PROCESS FOR CRUSHING AN ELECTROCHEMICAL GENERATOR

Abstract

A process for crushing an electrochemical generator comprising a negative electrode containing lithium or sodium and a positive electrode, the method comprising a step, in which the electrochemical generator is crushed in an ionic liquid solution comprising an ionic liquid and a so-called oxidizing redox species that can be reduced on the negative electrode so as to discharge the electrochemical generator.

Claims

1.-10. (canceled)

11. A method for crushing an electrochemical generator comprising a negative electrode containing lithium or sodium and a positive electrode, the method comprising a step wherein the electrochemical generator is crushed in an ionic liquid solution containing an ionic liquid and a so-called oxidising redox species that can be reduced at the negative electrode so as to discharge the electrochemical generator.

12. The method according to claim 11, wherein the ionic liquid solution contains a second so-called reducing redox species capable of being oxidised at the positive electrode, the so-called oxidising redox species and the so-called reducing redox species forming a redox species couple.

13. The method according to claim 11, wherein the redox species couple is a metal couple, an organic molecule couple, a metallocene couple or a halogenated molecule couple.

14. The method according to claim 13, wherein the redox species couple is a metal couple selected from the group consisting of Mn.sup.2+/Mn.sup.3+, CO.sup.2+/CO.sup.3+, Cr.sup.2+/Cr.sup.3+, Cr.sup.3+/Cr.sup.6+, V.sup.2+/N.sup.3+, V.sup.4+/V.sup.5+, Sn.sup.2+/Sn.sup.4+, Ag.sup.+/Ag.sup.2+, Cu.sup.+/Cu.sup.2+, Ru.sup.4+/Ru.sup.8+ or Fe.sup.2+/Fe.sup.3+.

15. The method according to claim 13, wherein the redox species couple is Fc/Fc.sup.+.

16. The method according to claim 13, wherein the redox species couple is a halogenated molecule couple selected from the group consisting of Cl.sub.2/Cl.sup.− or Cl.sup.−/Cl.sup.3−.

17. The method according to claim 11, wherein the ionic liquid solution contains an additional ionic liquid.

18. The method according to claim 11, wherein the ionic liquid solution forms a deep eutectic solvent.

19. The method according to claim 11, wherein the electrochemical generator is crushed in an inert atmosphere.

20. The method according to claim 11, wherein it comprises, prior to the step of crushing the electrochemical generator, a dismantling step or a sorting step.

21. The method according to claim 11, wherein it comprises, subsequent to the step of crushing the electrochemical generator, a pyrometallurgical or hydrometallurgical step.

22. The method according to claim 11, wherein the electrochemical generator is a lithium-ion generator or a sodium-ion generator.

23. The method according to claim 11, wherein the method is carried out at a temperature ranging from 0° C. to 100° C.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0063] The present invention will be better understood after reading the following description of example embodiments, given for purposes of illustration only and not intended to limit the scope of the invention, with reference to the accompanying drawings, wherein:

[0064] FIG. 1 diagrammatically shows a sectional view of an electrochemical generator according to one specific embodiment of the invention,

[0065] FIG. 2 diagrammatically shows a sectional view of an electrochemical generator according to one specific embodiment of the method of the invention.

[0066] The different parts shown in the figures are not necessarily displayed according to a uniform scale in order to make the figures easier to read.

[0067] The different possibilities (alternatives and embodiments) must be understood as not being exclusive with regard to one another and can be combined with one another.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

[0068] Hereinafter, even if the description refers to a Li-ion accumulator, the invention is transposable to any electrochemical generator, for example to a battery comprising a plurality of accumulators (also referred to as battery packs), connected in series or in parallel, depending on the nominal operating voltage and/or the amount of energy to be supplied, or to a battery cell.

[0069] These different electrochemical devices can be of the metal-ion type, for example lithium-ion or sodium-ion, or of the Li-metal type, etc.

[0070] It can also be a primary system such as Li/MnO.sub.2, or a redox flow battery.

[0071] An electrochemical generator with a potential greater than 1.5 V is advantageously chosen.

[0072] Reference is firstly made to FIG. 1, which shows a lithium-ion (or Li-ion) accumulator 10. A single electrochemical cell is shown, however the generator can comprise a plurality of electrochemical cells, each cell comprising a first electrode 20, in this case the anode, and a second electrode 30, in this case the cathode, a separator 40 and an electrolyte 50. According to another embodiment, the first electrode 20 and the second electrode 30 could be inverted.

[0073] The anode (negative electrode) 20 is preferably carbon-based, for example, made of graphite that can be mixed with a PVDF-type binder and deposited on a copper foil. It can also be a lithium mixed oxide such as lithium titanate Li.sub.4Ti.sub.5O.sub.12 (LTO) for a Li-ion accumulator or a sodium mixed oxide such as sodium titanate for a Na-ion accumulator. It could also be a lithium alloy or a sodium alloy depending on the technology chosen.

[0074] The cathode (positive electrode) 30 is a lithium-ion insert material for a Li-ion accumulator. This can be a lamellar oxide of the LiMO.sub.2 type, a LiMPO.sub.4 phosphate with an olivine structure or a LiMn.sub.2O.sub.4 spinel compound. M represents a transition metal. For example, a positive electrode made of LiCoO.sub.2, LiMnO.sub.2, LiNiO.sub.2, Li.sub.3NiMnCoO.sub.6, or LiFePO.sub.4 is chosen.

[0075] The cathode (positive electrode) 30 is a sodium-ion insert material for a Na-ion accumulator. This can be a sodium oxide type material containing at least one transition metal element, a sodium phosphate or sulphate type material containing at least one transition metal element, a sodium fluoride type material, or a sulphide type material containing at least one transition metal element.

[0076] The insert material can be mixed with a polyvinylidene fluoride type binder and deposited on an aluminium foil.

[0077] The electrolyte 50 contains lithium salts (for example LiPF.sub.6, LiBF.sub.4, LiClO.sub.4) or sodium salts (for example N.sub.3Na), depending on the accumulator technology chosen, solubilised in a non-aqueous solvent mixture. The solvent mixture is, for example, a binary or ternary mixture. The solvents are, for example, chosen from cyclic carbonate-based solvents (ethylene carbonate, propylene carbonate, butylene carbonate), linear or branched carbonate-based solvents (dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dimethoxyethane) in various proportions.

[0078] Alternatively, it could also be a polymer electrolyte containing a polymer matrix, made of organic and/or inorganic material, a liquid mixture containing one or more metal salts, and optionally a mechanical reinforcing material. The polymer matrix can contain one or more polymer materials, for example chosen from polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP) or a poly(ionic liquid) of the type poly(N-vinylimidazolium)bis(trifluoromethanesulfonylamide)), N,N-diethyl-N-(2-methoxyethyl)-N-methylammonium bis(trifluoromethylsulfonyl)imide (DEMM-TFSI).

[0079] The cell can be wound about itself around a winding axis or have a stacked architecture.

[0080] A casing 60, for example a polymer pouch, or a metal packaging, for example made of steel, is used to seal the accumulator.

[0081] Each electrode 20, 30 is connected to a current collector 21, 31 passing through the casing 60 and forming, outside the casing 60, the terminals 22, 32 respectively (also referred to as output terminals or electrical terminals or poles). The collectors 21, 31 have two functions: to provide mechanical support for the active material as well as electrical conduction to the terminals of the cell. The terminals (also referred to as electrical terminals or poles) form the output terminals and are intended to be connected to a “power receiver”.

[0082] According to some configurations, one of the terminals 22, 32 (for example that connected to the negative electrode) can be connected to the ground of the electrochemical generator. The ground is then said to be the negative potential of the electrochemical generator and the positive terminal is the positive potential of the electrochemical generator. The positive potential is thus defined as the positive pole/terminal as well as all metal parts connected by electrical continuity from this pole.

[0083] An intermediate electronic device can optionally be disposed between the terminal that is connected to the ground and the ground.

[0084] The electrochemical generator is crushed in the presence of an ionic liquid solution 100 (also referred to as a solution of ionic liquid) containing an ionic liquid and a redox species capable of reacting with the lithium so as to neutralise it, in order to make the electrochemical generator safe.

[0085] This ionic liquid solution 100 simultaneously prevents contact between the waste (battery cells or accumulators)/water/air and ensures the discharging of the waste via the electrochemical redox species present in the ionic liquid. The whole process is thus made safe as regards the fire triangle.

[0086] Preferably, the electrochemical generator 10 is completely discharged. The free ions are immobilised in the cathode 30, where they form a thermodynamically stable lithium metal oxide that does not react violently with water or air. This takes place at a low environmental and economic cost. Moreover, the treatment does not hinder recycling (and in particular the electrolyte does not decompose). The discharge time will be estimated according to the type of battery cells and accumulators and the charge rate.

[0087] The electrochemical generator 10 is at least partially covered by the ionic liquid solution. Preferably, it is completely immersed in the ionic liquid solution 100 (FIG. 2).

[0088] The ionic liquid solution 100 contains at least one ionic liquid LI.sub.1, referred to as a solvent ionic liquid, and a redox-active species A.

[0089] An ionic liquid is understood to mean the association of at least one cation and one anion that generates a liquid with a melting temperature of less than or about 100° C. These are molten salts.

[0090] A solvent ionic liquid is understood to mean an ionic liquid that is thermally and electrochemically stable, minimising decomposition of the medium during the discharge phenomenon.

[0091] The ionic liquid solution can further contain one or more (for example two or three) additional ionic liquids, i.e. it contains a mixture of several ionic liquids.

[0092] An additional ionic liquid, given the reference LI.sub.2, is understood to mean an ionic liquid that enhances one or more properties with respect to the making safe and discharge step. In particular, this can concern one or more of the following properties: extinction, flame retardant, redox shuttle, salt stabiliser, viscosity, solubility, hydrophobicity, and conductivity.

[0093] Advantageously, the ionic liquid, and optionally the additional ionic liquids, are liquid at ambient temperature (20 to 25° C.).

[0094] For the solvent ionic liquid and for the one or more additional ionic liquids, the cation is preferably chosen from the family: imidazolium, pyrrolidinium, ammonium, piperidinium and phosphonium.

[0095] Advantageously, a cation with a wide cationic window, large enough to envisage a cathodic reaction that prevents or minimises decomposition of the ionic liquid, is preferably chosen.

[0096] Advantageously LI.sub.1 and LI.sub.2 will have the same cation to increase the solubility of LI.sub.2 in LI.sub.1. Among the many possible systems, a low-cost, low environmental impact (biodegradability), and non-toxic medium is preferred.

[0097] Advantageously, anions are used to simultaneously provide a wide electrochemical window, moderate viscosity, a low melting temperature (liquid at ambient temperature) and good solubility with the ionic liquid and the other species in the solution, and which does not lead to hydrolysis (decomposition) of the ionic liquid.

[0098] The TFSI anion is one example that meets the aforementioned criteria for numerous associations with, for example, LI.sub.1: [BMIM][TFSI], or the use of an ionic liquid of the type [P66614][TFSI], the ionic liquid 1-ethyl-2,3-trimethyleneimidazolium bis(trifluoromethane sulfonyl)imide ([ETMIm][TFSI]), the ionic liquid N,N-diethyl-N-methyl-N-2-methoxyethyl ammonium bis(trifluoromethylsulfonyl)amide [DEME][TFSA], the ionic liquid N-methyl-N-butylpyrrolidinium bis(trifluoromethylsufonyl)imide ([PYR14][TFSI]), or the ionic liquid N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI). The anion can also be of the type bis(fluorosulfonyl)imide (FSA or FSI), such as the ionic liquid N-methyl-N-propylpyrrolidinium FSI (P13-FSI), N-methyl-N-propylpiperidinium FSI (PP13-FSI), or 1-ethyl-3-methylimidazolium FSI (EMI-FSI), etc.

[0099] The anion of the solvent ionic liquid LI.sub.1 and/or of the additional liquid LI.sub.2 can be a complexing anion to form a complex with the electrochemical shuttle.

[0100] Other associations are possible, with ionic liquids in which the cation is associated with an anion which can be organic or inorganic, preferably with a wide anodic window.

[0101] The ionic liquid solution 100 advantageously forms a deep eutectic solvent (or DES). This is a liquid mixture at ambient temperature obtained by forming a eutectic mixture of 2 salts, of the general formula:

[Cat].sup.+.Math.[X].sup.−Z[Y]

[0102] where:

[0103] [Cat].sup.+ is the cation of the solvent ionic liquid (for example ammonium),

[0104] [X].sup.− is the halide anion (for example Cl.sup.−),

[0105] [Y] is a Lewis or Brönsted acid which can be complexed with the X.sup.− anion of the solvent ionic liquid, and

[0106] z is the number of molecules Y.

[0107] The eutectics can be divided into three categories according to the nature of Y.

[0108] The first category corresponds to a type I eutectic:

Y=MCl.sub.x where, for example, M=Fe, Zn, Sn, Fe, Al, Ga

The first category corresponds to a type II eutectic:

Y=MClx.yH.sub.2O where, for example, M=Cr, Co, Cu, Ni, Fe

The first category corresponds to a type III eutectic:

Y═RZ where, for example, Z═CONH.sub.2, COOH, OH.

[0109] For example, the DES is choline chloride in association with a very low toxicity H-bond donor, such as glycerol or urea, which guarantees a non-toxic and very low-cost DES.

[0110] According to another example embodiment, choline chloride can be replaced by betaine. Although these systems have a limited electrochemical stability window, they can guarantee the flooding and deactivation of an optionally open accumulator.

[0111] Advantageously, a compound “Y” that can act as an electrochemical shuttle, which can be oxidised and/or reduced, is chosen. For example, Y is a metal salt, which can be dissolved in the ionic liquid solution to form metal ions. For example, Y contains iron.

[0112] By way of illustration, a eutectic can be formed between a chloride anion ionic liquid and metal salts FeCl.sub.2 and FeCl.sub.3 at different proportions and with different cations.

[0113] This type of reaction can also be carried out with type II eutectics, which incorporate water molecules into the metal salts; when the water content is low, this does not create a hazard. Low is typically understood to mean less than 10 wt % of the solution, for example 5 to 10 wt % of the solution.

[0114] Type III eutectics can also be used, which combine the ionic liquid and hydrogen bond donor species (Y), with a mixture of the type [LI.sub.1]/[Y] where LI.sub.1 can be a quaternary ammonium and Y can be a complexing molecule (hydrogen bond donor) such as urea, ethylene glycol, or thiourea, etc.

[0115] A mixture can also be made which will advantageously modify the properties of the solution for discharging the medium. In particular, a solvent ionic liquid of the type [BMIM][NTF.sub.2] which is very stable and liquid at ambient temperature, but which solubilises the electrochemical shuttle (or redox mediator) to a small extent, such as an iron chloride, can be combined.

[0116] For example, an additional ionic liquid LI.sub.2 of the type [BMIM][Cl] can be combined, which will enhance the solubilisation of a metal salt in the form of a chloride by complexation with the anion of LI.sub.2. This simultaneously allows for good transport properties and good solubility of the redox mediator, thus enhancing the discharge phenomenon.

[0117] The solution 100 contains a redox species. This is an ion or a species in solution form that can be oxidised at the negative electrode according to A.fwdarw.A* where A* is the oxidised form of the species A (FIG. 2). The redox species allows the accumulator to be made safe by extracting the lithium from the negative electrode.

[0118] The proposed method makes the accumulator non-reactive to air.

[0119] An electrochemical couple or a combination thereof can also be used. Preferably, this is a redox couple acting as an electrochemical shuttle (or redox mediator) to reduce decomposition of the medium, by carrying out redox reactions.

[0120] A redox couple is understood to mean an oxidising agent and a reducing agent in solution form, capable of being reduced and oxidised, respectively, at the electrodes of the battery cells. The oxidation/reduction thereof can, advantageously, allow the redox species initially present in solution form to be regenerated. The use of an electrochemical shuttle allows the device to be operated in a closed loop and reduces decomposition of the medium.

[0121] The oxidising agent and the reducing agent can be introduced in equimolar or non-equimolar proportions.

[0122] One of the redox species can originate from the generator itself. This can in particular be cobalt, nickel and/or manganese.

[0123] The redox couple can be an electrochemical metal couple or a combination thereof: Mn.sup.2+/Mn.sup.3+, Co.sup.2+/Co.sup.3+, Cr.sup.2+/Cr.sup.3+, Cr.sup.3+/Cr.sup.6+, V.sup.2+/V.sup.3+, V.sup.4+/V.sup.5+, Sn.sup.2+/Sn.sup.4+, Ag.sup.+/Ag.sup.2+, Cu.sup.+/Cu.sup.2+, Ru.sup.4+/Ru.sup.8+ or Fe.sup.2+/Fe.sup.3+.

[0124] The redox species and the redox couple can also be chosen from organic molecules, and in particular from: 2,4,6-tri-t-butylphenoxyl, nitronyl nitroxide/2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO), tetracyanoethylene, tetramethylphenylenediamine, dihydrophenazine, aromatic molecules for example with a methoxy group, an N,N-dimethylamino group such as methoxybenzene anisole, dimethoxybenzene, or an N,N-dimethylaniline group such as N,N-dimethylaminobenzene. Other examples include 10-methyl-phenothiazine (MPT), 2,5-di-tert-butyl-1,4-dimethoxybenzene (DDB) and 2-(pentafluorophenyl)-tetrafluoro-1,3,2-benzodioxaborole (PFPTFBDB).

[0125] This can also be from the family of metallocenes (Fc/Fc+, Fe(bpy).sub.3(ClO.sub.4).sub.2 and Fe(phen).sub.3(ClO.sub.4).sub.2 and its derivatives) or from the family of halogenated molecules (Cl.sub.2/Cl.sup.−, Cl.sup.−/Cl.sup.3− Br.sub.2/Br.sup.−, I.sub.2/I.sup.−, I.sup.−/I.sub.3.sup.−).

[0126] In particular, a bromide or a chloride is chosen. Preferably this is a chloride that can easily complex metals. For example, iron, complexed by the chloride anion, forms FeCl.sub.4, which can decrease the reactivity of the negative electrode.

[0127] This can also be tetramethylphenylenediamine.

[0128] A plurality of redox couples can also be combined, wherein the metals of the metal ions are the same or different.

[0129] For example, Fe.sup.2+/Fe.sup.3+ and/or Cu.sup.+/Cu.sup.2+ are chosen. The latter are soluble in their two oxidation states, are non-toxic and do not decompose the ionic liquid.

[0130] The solution can contain an extinguishing agent and/or a flame retardant to prevent thermal runaway, in particular in the event of opening the accumulator. This can be an alkyl phosphate, optionally fluorinated (fluorinated alkyl phosphate), such as trimethyl phosphate, triethyl phosphate, or tris(2,2,2-trifluoroethyl) phosphate.) The concentration of active species can be from 80 wt % to 5 wt %, preferably from 30 wt % to 10 wt %.

[0131] Optionally, the ionic liquid solution can contain a desiccant, and/or an agent enhancing the transport of material, and/or a protective agent which is a stabiliser/reducer of corrosive and toxic species, for example chosen from PF.sub.5, HF and POF.sub.3.

[0132] The agent enhancing the transport of material is, for example, a fraction of a co-solvent that can be added to reduce viscosity.

[0133] It can be a small proportion of water, such as 5% water.

[0134] Preferably, an organic solvent is chosen for effective action without creating discharge or flammability risks. This can be vinylene carbonate (VC), gamma-butyrolactone (γ-BL), propylene carbonate (PC), poly(ethylene glycol), or dimethyl ether.

[0135] The concentration of the agent enhancing the transport of material is advantageously from 1 wt % to 40 wt % and more advantageously from 10 wt % to 40 wt %.

[0136] The protective agent capable of reducing and/or stabilising corrosive and/or toxic elements is, for example, a compound of the butylamine type, a carbodiimide (of the type N,N-dicyclohexylcarbodiimide), N,N-diethylamino trimethyl-silane, tris(2,2,2-trifluoroethyl) phosphite (TTFP), an amine-based compound such as 1-methyl-2-pyrrolidinone, a fluorinated carbamate or hexamethyl-phosphoramide. It can also be a compound of the cyclophosphazene family such as hexamethoxycyclotriphosphazene.

[0137] Advantageously, the ionic liquid solution contains less than 10 wt % of water, preferably less than 5 wt %.

[0138] Even more preferably, the ionic liquid solution is devoid of water.

[0139] The method can be carried out at temperatures ranging from 0° C. to 100° C., preferably from 20° C. to 60° C. and even more preferably it is carried out at ambient temperature (20-25° C.).

[0140] The method can be carried out in air, or in an inert atmosphere, for example argon, carbon dioxide, nitrogen or a mixture thereof. It can also be carried out in an atmosphere with a controlled oxygen content.

[0141] In the case where the electrochemical generator is immersed in the ionic solution, the solution can be stirred to improve the reagent intake. For example, this can involve stirring at between 50 and 2,000 rpm, and preferably between 200 and 800 rpm.

[0142] By way of illustration, the crushing step is carried out in a recycling process which can comprise the following steps: sorting, dismantling, crushing and then recycling the elements to be recovered (for example by pyrometallurgy, hydrometallurgy, etc.).

[0143] The generator is safely opened to access the recoverable fractions thereof.

Illustrative and Non-Limiting Example of an Embodiment

[0144] In this example, discharge takes place in a glyceline-type medium (a mixture of choline chloride and glycerol).

[0145] The ionic liquid solution is an ionic liquid mixture containing choline chloride and glycerol with a volume ratio of 1:2 and a Cp of 2.2 J.Math.g.sup.−1.Math.K.sup.−1, with 5 wt % of trimethyl phosphate as an extinguishing agent. After the solution has dried, the crushing area of a sealed knife mill is filled with the solution. An 18650 Li-ion type battery cell is then injected into the mill at ambient temperature. Rotation takes place at 50 rpm. The crushing method simultaneously opens the battery cell and allows the reaction between the lithium and the bath to take place, thus discharging and making the battery cell safe.