DESCRIPTION

The invention concerns a process for the recovery of electrochemically active powder for use in new batteries.

Lithium-ion batteries were introduced to the market between the years 1985 and 1995. Technological development has gone hand in hand with the introduction of portable equipment such as telephones, laptops, and other applications.

Rechargeable batteries with NiMH chemistry and with lithium-ion chemistry in the years 1991-1995 were the basis for all the first applications on portable instruments, as well as for all other uses.

The use of NiMH and lithium-ion batteries has recently included many other applications concerning electric mobility, such as electric bikes with power- assisted pedalling, electric forklifts, electric motorbikes, hoovers, lawnmowers, as well as applications concerning the storage of electrical energy from renewable sources by means of solar photovoltaic, wind, water, tidal, thermal recovery systems, energy storage during peaks of excess energy in the grid, and the like.

Lithium-ion batteries are distinguished by the different electrode materials used, particularly cathode materials such as:

- LiCoO ₂ (LCO)

- LiNii. _x COxO ₂ (LNCO)

- LiNi _x Co _y Mn _z O ₂ (NCM)

- LiNi _x Co _y Al _z O ₂ (NCA)

- LMO (LiMn ₂ O ₄ )

- LiNio.5Mn1.5O4 (LNMO)

- LiFePO ₄ (LFP)

- LiMn _x Fe _1.x PO ₄ (LMFP).

The chemical composition of cathode powder has a predominant importance on determining production costs, due to the difficulty of finding metals, the increasing consumption quantities of cathode compounds, the complexity of the processes for producing them, the cost of recovering and reusing the metals present in the cells and batteries at the end of their life, and the impact on land and CO ₂ production due to the mining and refining of metals. Electrode powders, and thus the materials comprised in electrodes, are generally for the anode of carbonaceous materials or compounds forming alloys with lithium, such as graphite, tin or silicon compounds, and for the cathode oxides or phosphates of a transition metal and lithium with the generic formula Li _x M _y O2 or Li _x M _y PO4, such as for example LiCoO2 or LiFePO4.

Anode powder can be obtained, for example, by reducing carbonaceous or metallic materials in a furnace with a flow of inert gas at high temperature.

Cathode powder is synthesised, for example, by the chemical reaction of lithium carbonate and transition metal oxide in a high-temperature furnace. Cathodes are of different types, containing various metals, sometimes with a predominance of Nickel, Manganese and Aluminium, e.g. NCM, NCA, with varying values of Ni, Mn, Al, Cobalt. The formulation is different depending on the economic weight that each metal has with respect to the amount used, charge capacity, cyclability, voltage, durability and safety.

An interesting type of cathode material is lithium iron phosphate LiFePO ₄ (LFP). This cathode material has good characteristics of cyclability and durability, and has a lower price than other types mentioned. In addition, the strong P-0 bonds make the crystal structure very consistent, and the related battery is very stable and relatively safer compared to other types.

The olivine LiFePO ₄ is a Cathode Active Material (CAM), has a potential of 3.45 V/ Li/Li+ and a specific capacity of 170 mAh/g, however, it has low conductivity and has slow diffusion of Li+ ions, which necessitates the inclusion of a certain amount of carbon in the structure, about 3%, reducing the theoretical capacity to 165 mAh/g.

One of the preparations of LiFePO4 defined as “green” is as follows: plus volatile organic compounds, or

- Fe + 2FePO ₄ + Li ₃ PO ₄ *0.5H ₂ O > 3 LiFePO ₄ + 0.5 H ₂ O.

Other processes starting with lithium phosphate, or other Fe ⁺² compounds are also known.

The lithium-ion battery is obtained by coupling a cathode electrode film, an anode electrode film, and a polymeric separator and an electrolyte.

In general, an electrode film is obtained from an electrode powder that is mixed with conductive carbon in the amount of 2 - 10% and mixed with a binder, such as PVDF, in the amount of 1 - 5%. In practice, the preparation of the electrode film consists of mixing by means of a solvent, e.g. NMP, a conductive carbon, e.g. Super P, a binder, e.g. PVDF, and electrode powder with a particle size of 1 to 200 pm, e.g. LFP for the cathode or graphite for the anode. The cathode mixture is applied to an aluminium support, for the cathode, or to a copper support, for the anode, and then dried.

The most commonly used electrolyte is a solution of a lithium salt, e.g. LiPF ₆ , or LiBF ₄ , or LiCF ₃ SO ₃ , or LiTFSI, in an organic solvent typically formed by a mixture of ethylene carbonate (EC) and dimethyl carbonate (DMC), sometimes propylene carbonate (PC), or dimethyl sulphoxide (DMSO).

The LiFePO ₄ powder obtained by synthesis from one of the traditional industrial methods demonstrates a rate voltage of 3.5 volts.

The average composition of a lithium-ion cell, by weight, shows the following presence of metals and other compounds by weight:

- plastic container 5 - 15%;

- steel container 10 - 11%;

- copper sheet 8 - 9%;

- aluminium sheet 6 - 7%;

- polymer sheet 5 - 6%;

- solvents 4 - 5%;

- electrical contacts 2 - 3%;

- cathode powder 32 - 35%.

The percentage of coal in the cathode is approximately 4 - 8%, while the percentage of graphite in the anode is approximately 15 - 22%.

For example, an LFP prismatic cell with dimensions 26cm x 15cm x 4.5cm weighs about 1280 g.

Opening the same prismatic cell resulted in the following percentages of the different components:

- aluminium container 10%;

- PE of the separator 9%;

- aluminium foil 11 %;

- copper foil 12%;

- solvent + electrolyte 5%;

- LiFePO ₄ powder+Graphite 36%.

By substituting Cobalt- or Nickel-based compounds in the formulation of the cathode powder, LFP cells respond to the issue of the price of metals and their rarefaction on the market due to the quantities needed to meet consumption, the energy spent to produce them, and the burden on global pollution.

Lithium-ion batteries of the LCO, NCM, NCA, LT/LNiO, LPO, LMO type at the end of their life have an intrinsic value due to the economic value of the metal present therein.

In any case, the known hydro-metallurgical or thermal processes are aimed at recovering the metal contained inside the batteries to obtain pure metal for the purposes for which it is required, including the production of new cathode powder for batteries.

Considering an average battery life of 8 years, the amount of metal considered “strategic” also for other “pending” uses during the use phase of the batteries can be considered in the order of tens of thousands of tonnes.

Some pyrolysis-stable electrode recovery processes (such as lithiated lamellar oxides) tend to remove all the plastic and coal parts from the cell through high-temperature heat treatment (combustion). Other solutions involving heat treatments, such as the use of plasma, make it possible to obtain ‘slag’ and subsequently, after hydro-metallurgy, to obtain metals in acid or basic solution in the form of ions. Other solutions involve the extraction of black-mass from foils inside closed chambers and subsequent washing with water and drying.

Solutions other than the thermal and hydro-metallurgical routes involve obtaining a powder, called black-mass, from the grinding of cells, subsequent screening and separation of the ‘scrap’, where this term refers to the fragments of aluminium and copper foils.

The powder is dissolved in acid or basic solutions in order to obtain ions that can be separated by precipitation and thus metal salts such as sulphates, chlorides, carbonates, and the like.

Italian Invention Patent No. 102017000058654 with a filing date of 30/05/2017, owned by Laren Sri and entitled “Process for the recovery of metals from material derived from batteries, lithium-ion cells and the use of such recovered metals or metal compounds” describes methods for obtaining metal compounds from lithium-ion batteries/cells, and in particular from the compounds contained therein such as LiCoO ₂ , LiCo _x Ni _y O ₂ , LiNiO _y , LiMn _x Co _y O ₄ , LiMn ₂ O ₄ , LiCo _x Mn _y O ₂ , LiTi _x O _y /LiNiO _y , LiTi _x O _y /LiFePO ₄ .

Such substances or compounds belong to the class generically called lithium “spinels” and/or “olivines”, the crystals of which are understood to consist of bivalent and trivalent metal oxides as starting oxides.

The operation of these compounds allows the intercalation of lithium in the cathode, enabling the insertion and extraction of lithium-ions in a reversible manner without changes in structure and without the reactivity typical of lithium in an aqueous environment.

In the text, a series of hydro-metallurgical operations are described, ultimately obtaining metal carbonate compounds found in batteries and lithium-ion cells used in the field of production of metal pigments for various uses, including ceramics, metal glazes, and the like.

Italian Invention Patent No. 102019000018185, having a filing date of 08/10/2019, owned by Laren Sri and entitled “Device for inactivating batteries and method using such device”, describes the use of an apparatus inserted and integrated into a lithium-ion battery recycling and recovery system, in which a significant property is to inactivate batteries and cells in safe conditions and without explosions, without causing fire, without an uncontrolled temperature rise, and without chemical alteration of the cathode material.

The inactivation of a battery without an uncontrolled temperature rise and without modifying or altering the cathode compound allows the same cathode compound to be stored until the end of the cycle of recovery operations and until the end of compound recycling. The LFP compound remains intact despite being very sensitive to temperatures above 400°C and/or the presence of oxygen.

In particular, the compound LiFePO4 has a crystal structure identified as triphylite. It is a member of the olivine group with the chemical formula LiMPO. The ‘M’ group in the formula refers to the metal which may be Fe, Co, Ti.

Other compounds of the olivine group are A _y MPO, Lii. _x HMFePO and LiFePOzM.

All these crystalline compounds are referred to as LFP.

Italian Invention Patent No. VI2010A000232, with filing date of 10/08/2010, owned by Laren Sri and entitled “Process for the recovery of materials constituting batteries, cells and/or rechargeable lithium-ion cells and use of cathode material” describes a method for obtaining cathode material from lithium-ion batteries and/or cells, by wet and washing processes, in order to obtain new cathode material for use in new batteries. The objective of this invention is that during the entire sequence of process operations to which the batteries are subjected, from grinding to the final stages of concentration and screening, the cathode compound is not altered.

These methods and processes, while known and appreciated, have some aspects of perfectibility.

A first limitation is the fact that known methods and processes involve dissolution steps of the ground material in liquid, acid or basic or organic solutions, washing steps with water, and/or thermal melting or disintegration steps, or mixed hydro-metallurgical operations.

In methods and processes in which dissolution steps in liquid solutions and washing steps are not adopted, thermal inertisation steps require the batteries to reach temperatures in excess of 500°C, i.e. temperatures that lead to the degradation of the LiFePO ₄ cathode material, an event that is considered undesirable.

In general, therefore, the methods and processes known today are not particularly suitable for the recovery of batteries and cells with LFP cathode chemistry.

In addition, a further limitation of known methods and processes is that they are predominantly dedicated in an alternative way either to the recovery of cathode material, or to the recovery of metallic materials for reuse.

The task of the present invention is to develop a process for the recovery of electrochemically active powder for use in new batteries, capable of overcoming the aforementioned drawbacks and limitations of currently known methods and processes.

In particular, a purpose of the invention is to develop a process without steps requiring the use of solutions or water.

Another purpose of the invention is to develop a process that is more economical in terms of thermal and electrical energy consumption.

A further purpose of the invention is to develop a process that also allows the treatment of batteries and cells with cathode chemistry of the LFP type.

Furthermore, a purpose of the invention is to develop a process capable of recovering cathode material in such a way that such recovered cathode material has a better efficiency and yield than cathode material recovered by known methods and processes.

Another purpose of the invention is to develop a process that enables the simultaneous production of an electrochemically active material for new lithium-ion batteries and an inorganic inert pigment for the production of ceramic glazes, for example.

The above-mentioned task and purposes are achieved by a process for the recovery of electrochemically active powder for use in new batteries according to claim 1 .

Further characteristics of the process according to claim 1 are described in the dependent claims.

The task and the aforesaid purposes, together with the advantages that will be mentioned hereinafter, are highlighted by the description of an embodiment of the invention, which is given by way of non-limiting example with reference to the attached drawings, where:

- figure 1 represents a diagram of the sequence of steps in the process according to the invention;

- figure 2 represents a diagram of a further series of steps in the process according to the invention.

With reference to the above-mentioned figures, a process for the recovery of electrochemically active powder for use in new batteries according to the invention is collectively referred to by the numeral 10.

The steps that make up the process 10 according to the invention are shown with rectangles in figures 1 and 2 and each step is associated with a number, which is provided below in this description.

This process 10 comprises the following steps:

- a first step 11 of reducing the residual charge of the batteries to be treated;

- a second step 12 of disassembling cells from the batteries of which they are part;

- a third step 13 of inerting the cells to implement the controlled release of the energy still contained in the cells, without degrading the cathode compound;

- a fourth step 14 of grinding said cells, configured to cause the disintegration of the cells and the detachment of anode powder and cathode powder, with reduction of said cells to a ground material having a particle size substantially comprised between 1 pm and 2,500 pm;

- a fifth step 15 of screening, configured to separate a first fraction with a particle size comprised between 1 pm and 600 pm, so-called raw blackmass, and a second fraction with a particle size greater than 600 pm. For this first fraction with a particle size comprised between 1 pm and 600 pm, the following steps are provided:

- a sixth step 16 of pyrolysis in an inert atmosphere;

- a seventh step 17 of screening the so-called raw black-mass, configured to separate a first fraction of refined black-mass BMR1 having a particle size comprised between 1 pm and 100 pm, and preferably between 1 pm and 80 pm, a second fraction of refined black-mass BMR2 having a particle size comprised between 80 pm and 200 pm, and a third fraction of refined blackmass BMR3 having a particle size greater than 200 pm;

- an eighth step 18 of refining at least part of the black-mass obtained from the seventh step 17, which eighth step 18 is configured to separate electrode material from non-electrode materials.

A first implementation variant of this eighth step 18 includes the following operations:

- dispersing the black-mass in water or in a mixture of water and a solvent; this solvent may be NMP or DMF; during this operation, the graphite and coal tend to separate from the metal mass and float;

- separating by overflowing graphite and coal which float;

- filtering the remaining black-mass.

A black-mass is obtained, e.g. a wet mass of LiFePO ₄ , which must be dried in a furnace at a maximum drying air temperature of 150°C.

The operation involves the use of water or solvent, or however treatments in an aqueous or solvent phase.

A second embodiment of this eighth step 18 is applied to only the second refined black-mass fraction BMR2.

In this second embodiment, a zig-zag separation system is used.

Such a zig-zag separation system, to be understood as a known type in itself, is implemented in an appropriate shape and internal geometry specially designed for this purpose.

In particular, the difference in specific weight between graphite, coal and the cathode material, e.g. LiFePO4, is exploited, by working over a well-defined range of particle size fraction of the powder, i.e. the black-mass.

The narrower the particle size fraction, the greater the separation.

The 80 - 200 pm fraction was chosen because:

- it represents a large proportion of the black-mass; - coal and graphite have the largest presence in the particle size distribution between 1 pm and 80 pm;

- the fraction between 200 pm and 600 pm, while having a high fraction of cathode material, e.g. LiFePO4, and a low content of coal and graphite, contains small fractions of copper and aluminium from the anode and cathode foils.

The tested zig-zag separation system with continuous operation downstream of a screen, or discontinuous operation, has dimensions of e.g. 110 mm by 220 mm.

In the present non-limiting embodiment of the invention, the zig-zag separation system has 15 variations of trajectory formed by blades placed at 120° from each other.

The total height of such a zig-zag separation system is between 2 metres and 10 metres, and preferably 3 metres.

The section size is in a ratio of 1 to 1/10, and preferably .

For such a zig-zag separation system:

- the amount of incoming air is between 1 m ³ /h and 10 m ³ /h, and preferably of 3 m ³ /h;

- continuous feeding is between 20 kg/h and 1000 kg/h, and preferably is 40 kg/h;

- the head vacuum is between 3 mBar and 20 mBar, and preferably is 10 mBar.

The quantity of air sucked in by an extractor fan is kept constant.

The power supply is kept constant.

The suctioned air, containing graphite and coal powder and small fractions of cathode material, e.g. LiFePO4, and organic material, is conveyed into a cyclone and then to an absolute filter and then to an additional fine powder suppression filter.

The concentrated powder, collected continuously with a rotary valve under the zig-zag separation system, shows a concentration of graphite and coal of 8%, with graphite being the predominant value of 6% and coal the remaining 2%.

The zig-zag separation system thus allows the weight content of compounds other than LFP to be reduced from 14% to 8%.

It became apparent that while coal does not alter the performance of the cathode powder obtained from recycling, an excessive amount of graphite depresses the performance of recycled cathode powder.

The product obtained by the process 10 according to the invention, tested in the laboratory, allowed the construction of an LFP-type cell with a charge capacity of 80% compared to the same substance, e.g. LiFePO ₄ , obtained by synthesis, i.e. new.

As a non-exclusive example, the application of the process 10 according to the invention for the recovery of LiFePO ₄ -type cathode material from end-of-life lithium-ion cells using the same material is provided below.

The characteristics of cells whose electrode material is obtained from this recycled cathode powder must be equivalent in performance to at least 80% of those obtained from pure products: Cyclability: 1 ,800 cycles;

Charging capacity: 130 mAh/g (approx. 80% of the target value of 165 mAh/g, typical for a LiFePO ₄ material obtained by synthesis from pure oxides and carbonates);

Purity LiFePO ₄ : in the order of 85%;

Specific energy: 380 Wh/kg approx;

Voltage: 3.4 volts;

Particle size: 50 - 200 pm approx;

Coal content: in the order of 8%.

In the collection, storage, sorting of batteries and modules, the recognition of the chemistry is to be understood as a step preceding the procedure 10 described; this preliminary step is hereinafter referred to as A1.

These operations are widely known and carried out by collection systems, cell manufacturing companies, companies that assemble cells in modules and sell batteries for a variety of uses.

It remains essential, for the success of the process in general and to achieve consistent and reproducible quality, that the first step 11 be preceded by a preliminary step A1 of cell and battery selection so that they all have the same chemistry.

This preliminary step A1 must be accurate and error-free.

It is not possible to mix cells or batteries with different cathode chemistries.

The first step 11 of reducing the residual energy charge of the battery as a sum of several modules and cells involves connecting a battery with an apparatus that absorbs all residual energy due to fractions of the amount of lithium in the cell.

The well-known method consists of connecting the battery ends with a resistor, controlling and containing the discharge current within set limits to prevent overheating.

After the discharge step, the electrical, electronic and mechanical protective parts, as well as the battery cooling apparatus, if present in the battery, can be removed.

The resulting modules, i.e. groups of cells, are checked to see if they can be used for a second time (second life).

In this first step 11 of charge reduction, this charge reduction does not result in a complete discharge of the battery, but only partial.

Obsolete, non-rechargeable modules, e.g. with short-circuited cells, or with other problems, become waste and undergo subsequent corresponding treatments.

The second step 12 of disassembling the cells from the batteries involves disassembling the modules in order to separate the individual cells.

This operation removes the aluminium battery protectors, all plastic structural parts, which would otherwise remain in the black-mass.

Reducing the various types of “pollutants” in the black-mass allows the subsequent stages of the process 10 to continue by increasing the final concentration of cathode material in the black-mass itself.

The third step 13 of inerting the cells involves, before proceeding with thermal inactivation operations, checking that each individual cell has a near-zero residual charge. It is preferably performed with the same control and discharge apparatus used for the first step 11.

The third step 13 is to determine the controlled release of the energy still contained in a cell, i.e. the so-called ‘controlled runway’, without degrading the cathode compound, whether it is a lithium or olivine-type cathode compound.

This third step 13 of inerting the cells preferably, but not exclusively, employs a vertical induction furnace in which the cells are introduced from above.

Such a vertical furnace has a diameter/height ratio comprised between 1/10 and 1/3, and preferably is 1/7.

At the bottom of this vertical furnace there is a discharge hatch which is kept closed during loading and during inerting operations.

After closing the upper cell intake hatch, a 4 KHz inductive magnetic field is applied.

The power used is between 30 and 70 kW per 100 kg of cells, in a time frame of about 30 minutes.

The total time taken for the operation is between 40 minutes and 90 minutes.

The maximum temperature reached by the cells inside the vertical induction furnace is between 340°C and 420°C, and preferably is 400°C.

The pressure inside the vertical induction furnace is between -1 mBar and -15 mBar, and preferably is -10 mBar.

The pressure is kept constant.

There is no entry of air, but only CO ₂ or Argon in a final cooling step.

This third step 13 of inertisation consists of raising the temperature of the vertical furnace wall and thus of the parts subject to magnetic induction in the cells loaded into the vertical furnace.

At various increasing temperatures, the cells undergo gradual opening due to the expansion of the solvent ETC, or DMC, or the like, due to the chemical reactions taking place in the cells and also due to the weak presence of oxygen from the solvent molecules.

In this third step 13 a gradual controlled release of thermal and chemical energy takes place without overheating the cells beyond the degradation temperature of LiFePO ₄ , which as mentioned is about 400°C - 420°C.

The controlled partial ‘runaway’ takes place by regulating the ignition energy and is induced from the outside through the inductive system of the vertical induction furnace.

The continuous suction of hot gases from the cell opening causes them to pass through a scrubber with a KOH (or NaOH) solution to inhibit the gas mixture from the presence of hydrofluoric acid, which is absorbed.

Afterwards, the unburned gases and organic intermediates are sent to an afterburner and then into a second scrubber with NaOH solution.

The operation is described in Patent No. 102019000018185 in the name of Laren Sri, mentioned above.

To accelerate this third step 13, at the end, a cooling operation is carried out, e.g. CO ₂ or Argon is insufflated, which reduces the cell temperature to 50°C.

At the end of this third step 13 the discharge hatch is opened and the treated cells are discharged into a closed tank kept in depression.

The third step 13 can be repeated for a subsequent batch. At the end of this third step 13 the treated cells present themselves with opening holes or with the presence of weak lacerations, but without alteration to the structure of the cell or the internal parts such as the anode and cathode, nor alteration of the cathode powders and of the anode.

At the end of this third step 13 no solvents such as the aforementioned DMC, ETC, and the like are present, nor is the electrolyte.

This third step 13 of inertisation, which takes place as described in a vertical induction furnace specially sized and built for this purpose, allows, for example, in the case of LiFePO ₄ -type cells or batteries, to:

- not alter the LiFePO ₄ compound because the cell temperature always remains below 400°C - 420°C;

- not bring LiFePO ₄ into contact with oxygen (air) from outside;

- not induce oxidation of the cathode material due to the oxygen present in the solvent of the electrolyte, e.g. ETC (ethyl carbonate) and DMC (dimethyl carbonate), since the conditions in the vertical induction furnace only allow its evaporation, and outside the vertical induction furnace its possible destructive oxidation;

- induce, due to the temperature effect, a detachment of the anode powder and of the cathode powder from the foils, i.e. the aluminium and copper foils, which anode and cathode powder becomes fundamental in the subsequent grinding.

The aluminium and copper foils, after grinding, are thus almost free of anode powder and of cathode powder stuck to them.

This allows subsequent operations to continue without the creation of hazardous gases, and thus without the creation of hazardous closed environments.

The fourth step 14, of grinding said cells, is an operation, like the one conducted above, that is fundamental in the process and in the creation of new electrochemically active electrode material, such as recycled LFP, i.e. LiFePO ₄ .

This fourth step 14 is carried out using a blade-type grinder, with three rollers, with blades comprised between 5 mm and 15 mm thick, the blades themselves having a diameter between 120 mm and 220 mm, and with a rotation that allows the cell to be broken up and the cathode powder and the anode powder to be removed. The power input of the grinder is between 14 Kw and 28 Kw.

This fourth step 14 produces a ground material sized between 1 pm and 2,500 pm.

Aluminium, copper and plastic separators, e.g. PE, are in the form of free foils, ranging in size from 200 pm to 2,500 pm.

The grinding operation is carried out in the total absence of air.

The ground material is a mixture of foils and anode and cathode powders, and is collected in a special tank and sent to the subsequent fifth step 15.

This fourth step 14 of grinding is particularly advantageous because the blade rotation speed, between 2 rpm and 18 rpm, the size of the blades and the stability and condition of the cells have proven to be important aspects for the final product.

During the fourth step 14, conducted on a grinder with a capacity of 300 kg/h, the cells or batteries are shredded into pieces with a particle size of less than 2,500 pm, but with a strong and unexpected exfoliation of the cathode powder from the cathode foils, the latter e.g. made of aluminium, and of the anode powder from the anode foils, the latter e.g. made of copper.

This fourth step 14 is particularly advantageous in the overall process 10 when considered in combination with the above-mentioned third step 13.

The fifth step 15 of screening is configured to separate the powder, e.g. LFP powders, coal, graphite and other organic and metallic substances, from the scrap.

For example, four screens are used in cascade, in which the ground material is divided into as many fractions, which are then subjected to refining operations. A raw black-mass with a particle size ranging from about 1 pm to about 200 pm is obtained, which is understood to be the main fraction of raw blackmass, essentially consisting of cathode powder and of anode powder.

In the preferred, but not exclusive, example of the lithium-ion LFP/graphite cell, the resulting black-mass composition is as follows:

This fifth step 15 of screening also yields a fraction with a particle size larger than 600 pm, consisting of aluminium or steel derived from the ‘case’, i.e. the containment body, aluminium from the cathode foils and copper derived from the anode foils.

The metals are destined for subsequent separation operations.

The definition of the particle size fractions is crucial in establishing the quality of the product, e.g. LiFePO ₄ , and in defining the percentage yield in quantity.

The sixth step 16 of pyrolysis in an inert atmosphere, as mentioned, concerns the fraction with a particle size of less than 600 pm, which is subjected to pyrolysis in an inert atmosphere and is called raw black-mass.

In this sixth step 16 the fraction with a particle size of less than 600 pm is sent to an indirectly heated, continuous rotary furnace with a controlled atmosphere, in the total absence of air.

Such a furnace, for example, may have the following characteristics:

- length between 9,000 mm and 16,000 mm, and preferably 14,000 mm;

- diameter between 600 mm and 1 ,500 mm, and preferably 1 ,000 mm;

- rotation speed between 1 rpm and 12 rpm;

- depression created by an intake system between 1 mBar and - 20 mBar, and preferably - 5 mBar;

- maximum temperature between 360°C and 420°C, and preferably 400°C, maintained throughout the route;

- heat output between 10 MJ/h and 20 MJ/h.

Overhead cyclone separators are arranged to operate.

This step is carried out continuously and in total absence of air. In this sixth step 16 oxidation of the compound, which is e.g. LiFePO4, is prevented, while at the same time an organic syngas is formed due to the evaporation and breakdown of PE and other organic parts.

The route along the furnace pipe takes between 15 minutes and 60 minutes, preferably about 30 minutes.

Such a route in the above-mentioned furnace allows the elimination of organic parts such as PE and PP in the form of syngas.

The granulation of PVDF with coal and metal powder forms complex agglomerates of larger particle size that are removed in subsequent screening operations.

This sixth step 16 can also be carried out in a static furnace operating in discontinuous or batch mode.

At the end of the continuous rotary furnace, the treated powder is cooled down to 50°C by an indirect sprinkling system in the last section of the same furnace. The seventh step 17 of raw black-mass screening is configured to determine three fractions of refined black-mass.

The raw black-mass powder is dropped into a system consisting of three screens in cascade, in an operation known as ‘primary screening’.

The refined black-mass powder is then divided into three fractions:

- a first fraction BMR1 with a particle size less than a value between 40 pm and 100 pm, and preferably less than 80 pm;

- a second fraction BMR2 with a particle size comprised between 50 pm and 250 pm, and preferably comprised between 80 pm and 200 pm;

- a third fraction BMR3 with a particle size greater than a value between 180 pm and 300 pm, and preferably a particle size greater than 200 pm.

The first fraction BMR1 with a particle size of less than 80 pm is 30-35% by weight of the raw black-mass and was found to have the following composition:

- Graphite together with coal: between 50-60% and on average 54.5%;

- LiFePO4: between 40 and 45% and on average 40.8%;

- Aluminium: less than 0.1 %;

- Copper: between 1 and 2%, and on average 1.41 %.

The second fraction BMR2 of particle size between 80 pm and 200 pm is 36-40% by weight of the raw black-mass and has the following composition:

- Graphite together with coal: 10-14%;

- LiFePO ₄ : 75-85%; - Aluminium: 0.1 -0.3%;

- Copper: less than 0.1 %.

The third fraction BMR3 with a particle size of 200 to 600 pm is 25-30% by weight of raw black-mass and has the following composition:

- Graphite together with coal: 5-8%;

- LiFePO ₄ : 65-75%;

- Aluminium: 4-10%;

- Copper: 8-16%;

- Mixed organic fraction comprising metal, PVDF, graphite and coal: 2%.

This screening step results in three distinct fractions of refined black-mass that are themselves new.

The eighth step 18 of further refining the refined black-mass, which is configured to separate the electrode material from the non-electrode materials, provides that in order to perfect the purification of the electrode material, e.g. LiFePO ₄ , and make the compound suitable for use as an electrochemically active powder for the construction of new lithium-ion cells, it is necessary to reduce, and preferably eliminate, the presence of materials other than the electrode material to below 10 per cent by weight; such other materials may be e.g. graphite, or excess carbon, and other organic compounds found in the LiFePO ₄ -rich cathode compound.

For example, it has been seen in laboratory tests on cells made from recycled LiFePO ₄ according to a procedure as described above that it is possible to achieve up to 77% charge capacity compared to the pure (new) product when the presence of graphite with coal and minor impurities (Al, Cu and PVDF) reaches 15% by weight of the mass of the powder used in the cell.

According to the tests, the fraction of graphite, coal and minor impurities must be less than 10% if the charge capacity is to be further increased.

To refine the black-mass for the production of new cells, the two methods described above were tested as the first and second implementation variant of this eighth step 18, both with excellent results.

The regenerated powder obtained with the present invention has the following composition compared to a pure commercial powder:

The specific charge/discharge capacity of the regenerated powder obtained by a process 10 according to the invention is approximately 127 mAh/g.

The cathode active material obtained by the process 10 according to the invention and intended for the construction of new cells and batteries is also to be regarded as an object of the present invention.

The process 10 described above is aimed at obtaining a new powder (e.g. LFP) from an end-of-life lithium-ion battery type (e.g. LFP) for the production of new cells.

For example, LiFePO ₄ powder, although derived from a cell or battery classified as waste (EoL), is used as a substitute for the synthesis product. There is therefore no consumption of new lithium, no consumption of new iron, no consumption of new iron oxide, and no consumption of new phosphorus in the production of this LiFePO ₄ powder.

For the purposes of waste generation and the impact of carbon dioxide production, or fossil energy consumption in a plant for the implementation of the process 10 according to the invention, the following parameters were measured with reference to the preferred, but not exclusive, example of LiFePO ₄ .

The recovered cathode material obtained by the process 10 is not pure LFP, but a product with its own characteristics having a purity of between 90% and 100%.

The composition is therefore LFP plus impurities.

These impurities are:

- PVDF/salts < 0.1 - 3% by weight. This fraction has no impact on the functionality of the cell made from this recovered cathode material because, during the production of the cathode powder, the latter is added with new PVDF, in addition to the one already present and required;

- metals such as Cu and Al in the form of metal with a particle size of 1 - 80 pm; these metals within the cathode fraction are less than 1 % by weight; they are inert with respect to the functionality of the cell and only reduce its purity percentage compared to pure LFP;

- fluorine compounds present in an amount of less than 2% by weight, derived from the previous presence of LiPF ₆ and PVDF in the cell;

- lithium compounds such as l_i ₂ O, Li ₂ CO3, LiOH etc. present in the amount of 1 - 4% resulting from inertisation and calcination operations in the furnace forming aggregates larger than 80 pm; these lithium compounds do not intervene during the cell’s discharge and charge cycles.

In order to increase the quality of the cathode active material, known as CAM, the process 10 may include a ninth step 19 of vacuum pyrolysis, after the second variant of the eighth step 18, which employs the zig-zag separation system for the second black-mass fraction BMR2 only.

This ninth step 19 involves placing the powder in a furnace in an inert atmosphere using Argon, Nitrogen, in total absence of oxygen and in a vacuum.

In this ninth step 19 the second fraction BMR2 is heated up to 500 - 700°C, and the gases and the organic light molecules still present in the battery are extracted, which degrade and are thus eliminated.

The percentage of LFP in terms of purity increases by 2 to 6%, graphite and residual coal having been removed.

Subsequently, the powder coming out of the furnace in an inert atmosphere is ground in a tenth grinding step 20.

This tenth step 20 of grinding can be performed with a centrifugal mill or a paddle mill.

This tenth step 20 of grinding is configured to obtain a fourth fraction BMR4 with a particle size comprised between 30 pm and 160 pm, which defines the optimal recovered cathode active material.

This end product of the process 10 is called ‘P - RLFP’, and is not the same as the product placed on the market by LFP manufacturers obtained by synthesis. The product P - RLFP has its own identity and chemical composition and is suitable for the production of lithium-ion cells with its own characteristics.

The tenth step 20 of grinding is followed by an eleventh step 21 of screening, in which a fifth fraction BMR5 with a particle size comprised between 160 pm and 200 pm is separated.

The fifth fraction BMR5 is sent to a mixing step 22 with the first fraction BMR1 coming out of the seventh screening step 17.

The process 10 according to the invention also comprises an additional auxiliary grinding step 23 for the third fraction BMR3 with a particle size comprised between 200 and 600 pm.

This auxiliary grinding step 23 is followed by a secondary screening step 24, configured to separate:

- a new first fraction with a particle size of less than 80 pm, which is sent to the mixing step with the first fraction BMR1 and the fifth fraction BMR5;

- a new second fraction with a particle size between 80 and 200 pm, which is sent to a mixing step 25 with the second fraction BMR2 coming out of the primary screening step 17;

- a new third fraction with a particle size greater than 200 pm, which is returned to the auxiliary grinding step 23.

These auxiliary operations performed on the two fractions consisting of particle sizes 1 - 80 pm and greater than 200 pm have three purposes:

- to improve the weight % yield of the 80 - 200 pm powder to 65-75%;

- to increase the % fraction of LFP (>90%), due to the reduction of the graphite fraction in the product; a further increase in the charging capacity and performance of the powder can be achieved with the transition of the powder, after screening, into a zig-zag separator, which enables LFP to be obtained with a carbonaceous fraction ranging from 2 to 7%;

- to increase the value of cathode powder 1 - 80 pm and concentrated graphite powder derived from a zig-zag separation operation.

The cathode powder, from a screen with a particle size of less than 35 pm, consists of 90% lamellar natural graphite and is used as a new anode material. Thus, the present invention also relates to a cathode powder obtained by a process according to the invention, having a particle size of less than 35 pm, which consists of 90% lamellar natural graphite.

The two fractions consisting of particle size 1 - 80 pm and particle size greater than 200 pm, which are derived from primary screening, represent a new technical and economic value.

The fraction from the mixing step 22 can be subjected to an oxidation step in a furnace 26 and a subsequent transition to a separation step 27 in a zig-zag separator.

Material with a particle size larger than 600 pm separated with the fifth screening step 15 and denoted as BMR6 can be subjected to a grinding step 40, followed by a magnetic separation step 41 with extraction of iron and other magnetic materials.

What is not separated in the magnetic separation step 41 undergoes a densimetric separation step 42, whereby aluminium scrap 43 and copper scrap 44 are recovered.

A process for obtaining a powder of oxides and carbonates, e.g. non-exclusive iron oxides and carbonates, and lithium oxides and carbonates, which are used in the production of glazes and pigments used in ceramics, metal coatings, and coloured pigments for paints, is also an object of the present invention.

This process encompasses all the steps described above from the first step 11 to the fifth step 15 of screening.

All cathode powder from batteries, e.g. LiFePO ₄ , or individual fractions can undergo the described processes and be used to produce lithium oxides and carbonates and other metal compounds, e.g. phosphates and oxides of iron in the example of the LFP/Graphite battery.

The raw black-mass coming out of the fifth screening step 15, i.e. with a particle size of less than 600 pm, or fractions thereof, whose main compound is e.g. LiFePO ₄ , for the production of glass/ceramic pigments, undergoes a calcination step between 650°C and 850°C, and preferably equal to 700°C, in an oxidising atmosphere, which changes its composition.

This calcination step takes place by controlled combustion in a continuous rotary furnace or in a batch furnace.

This calcination step allows the carbonaceous fraction and all other organic fractions to be removed.

The chemical composition of the powder before the mixing steps 22 and 25, and before the subsequent refining steps, is in % by weight, and in the case of the LFP/Graphite battery is as follows:

- Graphite and coal 15-60%

- LiFePO ₄ 20-45%

- PVDF 2-6%

- Lithium compounds 2-5%

- Aluminium 1-4%

- Copper 1-4%. The composition of the powder after the refining steps is as follows:

- Graphite with coal 0.1-0.5%

- LiFePO ₄ 27.5-27.9%

- Iron phosphate 12%

- Iron oxide 5%

- Lithium oxide 27%

- Lithium phosphate 28%

- Lithium content as Li: 6.27%

- Total iron: 18%.

With reference to the use in the production of glazes and pigments, please note that in ceramics, the main components are:

- a vitrifying agent such as SiO ₂ , quartz and silica sands or P2O5;

- a stabiliser such as AI ₂ O ₃ ;

- a flux that may be K ₂ CO ₃ , CaCO ₃ , felspar and also lithium oxides.

In the composition of the black-mass powder resulting from the operations described, metallic compounds are present that participate in the formulation of an inorganic pigment.

The recycled cathode powder used for the formulation of inorganic pigments participates therein according to the production tests already performed and introduced with the product coming out of the process described above.

The present invention is therefore also intended to cover the use of cathode powder obtained from batteries (e.g. of the LFP type) treated by a process as described above to make inorganic pigments.

The cathode powder obtained by a process as described above according to the invention can thus be used in glazes, ceramics, inorganic pigments.

The procedure according to the invention responds, in its entirety, to the principle of total reuse of the substances and compounds contained in a battery at the end of its life.

The starting battery, e.g. of the LFP type, although containing metals other than Cobalt and Nickel, is completely reformulated and metals are used with the use of thermal energy and an emission factor of the CO ₂ contained.

Black-mass obtained by a process according to the above-described invention is an alternative to the use of new cathode material for LFP, LCO, NCM, NCA, LTO, NCO batteries and can also be used to replace metal compounds in the formulation of pigments. All types of black-mass which are obtained by the above-described process from Li-ion type cells are to be considered an object of the present invention and useful for the uses mentioned above, the cathode material of which is identified with the abbreviations:

- LCO i.e. cell in which the cathode contains LiCoO2;

- LMO i.e. cell in which the cathode contains LiMn ₂ O ₄ ;

- LFP i.e. cell in which the cathode contains LiFePO ₄ ;

- NCM i.e. cell in which the cathode contains LiNi _x Co _y Mn _z O _w ;

- NCA i.e. cell in which the cathode contains LiNi _x Co _y Al _z O _w ;

- LTO/NCO, LTO/LFP, i.e. cells in which the cathode contains LiTi _x O _y /Ni _x Co _y O _z /LiTi _x O _y /LiFePO ₄ ;

- LTO (lithium titanate) i.e. cell in which lithium titanate replaces graphite at the anode.

Also covered by the invention is the use of black-mass from lithium-ion batteries for the production of inorganic pigments.

In particular, to use black-mass in the formulation of inorganic pigments, it is necessary to carry out a process according to the invention using cells of the LCO, NCA, LFP type. Batches containing LMO- and NCM-type cells are excluded, as they are too rich in manganese, which leads the colour towards black.

It is also necessary to reduce the coal/graphite fraction by acting on the particle size fractions.

To obtain a refined black-mass useful for the production of inorganic pigments, the seventh screening step 17 is configured to separate fractions with the following particle sizes:

- a first fraction with a particle size of 1 - 50 pm;

- a second fraction with a particle size of 50 - 120 pm;

- a third fraction with a particle size of 120 - 200 pm;

- a fourth fraction with a particle size of 200 - 600 pm.

Next, a zig-zag separator, described above and forming part of the eighth step 18 of the process according to the invention, is used, in which the fraction of coal and graphite in the final product is reduced from 25 - 32% to 8 - 12%.

In the same process, the lithium fraction is also reduced from 4 - 8% by weight to 2 - 4%.

A content of 2 - 4% by weight of Li ₂ O or Li ₂ CO ₃ is considered sufficient to eliminate the effect on the vitreous amalgam.

The composition of black-mass for the production of inorganic pigments is related to the presence and percentage of metallic compounds that induce a variation on the colours to be produced.

For blue/black colours, for example, the black-mass obtained must have cobalt oxide as the predominant element and the rest of the elements must be weighted in the formula so as not to compromise the crystalline formation of the colour.

The proportion of coal/graphite must be reduced to below 15%.

In the preparation of inorganic pigments, the following components are mixed:

- aluminium oxide hydrate;

- cobalt oxide;

- coal.

In this case, black-mass, understood as the sum of Li ₂ CO ₃ and metal oxides such as Cobalt, Nickel, Manganese or Manganese oxide only (LMO) or Iron oxide only (LFP) - the object of the present invention - is included in the formula to develop blue-black-light blue-green-brown inorganic pigments.

The following is a standard formulation of an inorganic pigment and an example of a pigment formulation from black-mass LCO batteries: Standard formula with pure products:

- Hydrated alumina% 40-44

- Cobalt oxide% 24-26

- Quartz powder% 18-22

- Zinc oxide% 8-12

- China clay% 1-4;

Black-mass formula covered by the present invention:

- Hydrated alumina% 40-44

- Cobalt oxide% 20-25

- Quartz powder% 18-22

- Nickel oxide% 6-8

- Manganese oxide% 6-10

- Lithium oxide% 4-8, where cobalt oxide, nickel oxide, manganese oxide and lithium oxide are contained in the black-mass made by a process according to the invention.

An objective of the invention is to realise a black-mass that can be introduced into the formulations of glazes or coloured glass with low thermal expansion as well as glass for metal colouring.

The black-mass made by a process according to the invention results in a mixture suitable, with certain precautions, for inclusion in the formulation of coloured lithium glass.

For example, feldspar, quartz, kaolin and metal oxides are first melted resulting in vitrification between 1 ,100°C and 1 ,250°C; the resulting solid is then finely ground for use as coloured glass.

The cathode powder obtained by a process according to the invention as above-described, and which is also the object of the present invention, and which originates from LFP batteries (LiFePO ₄ ), is particularly suitable for the production of direct coloured glaze frits with various brown, black, and blue tones, containing both Li ₂ CO ₃ and dyeing iron oxides.

The presence of phosphorus (LiFePO ₄ ), which comes to P ₂ O ₅ (phosphorus pentoxide) when hot, is useful as a vitrifying agent because it makes the final glaze fusible.

A mixed cathode powder can thus be obtained, originating from LiFePO ₄ + LiNi _x COy AI _Z O _W .

A standard formula for the production of coloured glass from virgin raw materials is as follows: l_i ₂ O . 10

NaO . 20

K ₂ O . 15

CaO . 15

ZnO . 9

PbO . 30

CoO ₂ . 1.

A formula for producing coloured glass, with fractions taken from a recovered black-mass refined according to a process described above according to the invention, is as follows: l_i ₂ O . 10

NaO . 20

K ₂ O . 14

CaO . 15

ZnO . 8 PbO . 30

CoO ₂ . 1

NiO ₂ . 1

MnO ₂ . 1 , wherein the lithium, cobalt, nickel and manganese oxides come from cathode powder recovered and refined according to a process described above according to the invention.

The presence of coal, the particle size and the metal compounds in the blackmass are decisive for its use as a raw material in the vitreous formulae that are part of the present invention.

The product intended for inorganic pigment is indicated as ‘P - FE’.

The product P - FE for the formulation of inorganic pigments is placed on the market with its own formulation and composition.

Practically, it has been established that the invention achieves the intended task and objects.

In particular, the main reflection behind the cathode material recovery process according to the invention lies in the fact that LFP batteries (i.e. with LiFePO ₄ cathode) do not contain valuable metals such as Cobalt and Nickel. The only metal component, considered to be sensitive in terms of price and availability is Lithium. Iron and phosphorus have been available on the market for a long time and in large quantities.

Furthermore, the invention developed a process for recovering LiFePO ₄ powder to be reused in new batteries at a low cost compared to the cost of synthesising new cathode powder from precursors.

In addition, the invention developed a process for refining black-mass to obtain LiFePO ₄ , which consumes a modest amount of electrical and thermal energy to the point having no equal compared to the impact on the environment in terms of CO ₂ production and gas consumption, which the production of LiFePO ₄ from precursors has.

The process according to the present invention enables the processing of electrode materials that are sensitive to high temperatures, such as the nonexclusive LiFePO ₄ , which is “sensitive” to temperatures above 400°C in the presence of air or moisture. In fact, exposure to air of LiFePO ₄ generates the breakdown of the substance into a series of other substances with predominantly mixed iron oxides and phosphates. Thus, the process temperatures according to the invention preferably do not exceed 400°C.

The processes take place in the absence of air and thus oxygen.

In particular, the invention also developed a cathode powder, or black-mass, particularly rich in LiFePC

Further, the invention developed the use of black-mass from lithium-ion batteries for the production of inorganic pigments.

Furthermore, an inorganic pigment comprising substances in a refined blackmass made by the process according to the invention has been developed.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the inventive concept; moreover, all the details may be replaced by other technically equivalent elements.

In practice, the components and materials used, as long as they are compatible with the specific use, as well as the dimensions and the contingent shapes, can be any one according to requirements and the prior art.

Where the characteristics and techniques mentioned in any claim are followed by reference marks, those reference marks are intended to be affixed for the sole purpose of increasing the intelligibility of the claims and, consequently, those reference marks have no limiting effect on the interpretation of each element identified by way of example by those reference marks.