A process for recycling negative electrode electrochemical elements comprising an alkali metal

Abstract

Process for recycling negative electrode electrochemical elements comprising an alkali metal. The present invention relates to a process for recycling an electrochemical element comprising a negative electrode having a negative active layer comprising an alkali metal M in metallic form and / or in the form of an alloy, M being selected from Li, Na, and K. The process comprises a step (a) of contacting the alkali metal M with elemental sulfur to produce M2S, the contacting step (a) being carried out in the absence of solvent. Figure for the abstract: Figure 1

Description

Title of the invention: Process for recycling negative electrode electrochemical elements comprising an alkali metal

[0001] The present invention relates to a method for recycling an electrochemical element comprising a negative electrode having a negative active layer comprising an alkali metal M in metallic form and / or in the form of an alloy, M being chosen from Li, Na and K, the method comprising a step a) of contacting the alkali metal M with elemental sulfur to produce M2S, the step a) of contacting being carried out in the absence of solvent.

[0002] One of the biggest current challenges for the battery industry is their recycling, as many technical and technological barriers are slowing down the development of efficient methods.

[0003] The first step in a battery recycling process involving one or more electrochemical cells is, in principle, the isolation of each component. However, existing batteries have different design types (size, chemistry, technology), which require specific approaches. For example, liquid electrolyte batteries are primarily disassembled (unscrewed and / or desoldered), emptied of their electrolyte, and each component is sorted: the positive electrodes, the negative electrodes, and finally the metal parts. On the other hand, solid electrolyte batteries require new manufacturing processes such as compaction, co-lamination, densification, or bonding of different materials, which are incompatible with existing end-of-life recovery processes.

[0004] In the specific case of lithium-sulfur (Li-S) electrochemical elements, the sulfur-based positive electrode is of limited value due to the low cost of sulfur. The use of recycled materials in electrochemical elements is particularly complex in the case of all-solid Li-S electrochemical elements, since the most expensive material to produce is the solid electrolyte.

[0005] Consequently, there is an interest in a simple and economical process for recycling used electrochemical elements, in particular used all-solid electrochemical elements. There is particular interest in such a recycling process that maximizes the reuse of the materials constituting the electrochemical element, especially an all-solid electrochemical element.

[0006] To this end, the invention relates to a process for recycling an electrochemical element comprising a negative electrode having a negative active layer comprising an alkali metal M in metallic form and / or in the form of an alloy, M being chosen from Li, Na and K, the process comprising a step a) of contacting the alkali metal M with elemental sulfur to produce M2S, step a) of contacting being carried out in the absence of solvent.

[0007] The invention also relates to a recycled sulfide material, obtained by the process according to the invention, comprising M2S, M being chosen from Li, Na and K.

[0008] The invention further relates to a solid sulfide electrolyte obtained by reaction between the recycled sulfide material (and possibly the solid sulfide electrolyte used in the electrochemical element to be recycled, if present) and one or more reagents suitable for reacting with M2S to form a solid sulfide electrolyte, such as P2S5, LiX (X = Cl, Br, I), in stoichiometric quantities, in order to form a solid sulfide electrolyte, such as Li6PS5Cl or Li3PS4.

[0009] For example, in the case of an electrochemical element Li-S using a solid electrolyte of the type Li6PS5Cl:

[0010] a Li2S + Li6PS5Cl + b P2S5 + c LiCl => d Li6PS5Cl

[0011] In order to maintain the stoichiometry of the reaction, it follows that:

[0012] a Li2S + Li6PS5Cl + a / 5 P2S5 + 2.a / 5 LiCl => (l+2a / 5) Li6PS5Cl

[0013] For a Li3PS4 electrolyte, the reaction would be as follows:

[0014] a Li2S + b P2S5 -> c Li3PS4

[0015] with a = 3, b = 1, and c = 2

[0016] The invention also relates to a recycled electronically conductive additive, obtained by the process of the invention, comprising, or even consisting of, at least one electronically conductive material and optionally at least one binder.

[0017] The process according to the invention makes it possible to recover value from the end-of-life electrochemical element by producing high value-added materials such as solid sulfide electrolytes. The term "solid sulfide electrolyte" refers to solid electrolytes based on sulfur. DETAILED DESCRIPTION

[0018] Electrochemical element to be recycled

[0019] The process according to the invention makes it possible to recycle an electrochemical element comprising a negative electrode having a negative active layer comprising an alkali metal M in metal form and / or in the form of an alloy.

[0020] The term "electrochemical element" means a basic electrochemical cell comprising an assembly of positive and negative electrodes, electrolyte, optionally separators, a container, and terminals for storing the electrical energy supplied by a chemical reaction and releasing it in the form of current. The electrolyte may be solid or liquid.

[0021] The electrochemical element can be of primary or secondary type.

[0022] Preferably, the capacitance of the negative electrode of the electrochemical element is strictly greater than the capacitance of the positive electrode of the electrochemical element, preferably greater than 20% of the capacitance of the positive electrode. Put another way, the electrochemical element has a ratio between the capacitance of the negative electrode and the capacitance of the positive electrode strictly greater than 1.0, preferably between 1.0 and 3.0, preferably between 1.2 and 3.0.

[0023] This indicates that for any state of charge of the electrochemical element (fully charged to totally discharged), it still necessarily contains metal M. The process of the invention is therefore particularly advantageous for this type of electrochemical elements, since it allows the recycling of the excess metal M which even a complete discharge of the electrochemical element does not allow to be recovered.

[0024] The term "positive electrode" refers to the electrode operating as a cathode when the electrochemical element is discharging, and the electrode operating as an anode when the electrochemical element is charging.

[0025] The positive electrode includes a current collector, at least one face of which is coated with a layer of a composition of positive active materials (also called the "positive active layer"). By "composition of active materials" is meant a composition comprising one or more active materials and preferably one or more binders, and / or one or more electronically conductive materials.

[0026] The current collector of the positive electrode is generally an aluminum strip or an alloy consisting mainly of aluminum. The positive electrode strip typically has a thickness of 6 µm to 30 µm.

[0027] The positive active material can be any positive active material known in the technology of lithium, sodium or potassium electrochemical elements, preferably selected from the lithia, sodium or potassium oxides of at least one transition metal, the lithia, sodium or potassium phosphates of at least one transition metal, and a mixture including elemental sulfur.

[0028] The term "negative electrode" refers to the electrode operating as an anode when the electrochemical element is discharging, and the electrode operating as a cathode when the electrochemical element is charging.

[0029] The negative electrode includes a current collector, at least one of whose faces is coated by a layer of a composition of negative active materials (also called "negative active layer").

[0030] The current collector of the negative electrode is generally a copper strip or an alloy comprising mainly copper. The strip of The negative electrode typically has a thickness of 4 pm to 18 pm, preferably 4 pm to 10 pm.

[0031] The negative active layer of the negative electrode of the electrochemical element comprises an alkali metal M in metallic form and / or in the form of an alloy. When the negative active layer comprises the metal M in the form of an alloy, it may further comprise one or more electronically conductive materials, and / or one or more binders. If the alkali metal M is in metallic form, the active layer comprises, or even consists of, a strip of the metal M.

[0032] The metal alloys M are preferably M-Ag, M-Si, M-Al, M-Sb or M-Sn alloys or a mixture of these elements.

[0033] Preferably, the negative active layer of the negative electrode of the electrochemical element is an alkali metal strip M.

[0034] Preferably, M = Li.

[0035] Thus, preferably, the positive active material can be any positive active material known in lithium electrochemical element technology. It can be, for example, MnO2, a CFx, a lithiated oxide of at least one transition metal, a lithiated phosphate-type active material of at least one transition metal or a fluorinated phosphate such as LVPF, or mixtures thereof, or a mixture comprising elemental sulfur, Li2S or FeS2.

[0036] The lithium oxide of at least one transition metal may be chosen from:

[0037] i) a lithium oxide of nickel, manganese and cobalt of formula Liw(NixMnyCozMt)O2(NMC) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ;

[0038] ii) a lithium oxide of nickel, cobalt and aluminium of formula Liw(NixCoyAlzMt)O2(NCA) where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Mn, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ; iii) a compound of formula Lii+xMi.xO2.yFy with cubic crystal structure where 0 <x<0,5 et 0<y<l et M représente un élément choisi dans le groupe constitué de Na, K, Mg, Ca, B, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Al, Y, Zr, Nb, Mo, Ru, Ag, Sn, Sb, Ta, W, Bi, La, Pr, Eu, Nd et Sm et des mélanges de ceux-ci ;

[0039] iv) a lithium nickel manganese oxide (NMX) of formula Lia(Nii.xyzMnxCoyMz)O2 with 0.9 <a<l,l ; 0,60<l-x-y-z<0,80 ; 0<x ; 0<y<0,02 ; 0<z ; et M étant choisi dans le groupe consistant en Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ga, Ta, Nd, Pr, La et des mélanges de ceux-ci ;

[0040] v) a lithium nickel and manganese oxide of formula Liw(NixMnyCozMt)O2 where 1.1 <w<1,6 ; 0<x ; 0,50<y<0,80 ; 0<z<0,02 ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Fe, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci.

[0041] vi) a lithium nickel manganese oxide of formula LixMn2_y_zM'yM"zO4_s where M' and M" are chosen from the group consisting of B, Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb and Mo; M' and M" being different from each other, and 1 <x<1,4 ; 0<y<0,6 ; 0<z<0,2 ; 0<ô<l,

[0042] and mixtures of different compounds of categories i) to vi).

[0043] The lithium phosphate of at least one transition metal may be chosen from: a) a lithium iron phosphate of formula LixFei yMyP04 (LFP), where 0.8 <x<l,2 ; 0<y<0,6 et M est choisi dans le groupe consistant en Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Mn, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ;

[0044] b) a lithium manganese phosphate of formula LixMni yMyP04 (LMP), where 0.8 <x<l,2 ; 0<y<0,6 et M est choisi dans le groupe consistant en Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Fe, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ;

[0045] c) a lithium manganese and iron phosphate of formula: LixMni y zFeyMzPO4 (LMFP) where 0.8 <x<l,2 ; 0,5<l-y-z<l; 0<y+z<0,5 ; 0<y<0,50 et 0<z<0,2 et M est choisi dans le groupe constitué de Al, B, Mg, K, Si, Ca, Ti, V, Cr, Co, Cu, Ni, Zn, Y, Zr, Nb, W, Pb, Mo, S et des mélanges de ceux-ci ;

[0046] d) an active substance of the fluorinated phosphate (LVPF) type corresponding to the formula Lii+X Vi yMyPO4Fz with 0 <x<0,15, 0<y<0,5, 0.8<z<l,2, et M est choisi parmi le groupe consistant en Ti, Al, Mg, Mn, Fe, Co, Y, Cr, Cu, Ni et Zr ;

[0047] e) and mixtures of different compounds of categories a) to d).

[0048] The positive active material may also include a mixture of elemental sulfur, at least one electronically conductive material, and at least one binder.

[0049] The term “conductive material” typically refers to an electronic conductor, such as a carbonaceous material, for example graphite, carbon black, acetylene black, soot, graphene, carbon nanotubes (CNTs), activated carbon, or a mixture thereof. In one embodiment, the conductive material is selected from carbon black and carbon nanotubes.

[0050] These electronically conductive materials can typically be used for the positive electrode and / or the negative electrode.

[0051] The term “binder” means a compound that strengthens the cohesion between the particles of active materials and improves the viscosity and / or adhesion of the negative active layer with the current collector.

[0052] The binder can be selected from butadiene-styrene copolymer (SBR), polyethylene oxide (PEO), polyamideimide (PAI), polyimide (PI), polyvinyl alcohol, functionalized or non-functionalized polyvinylidene fluoride (PVDF), vinylidene fluoride copolymers such as polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP), polytetrafluoroethylene (PTFE) and its copolymers, polyacrylonitrile (PAN), poly(methyl)- or (butyl)methacrylate, polyvinyl chloride (PVC), poly(vinyl formaldehyde), polyesters, sequenced polyetheramides, acrylic acid polymers, methacrylic acid, acrylamide, itaconic acid, sulfonic acid, elastomers such as poly(styrene / butadiene) (SBR) and hydrogenated butadiene-acetonitrile copolymers (HNBR), cellulosic compounds such as carboxymethylcellulose (CMC) and any of their mixtures.

[0053] Preferably, the binder can be chosen from carboxymethylcellulose (CMC), styrene-butadiene (SBR), lithium polyacrylic acid (LiPAA) and non-lithiumized polyacrylic acid (PAA, PAAH or PAAN).

[0054] These binders can typically be used for the positive electrode and / or the negative electrode.

[0055] The active material can also be SOC12 or SO2, which is then dissolved in the electrolyte; the positive electrode comprises only at least one conductive material (porous carbon type) and at least one binder.

[0056] If M = Na, the positive active substance can be, for example:

[0057] - a lamellar oxide of formula NaMO2 where M designates at least one metal of transition, for example Naw(NixFeyMnzMt)O2where 0.9 <w<l,l ; 0<x ; 0<y ; 0<z ; 0<t ; M étant choisi dans le groupe constitué de Al, B, Mg, Si, Ca, Ti, V, Cr, Cu, Zn, Y, Zr, Nb, W, Mo, S, Sr, Ce, Ta, Ga, Nd, Pr, La et des mélanges de ceux-ci ;

[0058] - a polyanion, for example phosphates, such as Na3V2(PO4)3 and Na3V2(PO4)2F3;

[0059] - a compound of Prussian blue or its analogues whose formula is AxP[R(CN)6]y .zH2O, where A is an alkali cation, and P and R are divalent or trivalent transition metal cations, 0 <x<2 ; y<l ; 0<z, par exemple Na2Mn[Fe(CN)6].

[0060] If M = K, the positive active substance can be, for example:

[0061] - The Prussian blues mentioned above with A=K;

[0062] - KVPO4F, K3V2(PO4)2F3;

[0063] - KCoO2;

[0064] - KMnO2.

[0065] Preferably, the electrochemical element is a Li-S electrochemical element.

[0066] An electrochemical element Li-S is traditionally composed of:

[0067] - a negative electrode as defined above, in which M = Li, of preferably having an active layer of Li, and optionally a current collector,

[0068] - a positive electrode having an active material comprising elemental sulfur, at at least one electronically conductive material (as defined above), and at least one binder (as defined above), and

[0069] - an electrolyte (solid or liquid).

[0070] The electrolyte may be an inorganic solid, for example of the sulfide type. Examples of sulfide electrolytes may be selected from sulfides of composition of the general formula LiaPbScXzOt where l <a<7 ; 0,50<b<2; 2<c<6 ; 0<z<2 ; 0<t<4, de type argyrodite (structure cubique, groupe d’espace F43m) ou de de type LGPS (structure de symétrie tétragonale, groupe d’espace P42 / nmc) ou être des matériaux amorphe ou vitrocéramique dont la composition élémentaire correspond aussi à la même formule générale.

[0071] The electrolyte may also be liquid, and comprise a lithium salt dissolved in an organic solvent. This lithium salt can be chosen from lithium perchlorate LiC104, lithium hexafluorophosphate LiPF6, lithium tetrafluoroborate LiBF4, lithium trifluoromethanesulfonate LiCF3SO3, lithium bis(fluorosulfonyl)imide Li(FSO2)2N (LiFSI), lithium trifluoromethanesulfonimide LiN(CF3SO2)2 (LiTFSI), lithium trifluoromethanesulfonemethide LiC(CF3SO2)3 (LiTFSM), lithium bisperfluoroethylsulfonimide LiN(C2F5SO2)2 (LiBETI), lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI), lithium bis(oxalatoborate) (LiBOB), lithium difluoro(oxalato)borate (LIDFOB), lithium tris(pentafluoroethyl)trifluorophosphate LiPF3(CF2CF3)3 (LiFAP), lithium nitrate LiNO3 and mixtures thereof.

[0072] The solvent may be selected from saturated cyclic carbonates, unsaturated cyclic carbonates, non-cyclic carbonates, alkyl esters, ethers, nitrile-type solvents, tetrahydrothiophene dioxide (sulfolane), and ethylene sulfate (ESA). Saturated cyclic carbonates include ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylene carbonate (PC), butylene carbonate (BC), and mixtures thereof. Unsaturated cyclic carbonates include vinylene carbonate (VC). Non-cyclic carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate (DPC), and mixtures thereof. Alkyl esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, butyl propionate, methyl butyrate, ethyl butyrate, propyl butyrate, and mixtures thereof.Ethers include dimethyl ether (DME), diethyl ether (DEE) and mixtures thereof.

[0073] If the electrolyte is liquid, the electrochemical element further comprises a separator, which includes the liquid electrolyte. The separator is typically located between the positive and negative electrodes. The purpose of the separator is to prevent short circuits while remaining permeable to lithium ions. It may, in particular, be made of a non-woven fabric or a polymer film. The separator may consist of a layer of polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE), polyacrylonitrile (PAN), polyester such as polyethylene terephthalate (PET), poly(butylene) terephthalate (PBT), cellulose, polyimide, glass fibers, or a mixture of layers of different materials. The polymers mentioned can be coated with a ceramic layer and / or polyvinylidene difluoride (PVdF) or poly(vinylidene-hexafluoropropylene fluoride (PVdF-HFP) or acrylates.

[0074] Preferably, the negative active layer consists of lithium metal.

[0075] Preferably, the electrochemical element is an electrochemical element comprising an all-solid type electrolyte.

[0076] An all-solid electrochemical element is characterized in that it comprises electrochemical elements comprising a positive electrode / electrolyte / negative electrode stack.

[0077] The negative electrode is as defined above, according to any embodiment.

[0078] The positive electrode is as defined above, according to any embodiment.

[0079] The electrolyte is in particular a solid, inorganic, polymeric or hybrid electrolyte.

[0080] Among inorganic solid electrolytes, we can distinguish: electrolytes based on metal oxides such as LISICON, NASICON, perovskites and Garnet type electrolytes; electrolytes based on sulfides, such as materials that can be synthesized from at least one of the precursors Li2S and P2S5, or thio-phosphates of the type LiiOGeP2Si2 and its derivatives; electrolytes based on nitrides, such as lithium nitride or LiPON.

[0081] Among solid polymer electrolytes, we can distinguish those based on polyethylene oxide, polyacrylonitrile, polyvinyl chloride, polyvinylidene fluoride, polymethyl methacrylate; and those based on lithium salts (LiPF6, LiFSI, LiTFSI, ...) dissolved in polyethylene oxide.

[0082] Hybrid solid electrolytes include, for example, non-lithianed salts (such as oxides, MOFs, graphene) in polymers such as listed above for polymer solid electrolytes, or a mixture of these polymers with an inorganic solid electrolyte material such as those detailed above.

[0083] Advantageously, the electrochemical element is an all-solid Li-S electrochemical element, that is, an electrochemical Li-S element as defined above with a solid electrolyte, preferably a sulfide-type electrolyte as defined above.

[0084] The electrochemical element is therefore advantageously an electrochemical element comprising:

[0085] - a negative electrode comprising a current collector in the form of a copper foil and an active layer in the form of a Li foil, or being made of a Li foil,

[0086] - a positive electrode comprising a current collector in the form of a aluminum foil, and an active layer comprising elemental sulfur, at least one electronically conductive material (as defined above), and at least one binder (as defined above), preferably further comprising a solid electrolyte, and

[0087] - a solid sulfide electrolyte as defined above.

[0088] Process

[0089] The process according to the invention includes a step a) of contacting the alkali metal M with elemental sulfur to produce M2S, this step a) being carried out in the absence of solvent.

[0090] The absence of solvent improves the efficiency of the process because it allows direct contact of the sulfur with the metal M, enabling the formation of M2S.

[0091] Elemental sulfur can be in solid (crystalline or amorphous), liquid, or gaseous form. If the sulfur is in solid or liquid form, the alkali metal M is brought into contact with the elemental sulfur by mixing (or stirring) it. If the sulfur is gaseous, the alkali metal M is placed in a sulfur gas atmosphere.

[0092] Step a) of making contact is preferably carried out at a temperature ranging from 20°C to 500°C, preferably from 20°C to 300°C.

[0093] Preferably, step a) of contacting with elemental sulfur is carried out in the presence of an excess of elemental sulfur.

[0094] An excess typically represents a molar quantity 1.1 to 2 times greater than the quantity of lithium to be converted. The quantity of lithium to be converted is approximately equal to the difference in capacitance between the negative and positive electrodes.

[0095] This excess sulfur ensures that all the metal has reacted while being easily removed at the end of the reaction, for example by vaporization, during a step a4) of removing excess elemental sulfur. This sulfur is easily recyclable in a future step a) for the recycling of another electrochemical element.

[0096] Thus, when an excess of elemental sulfur is used during step a), the process advantageously includes a step a4) for separating the excess elemental sulfur. This step a4) is preferably carried out by evaporating said excess elemental sulfur followed by a condensation step at a temperature below the melting point of sulfur.

[0097] Preferably, the process further includes a step a1) of discharging the electrochemical element before the step a) of contacting it with elemental sulfur.

[0098] This step improves the safety of the process, particularly during the subsequent grinding step a2).

[0099] In the case where the electrochemical element includes as a container a flexible envelope (of the "pouch" type), the discharge step a1) can be followed by a step a2) of removing the flexible envelope from the electrochemical element.

[0100] Preferably, the process according to the invention further comprises a step a3) of grinding the electrochemical element. This step a3) can be carried out before step a) or at the same time as step a).

[0101] Preferably, the electrochemical element is ground to obtain a D90 particle size less than or equal to 1 mm, preferably less than or equal to 100 pm, preferably between 10 pm and 1 mm (for example determined by laser diffraction according to ISO 13320:2020 or measured by scanning electron microscopy).

[0102] When steps a3) and a) are carried out simultaneously, the electrochemical element (if necessary stripped of its flexible casing) is ground in the presence of elemental sulfur in solid, liquid or gaseous form.

[0103] The simultaneous steps a3) and a) are typically carried out at a temperature ranging from 20 to 500°C, preferably in the presence of an excess of elemental sulfur.

[0104] The grinding step a3) is particularly advantageous if the elemental sulfur is in solid form, whereas it is possible to implement the step a) of contacting elemental sulfur directly after the step a0), or a1) or a2), if the elemental sulfur is liquid or gaseous, therefore without the grinding step a3).

[0105] Preferably, the method according to the invention further comprises:

[0106] - a step b) of dissolving M2S comprising adding a solvent to the crude reaction obtained in step a), and the obtaining of a solid / liquid mixture, and

[0107] - a step c) of separating the solid / liquid mixture obtained in step b) and obtaining a solid, and a solution comprising the M2S and the solvent.

[0108] If the electrochemical element to be recycled includes a solid sulfide electrolyte, the solution further includes the sulfide compounds from the solid sulfide electrolyte.

[0109] The solvent in step b) is chosen to selectively dissolve M2S, and sulfide compounds from the solid sulfide electrolyte.

[0110] This step yields a solid / liquid mixture in which the liquid phase is a solution comprising M2S and sulfide compounds from the solid sulfide electrolyte, and in which the solid phase comprises all compounds insoluble in the solvent, typically electronic conductors and any binders from the positive electrode, and possibly from the negative electrode. This solid is therefore advantageously an electronically conductive solid.

[0111] This solid may further comprise metallic sulfides resulting from the reaction between elemental sulfur and the ground-up current collectors of the electrochemical element's electrodes, typically copper sulfides and potentially aluminum sulfides. This solid may further comprise metallic residues, typically aluminum and / or copper, resulting from the grinding of the electrochemical element's current collectors that did not react with elemental sulfur. When the electrochemical element to be recycled does not contain sulfur, the solid from step c) may also optionally comprise the active materials of the positive electrode, typically NMC compounds. When the electrochemical element comprises a solid electrolyte other than a sulfide electrolyte (for example, an oxide-type electrolyte), the solid from step c) may also optionally comprise compounds of the solid electrolyte.When the electrochemical element includes a liquid electrolyte, the solid obtained from step c) may also possibly include compounds from the electrochemical element separator.

[0112] The solvent used in step b) is preferably chosen from ethanol, methanol, propanol, butanol, acetonitrile, or tetrahydrofuran, all of these solvents being in anhydrous form.

[0113] Step c) of separation is typically a filtration step.

[0114] The composition of the solution and the solid obtained at the end of step c) is variable depending on the nature of the recycled electrochemical element.

[0115] If the electrochemical element to be recycled includes a solid sulfide electrolyte, the sulfide compounds of the solid sulfide electrolyte are predominantly present in the solution obtained in step c).

[0116] Alternatively, if the electrochemical element to be recycled includes a solid oxide electrolyte, the oxides of this electrolyte are predominantly present in the solid obtained in step c).

[0117] In a manner combinable with the above embodiments, if the electrochemical element to be recycled comprises a positive electrode whose active material comprises, or even consists of, a lithium, sodium or potassium oxide of at least one transition metal or a lithium sodium or potassium phosphate of at least one transition metal (preferably a lithium oxide of at least one transition metal), this active material is predominantly present in the solid obtained in step c).

[0118] In a manner combinable with the above embodiments, if the electrochemical element to be recycled comprises a liquid electrolyte, the process according to the invention further comprises a step a3') of washing the ground material obtained in step a3). According to this embodiment, step a3) is therefore preferably prior to step a).

[0119] Step a3') of washing comprises adding a solvent to the ground material obtained in step a3), and optionally stirring the resulting solid-liquid mixture, followed by liquid / solid separation, for example by filtration. This allows the liquid electrolyte to be removed from the ground material obtained in step a3). This step can be repeated several times, for example 2, 3, or 4 times. The solvent is preferably chosen from carbonates (DMC, DEC, etc.) or DMF.

[0120] Preferably, the solid and the solution obtained at the end of step c) are then treated according to separate processes.

[0121] Preferably, the method according to the invention further comprises:

[0122] - a step dl) of evaporation of the solvent from the solution obtained in step c). This This step allows the M2S compound to be recovered in solid form, alone or with the sulfide electrolyte in the case of an electrochemical element consisting of a solid sulfide electrolyte.

[0123] This process may further include a step d2) of heat treatment of the solid obtained in step d1) at a temperature between 200°C and 550°C. This step d2) advantageously makes it possible to obtain an M2S material suitable for use as an active material for a positive electrode.

[0124] Alternatively, the method according to the invention further comprises:

[0125] - either a step e1) of adding a reagent to the solution obtained in step c), and a step e2) of evaporation of the solvent from the solution obtained in step e1),

[0126] - either a step e2') of evaporation of the solvent from the solution obtained in step c) then a step e2') of adding a reagent to the solid obtained in step e2').

[0127] Step el) allows the reactants to be dissolved and the sulfide materials to be homogenized in the liquid phase, and the reaction between M2S and the reactant in the liquid phase to be caused.

[0128] Step el') allows the reaction between M2S and the reactant to be induced in the solid phase.

[0129] The reagent added in step el) or el') is typically chosen from P2S5, LiX (with X=C1, Br or I), possibly with Li2O or any other sulfide precursor of an electrochemical element constituting a sulfide electrolyte.

[0130] Step el) or step el') allows obtaining a sulfide material with ionic conduction properties.

[0131] During step e1), the liquid reaction mixture is stirred and may also be heated, preferably between 25°C and 80°C.

[0132] During step el'), reactants are added and stirred to obtain a solid reaction mixture.

[0133] This process preferably further includes a step e3) of heat treatment of the solid obtained in step e2) or e1) at a temperature between 150°C and 550°C, in order to obtain a sulfide material suitable for use as a solid sulfide electrolyte material.

[0134] As mentioned above, the solid obtained in step c) is advantageously an electronically conductive solid.

[0135] Thus, preferably, the solid obtained in step c) comprises at least one electronically conductive material (as defined above in the description of the negative and positive electrodes), at least one binder (as defined above in the description of the negative and positive electrodes), optionally metallic residues, and / or optionally at least one metallic sulfide other than M2S.

[0136] The metallic residues are typically aluminum and copper residues from the current collectors of the electrochemical element that did not react during step a). The metal sulfides other than M2S are typically metal sulfides resulting from the reaction during step a) between the metals in the current collectors of the electrochemical element and elemental sulfur. These may, in particular, be copper and aluminum sulfides, especially Al2S3, CuS, or Cu2S.

[0137] According to this embodiment, the method according to the invention preferably further comprises:

[0138] - a step f0) of possible washing and drying of the conductive solid obtained in the step c), and / or

[0139] - a step fl) of removing metallic residues, and / or

[0140] - a step f2) of removing the metal sulfide(s) other than M2S, and / or

[0141] - a step f3) of separation of the binder(s).

[0142] The step fl) of removing metallic residues is typically implemented in using gravimetric or eddy current separation methods.

[0143] Step f2) of removing the other metal sulfide(s) from M2S is typically implemented using gravimetric separation methods or by adding a solvent for the metal sulfides.

[0144] Step f3) of separating the binder(s) is typically carried out by using a solvent for the binders (for example N-methylpyrrolidone) and then filtering and evaporating the solvent from the filtrate to recover the binder(s).

[0145] The process according to the invention may also include a step f2') of filtration and drying. This preferably involves filtering the suspension obtained in step f2) when a metal sulfide solvent is used, and drying the resulting solid. If both steps fl) and f2) are present, fl) may be carried out before f2), or f2) may be carried out before fl), preferably fl) is carried out before f2).

[0146] The process may further include a heat treatment step f4) at a temperature ranging from 350°C to 700°C, to remove electronically conductive materials present in the solid recovered at the end of step f3), which makes it possible to recover a solid free of electronically conductive materials.

[0147] Advantageously, the process comprises, at the end of step c):

[0148] - the treatment of the solution obtained in step c) following steps e2'), then el') then e3) or e1) then e2) then e3), as described above, and

[0149] - the treatment of the solid obtained in step c) following steps f0), then fl), then possibly f2) (if Cu sulfide is present) and possibly f2' (if step f2 presents and uses a solvent for metallic sulfides), then f3), and possibly f4), as described above. DESCRIPTION OF THE FIGURES

[0150] The invention will become clearer upon reading the following description, given solely by way of non-limiting example, and made with reference to the drawings in which:

[0151] [Fig. 1] [Fig. 1] is a schematic representation of a recycling process of an all-solid Li-S electrochemical element with sulfide electrolyte according to a first specific embodiment of the invention;

[0152] [Fig.2] [Fig.2] is a schematic representation of a recycling process of an all-solid Li-NMC electrochemical element with sulfide electrolyte according to a second specific embodiment of the invention;

[0153] [Fig.3] [Fig.3] is a schematic representation of a recycling process of an all-solid Li-S electrochemical element with oxide electrolyte according to a third specific embodiment of the invention;

[0154] [Fig.4] [Fig.4] is a schematic representation of a process for recycling an electrochemical element Li-S with liquid electrolyte according to a fourth specific embodiment of the invention.

[0155] A first process 10 according to the invention is schematically illustrated in [Fig.1], and represents a process for recycling an all-solid electrochemical element Li-S.

[0156] The process 10 first comprises a step aO) of recovering an all-solid electrochemical element Li-S. Typically, an all-solid electrochemical element Li-S comprises:

[0157] - a negative electrode comprising an active layer of lithium metal and a copper current collector,

[0158] - a positive electrode comprising an aluminum current collector and a active positive layer comprising elemental sulfur, at least one electronic conductor such as a mixture of carbon and carbon nanotubes, and at least one polymeric binder such as PVDF, and

[0159] - an inorganic solid electrolyte of the sulfide type. Examples of electrolytes sulfides can be selected from among the sulfides of composition of the general formula LiaPbScXzOt where l <a<7 ; 0,50<b<2; 2<c<6 ; 0<z<2 ; 0<t<4, de type argyrodite (structure cubique, groupe d’espace F43m) ou de de type LGPS (structure de symétrie tétragonale, groupe d’espace P42 / nmc) ou être des matériaux amorphe ou vitrocéramique dont la composition élémentaire correspond aussi à la même formule générale.

[0160] The process 10 then includes a step a1) of discharging the electrochemical element. This step is implemented by connecting the electrochemical element to an external circuit and applying a discharge current until the voltage is less than IV.

[0161] In the case where the electrochemical element includes a flexible pouch-type envelope, the discharge step a1) can be followed by a step a2) of removing the envelope of the electrochemical element to isolate the beam.

[0162] The process 10 then includes a step a3) of grinding the electrochemical element (or the bundle without its casing). The grinding can be carried out by any means known to those skilled in the art, for example with a rotary shear, to a particle size of 5 mm or less, preferably less than 2 mm.

[0163] The ground materials obtained at the end of step a3) are then brought into contact with elemental sulfur in a step a). This step aims to transform the lithium metal into Li2S.

[0164] The contacting step is typically a heat treatment step of the ground material in the presence of elemental sulfur. The ground material is, for example, heated between 150 and 500 °C.

[0165] Step a) of establishing contact is implemented for a period ranging, for example, from 1 hour to 3 hours.

[0166] Elemental sulfur can be in solid (crystalline or amorphous), liquid, or gaseous form. If the sulfur is in solid or liquid form, contact can be achieved, for example, by mixing the ground material with the sulfur in a mixer.

[0167] If the sulfur is gaseous, the ground materials are placed in a sulfur gaseous atmosphere.

[0168] Advantageously, an excess of sulfur is introduced (molar quantity 1.1 to 2 times greater than the quantity of lithium to be converted).

[0169] In [Fig.1], step a3) is carried out before step a) of contacting elemental sulfur, but according to a variant of the process, step a3) and step a) can be carried out simultaneously, i.e. the electrochemical element (or the bundle devoid of its envelope) is ground in the presence of elemental sulfur in solid, liquid or gaseous form.

[0170] When an excess of elemental sulfur is used, step a) is followed by a step a4) for separating the excess sulfur remaining at the end of the reaction, for example by evaporating the sulfur. This removed sulfur can be reused in a future step a) for recycling a new electrochemical element.

[0171] The next step is a step b) of adding a solvent to the crude reaction obtained at the end of step a4). This solvent is chosen to selectively dissolve the sulfide compounds, i.e. the Li2S formed during step a), and the compounds of the solid sulfide electrolyte of the electrochemical element.

[0172] This step yields a solid / liquid mixture in which the liquid phase is a solution comprising the sulfide compounds (the Li2S formed during step a) and the sulfide compounds from the solid electrolyte), and in which the solid phase comprises all the compounds insoluble in the solvent. These are typically electronic conductors, binders from the positive electrode, and metallic sulfides resulting from the reaction between the ground current collectors and elemental sulfur.

[0173] The solvent used in step b) is typically ethanol, methanol, propanol, butanol, acetonitrile, or tetrahydrofuran, all of these solvents being in anhydrous form.

[0174] The liquid and solid phases of the solid / liquid mixture obtained in step b) are then separated in a step c), typically by filtration.

[0175] The sulfide compounds included in the solution obtained after filtration c) can be directly recovered during a step dl) of solvent evaporation.

[0176] A heat treatment step d2) at 450°C allows the material to be homogenized and a solid sulfide electrolyte to be obtained with a sufficiently high crystallinity to obtain sufficient ionic conductivity combined with a positive electrode active material (Li2S) of the all-solid lithium-sulfur electrochemical element.

[0177] This sequence of steps is represented by the arrows with the stripes.

[0178] Alternatively (dotted arrows), one or more reagents may be added to the solution from step c) to produce a sulfide material suitable for use as a solid sulfide electrolyte material (step e 1)). In particular, this involves transforming the Li2S mixture with the recovered sulfide electrolyte, the resulting composition of which does not exhibit high ionic conductivity, into a solid sulfide electrolyte with high ionic conductivity, by reacting it with reagents such as P2S5, LiX (with X=C1, Br or I), for example, in stoichiometric amounts that yield electrolyte compositions with high ionic conductivity. The operating conditions for these reactions are known to those skilled in the art and are typically, for example, in the case of an electrolyte with the formula Li6PS5Cl:

[0179] a Li2S + Li6PS5Cl + a / 5 P2S5 + 2.a / 5 LiCl => (l+2a / 5) Li6PS5Cl

[0180] Step e1) is followed by a step e2) of solvent evaporation.

[0181] A heat treatment step e3) at 450°C allows for the homogenization of the components of the mixture and to form a suitable crystalline phase to obtain a material usable as a solid sulfide electrolyte material, by solid-state reaction between all the compounds.

[0182] Alternatively, the evaporation and reagent addition steps can be reversed, and the process then comprises a step e2') of evaporating the solvent from the solution obtained in step c), followed by a step el') of adding a reagent as described above, in order to produce a sulfide material suitable for use as a solid sulfide electrolyte material. This alternative allows the reagents to react in the solid phase, which can be advantageous if some reagents are not soluble in the solvent of the solution obtained in c). Step el') is also followed by the heat treatment step e3) as described above.

[0183] Advantageously, the solvent recovered during step dl), e2) or e2') is recycled for reuse in a subsequent step b).

[0184] In parallel, the solid recovered after filtration c) is dried during a drying step fO).

[0185] In principle, the solid obtained at the end of step c) comprises, in addition to the electronic conductors and the binders of the positive electrode, metallic residues from the current collectors of the electrochemical element, and possibly metallic sulfides (other than Li2S or sulfides from the sulfide electrolyte obtained in step a)), such as Cu and / or Al sulfides, such as Al2S3, CuS, or Cu2S. A treatment f1) enabling the separation of these metallic residues is carried out, for example by sorting by gravity separation. If metallic sulfides are present, the The process then includes a step f2) for separating the metallic residues (Al and Cu), for example, by acid-base or organic dissolution, for example in a nitric acid IM solution, allowing for the selective solubilization of sulfides. When step f2) is present, a step f2') for filtering the suspension obtained in step f2) and washing (with water) the resulting solid is carried out. In [Fig. 1], step f1) is carried out before step f2) (which is the preferred option), but carrying out step f2) before step f1) is also possible.

[0186] Following this series of steps, a mixture of electronically conductive additives (carbon and carbon nanotubes) and binders is obtained. This mixture can be used as is in the formulation of a new active electrode layer, or optionally separated in a step f3) of binder separation by solubilization, for example, in an NMP-based solution to dissolve the binder, followed by a step of filtration and drying of the solid and the liquid portion obtained from the filtration. The solid obtained from drying the solid portion can be used as an electrode conductor, for example, for a Li-S cathode, and the solid obtained from drying the liquid portion can be reused as a Li-S cathode binder.

[0187] A second process 20 according to the invention is schematically illustrated in [Fig.2], and represents a process for recycling an all-solid electrochemical element such as lithium Li-oxide, for example NMC.

[0188] Compared to the all-solid electrochemical element Li-S of [Fig. 1], the electrochemical element Li-NMC differs in the nature of the positive electrode, which is here a lithium oxide of nickel, manganese, and cobalt (NMC), of formula (1a)Liw(NixMnyCozMt)O2 where 0.9 < w < 1.1; 0 <x<l,l ; 0<y< 1,1 0<z<l,l 0<t<l, 1 m étant au moins un élément choisi dans le groupe constitué de al, b, mg, si, ca, ti, v, cr, fe, cu, zn, y, zr, nb, w, mo, sr, ce, ta, ga, nd, pr et la, plus particulièrement 0,5 < x. l’électrode positive peut par exemple être du lini0.6mn0.2co0.2o2 (nmc 622), ou lini0.smn0.1co0.1o2 811).

[0189] The steps of process 20 are identical to the steps of process 10, except with regard to the nature of the solid recovered after the filtration step c). The solvents used for step b) are similar to those of process 10, i.e. they can be ethanol, methanol, propanol, butanol, acetonitrile, or tetrahydrofuran in anhydrous form.

[0190] In the case of an all-solid electrochemical element Li-NMC, this solid comprises the NMC in addition to the conductive materials, the binders of the positive electrode, metallic residues (Al and Cu), and any metallic sulfides of Al and Cu (and the solution from filtration c) comprises the Li2S formed during step a) and the sulfide compounds of the solid electrolyte). The treatment of the solution from filtration c) is so the same as in the process of [Fig.1], but the treatment of the solid phase is a little different.

[0191] In particular, the mixture resulting from steps f0), f1), f2), and f2') comprises the NMC in addition to the conductive materials and binders of the positive electrode. A binder separation step f3) can be implemented in the same way as in the process of [Fig. 1], followed by a heat treatment f4) under air at 700°C, which eliminates the electronic conductors. The NMC powder thus obtained can be reused as the positive active material of a new electrochemical element, after the addition of a lithium-based precursor to compensate for the lithium loss associated with the cycling of the recycled electrochemical element and to restore its nominal capacity.

[0192] A third process 30 according to the invention is schematically illustrated in [Fig. 3], and represents a process for recycling an all-solid Li-S electrochemical element with an oxide-type electrolyte. Compared to the all-solid Li-S electrochemical element of [Fig. 1], this electrochemical element differs in the nature of its solid electrolyte, which is an oxide electrolyte, for example, of the Garnet type.

[0193] The steps of process 30 are identical to the steps of process 10, except with regard to the nature of the solid and the solution recovered after the filtration step c).

[0194] In this third embodiment, the solution obtained at the end of filtration step c) comprises Li2S but no sulfide compounds from the solid electrolyte, because the compounds from the oxide electrolyte are found in the solid portion. The solvents used for step b) are similar to those of process 10, i.e., they can be ethanol, methanol, propanol, butanol, acetonitrile, or tetrahydrofuran in anhydrous form.

[0195] The treatment of the solution comprising the Li2S includes the same steps as in the case of the process of [Fig.1].

[0196] The treatment of the solid phase from step c) is very similar to that of process 20 in [Fig.2]. It allows the Garnet to be recovered from the electrolyte on one side, by removing the electronic conductors by heat treatment, and on the other side the binders.

[0197] A fourth process 40 according to the invention is schematically illustrated in [Fig. 4], and represents a process for recycling an electrochemical element Li-S with a liquid electrolyte. Compared to the all-solid electrochemical element Li-S of [Fig. 1], this electrochemical element differs in the nature of its electrolyte, which is liquid instead of solid, and which includes a separator, for example, made of polypropylene, comprising an electrolyte comprising, for example, LiTFSI (IM) and LiNO3 (0.1 M) in dioxolane (DOL) and dimethoxyethane (DME).

[0198] Compared to process 10 of [Fig. 1], process 40 differs in that it includes a washing step a3') between grinding steps a3) and a), which are therefore not concurrent.

[0199] Step a3') of washing comprises adding a solvent to the homogenates obtained in step a3) in order to separate the liquid electrolyte from the homogenates. The resulting liquid / solid mixture is triturated, and then the liquid phase is separated from the solid phase. This step can be repeated several times, for example, 2, 3, or 4 times. The solvent can, for example, be a carbonate (DMC, DEC, etc.) or DMF.

[0200] In this fourth embodiment, the solution obtained at the end of step c) of filtration comprises Li2S but no sulfide compounds from the solid electrolyte, and the solid phase obtained at the end of step c) comprises a mixture of electronically conductive materials, binders, the electrochemical element separator, metallic residues Al and Cu and optionally metallic sulfides Al and Cu.

[0201] The treatments of the solution and the solid from step c) include the same steps as in the case of the process in [Fig.1].

Claims

Demands

1. A process for recycling an electrochemical element comprising a negative electrode having a negative active layer comprising an alkali metal M in metallic form and / or in the form of an alloy, M being selected from Li, Na and K, the process comprising a step a) of contacting the alkali metal M with elemental sulfur to produce M2S, the step a) of contacting being carried out in the absence of solvent.

2. A method according to claim 1, wherein the capacitance of the negative electrode of the electrochemical element is strictly greater than the capacitance of the positive electrode of the electrochemical element, preferably greater than 20% of the capacitance of the positive electrode.

3. A method according to claim 1 or 2, wherein M = Li, preferably wherein the electrochemical element is a Li-S electrochemical element.

4. A method according to any one of the preceding claims, wherein the negative active layer consists of lithium metal.

5. A method according to any one of the preceding claims, wherein the electrochemical element is an electrochemical element comprising an all-solid type electrolyte.

6. A method according to any one of the preceding claims, further comprising a step a1 of discharging the electrochemical element before step a) of contacting it with elemental sulfur.

7. A method according to any one of the preceding claims, wherein step a) of contacting with elemental sulfur is carried out in the presence of an excess of elemental sulfur.

8. A method according to any one of the preceding claims, further comprising a step a3) of grinding the electrochemical element, carried out before or at the same time as step a) of contacting with elemental sulfur.

9. A process according to any one of the preceding claims, further comprising: - a step b) of dissolving M2S comprising adding a solvent to the crude reaction mixture obtained in step a), and obtaining a solid / liquid mixture, and - a step c) of separating the solid / liquid mixture obtained in step b) and obtaining a solid, and a solution comprising the M2S and the solvent.

10. A process according to claim 9, further comprising a step d1) of evaporating the solvent from the solution obtained in step c), and optionally a step d2) of heat treating the solid obtained in step d1) at a temperature between 200°C and 550°C.

11. A process according to claim 9, further comprising: - either a step e1) of adding a reagent to the solution obtained in step c), and a step e2) of evaporating the solvent from the solution obtained in step e1), - or a step e2') of evaporating the solvent from the solution obtained in step c) and then a step e1') of adding a reagent to the solid obtained in step e2').

12. A process according to any one of claims 9 to 11, wherein the solid obtained in step c) comprises at least one electronically conductive material, at least one binder, and optionally metallic residues and / or optionally at least one metal sulfide other than M2S, the process further comprising: - a step f0) of optional washing and drying of the conductive solid obtained in step c), and / or - a step f1) of removing metallic residues, and / or - a step f2) of removing the metal sulfide(s) other than M2S, and / or - a step f3) of separating the binder(s).

13. Recycled sulfide material, obtained by the process according to any one of claims 1 to 12, comprising M2S, M being selected from Li, Na and K.

14. Solid sulfide electrolyte obtained by reaction of the material according to claim 13 and one or more reagents suitable for reacting with M2S to form a solid sulfide electrolyte, such as P2S5, LiX (X = Cl, Br, I), in stoichiometric quantities, in order to form a solid sulfide electrolyte, such as Li6PS5Cl or Li3PS4.

15. Recycled electronic conductive additive, obtained at the end of step c), or f0), or fl), or f2) or f3) of the process according to any one of claims 9 to 12, comprising, or even consisting of, at least an electronically conductive material and possibly at least one binder.

Images