Method for recycling a coating ink for a lithium battery electrode

Abstract

The present invention relates to a method for recycling a coating ink for a lithium battery electrode comprising a mixture, in an organic solvent, of a cathode active material based on lithium metal oxides, of a binder and of an electron conductor. The recycling is carried out in particular by leaching in the presence of an aqueous sulfuric acid solution, followed by a step of co-precipitation of the metal sulfates of the cathode active material which are contained in the leachate. The precipitate obtained can subsequently be treated in order to be used as starting material in the refining of battery-grade sulfate salt.

Description

[0001] METHOD FOR RECYCLING A COATING INK

[0002] FOR LITHIUM BATTERY ELECTRODE

[0003] technical field

[0004] The present invention relates to the recycling of cathode coating ink from lithium ion type batteries.

[0005] Previous technique

[0006] Cathodic coating inks are used during the production operation of lithium-ion battery cathode (also called Li-ion here).

[0007] A lithium-ion battery cathode typically contains a cathode active material (CAM) that allows for the reversible insertion and removal of lithium within the cathode. The choice of cathode active material is a crucial factor that determines the energy density of the lithium-ion battery through its voltage and capacity. One of the most widely used cathode active materials is lithium-nickel-manganese-cobalt (also known as NMC). This is largely due to its high energy density and long lifespan compared to other cathode materials.

[0008] In addition to the CAM, the cathode also contains an electrically conductive compound, such as carbon black, and a binder to ensure the electrode's mechanical strength and cohesion. Commonly used cathode electrode binders today are polymer binders such as polyvinylidene fluoride (also known as PVDF).

[0009] Li-ion battery cathodes are most often manufactured using a process that successively involves dissolving or dispersing the various cathode components in a solvent to form an ink, also called a coating ink. This is followed by contacting the resulting coating ink with a metallic current collector, and finally, evaporating the solvent by convective stripping. The solvent commonly used in the coating ink manufacturing step is N-methyl-2-pyrrolidone (also known as NMP). Thus, in the case of Li-ion battery cathode manufacturing, the process consists of applying a coating ink to the surface of an electrode, which is generally made of aluminum, resulting in a CAM coating that is bonded to the electrode by the polymer binder.

[0010] However, on an industrial scale, manufacturing coating ink for Li-ion battery cathodes is not without its drawbacks. Indeed, during the coating ink preparation process, it appears that the ink can only be stored for a limited time, beyond which the final performance of the Li-ion battery is compromised. Furthermore, the presence of contaminants within the CAM (Computer-Aided Material), or the presence of sulfate ions in the ink solution, can cause adverse reactions with the solvent and the polymer binder, making uniform application of the ink onto the current collector difficult. Finally, the coating machines used in large-scale factories (gigafactories) require regular cleaning, which leads to a "purge" of the coating ink.Thus, factories manufacturing Li-ion batteries generate a significant amount of waste in the form of coating inks. Depending on the formulation, these inks can contain a dry extract of between 40 and 80% by weight of cathode active material (CAM), polymer binder, and carbon black, which can vary in proportions ranging from 90 / 5 / 5 to 98 / 1 / 1.

[0011] Therefore, one objective of the present invention is to propose a process for recycling used and / or unused coating ink in order to recover its constituent elements for closed-loop recycling in the production of Li-ion batteries.

[0012] Objects of the invention

[0013] The present invention relates to a process for recycling a coating ink for lithium battery electrode comprising a mixture in an organic solvent of a metal oxide and lithium-based cathode active material, a binder and an electronic conductor, comprising at least the following steps: aO) optionally, a liquid / solid separation step to obtain a first liquid effluent comprising at least a part of said organic solvent and said binder, and a wet cake comprising said metal oxide and lithium-based cathode active material, said electronic conductor, and at least another part of said organic solvent and said binder;a) a drying step of the coating ink, optionally of the wet cake obtained at the end of step a0), at a temperature below 160°C and at a pressure below atmospheric pressure to obtain a dry cake comprising said metal oxide and lithium-based cathode active material, said electronic conductor and at least a part of said binder and a gaseous phase comprising said organic solvent; b) a leaching step by contacting the dry cake obtained at the end of step a) with an aqueous solution comprising sulfuric acid and a reducing agent to obtain a suspension comprising a liquid fraction comprising metal sulfates of the cathode active material and lithium sulfate, and a solid fraction comprising said electronic conductor and at least a part of said binder;c) a step of separating the suspension obtained at the end of step b) to obtain a liquid fraction comprising essentially metal sulfates of the active cathode material and lithium sulfate and a solid fraction comprising the binder and the electronic conductor.;

[0014] The process according to the invention thus makes it possible to recycle battery electrode coating ink by offering a specific pretreatment, optionally including a separation step, preferably by centrifugation, and a vacuum drying step, which allows:

[0015] - to recover the solvent and binder contained in the initial coating ink without major alteration of their physicochemical properties. Thus, the recovered solvent and binder can be recycled or even reused for the reformulation of coating ink;

[0016] - to simplify the recovery of a solution of metallic sulfates directly recyclable in the synthesis of active cathode material.

[0017] According to one or more embodiments of the invention, said process further comprises the following steps: d) a precipitation step of the liquid fraction obtained at the end of step c) to obtain a suspension comprising a precipitate based on metal hydroxides of the active cathode material and a liquid phase comprising at least lithium sulfate; e) a separation step of the suspension obtained at the end of step d) to obtain a precipitate comprising the metal hydroxides of the active cathode material and a second liquid effluent comprising at least lithium sulfate.

[0018] According to one or more embodiments of the invention, step aO) is mandatory and is carried out by centrifugation with a centrifugal force between 1000 G and 16000 G.

[0019] According to one or more embodiments of the invention, in step b) the concentration of sulfuric acid in the aqueous solution is between 1 and 10 mol / L.

[0020] According to one or more embodiments of the invention, in step b) the concentration of reducing agent in the aqueous solution is between 0.1 and 1.5 mol / L.

[0021] According to one or more embodiments of the invention, leaching step b) is carried out in a countercurrent flow through "n" leaching substeps, "n" being greater than or equal to 2, by countercurrently contacting the dry cake obtained at the end of step a) with an aqueous solution comprising sulfuric acid and a reducing agent, fed continuously and flowing through each of the leaching substeps in the opposite direction to the flow of the dry cake. According to one or more embodiments of the invention, when said leaching step b) is carried out in a countercurrent flow, then steps b) and c) are carried out simultaneously, each leaching substep being followed by a solid / liquid separation step.

[0022] According to one or more embodiments of the invention, a sacrificial solid is added to the aqueous solution supplied in step b) of leaching.

[0023] According to one or more embodiments of the invention, said gaseous phase obtained at the end of step a) of drying is condensed to obtain a liquid phase comprising the organic solvent.

[0024] According to one or more embodiments of the invention, at the end of step b) of leaching, said sacrificial solid is at least partially washed with said liquid phase comprising the organic solvent.

[0025] According to one or more embodiments of the invention, step d) is carried out by adding an aqueous solution or aqueous suspension containing at least one hydroxide compound so as to achieve a pH greater than 8.

[0026] According to one or more embodiments of the invention, said at least one hydroxide compound is chosen from sodium hydroxide, calcium hydroxide and lithium hydroxide, taken alone or in mixture.

[0027] According to one or more embodiments of the invention, at least a portion of the liquid fraction obtained at the end of step c) is sent to a cathode active material precursor synthesis unit.

[0028] According to one or more embodiments of the invention, step a) of drying is carried out by conductive means at a pressure between 0.0001 and 0.09 MPa absolute.

[0029] According to one or more embodiments of the invention, the second liquid effluent comprising at least the lithium sulfate obtained at the end of step e) is sent at least in part to an electrolysis or electrodialysis step f) to obtain at least a lithium hydroxide solution and a sulfuric acid solution.

[0030] According to one or more embodiments of the invention, the lithium hydroxide solution obtained at the end of step f) is recycled at least in part in the precipitation step d) and / or the sulfuric acid solution obtained at the end of step f) is recycled at least in part in the leaching step b).

[0031] According to one or more embodiments of the invention, a purification step of the liquid fraction (leachate) obtained at the end of step c) is carried out by contacting at least part of the liquid fraction with an adsorbent, in order to eliminate the presence of organic solvent.

[0032] According to one or more embodiments of the invention, said metals of said active cathode material are selected from nickel, cobalt and manganese and mixtures thereof.

[0033] According to one or more embodiments of the invention, the active cathode material (CAM) based on metal oxides and lithium corresponds to the following formula:

[0034] LiNixMn y COz02 with x > 0, y > 0, z > 0 and x + y + z = 1.

[0035] According to one or more embodiments of the invention: x = 0.6; y = 0.2 and z = 0.2; or x = 0.8; y = 0.1 and z = 0.1; or x = 0.9; y = 0.05 and z = 0.05.

[0036] According to one or more embodiments of the invention:

[0037] - said electronic conductor is carbon black; and / or

[0038] - said organic solvent is N-Methyl-Pyrrolidone (NMP); and / or

[0039] - said binder is a polymer binder based on polyvinylidene fluoride (PVDF).

[0040] Definitions

[0041] In the sense of the present invention, the different embodiments presented can be used alone or in combination with each other, without limitation of combination.

[0042] In the context of the present invention, different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the context of the present invention, a preferred range of pressure values ​​can be combined with a preferred range of temperature values.

[0043] In the following text, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included within the described range of values. If this were not the case and the limit values ​​were not included within the described range, this clarification will be provided by the present invention.

[0044] In this description, the term "include" is synonymous with (means the same as) "include" and "contain," and is inclusive or open-ended, not excluding other elements not mentioned. It is understood that the term "include" includes the exclusive and closed term "consist."

[0045] According to the present invention, pressures are absolute pressures, also noted as abs., and are given in absolute MPa (or abs. MPa), unless otherwise indicated.

[0046] In the sense of the present invention, the different embodiments presented can be implemented separately or in combination with each other, without limitation of combinations when this is technically feasible.

[0047] In the context of the present invention, different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the context of the present invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0048] The metal content is measured by X-ray fluorescence.

[0049] For the purposes of the present invention, a "lithium battery electrode coating ink" means a fluid composition formulated for the preparation of a battery electrode, said ink comprising at least one active cathode material, a binder, optionally an electronic conductor, and a solvent.

[0050] The coating ink is intended to be deposited onto a conductive current collector by coating, in order to form an electroactive layer after drying. It is not derived from the processing, grinding, or dispersion of a used electrode, nor from material extracted from an end-of-life or partially used battery. In other words, the coating ink as defined in the present invention is formulated from new or industrial-grade components specifically prepared for initial electrochemical application.

[0051] List of figures

[0052] Figure 1 shows a diagram according to an embodiment of the invention comprising steps a0) to e) as described below

[0053] Detailed description

[0054] The present invention relates to a method for recycling a coating ink for lithium battery electrodes, comprising a mixture in an organic solvent of a cathode active material (CAM) based on metal oxides and lithium, a binder, and an electronic conductor. Preferably, the metals of said cathode active material are selected from nickel, cobalt, and manganese and mixtures thereof.

[0055] Other metals may be present in the active cathode material, for example as dopant(s). In one embodiment, the active cathode material further comprises a dopant selected from aluminum, titanium, zirconium, or magnesium, alone or in a mixture, at a content of between 0 and 3% by weight relative to the total weight of the active cathode material. In another embodiment according to the invention, the active cathode material further comprises a dopant selected from chromium, tungsten, copper, or molybdenum, alone or in a mixture, at a content of between 0 and 2% by weight relative to the total weight of the active cathode material.

[0056] Preferably, the active cathode material (CAM) based on metal oxides and lithium corresponds to the following formula:

[0057] LiNixMnyCOzO? with x > 0, y > 0, z > 0 and x + y + z = 1.

[0058] In an embodiment according to the invention x = 0.6; y = 0.2 and z = 0.2.

[0059] In another embodiment of the invention x = 0.8; y = 0.1 and z = 0.1. In another embodiment of the invention x = 0.9; y = 0.05 and z = 0.05.

[0060] The present invention relates to a process for recycling a coating ink for lithium battery electrode comprising a mixture in an organic solvent of a metal oxide and lithium-based cathode active material, a binder and an electronic conductor, comprising at least the following steps: aO) optionally, a liquid / solid separation step to obtain a first liquid effluent comprising at least a part of said organic solvent and said binder, and a wet cake comprising said metal oxide and lithium-based cathode active material, said electronic conductor, and at least another part of said organic solvent and said binder;a) a drying step of the coating ink, optionally of the wet cake obtained at the end of step a0), at a temperature below 160°C and at a pressure below atmospheric pressure to obtain a dry cake comprising said metal oxide and lithium-based cathode active material, said electronic conductor and at least a part of said binder, and a gaseous phase comprising said organic solvent; b) a leaching step by contacting the dry cake obtained at the end of step a) with an aqueous solution comprising sulfuric acid and a reducing agent to obtain a suspension comprising a liquid fraction comprising metal sulfates of the cathode active material and lithium sulfate, and a solid fraction comprising said electronic conductor and at least a part of said binder;c) a step of separating the suspension obtained at the end of step b) to obtain a liquid fraction comprising essentially metal sulfates from the active cathode material and lithium sulfate and a solid fraction comprising the binder and the electronic conductor; d) optionally, a step of precipitating the liquid fraction obtained at the end of step c) to obtain a suspension comprising a precipitate based on metal hydroxides from the active cathode material and a liquid phase comprising at least lithium sulfate; e) optionally, a step of separating the suspension obtained at the end of step d) to obtain a precipitate comprising the metal hydroxides from the active cathode material and a second liquid effluent comprising at least lithium sulfate.

[0061] All steps aO) to e) are described in detail below.

[0062] When the coating ink supplied in the process according to the invention contains a low solids content, i.e., a dry extract of less than 30% by weight of solid matter relative to the total weight of the coating ink, said ink advantageously undergoes a first liquid / solid separation step (step aO) of the process according to the invention to obtain a first liquid effluent comprising at least a portion of the organic solvent and binder, and a wet cake comprising the metal oxide and lithium-based cathode active material, the electronic conductor, and at least another portion of the organic solvent and binder. This optional separation step allows for the recovery of a liquid effluent that is free of cathode active material (CAM).Therefore, depending on the type of degradation of the initial coating ink, the liquid effluent obtained after this separation step can be reused either to generate new coating ink or recycled in an open loop, i.e., for a use other than coating ink production. The requirement for the absence of a solid fraction in the liquid effluent results in a wet cake containing a residual liquid fraction. Nevertheless, this step allows for the removal of a significant amount of liquid from the wet cake, which substantially reduces the energy cost of the subsequent drying step. Thus, the residual liquid content in the wet cake is the result of a fine-grained optimization between the absence of solids in the liquid fraction and the minimization of the energy cost of downstream steps.The liquid / solid separation step also removes a major part of the binder, which greatly facilitates the management of subsequent drying and leachate separation and / or purification steps.

[0063] The liquid / solid separation step can be carried out by any separation technique known to those skilled in the art, and is preferably performed by decantation, centrifugation, filtration, or any other physical means. Preferably, the separation step is carried out by centrifugation. Advantageously, the centrifugal force is between 1000 G and 16000 G, preferably between 2000 G and 8000 G, and preferably between 3000 G and 6000 G. Those skilled in the art may use any type of centrifuge technology, in particular a plate centrifuge or a decanter centrifuge. The centrifugation time is advantageously between 30 seconds and 30 minutes, preferably between 1 minute and 20 minutes, and more preferably between 2 minutes and 10 minutes.

[0064] The resulting liquid effluent contains at least some of the organic solvent and binder. The organic solvent and binder can thus be reused as a basis for formulating a coating ink, either directly or by carrying out a further step of distilling the liquid effluent under reduced pressure to recover the solvent on one hand, and the binder on the other.

[0065] Step a)

[0066] According to the invention, the initial coating ink, or optionally the wet cake obtained at the end of the optional step a0), is dried at a temperature below 160°C, preferably below 140°C, preferably below 120°C, and most preferably below 100°C, and at a pressure below atmospheric pressure to obtain a dry cake comprising the cathode active material (CAM) based on metal oxides and lithium, the electronic conductor, and at least a portion of the binder. This drying step is carried out at a relatively low temperature so as not to thermally degrade the binder. Preferably, the binder is a polymer binder, and more preferably, the polymer binder is PVDF.When the solvent used is N-methyl-2-pyrrolidone (NMP - boiling point of 202°C at atmospheric pressure) and when the binder used is polyvinylidene fluoride (PVDF - melting point between 170°C and 180°C at atmospheric pressure) then the drying step is advantageously carried out at a pressure lower than atmospheric pressure, and preferably lower than 0.1 MPa, and more preferably at a pressure between 0.001 MPa and 0.09 MPa in order to evaporate the polymer binder at a temperature lower than the decomposition temperature of PVDF.

[0067] Advantageously, during the drying step, the gaseous fraction formed includes the evaporated organic solvent, which can then be condensed and reused in the preparation of a cathodic coating ink or recycled in an open loop. In one embodiment of the invention, an organic solvent solution is recovered, which can be used as a washing solution for the sacrificial solid used in an embodiment of step c) of the process according to the invention.

[0068] Step a) of drying can be carried out by conduction or convection. Preferably, the drying step is carried out by conduction in order to reduce the presence of solid CAM particles in the gaseous fraction resulting from the drying.

[0069] At the end of the drying step a) a dry cake is obtained comprising the active cathode material based on metal oxides and lithium, the electronic conductor and at least part of the binder.

[0070] According to the invention, a leaching step is carried out by contacting the dry cake obtained at the end of step a) with an aqueous solution comprising sulfuric acid and a reducing agent, preferably hydrogen peroxide, to obtain a suspension comprising a liquid fraction called the leachate comprising metal sulfates of the active cathode material and lithium sulfate, and a solid fraction comprising said electronic conductor and at least a part of said binder.

[0071] The concentration of sulfuric acid in the aqueous solution is generally between 1 and 10 mol / L, preferably between 1.5 and 4.5 mol / L.

[0072] The concentration of reducing agent in the aqueous solution is generally between 0.1 and 1.5 mol / L, preferably between 0.1 and 1.3 mol / L. Preferably, the reducing agent is hydrogen peroxide.

[0073] The contacting of the dry cake and the aqueous solution can be achieved by any method known to those skilled in the art, for example by suspending the dry cake in the leaching solution using a rotary agitator or by fluidization, or by percolating the leaching solution through a fixed bed containing the dry cake.

[0074] The contact is established under the following operating conditions:

[0075] - the temperature is generally between 0°C and 300°C, preferably between 10°C and 100°C, and more preferably between 15°C and 40°C. Particularly preferably, the temperature is ambient temperature;

[0076] - the pressure is generally between atmospheric pressure and 20 bars (2 MPa), preferably between atmospheric pressure and 10 bars (1 MPa); - the duration of contact is generally between 5 minutes and 20 hours, preferably between 15 minutes and 300 minutes, preferably between 15 minutes and 240 minutes, even more preferably between 20 minutes and 180 minutes.

[0077] The quantity of leaching solution used is preferably as small as possible to achieve the desired effect, as indicated above. Preferably, the liquid / solid ratio, expressed as mass of leaching solution per mass of dry cake to be treated, is between 1 and 15, preferably between 2 and 12, and preferably between 3 and 10.

[0078] The leaching rate is generally greater than 50%, preferably greater than 60%, preferably greater than 70%, and even more preferably greater than 90%. The leaching rate corresponds to the mass of the metal(s) extracted in the final solution relative to the mass of metal(s) initially present on the dry cake.

[0079] In one embodiment of the invention, leaching step b) is carried out in a countercurrent flow through "n" leaching substeps, "n" being greater than or equal to 2, preferably between 2 and 20, and even more preferably between 2 and 6, by contacting the dry cake obtained at the end of step a) in countercurrent flow with an aqueous solution comprising sulfuric acid and a reducing agent, preferably hydrogen peroxide, fed continuously and flowing through each of the leaching substeps in the opposite direction to the flow of the dry cake. Thus, in this specific embodiment, step b) is characterized by the fact that the leaching solution is fed continuously and flows through the different substeps in the opposite direction to the flow of the solid, i.e., the cake. In this specific embodiment, leaching step b) is carried out simultaneously with separation step c) described below.Indeed, each leaching substep is followed by a solid / liquid separation step to separate the resulting suspension and obtain a liquid fraction (leachate) consisting mainly of metal sulfates from the active cathode material and lithium sulfate and a solid fraction consisting of the binder and the electronic conductor.

[0080] In this way, the dry cake supplied in the first leaching substage always first encounters the solution most enriched in metal sulfates from the cathode active material and lithium sulfate. Subsequent leaching / separation stages then follow, with the cake becoming increasingly leached of these metals and solutions with progressively lower concentrations of extracted metals, culminating in the final stage (stage "n") which uses a metal-free leaching solution. Thus, at each substage, a suspension is recovered comprising a liquid fraction enriched with extracted metal(s) and a solid fraction (cake) depleted in metals. This principle ensures a higher overall metal recovery rate from the final solution by optimizing the amount of sulfuric acid and reducing agent.

[0081] The circulation of the solid can be achieved by any method known to those skilled in the art, for example, by moving baskets, a conveyor belt, a moving grid, a screw conveyor, or by suspension with the leaching solution (also called "slurry" in Anglo-Saxon terminology). The circulation of the solid can also be simulated by permuting the injection point of the leaching solution. Indeed, if the injection point is periodically moved from step i to i+1, the solid moves in the opposite direction to the liquid, relative to its injection point.

[0082] Each substep of liquid / solid separation can be carried out by any method known to those skilled in the art, for example by sedimentation, filtration, draining, gravity flow, and / or centrifugation.

[0083] In one embodiment of the invention, a sacrificial solid is supplied in leaching step b). The addition of the sacrificial solid allows the electronic conductor, such as carbon black, and the binder, such as PVDF, to bind to it. The sacrificial solid becomes saturated with the electronic conductor and binder and is then separated via the liquid / solid separation steps described above. The sacrificial solid used must have a suitable porosity and size, which is determined by those skilled in the art based on the composition of the cake upstream of leaching step b. Preferably, the sacrificial solid is a carbon compound, such as carbon black or graphite, in a divided form with an average diameter of less than 1 cm. The sacrificial solid may be in the form of a powder, beads, or extrudates.

[0084] In one embodiment of the invention, the sacrificial solid loaded with binder and electronic conductor is washed with at least a portion of the solvent solution recovered after condensation of the gaseous phase during step a) of drying. Following this washing step, the loaded sacrificial solid can be sent to step a) of the process according to the invention. This embodiment has the advantage of incorporating the sacrificial solid into the dry cake before step b) of leaching. The organic solvent loaded with polymer binder can be recycled in an open loop or, as in step a0), be treated in a complementary distillation step under reduced pressure to recover, on the one hand, the solvent, and on the other hand, the binder, each of which can be recycled in an open or closed loop where possible.

[0085] Step c) According to the invention, a liquid / solid separation step c) is carried out on the suspension obtained at the end of step b) to obtain a liquid fraction (called leachate) comprising essentially metal sulfates of the active cathode material and lithium sulfate, and a solid fraction comprising the binder and the electronic conductor (cake). The liquid / solid separation step can be carried out by any method known to those skilled in the art, for example by sedimentation, filtration, draining, gravity flow, and / or centrifugation.

[0086] As described above, when leaching step b) is carried out counter-currently in "n" leaching substeps, leaching step b) is performed concurrently with separation step c), meaning that each leaching substep is followed by a solid / liquid separation step to separate the suspension and obtain a liquid fraction called leachate, consisting mainly of metal sulfates from the cathode active material and lithium sulfate, and a solid fraction consisting of the binder and the electronic conductor.

[0087] In one embodiment according to the invention, an additional step (step c')) is carried out to purify the liquid fraction (leachate) obtained at the end of step c) by contacting at least part of the liquid fraction with an adsorbent, preferably activated carbon, in order to eliminate the possible presence of solvent, such as NMP.

[0088] In one embodiment according to the invention, at least a portion of the liquid fraction (leachate) obtained at the end of step c) is sent to a cathode active material precursor synthesis unit. Indeed, this liquid fraction, due to its composition of cathode active metals and the stoichiometry maintained between the different cathode active metals, can be directly sent to such a unit in order to reformulate the cathode active material initially contained in the coating ink supplied in the process according to the invention.

[0089] In one embodiment of the invention, the process according to the invention includes a step d) of precipitating the liquid fraction (leachate) obtained at the end of step c) in a basic medium. In this embodiment, advantageously, an aqueous solution or an aqueous suspension containing a hydroxide compound, preferably selected from sodium hydroxide, calcium hydroxide, and lithium hydroxide, taken alone or in a mixture, is added so as to achieve a pH greater than 8, preferably greater than or equal to 9, and even more preferably between 9 and 11, to obtain a suspension comprising a precipitate based on nickel hydroxide, cobalt hydroxide, and manganese hydroxide, and a liquid phase based on at least lithium sulfate and / or sodium sulfate, and optionally calcium sulfate.

[0090] Step d) is preferably carried out at a temperature between 15°C and 80°C, preferably between 20°C and 75°C, and even more preferably between 25°C and 70°C.

[0091] In an embodiment according to the invention, the process according to the invention includes a step of separating the suspension obtained at the end of step d). The separation step can be carried out by any separation technique known to those skilled in the art, and is preferably carried out by decantation, centrifugation, filtration, or any other physical means. Preferably, the separation step is carried out by filtration.

[0092] At the end of step e), a precipitate is obtained comprising the metallic hydroxides of the active cathode material and a second liquid effluent comprising lithium sulfate and / or sodium sulfate, and possibly calcium sulfate.

[0093] The precipitate is advantageously washed, preferably with water or solvent when it still contains residual traces of sulfates or binder, respectively, and then dried at a temperature between 50°C and 200°C, preferably between 75°C and 180°C, for a period of between 10 minutes and 36 hours, more preferably between 1 and 15 hours. This drying step yields a solid containing metallic hydroxides of the active cathode material. This solid can then be used as a raw material for refining battery-grade sulfate salt.

[0094] In one embodiment of the invention, the second liquid effluent, comprising lithium sulfate and / or sodium sulfate, and optionally traces of calcium sulfate, is sent at least partially to a conversion step (f), preferably by electrolysis or electrodialysis, to obtain at least one lithium hydroxide solution and one sulfuric acid solution. The lithium hydroxide solution obtained at the end of step (f) is advantageously recycled at least partially to the precipitation step (d), and / or the sulfuric acid solution obtained at the end of step (f) is advantageously recycled at least partially to the leaching step (b).

[0095] To better understand the invention, the following description, by way of application example, relates to a process for recycling a coating ink for lithium battery electrodes, comprising an electrodialysis step of the resulting liquid effluent containing lithium sulfate (Figure 1). In this example, the coating ink has the following composition:

[0096] - organic solvent: NM P;

[0097] - metal oxides: NMC (nickel, manganese, cobalt) of type 622 or 811 or 9-0, 5-0, 5.

[0098] - binder: PVDF;

[0099] - electronic conductor: carbon black.

[0100] Referring to Figure 1, representing a first embodiment according to the invention, a coating ink 1 comprising a dry extract of less than 30% by weight of solid matter relative to the total weight of the coating ink is sent to a first liquid / solid separation step aO) to obtain a first liquid effluent 3 comprising at least a portion of NMP and PVDF which can be reused in the preparation of a cathodic coating ink or separated by distillation, and a wet cake 2 comprising the active cathode material (CAM), carbon black, and at least a portion of NMP and PVDF.The wet cake 2 is then sent to a drying step a) at a temperature below 160°C, preferably below 140°C, more preferably below 120°C, and even more preferably below 100°C, and at a pressure below atmospheric pressure to obtain a dry cake 5 based on CAM, carbon black, and a portion of PVDF. During the drying step, the gaseous phase 4, including the NMP, can be recovered by condensation for reuse in the preparation of a cathodic coating ink. The dry cake 5 is then sent to a leaching step b) in the presence of an aqueous solution 6 comprising sulfuric acid and hydrogen peroxide to obtain a suspension 7 comprising a liquid fraction (leachate) including the metal sulfates of the active cathode material and lithium sulfate, and a solid fraction including the electronic conductor and at least a portion of the binder.The suspension 7 is then sent to a liquid / solid separation step (c) to obtain a leachate 9 consisting essentially of metal sulfates from the cathode active material and lithium sulfate. This step removes carbon black and PVDF via line 8. The leachate 9, optionally purified with activated carbon, is then sent to a precipitation step (d) by adding an aqueous solution or aqueous suspension 10 based on lithium hydroxide to obtain a suspension 11 consisting of a precipitated solid comprising metal hydroxides from the cathode active material and lithium sulfate. The suspension 11 is then sent to a liquid / solid separation step (e) to obtain a precipitate 12 comprising metal hydroxides from the cathode active material and a second liquid effluent 13 comprising lithium sulfate of the U2SO4 type.The second liquid effluent 13 from step e) of liquid / solid separation is sent to an electrodialysis step f) to obtain a lithium hydroxide solution 15 and a sulfuric acid solution 16. The lithium hydroxide solution 15 is advantageously recycled in the precipitation step d) and / or the sulfuric acid solution 16 is advantageously recycled in the leaching step b).

Claims

DEMANDS 1. A process for recycling a lithium battery electrode coating ink comprising a mixture in an organic solvent of a metal oxide and lithium-based cathode active material, a binder and an electronic conductor, comprising at least the following steps: aO) optionally, a liquid / solid separation step to obtain a first liquid effluent comprising at least a portion of said organic solvent and said binder, and a wet cake comprising said metal oxide and lithium-based cathode active material, said electronic conductor, and at least another portion of said organic solvent and said binder;a) a drying step of the coating ink, optionally of the wet cake obtained at the end of step a0), at a temperature below 160°C and at a pressure below atmospheric pressure to obtain a dry cake comprising said metal oxide and lithium-based cathode active material, said electronic conductor and at least a part of said binder, and a gaseous phase comprising said organic solvent; b) a leaching step by contacting the dry cake obtained at the end of step a) with an aqueous solution comprising sulfuric acid and a reducing agent to obtain a suspension comprising a liquid fraction comprising metal sulfates of the cathode active material and lithium sulfate, and a solid fraction comprising said electronic conductor and at least a part of said binder;c) a step of separating the suspension obtained at the end of step b) to obtain a liquid fraction comprising essentially metal sulfates of the active cathode material and lithium sulfate and a solid fraction comprising the binder and the electronic conductor.; 2. A process according to claim 1 further comprising the following steps: d) a precipitation step of the liquid fraction obtained at the end of step c) to obtain a suspension comprising a precipitate based on metal hydroxides of the active cathode material and a liquid phase comprising at least lithium sulfate; e) a separation step of the suspension obtained at the end of step d) to obtain a precipitate comprising the metal hydroxides of the active cathode material and a second liquid effluent comprising at least lithium sulfate.

3. A method according to any one of claims 1 or 2, wherein step aO) is mandatory and is carried out by centrifugation with a centrifugal force between 1000 G and 16000 G.

4. A method according to any one of claims 1 to 3, wherein in step b) the concentration of sulfuric acid in the aqueous solution is between 1 and 10 mol / L.

5. A process according to any one of claims 1 to 4, wherein in step b) the concentration of reducing agent in the aqueous solution is between 0.1 and 1.5 mol / L.

6. A method according to any one of claims 1 to 5, wherein the leaching step b) is carried out in counter-current flow in "n" leaching sub-steps, "n" being greater than or equal to 2, by contacting the dry cake obtained at the end of step a) in counter-current flow with an aqueous solution comprising sulfuric acid and a reducing agent fed continuously and flowing through each of the leaching sub-steps in the opposite direction to the cake flow.

7. A method according to claim 6, wherein when said leaching step b) is carried out in counter-current flow, steps b) and c) are carried out simultaneously, each leaching substep being followed by a solid / liquid separation step.

8. A method according to any one of claims 1 to 7, wherein a sacrificial solid is added to the aqueous solution supplied in leaching step b).

9. A process according to any one of claims 1 to 8, wherein said gaseous phase obtained at the end of step a) of drying is condensed to obtain a liquid phase comprising the organic solvent.

10. A process according to any one of claims 8 or 9, wherein at the end of leaching step b), said sacrificial solid is at least partially washed with said liquid phase comprising the organic solvent.

11. A method according to any one of claims 2 to 10, wherein step d) is carried out by adding an aqueous solution or aqueous suspension containing at least one hydroxide compound so as to achieve a pH greater than 8.

12. A method according to claim 11, wherein said at least one hydroxide compound is selected from sodium hydroxide, calcium hydroxide and lithium hydroxide, taken alone or in mixture.

13. A method according to any one of claims 1 to 12, wherein at least a portion of the liquid fraction obtained at the end of step c) is sent to a cathode active material precursor synthesis unit.

14. A method according to any one of claims 1 to 13, wherein step a) of drying is carried out by conductive means at a pressure between 0.0001 and 0.09 MPa absolute.

15. A process according to any one of claims 2 to 14, wherein the second liquid effluent comprising at least the lithium sulfate obtained at the end of step e) is sent at least in part to an electrolysis or electrodialysis step f) to obtain at least one lithium hydroxide solution and one sulfuric acid solution.

16. A process according to claim 15, wherein the lithium hydroxide solution obtained at the end of step f) is recycled at least in part in the precipitation step d) and / or the sulfuric acid solution obtained at the end of step f) is recycled at least in part in the leaching step b).

17. A method according to any one of claims 1 to 16, wherein a purification step is carried out on the liquid fraction obtained at the end of step c) by contacting at least a part of the liquid fraction with an adsorbent, in order to eliminate the presence of organic solvent.

18. A method according to any one of claims 1 to 17, wherein said metals of said active cathode material are selected from nickel, cobalt and manganese and mixtures thereof.

19. A method according to any one of claims 1 to 18, wherein the active cathode material based on metal oxides and lithium corresponds to the following formula: LiNuMnyCOzCh with x > 0, y > 0, z > 0 and x + y + z = 1.

20. Method according to the preceding claim wherein: x = 0.6; y = 0.2 and z = 0.2; or x = 0.8; y = 0.1 and z = 0.1; or x = 0.9; y = 0.05 and z = 0.

05.

21. A method according to any one of claims 1 to 20, wherein: - said electronic conductor is carbon black; and / or - said organic solvent is N-Methyl-Pyrrolidone (NMP); and / or - said binder is a polymer binder based on polyvinylidene fluoride (PVDF).

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