imide (LiFSI), lithi
um bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium nitr
ate (LiNO 3 ), lithium chlrode (LiCl), lithium bromide (LiBr), lithium iodode (LiI),
cholorobenzene (C 6 H 5 Cl), dicholorbenze (C 6 H 4 Cl 2 ), trichlorobenze (C 6 H 3 Cl 3 ), hexacholorbenzene (C 6 Cl 6 ), dibromobenzene (C 6 H 4 Br 2 ), chloromethane (CH 3 Cl), dicholoromethane (CH 2 Cl 2 ), trichloromethane (CHCl 3 ), tetrachloro carbon (CCl 4 ), and tetrabromo carbon (CBr 4 ), Page 6 of 33 Docket No. GRUEP026WO pitch, acetylene (C 2 H 2 ), methane (CH4 ) , propylene (C 3 H 6 ), methanol (CH 3 OH), ethanol (C 2 H 5 OH), isopropanol (C 3 H 8 O), acetonitrile (CH 3 CN), benzene (C 6 H 6 ), toluene (C 6 H 5 CH 3 ), propylene carbonate, glucose, dopamine, polyet
hylene glycol (PEG), melamine, phenol formaldehyde resin, polyimide resin,
epoxy resin, cane sugar, and graphite powder. [0039] These and other embodiments are described further bel
ow with reference to the figures. BRIEF DESCRIPTION OF THE DRAWINGS [0040] FIG. 1A is an example of a carbon‐containing struc
ture prior to forming a silicon‐containing structure/layer on the exterior su
rface of the carbon‐containing structures, providing an illustration of pre‐filled
carbon‐structure pores. [0041] FIGS. 1B is an example of a carbon‐silicon composi
te structure comprising carbon‐containing structures and silicon‐containing
structures (e.g., formed as a layer on the exterior surface of the carbon‐containing st
ructures) providing an illustration of post‐filled pores. [0042] FIG. 1C is an example of a carbon‐silicon composit
e structure similar to the one in FIG. 1B but with the internal voids sealed from
the environment by an additional structure, in accordance with some examples. [0043] FIG. 2 is a process flowchart corresponding to a me
thod for producing carbon‐ silicon composite structures, in accordance with some
examples. [0044] FIG. 3A is a schematic illustration of an enclosure
containing a precursor liquid solution and carbon‐containing structures dispersed w
ithin the solution, in accordance with some examples. [0045] FIG. 3B is a block diagram illustrating various comp
onents of the precursor liquid precursor, in accordance with some examples. s
olution [0046] FIG. 4A is a schematic illustration of a reducing l
iquid solution and carbon‐ containing structures dispersed within the reducing li
quid solution such that the carbon‐containing structures contain some residual pr
ecursor liquid solution within the pores, in accordance with some examples. [0047] FIG. 4B is a block diagram illustrating various comp
onents of the reducing liquid precursor, in accordance with some examples. Page 7 of 33 Docket No. GRUEP026WO [0048] FIG. 5 is a schematic illustration of an electrochem
ical device configured to form silicon‐containing structures at least within t
he pores of carbon‐containing structures, in accordance with some examples. [0049] FIG. 6A is a schematic illustration of an additional
precursor liquid solution and carbon‐silicon composite structures dispersed within
this solution, in accordance with some examples. [0050] FIG. 6B is a block diagram illustrating various comp
onents of the additional precursor liquid precursor, in accordance with some e
xamples. [0051] FIGS. 7A and 7B are various experimental results sho
wing the performance of carbon‐silicon composite structures in comparison to
carbon‐containing structures. [0052] FIG. 8 is a schematic illustration of an electrochem
ical cell, fabricated with carbon‐silicon composite structures on the negative
electrode, in accordance with some examples. DETAILED DESCRIPTION [0053] In the following description, numerous specific detail
s are outlined to provide a thorough understanding of the presented concepts. The
presented concepts may be practiced without some or all of these specific deta
ils. In other instances, well‐known process operations have not been described in detail
to not unnecessarily obscure the described concepts. While some concepts will be descr
ibed in conjunction with the specific embodiments, it will be understood that thes
e embodiments are not intended to be limiting. Example of Methods for Producing Carbon‐Silicon Comp
osite Structures [0054] As noted above integrating silicon and carbon structu
res has been challenging, in particular using gas phase deposition of silicon.
Described herein are carbon‐silicon composite structures and liquid‐based methods of pro
ducing such structures. A carbon‐silicon composite structure comprises one or
more carbon‐containing structures that serve as base structures or shells a
nd that comprise pores. These pores may be referred to as pre‐filled carbon‐structure
pores. The carbon‐silicon composite structure also comprises silicon‐containing structures
that at least partially fill the voids and that are formed using liquid‐based deposition t
echniques (e.g., chemical or Page 8 of 33 Docket No. GRUEP026WO electrochemical reactions within liquid solutions). The
carbon‐containing structures provide support, electronic conductivity, and, in some
examples, ionic conductivity to silicon‐containing structures. At the same time, sil
icon‐containing structures contribute to the overall capacity of carbon‐silicon composite
structures by accepting and releasing lithium. As noted above, the theoretical ca
pacity of silicon is substantially higher than that of graphite. However, silicon suffer
s from excessive volume changes and provides poor support to SEI layers (due to sil
icon volume changes). Carbon‐silicon composite structures address these challenges by provi
ding sufficient support to silicon‐containing structures (e.g., in the form of
void walls of the carbon‐containing structures) and space to expand to (e.g., the voids)
. Furthermore, in some examples, these voids are protected from the electrolyte, e.g.,
by forming blocking structures covering void entrances (after silicon‐containing str
uctures have been already formed within the pores thereby forming silicon plugs or po
res with at least some silicon boundaries). In some examples, silicon‐containing str
uctures within these pores/voids can be isolated from electrolytes, and SEI layers ar
e not formed on these structures. [0055] Carbon‐silicon composite structures 100 can be forme
d by forming one or more silicon‐containing structures 120 over one or
more carbon‐containing structures 110. FIGS. 1A is an example of a carbon‐containing
structure 110 prior to forming a silicon‐containing structure/layer on the exterior su
rface 112 of the carbon‐containing structure 110, providing an illustration of pre‐fill
ed carbon‐structure pores 130. These pre‐filled carbon‐structure pores 130 can include
pre‐filled carbon‐structure open pores 139 and carbon‐structure closed pores 136. Th
e carbon‐structure closed pores 136 may remain unchanged during the formation of the
silicon‐containing structure 120 (e.g., the silicon‐containing structure 120 is
not able to reach these carbon‐ structure closed pores 136). However, the pre‐filled
carbon‐structure open pores 139 can receive at least some of the silicon‐containing
structure 120 as further described below with the reference to FIG. 1B. [0056] For purposes of this disclosure, a pore is defined
as a void space with the boundary at least partially defined by a solid‐gas/
liquid interface. It should be noted that the gas/liquid interface depends on the environm
ent of the structure containing this pore. Furthermore, a pore may be partially or
fully filled with another solid thereafter, which transforms this solid‐gas/liquid in
terface into a solid/solid interface. When the pore is partially filed, a new solid‐gas/
liquid interface can be created, i.e., by the material filling the original pore. Page 9 of 33 Docket No. GRUEP026WO [0057] A closed pore has the entire boundary defined by a
solid‐gas/liquid interface. An open pore has at least a portion of the boundar
y defined as a non‐solid interface (e.g., gas‐gas or liquid‐liquid). This non‐solid
interface can be defined by extending the external surface contour (shown with dashed lines in
FIG. 1A) of the particle, which contains this pore and can be also referred to as
a pore opening. To differentiate, a pore from a surface roughness, the non‐solid interf
ace is less than 25% of the entire pore boundary or even less than 10%. In some exampl
es, the non‐solid interface is defined as a “neck” (narrowing) portion separating
two wider portions, e.g., one exterior of the pore and one within the pore. Anoth
er aspect of this non‐solid interface can be defined by completing an imaginary enclosed s
hape outside of the pore using pore surfaces approaching this non‐solid interface.
In other words, the non‐solid interface separates the solid‐gas/liquid interface wi
thin the pore and the imaginary enclosed shape outside of the pore such that the su
rface area of the solid‐gas/liquid interface within the pore is greater than the surfac
e area of the imaginary enclosed shape outside of the pore. [0058] FIGS. 1B and 1C are two examples of carbon‐silicon
composite structures 100. Each carbon‐silicon composite structure 100 comprises
one or more carbon‐containing structures 110 and one or more silicon‐containing s
tructures 120 disposed within pores 130 and on exterior surface 112 of carbon‐co
ntaining structures 110. While FIGS. 1B and 1C illustrate examples in which carbon‐silic
on composite structure 100 is formed by a single carbon‐containing structure 110
and silicon‐containing structure 120 (e.g., as a layer or, in more specific examples
, a conformal layer), other examples are also within the scope. For example, multiple car
bon‐containing structures 110 can cluster together (e.g., forming a secondary structure)
which share silicon‐containing structures 120 in the same carbon‐silicon composite
structure 100. Furthermore, silicon‐containing structures 120 can be in the for
m of disjoined structures, e.g., patches, that only partially cover the surface of ca
rbon‐containing structures 110. [0059] In some examples, at least some pores 130 (with sil
icon‐containing structures 120 positioned therein) remain open as, e.g., schemat
ically shown in FIG. 1B. For purposes of this disclosure, the pores 130 with sili
con‐containing structures 120 positioned therein can be also referred to as voids
to indicate free space within carbon‐silicon composite structures 100. These free
spaces may be smaller than the original pores 130 in carbon‐containing structures 1
10 since a part of the original volume is now occupied by silicon‐containing structu
res 120. Returning to an example Page 10 of 33 Docket No. GRUEP026WO in FIG. 1B, the electrolyte can enter open pores an
d directly interface with silicon‐ containing structures 120 positioned therein. In some
examples, some openings into even open pores are too small for the electrolyte t
o enter. Furthermore, additional pores may be closed. Finally, some of the original
pores 130 in carbon‐containing structures 110 may be completely filled. Different ty
pes of pores will now be described. [0060] Specifically, FIGS. 1B provides an illustration of po
st‐filled pores 131, formed from the original pores 130 in carbon‐containing st
ructure 110 when a silicon‐ containing structure 120 is formed over a carbon‐si
licon composite structure 100. As noted above, the carbon‐structure closed pores 136
may remain unchanged and now are a part of the post‐filled pores 131. However,
the pre‐filled carbon‐structure open pores 139 can receive some of the silicon‐containin
g structure 120 and are converted into silicon‐structure pores 132, carbon‐silicon op
en pores 137, carbon‐silicon closed pores 138, and silicon plugs 122. Specifically, the
silicon‐structure pores 132 are the pores that fully reside within the silicon‐containin
g structures 120 (and do not extend to carbon‐containing structures 110). More specific
examples of such silicon‐structure pores 132 include silicon‐structure open pores 133
and silicon‐structure closed pores 134. [0061] The silicon‐structure open pores 133 are defined by
the boundary of the silicon‐gas/liquid interface as well as the non‐so
lid (silicon) interface (at the opening). The silicon‐structure closed pores 134 are fully de
fined by the silicon‐gas/liquid interface. The electrolyte may or may not enter such
pores. In some examples, these pores remain filled with the gas present during the
deposition of silicon‐containing structures 120. The carbon‐silicon open pores 137 h
ave both a silicon‐gas/liquid interface and a carbon‐gas/liquid interface as well
as a non‐solid interface (at the opening). [0062] Referring to FIG. 1C, in some examples, substantially
all of the original pores 130 (e.g., more than 95 of all pores) are turned i
nto closed pores. As noted above, after depositing silicon‐containing structures 120, s
ome pores (e.g., carbon‐silicon open pores 137 and silicon‐structure open pores 133
) may remain open. One or more additional structures 140 (e.g., additional silicon‐c
ontaining structures) may be formed over silicon‐containing structures 120 to seal these
pores thereby forming sealed pores 141. As such, all pores in such structures are clos
ed pores, e.g., originally closed pores (e.g., carbon‐structure closed pores 136), closed po
res formed during the deposition of Page 11 of 33 Docket No. GRUEP026WO the silicon‐containing structures 120 (e.g., silicon
structure closed pores 134, carbon‐ silicon closed pores 138), and closed/sealed pores fo
rmed during the deposition of the additional structures 140 (e.g., sealed pores 141 for
med from carbon‐silicon open pores 137 and silicon‐structure open pores 133). [0063] In these examples, silicon‐containing structures 120
(disposed inside closed pores 130) do not directly interface with the electr
olyte but receive lithium through carbon‐containing structure 110 that is interfaced b
y the silicon‐containing structures 120. It should be noted that, even in these example
s with the closed pores, some silicon‐containing structures 120 (e.g., disposed on
the exterior surface 112 of carbon‐ containing structures 110) and/or additional structures
140 (e.g., disposed over silicon‐ containing structures 120) can still interface electro
lyte. In some examples, the additional structures 140 are formed from silicon. In
some examples, these additional structures 140 have a thickness of 1 ‐ 2000 nm o
r, more specifically, 1 – 200 nm. [0064] It should be also noted that regardless of the natu
re of these pores (closed pores or open pores), pores 130 can be used to acc
ommodate the volumetric expansion of silicon‐containing structures 120 during
their lithiation, thereby reducing the overall swelling/expansion of carbon‐silicon comp
osite structures 100. For example, the free space (at no lithiation of silicon
‐containing structures 120) can be greater than the expansion of silicon‐containing str
uctures 120 corresponding to the maximum lithiation levels (e.g., set by the cutoff c
harging condition). In this example, carbon‐silicon composite structures 100 do not exper
ience the overall volume change (which can be otherwise detrimental to the battery c
ycle life). [0065] Some examples of carbon‐containing structures 110 in
clude, but are not limited to, graphite, hard carbon, glassy carbon, car
bon foam, carbon paper, carbon molecular sieve, carbon black, activated carbon, carbo
n fibers, carbon nanotubes, graphene and graphene derivatives, and zero‐dimension
al fullerene and fullerene derivatives. For example, graphite provides excellent
electronic conductivity and is operable as an active material for lithium storage (
acts as a lithium intercalation material). Carbon foam, paper, and molecular sieves p
rovide three‐dimensional structures and a wide range of surface areas that c
an be utilized for different silicon loadings, e.g., with larger surface areas providing m
ore sites for depositing silicon‐ containing structures 120 without excessively increasin
g the thickness of silicon‐ containing structures 120. Carbon black can be cost
effective with highly tunable size and pore structures. Activated carbon is microporous
with very high specific surface Page 12 of 33 Docket No. GRUEP026WO areas (e.g., greater than 3000 m 2 /g), which can be leveraged to increase silicon
loading. Carbon fibers and carbon nanotubes can provi
de high levels of interconnectivity among deposited silicon‐containing s
tructures 120. Graphene and its derivatives have a high surface area (e.g., in compa
rison to graphite). Finally, zero‐ dimensional fullerene and derivatives are a family of
cage‐like carbon molecules with various pore structures that can be used for the co
‐deposition of silicon into some larger pores or as fillers to buffer expansion. [0066] In some examples, before forming silicon‐containing
structures 120, carbon‐ containing structures 110 have a porosity of at leas
t 1 m 2 /g or, more specifically, at least 5 m 2 /g or even at least 20 m 2 /g, e.g., between 10 m 2 /g and 3000 m 2 /g or, more specifically, between 100 m 2 /g and 1000 m 2 /g. In some examples, the pore sizes are between 0.5 nanometers and 1000 nanometers or, more
specifically, between 5 nanometers and 200 nanometers. It should be noted th
at smaller pores may prevent liquid solutions from entering the pores (these solut
ions are needed to form silicon‐ containing structures 120 with the pores). On the ot
her hand, having excessively large pores reduces the surface area of carbon‐containing
structures 110 available for deposition of silicon‐containing structures 120 (with
smaller pores corresponding to larger surface areas for the same size/weight of car
bon‐containing structures 110). It should be noted that these pores (before forming sil
icon‐containing structures 120) are open pores to ensure that liquid solutions can
enter the pores. Once silicon‐ containing structures 120 are formed the pores can b
e closed while retaining voids with carbon‐silicon composite structures 100 availabl
e for the expansion of silicon‐ containing structures 120 during their lithiation. In
more specific examples, these pores (before forming silicon‐containing structures 1
20) are “bicontinuous”, which means that the pores are interconnected (forming cont
inuous pathways for the liquid solution to soak in) while the solid portions of ca
rbon‐containing structures 110 are interconnected to maintain the structural integrity. [0067] For example, the pore size, specific area, and pore
configurations can be used to characterize porosity using either gas or liquid
absorption methods, such as Brunauer–Emmett–Teller BET and mercury intrusion po
rosimeter. Another important measurement is the oil absorption number (OAN) used
for carbon black materials, which characterizes the amount of oil a carbon mater
ial can uptake. [0068] It should be noted that once silicon‐containing str
uctures 120 are formed within the pores, the size of the remaining pores o
r voids (in the resulting carbon‐ Page 13 of 33 Docket No. GRUEP026WO silicon composite structures 100) can be significantly
reduced, e.g., by a factor of at least 2 or, more specifically, at least 5, or even
at least 10. As such, in some examples, most of the initial pore volume (in carbon‐containi
ng structures 110 before forming silicon‐containing structures 120) can be filled by
silicon‐containing structures 120 once these silicon‐containing structures 120 are for
med. Similarly, the pore surface (measured in m 2 /g) can be similarly reduced, e.g., by a facto
r of at least 2 or, more specifically, at least 5, or even at least 10. [0069] In some examples, the average cross‐sectional dimens
ion (D1) of carbon‐ silicon composite structures 100 can be large directl
y after synthesis. The initial size of the can be 1‐10 mm, 0.1‐1 mm, 10‐100 micromete
rs, or 5‐10 micrometers. The large size of the initial particles can be further reduced
by mechanical pulverization. In some examples, the average cross‐sectional dimension (D1)
of carbon‐silicon composite structures 100 is between 1 nanometer and 100 microm
eters or, more specifically, between 10 nanometers and 1 micrometer or even betwe
en 10 nanometers and 100 nanometers. In some examples, the average cross‐sect
ional dimension (D1) is between 1 nanometer and 50 nanometers, between 10 nanometers
and 200 nanometers, between 100 nanometers and 1 micrometer, or between
500 nanometers and 100 micrometers. While the larger carbon‐silicon composit
e structures 100 may be beneficial from the integration of silicon and carbon
materials, these carbon‐silicon composite structures 100 need to be processable in v
arious downstream operations such as mixing into a slurry, slurring coating onto
a substrate, as well as other electrode fabrication and handling operations. [0070] In some examples, silicon‐containing structures 120
comprise a layer (e.g., a conformal layer) coating the interior surfaces of por
es 130 and the exterior surface 112 of carbon‐containing structures 110. For example, th
e average thickness (T) of this layer (formed by silicon‐containing structures 120)
is between 1 nanometer and 50 micrometers or, more specifically, between 10 nanomete
rs and 1 micrometer or even between 10 nanometers and 100 nanometers. In some ex
amples, the average thickness (T) is between 1 nanometer and 10 nanomete
rs, between 5 nanometers and 50 nanometers, between 20 nanometers and 200 nanomete
rs, between 100 nanometers and 1000 nanometers, or between 200 nanome
ters and 50 micrometers. [0071] In some examples, the weight ratio of silicon in ca
rbon‐silicon composite structures 100 is between 0.1% ‐ 99% or, more spe
cifically, between 1% ‐ 90% or even between 5% ‐50%. When silicon‐containing structures
120 represent a minor Page 14 of 33 Docket No. GRUEP026WO component of carbon‐silicon composite structures 100,
the weight ratio can be between 0.1% ‐ 5%, between 1% ‐ 10%, or between
1 ~ 50%. When silicon‐containing structures 120 represent a major component of carbon
silicon composite structures 100, the weight ratio can be between 30% ‐ 60% o
r 50% ‐ 99%. Example of Methods for Producing Carbon‐Silicon Comp
osite Structures [0072] FIG. 2 is a process flowchart of method 200 for pr
oducing carbon‐silicon composite structures 100, in accordance with some exa
mples. Various aspects of carbon‐silicon composite structures 100 are described
above. [0073] In some examples, method 200 comprises (block 210) s
ubmerging carbon‐ containing structures 110 into precursor liquid soluti
on 310 as, e.g., schematically shown in FIG. 3A (for chemical deposition of silicon
‐containing structures 120) and FIG. 5 (for electrochemical deposition of silicon‐co
ntaining structures 120). As shown in FIG. 3B, precursor liquid solution 310 comprises prec
ursor 320 and solvent 330. In some examples, precursor liquid solution 310 also com
prises one or more additives 340. These components of precursor liquid solution 31
0 are further described below. In general, the composition of precursor liquid solut
ion 310 depends on the deposition methods (e.g., chemical, electrochemical) that are use
d to form silicon‐containing structures 120. [0074] As shown in FIG. 3A, carbon‐containing structures 1
10 comprise pores 130. Exterior surface 112 of carbon‐containing structures
110 extend among pores 130. The size of pores 130 may be sufficiently small for pre
cursor liquid solution 310 to enter pores 130 without any additional stimulation (e.g., r
educing the pressure over surface 311 of precursor liquid solution 310). Overall, the
pressure‐reducing operation (which may be also referred to as “degas”) can be used
to improve wetting and facilitate liquid replacement into the pores. For example, the density
measurement can be used to check for the gas portion still present in the liqu
id suspension. Specifically, the “fully‐ filled” density can be determined by the actual de
nsities of the liquid solution and the material of carbon‐containing structures 110, both o
f which are much higher than the air density (or, more generally, the density of gase
s) that would otherwise fill the voids. If gases are still present in pores, there will be
some deviation from the expected true density. Furthermore, a liquid suspension with a lot
of trapped gas would expand significantly when the environmental pressure is reduc
ed. At the same time, Page 15 of 33 Docket No. GRUEP026WO introducing precursor liquid solution 310 into pores
130 is essential to ensure that silicon‐containing structures 120 are formed within
pores 130. It should be noted that the total surface area of carbon‐containing structur
es 110 is much greater than its exterior surface 112 because a large portion of the
total surface area is within pores 130. Utilizing as much of this total surface area a
s possible is beneficial to ensure a higher silicon loading in carbon‐silicon composite s
tructures 100 while maintaining the thickness of silicon‐containing structures 120 as sm
all as possible (e.g., to reduce the pulverization aspects during lithiation). Furthermore,
depositing silicon‐containing structures 120 within pores 130 may reduce subsequent
contact of silicon‐containing structures 120 with the electrolyte. [0075] In some examples, precursor 320 is one or more of
SiCl 4 , SiHCl 3 , SiH 2 Cl 2 , (SiHCl 2 ) 2 , and SiCl 2 [Si(CH 3 ) 3 ] 2 , SiF 4 , SiBr 4 , and SiI 4 . Some other polysilanes with (‐SiR 2 ‐) n formula can be used as well, such as cyclopentasilan
e (Si 5 H 10 , here R = H, n = 5). Many other chlorosilanes with a general formula of R m SiCl n (R = C X H Y ), such as diphenyldichlorosilane (R = C 6 H 5 , m = n = 2) can be used as liquid Si prec
ursors. These precursor 320 can operate similarly to forming silico
n layers during atomic layer deposition (ALD). However, it should be noted that i
n ALD, precursors are supplied as gases (vaporized) and are used to form monolayers on
the deposition surface by absorption to achieve very precise (and very slow) l
ayer‐by‐layer deposition. Liquid‐ phase precursor supply and reactions are much quicker
and produce bulkier silicon‐ containing structures 120, which are needed to ensure
adequate loading of silicon‐ containing structures in carbon‐silicon composite str
uctures 100. In other words, ALD is not able to form sufficiently large silicon‐cont
aining structures in a fast and cost‐ efficient manner. [0076] In some examples, solvent 330 of the precursor liqui
d solution 310 comprises one or more of cyclic carbonates (e.g., ethylene car
bonate (EC), propylene carbonate (PC), butylene carbonate (BC) and vinylethylene carbon
ate (VEC)), lactones (e.g., gamma‐butyrolactone (GBL), gamma‐valerolactone (GVL)
and alpha‐angelica lactone (AGL)), linear carbonates (e.g., dimethyl carbonate (D
MC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), methyl propyl carbonat
e (MPC), dipropyl carbonate (DPC), methyl butyl carbonate (NBC) and dibutyl carbo
nate (DBC)), ethers (e.g., tetrahydrofuran (THF), 2‐methyltetrahydrofuran, 1,4‐d
ioxane, 1,2‐dimethoxyethane (DME), 1,2‐diethoxyethane and 1,2‐dibutoxyethane), n
itriles (e.g., acetonitrile and adiponitrile) linear esters (e.g., methyl propionate,
methyl pivalate, butyl pivalate and Page 16 of 33 Docket No. GRUEP026WO octyl pivalate), amides (e.g., dimethyl formamide), di
glyme, triglyme, tetragylme, acetonitrile, and one or more ionic liquids. Some ex
amples of these ionic liquid species include, but are not limited to, 1‐Ethyl‐3‐methy
limidazolium bis(trifluoromethylsulfonyl)imide (EMIMTFSI), 1‐Butyl‐
1‐methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMPTFSI), 1‐propyl
1‐methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PMPTFSI), or 1‐Buty
l‐3‐methylimidazolium tetrafluoroborate (bmimBF 4 ). Solvents 330 are selected to ensure that th
e precursors can dissolve at given concentrations and temperatures.
Without being restricted to any particular theory, it is believed that the liste
d solvent examples provide good solubility to the listed precursors and are stable d
uring various deposition conditions (e.g., voltage, current during electrodeposition) descr
ibed below (when applicable). [0077] In some examples, precursor liquid solution 310 compr
ises a supporting salt (e.g., as an additive 340) to enhance the conductivi
ty of precursor liquid solution 310, e.g., when silicon‐containing structures 120 are for
med by electrodeposition. Some examples of supporting salt include, but are not lim
ited to, tetrabutylammonium chloride (Bu 4 NCl), tetrapropylammonium chloride (Py 4 NCl), tetraethylammonium chloride (Et 4 NCl), lithium chloride (LiCl), 1‐Butyl‐1‐met
hylpyrrolidinium chloride (PYR 14 Cl), 1‐Propyl‐1‐methylpyrrolidinium chloride
(PYR 13 Cl), and other soluble salts. Additional examples of salts include NaCl, KCl, MgCl2
, AlCl3, TMACl, TEACl, TPACl, TBACl, TBABr, NaPF6, NaClO4, LiTFSI, LiFSI, NaTFSI, N
aFSI, CsCl, LiPF 6 , LiBF 4 , LiClO 4 LiAsF 6 , LiN(CF 3 SO 2 ) 2 , LiN(C 2 F 5 SO 2 ) 2, LiCF 3 SO 3 , LiC(CF 3 SO 2 ) 3 , LiPF 4 (CF 3 ) 2 , LiPF 3 (C 2 F 5 ) 3 , LiPF 3 (CF 3 ) 3 , LiPF 3 (iso‐C 3 F 7 ) 3 , LiPF 5 (iso‐C 3 F 7 ), lithium salts having cyclic alkyl groups (e.g., (CF 2 ) 2 (SO 2 ) 2x Li and (CF 2 ) 3 (SO 2 ) 2x Li), and combination of thereof. [0078] In some examples, precursor liquid solution 310 compr
ises one or more additives 340. One example of additive 340 includes
a surfactant, such as polyvinylpyrrolidone (PVP), ethers (e.g., polyoxyethylen
e glycol octylphenol and polyoxyethylene glycol alkylphenol), block copolymers o
f polyethylene glycol (PEG) and polypropylene glycol (PPG), and siloxanes (e.g., hexam
ethylcyclotrisiloxane [(CH 3 ) 2 SiO) 3 ]). For example, between 0.1% and 10% by weigh
t of a surfactant (e.g., PEG and/or PVP) can be added to precursor liquid solutio
n 310 with stirring. The surfactant reduces the surface tension of precursor liquid solut
ion 310 thereby enabling penetration of precursor liquid solution 310 into por
es 130. [0079] Another example of additive 340 is solid particles f
orming suspension/slurry. Such particles can be used to tune the characteristi
cs of precursor liquid solution 310. Page 17 of 33 Docket No. GRUEP026WO Some examples of such particles include, but are not
limited to, carbon fillers, metal nanoparticles, and void‐forming precursors (e.g., pol
ymers with low char yields which can convert to carbon in the following heat treatmen
t). [0080] If pores are small in carbon materials, molecule siz
es could be an important parameter like molecular sieves for selective absorpti
on. Specifically, when the pores are very small (e.g., less than 2 nanometers), the
host materials effectively become molecular sieves in which only certain molecules (wit
h the proper/smaller size) can assess the pores. As such, for some operations, prec
ursors with specific molecular weights/sizes can be used. For example, small‐sized
precursors 320 can be used in precursor liquid solution 310 to ensure the penetrati
on of these precursors 320 into these pores. However, when additional structures 140
are formed to close these pores, the precursors used for these additional structures 1
40 can have molecular sizes that do not allow them to enter the pores resulting in
additional structures 140 forming outside of the pores. Precursors with larger molecula
r weight or with polymerization reaction after ring‐opening, such as cyclopentasilane
or cyclohexasilane, can be used for the synthesis of such additional structures. This
outside‐pore formation of additional structures 140 also ensures that at least
a portion of the original pores remains unfilled providing the space for silicon‐con
taining structures 120 to expand into. [0081] In some examples, the surface of carbon‐containing
structures 110 may be activated in a plasma (e.g., O 2 /NO) or in a chemical bath (e.g., acid or bas
e treatment). For example, a solution can comprise 1 mol/L phospho
ric acid (H 3 PO 4 ) or 0.5 mol/L hydrochloride (HCl) aqueous solution (other materials
and concentrations are also within the scope) and can be used for a duration o
f 1‐10 hours (e.g., for 4 hours) to treat carbon‐containing structures 110. The solution
removes the metal and oxide impurities and contaminants and introduces carbonyl‐,
carboxyl‐, or hydroxyl‐ function groups to the surface of carbon‐containing structure
s 110. These functional groups increase the surface energy and, in turn, facilitate
the wetting process with liquids (e.g., precursor liquid solution 310) having low surf
ace tensions. [0082] In some examples, method 200 comprises (block 220) r
educing the gas pressure over surface 311 of precursor liquid solutio
n 310 thereby driving precursor liquid solution 310 into pores 130 of carbon‐contai
ning structures 110. For example, the pressure can be reduced to below 1Pa or, more
specifically, to below 0.1 Pa. The vapor pressure of precursor liquid solution 310 is a
n important consideration during Page 18 of 33 Docket No. GRUEP026WO this operation as various components of precursor liq
uid solution 310 can evaporate during this operation. When the vapor pressure is lo
w (e.g., as is the case for ionic liquids), solvents 330 can be difficult to remove by
evaporation. In such cases, thermal decomposition at high temperatures can be used for r
emoving solvents and reaction byproducts. In some examples, the pressure is reduced
in short pulses to mitigate the evaporation while providing a driving force for precu
rsor liquid solution 310 (to penetrate into pores 130). Overall, various combinatio
ns of vacuum levels and durations can be used to minimize processing time. V
acuum levels and duration can be chosen to achieve different levels of pore‐filling.
A thorough degas, such as at 10 mTorr for 30 min, would remove most of the gas trapped i
n the structures. In another example, a shorter degas for 10 min, would improve
the processing time and leave some unfilled pores, which is beneficial for porosity
control and mitigate Si swelling. In some examples, agitation is used when precursor liqui
d solution 310 has multiple components to reduce concentration gradients while pre
cursor liquid solution 310 enters pores 130. [0083] In some examples, method 200 comprises (block 230) f
orming silicon‐ containing structures 120 from precursor 320 within p
ores 130 and on the exterior surface 112 of carbon‐containing structures 110 ther
eby producing carbon‐silicon composite structures 100. [0084] In more specific examples, (block 230) forming silico
n‐containing structures 120 comprises (block 240) removing carbon‐containing
structures 110 from a bulk of precursor liquid solution 310 and (block 242) submerg
ing carbon‐containing structures 110 into reducing liquid solution 410. This type of
operation may be referred to as the chemical deposition of silicon‐containing structures
120. This operation is schematically shown in FIG. 4A. The composition of r
educing liquid solution 410 will now be described with reference to FIG. 4B. When ca
rbon‐containing structures 110 are removed from the bulk of precursor liquid soluti
on 310, a portion of precursor liquid solution 310 remains within pores 130 of carb
on‐containing structures 110 and on exterior surface 112. This portion of precursor l
iquid solution 310 remains within pores 130 and on the exterior surface 112 of carbon
‐containing structures 110 when carbon‐containing structures 110 are submerged into
reducing liquid solution 410. Reducing liquid solution 410 comprises reducing reagen
t 420 that reacts with precursor 320 in that portion of precursor liquid so
lution 310 (remaining within pores 130 and on exterior surface 112) forms silicon‐cont
aining structures 120 at least within Page 19 of 33 Docket No. GRUEP026WO pores 130 and, in some examples, on exterior surface
112. Limiting the silicon deposition only within the pores is desired but can
be difficult to achieve. When silicon‐containing structures 120 are contained mostl
y in the pores, cycling stability improves. In this example, the surfaces of carbon‐s
ilicon composite structures 100 and/or any secondary structures formed from carbon‐s
ilicon composite structures 100 can remain relatively intact for better inter‐partic
le electronic contact and electron transport. Furthermore, this exterior surface (i.e., t
he surface outside the pores) remains reserved for later coating or SEI formation
(to keep it more stable). In some examples, high concentrations of precursor 320 can be
used for soaking while low‐ concentration of reducing reagents 420 can be used t
o reduce the deposition of the exterior surface. Furthermore, an intermediate washing
operation can be used to remove precursor 320 from the exterior surfaces befor
e introducing reducing reagents 420. [0085] In some examples, reducing reagent 420 is one or mo
re sodium borohydride (NaBH 4 ) and lithium aluminum hydride (LiAlH 4 ). Similar to precursor liquid solution 310, reducing liquid solution 410 needs to balance p
hysical properties viscosity, surface tension, and vapor pressure with chemical pro
perties reduction speed, pH, and salt removal. In one example, NaBH 4 solution (e.g., 12 wt%) in 14 mol/L NaOH is
used. The initial pH can be tuned in the range of 14 ~
10 by diluting with the silicon precursor solution. With higher pH, the reaction is quicker an
d the deposition of silicon is faster. With a lower pH (of about 10), the silicon depositi
on is slower and the coating is more conformal due to less concentration gradient. In some
examples, agitation is used to uniformly supply reducing reagent 420 and to avoid l
iquid intermixing as well as avoid deposition in the unwanted site. Furthermore, agitatio
n can help with the removal of the byproducts of salts that need to be removed. [0086] One example of chemical deposition involves a chemica
l reduction of SiCl 4 with different reducing agents such as hydrides including
sodium borohydride (NaBH 4 ), lithium aluminum hydride (LiAlH 4 ), sodium hydride (NaH), silicon hydride (SiHx),
sodium biphenyl, lithium biphenyl, potassium biphenyl,
sodium naphthalene, lithium naphthalene, potassium naphthalene, potassium crown eth
er, such as: Specifically, in the presence of OH ‐ groups in a base solution to stabilize NaBH 4 , the salt byproducts can be soluble in the solutions and washe
d away during filtration: Page 20 of 33 Docket No. GRUEP026WO 2 SiCl 4 + NaBH 4 + 8 NaOH ^ 2 Si ^ + NaBO 2 (aq.) + 8 NaCl (aq.) + 6 H 2 O The synthesis can be fluidized for continuous product
ion if the filtration (filling porous carbon) and reduction processes are arranged in seque
nce. [0087] In some examples, (block 240) removing carbon‐contai
ning structures 110 from the bulk of precursor liquid solution 310 compr
ises one of centrifuging and filtering. The same techniques can be used for (bloc
k 260) removing carbon‐containing structures 110 from reducing liquid solution 410. Fur
thermore, it should be noted that when silicon‐containing structures 120 are formed el
ectrochemically (as further described below), reducing liquid solution 410 may no
t be used, As such, removing carbon‐containing structures 110 from the bulk of p
recursor liquid solution 310 is performed after (block 230) forming silicon‐containin
g structures 120 (as shown with block 260) rather than a part of the forming operat
ion (as shown with block 240). [0088] In some examples, the weight ratio of the portion o
f precursor liquid solution 310 remaining within pores 130 and on exterior surfa
ce 112 of carbon‐containing structures 110, after (block 240) removing carbon‐co
ntaining structures 110 from the bulk of precursor liquid solution 310, is between 0.
01 and 1000 based on the total weight of carbon‐containing structures 110 and the
remaining portion of precursor liquid solution 310. [0089] In some examples, liquid solution 410 further compris
es a stabilizing reagent (as additive 430) configured to form a byproduct sol
uble in reducing liquid solution 410 when a combination of reducing reagent 420 and stabi
lizing reagent reacts 430 with precursor 320. Some examples of the stabilizing reage
nt include, but are not limited to, NaOH, LiOH, and KOH. Bases (e.g., LiOH, KOH) and su
rfactants to improve wetting such as Polyvinylpyrrolidone PVP or PEG, etc. Nano‐Si co
uld react with a strong base too so it helps protect deposited Si. [0090] Referring to FIG. 5, in some examples, carbon‐conta
ining structures 110 are supported on working electrode 510. The reference ele
ctrode 520 is further submerged into precursor liquid solution 310. The for
ming operation (block 230) comprises (block 250) applying a potential between th
e working electrode 510 and reference electrode 520 thereby electrochemically formi
ng silicon‐containing structures 120. [0091] In some examples, a porous carbon material (used as
carbon‐containing structures 110) can be pressed into pellets (e.g., w
ith a nominal density of 0.1‐10 g/cm 3 Page 21 of 33 Docket No. GRUEP026WO or, more specifically, between 0.5‐2 g/cm 3 that may correspond to 10‐90% porosity or,
more specifically, between 30‐70% porosity). These p
ellets can be attached to a working electrode (WE) in an electrochemical cell. Th
e solution may contain SiCl 4 as a precursor 320 and tetrabutylammonium chloride (Bu 4 NCl) as a conductive agent in a propylene carbonate solvent. The working electrode is
then biased in cathodic conditions with potentials of ‐0.5 to ‐10 V vers
us the reference electrode, which causes silicon‐containing structures 120 to be reduced from
SiCl 4 and deposited onto the surfaces and into the pores. [0092] In some examples, the potential applied between the
working electrode 510 and reference electrode 520 is between ‐0.5V to
10V or, more specifically, between ‐ 1V and ‐8V, or even between ‐5V and ‐7V. Thes
e values are specifically selected to ensure the bonding of silicon‐containing structures
120 and carbon‐containing structures 110. [0093] In some examples, precursor liquid solution 310 furth
er comprises one or more precursors and one or more solvents. For exampl
e, the one or more precursors of the electroplating solution are selected from the
group consisting of trichlorosilane (SiHCl 3 ), dichlorosilane (SiH 2 SiCl 2 ), silicon tetrachloride (SiCl 4 ), silicon tetrabromide (SiBr 4 ), silicon tetraiodide (SiI 4 ), germanium halides (e.g., GeCl 4 ), tin halides (SnCl 2 ), lithium‐containing salts (e.g., LiPF 6 , LiClO 4 , LiFSI, LiTFSI, LiNO 3 , LiCl, LiBr, and LiI), other salts (e.g., AlCl 3 , PCl 3 ) and graphite powder. It should be noted that
some materials of these precursors (e.g., lithium, graphite powder) can
be incorporated into carbon‐ silicon composite structures 100 (in addition to sili
con). [0094] Overall, the silicon‐containing structures 120 may c
omprise silicon, silicon‐ metal alloy, silicon suboxide (SiO X , where 0<x<2), silicon carbide, silicon n
itride, doped silicon, silicon‐lithium alloy, or silicon oxy‐carb
ide. In other examples, silicon may be substituted (partially or fully) by tin or germanium.
The structures in which silicon is fully substituted by tin may be referred to as tin
containing structures. The structures in which silicon is fully substituted by germanium m
ay be referred to as germanium ‐ containing structures. [0095] In some examples, the silicon‐containing structures
120 may further compromise (e.g., in addition to silicon) one or mor
e of the elements selected from the group of hydrogen (H), lithium (Li), boron (B), carb
on (C), nitrogen (N), oxygen(O), fluorine (F), sodium (Na), magnesium (Mg), aluminum (
Al), phosphorous (P), sulfur (S), chlorine (Cl), potassium (K), calcium (Ca), scandium
(Sc), titanium (Ti), vanadium (V), Page 22 of 33 Docket No. GRUEP026WO chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co)
, nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), bromine (Br), strontium (Sr), zir
conium (Zr), niobium (Nb), molybdenum (Mo), indium (In), lanthanum (La), cerium
(Ce), tantalum (Ta), tungsten (W), tin(Sn), germanium (Ge), and bismuth (Bi). [0096] The composition of the silicon‐containing structures
120 can be expressed in the form of SiMxNy where M is one or more of meta
l, dopant (e.g., As, B, N, and/or P), or carbon elements and N can be one or more of an
ions. The range of x can be from 0.01 to 99.99%, 0.1 to 99.9%, 0.1 to 99 %, 0.1 to
75%, 0.1 to 50%, 0.1 to 25%, 0.1 to 10%, 0.1 to 5%, 0.1 to 1%, 1 to 50%, 1 to 25%,
1 to 10%, 1 to 5%, 2 to 50%, 2 to 25%, 2 to 10%, 2 to 5%, 5 to 25%, 10 to 25%, 10 to 25%
, 15 to 25%, 20 to 25%, 5 to 75%, 5 to 50%, 5 to 25%, 5 to 15%, and 5 to 10%. The range
of y can be from 0.01 to 99.99%, 0.1 to 99.9%, 1 to 99 %, 1 to 75%, 1 to 50%, 1 to
25%, 5 to 25%, 10 to 25%, 10 to 15%, 1 to 10%, 1 to 5%, 2 to 5%, 5 to 75%, 5 to 50%, 5 t
o 25%, 5 to 15%, and 5 to 10%. [0097] The precursor for the silicon‐containing structures
120 may contain metal salts, silane, chlorosilane, organosilane, silicon hali
de, polymers, or sugars. In the same or other examples, silicon, germanium or tin containi
ng precursors can be selected from the group consisting of SiF 4 , SiCl 4 , SiBr 4 , SiI 4 , HSiF 3 , H 2 SiF 2 , H 3 SiF, HSiCl 3 , H 2 SiCl 3 , H 3 SiCl, HSiBr 3 , H 2 SiBr 2, H 3 SiBr, HSiI 3 , H 2 SiI 2 , H 3 SiI, GeCl 4 , GeBr 4 , GeI 4 , SnCl 4 , SnBr 4 , Sn(NO 3 ) 4 , SnCl 2 , AlCl 3 , and PCl 3 . Specific examples of organosilanes include trichlorosilane, trichloromethylsilane (SiHCl 3 ), trichloroethylsilane, (SiCH 3 Cl 3 ), trichlorophenylsilane (Si(C 2 H 5 )Cl 3 ), and dichlorodimethylsilane (Si(CH 3 ) 2 Cl 2 ), diethyldichlorosilane, diethylsilane, dimethylsilane, tri
methylsilane, and chloro(dimethyl)phenylsilane, 1,3,5,7‐tetravinyl‐1,3,5,
7‐tetramethylcyclotetrasiloxane. [0098] In some examples, the silicon‐containing structures
120 also comprise carbon. Such silicon‐containing structures 120 can be formed
using one or more carbon‐ generating precursors selected from the group consisti
ng of cholorobenzene (C 6 H 5 Cl), dicholorbenze (C 6 H 4 Cl 2 ), trichlorobenze (C 6 H 3 Cl 3 ), hexacholorbenzene (C 6 Cl 6 ), dibromobenzene (C 6 H 4 Br 2 ), chloromethane (CH 3 Cl), dicholoromethane (CH 2 Cl 2 ), trichloromethane (CHCl 3 ), tetrachloro carbon (CCl 4 ), and tetrabromo carbon (CBr 4 ), pitch, acetylene (C 2 H 2 ), methane (CH4 ) , propylene (C 3 H 6 ), alcohol (e.g., methanol, ethanol, isopropanol alcohol), acetonitrile, benzene, t
oluene, propylene carbonate, glucose, dopamine, polyethylene glycol (PEG), melamine,
phenol formaldehyde resin, polyimide resin, epoxy resin, and cane sugar. Page 23 of 33 Docket No. GRUEP026WO [0099] In some examples, one or more precursors (used to f
orm the silicon‐containing structures 120) comprise a halide selected from the
group consisting of a metal halide, a non‐metal halide, an amine, and an amide. For e
xample, the metal halide is selected from the group consisting of titanium tetrachloride (
TiCl 4 ), iron(III) chloride (FeCl 3 ), aluminum chloride (AlCl 3 ), and magnesium chloride (MgCl 2 ). The non‐metal halide selected from the group consisting of phosphorus tric
hloride (PCl 3 ), phosphorus pentachloride (PCl 5 ), boron trichloride (BCl 3 ), LiPF 6 , LiClO 4 , LiFSI, LiTFSI, LiNO 3 , LiCl, LiBr, LiOH, Li2CO3, Li2C2O4, Li2O2, Li2O, LiO2, Li3N, Li2S,
Li3PO4, Li2SO4, Li3BO3, Li(CH3COO), Lithium citrate, Li‐EDTA, LiBOB, and LiI
. The amine can be selected from the group consisting of trimethylamine ((CH 3 ) 3 N) and melamine (C 3 H 6 N 6 ). The amide can be dimethylformamide (C 3 H 7 NO). [00100] In some examples, one or more precursors (used to f
orm the silicon‐containing structures 120) comprise one or more oxygen‐generati
ng precursors selected from the group consisting of water (H 2 O), dissolved oxygen, carbon dioxide (CO 2 ), alcohol (e.g., ethanol (CH 3 CH 2 OH)), an oxalate salt (e.g., ammonium oxalate (
e.g. (NH 4 ) 2 C 2 O 4 )), a carbonate (e.g. (NH4)2CO3), an oxide (e.g. Li2O, Al2O
3), hydroxide (e.g. NaOH), and a nitrate salt (e.g., ammonium nitrate(NH 4 NO 3 )). [00101] In some examples, method 200 further comprises (block
270) submerging carbon‐silicon composite structures 100 into addition
al precursor liquid solution 610, e.g., as schematically shown in FIG. 6A. At this st
age, carbon‐silicon composite structures 100 comprise silicon‐containing structures
120 at least with pores 130 of carbon‐containing structures 110. Furthermore, during
this operation, pores 130 remain substantially free from additional precursor li
quid solution 610. Method 200 proceeds with (block 272) forming additional structure
s 140 at openings of pores 130 thereby sealing pores 130 from the environment. It s
hould be noted that since additional precursor liquid solution 610 is not intro
duced into pores 130, additional structures 140 are generally not formed within these
pores 130. As such, pores 130 remain available, and silicon‐containing structures 1
20 can expand into these pores during lithiation. For example, additional precursor 6
20 (used in additional precursor liquid solution 610) may have a molecular size that
is larger than the pore opening. As such, these pore openings are operable as molecular
sieves as further described above. Additional components of additional precursor liquid s
olution 610 include but are not limited to additional solvents 630 and/or additional
additives 640, e.g., as schematically shown in FIG. 6B. Page 24 of 33 Docket No. GRUEP026WO [00102] In some examples, carbon‐containing structures 110 a
re formed by repeating the electrochemical or chemical reduction of silicon
containing structures 120 from a liquid precursor. An example is that the product fro
m the previous examples can be used as a precursor for another soaking‐reduction p
rocess to produce further functionalized surface coatings. The yield of the sec
ond precursor can be chosen to yield voids to allow silicon expansion yet maintain
a low surface area of the particle on the microscale. Such a design can reduce the consump
tion of electrolytes on the active material’s surfaces and reduce exposure to newly fo
rmed surfaces during cycling. [00103] In some examples, additional precursor liquid solution
610 can be used for other types of structures, e.g., carbon structures ov
er previously‐formed silicon‐ containing structures 120 and pore openings. [00104] It should be noted that additional precursor liquid
solution 610 can have specific properties (viscosity, surface tension) that
prevent its penetration into pores 130. Furthermore, pores 130 are already partially fil
led with silicon‐containing structures 120. [00105] In some examples, additional precursor liquid solution
610 comprises water‐ soluble molecules (e.g., glucose dissolved in water)
or oil‐soluble polymers (e.g., polyamide imides dissolved in NMP). For example, PAI/
NMP soaking would only create carbon‐containing molecules on surfaces due to visco
sity. [00106] In some examples, additional precursor liquid solution
610 and precursor liquid solution 310 differ in one or more of viscosity, su
rface tension, and temperature. [00107] In some examples, the exposed surface area of carbon
‐silicon composite structures 110 is reduced by at least two times aft
er depositing additional structures 140 at openings of pores 130. In some examples, the
porosity of carbon‐silicon composite structures 100, after depositing the additio
nal structures 140 at openings of pores 130, is at least 30%. [00108] In some examples, method 200 further comprises (block
280) annealing carbon‐silicon composite structures 100 thereby conve
rting silicon‐containing structures 120 from an amorphous state to at least
a partially crystalline state or, more specifically, to a substantially crystalline state. Fo
r example, the annealing can be performed in an environment comprising at least one
of argon, hydrogen, and nitrogen. In some examples, the annealing is performe
d at a temperature less than 900°C or even less than 800°C. Page 25 of 33 Docket No. GRUEP026WO [00109] Alternatively, silicon‐containing structures 120 can
remain substantially amorphous (e.g., greater than 50% amorphous by volume
, greater than 75%, or even greater than 90%). The annealing operation may not b
e performed in some examples. It should be noted that silicon‐containing structure
s 120 can be substantially amorphous in a deposited state. Experimental Results [00110] FIGS. 7A and 7B are various experimental results sho
wing the performance of carbon‐silicon composite structures in comparison to
carbon‐containing structures. Specifically, carbon‐silicon composite structures were
prepared by filtrating porous carbon material with SiCl 4 under vacuum (‐90 kPa) for 15 min. The pow
der was centrifuged to remove excess liquid and subsequently
added to sodium borohydride (NaBH 4 ) and sodium hydroxide (NaOH) aqueous solution
and stirred for 30 min. The resultant powder was rinsed and filtered with de‐io
nized water 3 times to remove the salt byproducts (NaBO 2 and NaCl) thereby forming carbon‐silicon comp
osite structures. Porous carbon was used as a reference material (carb
on‐containing structures) and did not contain any silicon. [00111] Both carbon‐silicon composite structures and carbon
containing structures were used to prepare test cells. Specifically, these
structures (in a powder form) were mixed into a slurry containing 80% of these structur
es, 10% carbon black, and 10% PAA. This slurry was coated and tested in a half‐
cell configuration with a voltage range of 10 mV – 2 V at a 0.1C rate. FIG. 7A shows
that the cells with carbon‐silicon composite structures had a higher specific capacity (
about 20% improvement) than the cells with carbon‐containing structures (“carbon on
ly”). The slanted voltage in the range of 0.25 ~ 1 V of the Si/carbon composite ind
icates the Si exhibits the amorphous the wet chemical process and is beneficial for stabl
e cycling. [00112] In another test, carbon‐silicon composite structures
and, separately, carbon‐ containing structures were formed into negative electr
odes that were combined with NCM622‐based positive electrodes to form full cells.
The amounts of the carbon‐silicon composite structures and carbon‐containing structures
in these cells were specifically selected to achieve the same capacity. The electrolyt
e is 1M LiPF 6 dissolved in EMC/EC Page 26 of 33 Docket No. GRUEP026WO (3:7 by weight) solvents with a 5% FEC additive. Th
e full cells were cycling in the voltage range of 2.8 – 4.2 V at a 1C rate. The
control sample is a Si/graphite reference anode by blending nano‐Si (200 ~ 500 nm in size)
and graphite powder. FIG. 7B shows that with the same design of cell balance, the C‐
coated Si‐loaded porous carbon shows better retention (~ 5% better at the end of the 50
0 th cycle) than the conventional Si/graphite mixed composite. Examples of Electrochemical Cells [00113] FIG. 8 is a schematic illustration of electrochemical
cell 450, comprising first electrode 470, second electrode 480, and separator 49
0 arranged in a stack, wound jelly‐roll, or any form. One of these electrodes c
an be a negative battery electrode fabricated with carbon‐silicon composite structures,
described above. Separator 490 is disposed between first electrode 470 and second elect
rode 480 to prevent direct contact between first electrode 470 and second electr
ode 480 yet allows ionic communication (by being soaked with electrolyte) betwe
en these electrodes. Specifically, separator 490 may include pores allowing
ions to pass. [00114] Electrochemical cell 450 also includes electrolyte, wh
ich operates as a carrier of ions during the cycling of electrochemical cell 4
50. First electrode 470, second electrode 480, and other components of the cell may
be enclosed and separated from the environment by case 460 and lid 462. In some e
xamples, case 460 and/or lid 462 may operate as terminals of electrochemical cell 450,
in which case current collectors of first electrode 470 and/or second electrode 480 m
ay be connected to case 460 and/or lid 462. Some examples of such electrochemical
cells include, but are not limited to, lithium‐ion batteries, lithium polymer b
atteries, lithium‐air batteries, lithium sulfite batteries, lithium metal batteries, solid‐sta
te batteries, supercapacitors, and the like. [00115] In some examples, case 460 is rigid (e.g., the case
is a steel can). Other types of cells may be packed into a flexible, foil‐type (e.
g., polymer laminate) case. The case material selection depends on the polarity of case 4
60 (e.g., neutral, connected to positive electrodes, connected to negative electrodes)
as well as the composition of the electrolyte, operating potentials of electrochemica
l cell 450, and other factors. For example, when case 460 is connected to a positive e
lectrode, case 460 may be formed from titanium, titanium alloys, aluminum, aluminum all
oys, and/or stainless steel. On Page 27 of 33 Docket No. GRUEP026WO the other hand, if case 460 is connected to a nega
tive electrode, then case 460 may be made from titanium, titanium alloys, copper, nickel,
lead, and stainless steel. The electrical connection between case 460 and an electro
de may be established by direct contact between case 460 and this electrode (e.g., a
n outer wound of the jelly roll), by a tab connected to the electrode and case 460, and
other techniques. [00116] The top of case 460 may be open and used for inse
rtion of the electrode assembly (e.g., a jelly roll) and then capped with
a header assembly, which may include a weld plate, a rupture membrane, a PTC‐based rese
ttable fuse, and an insulating gasket. The insulating gasket is used to support the
conductive components of the header assembly and to insulate these components from
case 460. In some examples, a PTC‐based resettable fuse is disposed between the
edges of the rupture membrane and the edges of the header cup, effectively interco
nnecting these two components. At normal operating temperatures, the resistance of PTC
based resettable fuse is low. However, its resistance increases substantially when h
eated. For example, the PTC‐ based resettable fuse may be a thermally activated c
ircuit breaker that can electrically disconnect the rupture membrane from the header cup.
Conclusion [00117] Although the foregoing concepts have been described i
n some detail for purposes of clarity of understanding, it will be app
arent that certain changes and modifications may be practiced within the scope of t
he appended claims. It should be noted that there are many alternative ways of implem
enting processes, systems, and apparatuses. Accordingly, the present embodiments are
to be considered illustrative and not restrictive. Page 28 of 33