Binder material

Abstract

The invention relates to a binder material of an electrode of a battery or of an accumulator, which binder material is in the form of a polymer which is produced by the cross-linking polymerization of monomers, wherein: the monomers comprise - either carboxylate-group-carrying acrylamides or methacrylamides, the carboxylate group being bonded to the nitrogen atom of the acrylamide or methacrylamide via a carbon chain, - or the monomers comprise carboxylate-group-carrying acrylates or methacrylates, the carboxylate group being bonded to the oxygen atom of the acrylate or methacrylate via a carbon chain; and in both cases, the chain length of the carbon chain is at least 4 and at most 22, and the binder material is fluorine-free.

Description

[0001] Binder material

[0002] The invention relates to a binder material for electrodes, in particular for positive electrodes.

[0003] A binder material is a polymer material that is mixed with active material and conductive carbon as an additive on a current collector of a battery electrode or accumulator electrode. To produce the electrode, the binder is mixed with the active material, carbon particles, and a solvent, applied to the current collector, and dried. The currently conventionally used polymer binder is polyvinylidene fluoride (PVDF). N-methylpyrrolidone (NMP) is used as the solvent, since PVDF cannot be processed in aqueous media. Disadvantages include the use of fluorinated, environmentally harmful polymers and, in some cases, the use of toxic solvents.

[0004] WO 2024034442 A1 relates to a binder material for negative electrodes and comprises two different polymers. In embodiment 1 of WO 2024034442 A1, the positive electrode is produced using polyvinylidene fluoride (PVDF) and methylpyrrolidone (NMP) as solvents; thus, the positive electrode and thus the resulting battery are not fluorine-free.

[0005] The object underlying the invention is to provide an improved binder material.

[0006] To achieve this object, a binder material according to claim 1 is proposed.

[0007] In a preferred embodiment, the binder material is the binder material of a positive electrode. The binder material is present at the positive electrode of a battery or accumulator. In one embodiment, the binder material of the negative electrode is also present according to the present invention, so that the battery or accumulator has fluorine-free binder material at both electrodes.

[0008] The binder material is a polymer which is made from monomers, wherein the monomers comprise either acrylamides or methacrylamides carrying carboxylate groups, wherein the carboxylate group is bonded to the nitrogen atom of the acrylamide or methacrylamide via a carbon chain, or comprise acrylates or methacrylates carrying carboxylate groups, wherein the carboxylate group is bonded to the oxygen atom of the acrylate or methacrylate via a carbon chain, wherein in both cases the chain length of the carbon chain is at least 4 and at most 22.

[0009] The term carboxylate group also includes a protonated carboxylate group, which is called a carboxylic acid.

[0010] In the case of acrylamide, the monomer has the following

[0011] Structural formula, where X is at least 4 and at most 22:

[0012] In the case of a methacrylamide, the monomer has the following

[0013] Structural formula, where X is at least 4 and at most 22:

[0014]

[0015] In the case of an acrylate, the monomer has the following structural formula, where X is at least 4 and a maximum of 22:

[0016] In the case of a methacrylate, the monomer has the following

[0017] Structural formula, where X is at least 4 and at most 22:

[0018] In one embodiment, the polymer comprises only one of these four monomers.

[0019] In one embodiment, the polymer can contain several such

[0020] Contain monomers that differ in their chain length and / or chemical structure.

[0021] The polymerization of the monomers occurs by chain formation at the carbon double bond of acrylamide, methacrylamide,

[0022] Acrylate or methacrylate. Polymerization can occur by free radical polymerization. The carboxylate group of the monomer can be protonated as a carboxylic acid or deprotonated as a carboxylate.

[0023] The carboxylate group may contain l-valent or polyvalent cations. The cation may, in particular, be an alkali metal. A preferred alkali metal is lithium.

[0024] In the case of lithium as a cation, the acrylamide, methacrylamide, acrylate or methacrylate of the monomer carries a lithium carboxylate group.

[0025] The monomer can in particular be based on an 11-acrylamidoundecanoic acid (AAmUDA), where X is equal to 10.

[0026] The monomer can, for example, be based on a 6-acrylamidohexanoic acid, where X is 5.

[0027] Preferably, the chain length of the carbon chain is at least 4 and a maximum of 12 .

[0028] Chain length is the number of carbon atoms present between the nitrogen atom or oxygen atom and the carbon atom of the carboxylate group.

[0029] Without wishing to be bound by theory, it is assumed that the chain length between the acrylamide, methacrylamide, acrylate, or methacrylate and the carboxylate group improves the flexibility of the binder during electrode manufacture and use. Furthermore, surfactant-like surface-active properties and better compatibility between the materials (active material, conductive carbon additive, current collector, processing solvent) result.

[0030] In one embodiment, the binder material is a homopolymer, so that it only comprises the described monomer and no comonomer. In another embodiment, the polymer comprises such a monomer and at least one comonomer, which comonomer comprises a vinyl group, acrylic group, or methacrylic group. The polymerization of the monomers with the comonomers takes place by chain formation at the carbon double bond of the monomer and the carbon double bond of the vinyl group, acrylic group, or methacrylic group of the comonomer. The polymerization can take place by free radical polymerization. The comonomer can be polar or non-polar.

[0031] The comonomer is preferably an acrylamide, methacrylamide, acrylate or methacrylate.

[0032] In one embodiment, the comonomer comprises at least one nitrile group, i.e. one or more nitrile groups.

[0033] The comonomer is selected, for example, from: dimethylacrylamide (DMA), polyethylene glycol methyl ether acrylate (mPEGa), acrylic acid, N-alkylacrylamide (with 8-18 C atoms), lithium acrylate (LiAA), N-dodecylacrylamide (DDAM), methionine acrylamide, acrylonitrile, cyanoacrylate, cyanoacrylamide. The comonomer is an optional additional monomer that can be used to modify the properties of the polymer.

[0034] A further modification can be achieved by the ratio in which monomer and at least one comonomer are used to form the polymer. In the case of two comonomers, the polymer is present as a terpolymer, but other multicomponent mixtures with more than two comonomers can also be produced.

[0035] In one embodiment, a binder material in the form of a polymer is proposed which is produced from at least two different types of monomers, wherein a first type of monomer is in the form of acrylamides, methacrylamides, acrylates or methacrylates carrying carboxylate groups, wherein the carboxylate group is bonded via a carbon chain, wherein the chain length of the carbon chain is at least 4 and a maximum of 22, wherein a second type of monomer is a comonomer, which comonomer comprises a vinyl group, acrylic group or methacrylic group.

[0036] The vinyl group, acrylic group or methacrylic group of the comonomer provides a reactive double bond for polymerization to the polymer.

[0037] To produce an electrode, the binder in question is mixed with active material and with current-conducting material and applied to a current collector, preferably to the current collector of the positive electrode.

[0038] In one variant, the application is carried out by dry coating on the current collector. Dry coating involves working with polymers made from the monomers and optionally comonomers. These polymers, particularly in powder form, are dry-mixed with the active materials, applied dry, and melted under the influence of heat and pressed into a layer. Dry coating can be achieved by heating and the optional use of an adhesion promoter.

[0039] In one embodiment, the monomers are mixed with active material and with electrically conductive material, preferably in powder form. Comonomers, if present, can be in powder or liquid form. The powder is applied to the current collector by reactive coating, in which the powdery mixture is mixed with solvent before or during application to the current collector. Mixing in powder form achieves improved mixing. The powdery mixture subsequently mixed with solvent is referred to as slurry.

[0040] A reactive coating is understood to mean that the starting materials of the binder are present as monomers in the slurry, and the polymerization of the monomers to form a polymer binder occurs in the slurry and / or only during drying on the current collector. Through the polymerization of the monomers, the active material and the current-conducting material are encapsulated in the polymer matrix.

[0041] Particularly in reactive coatings, the binder material in question offers a beneficial effect: it counteracts the pH increase that occurs during processing of the active material. Adjusting the pH by adding an acid is therefore unnecessary, eliminating the need for a single work step and an additional additive.

[0042] In another embodiment, the already polymerized polymer, with the active material and conductive material enclosed therein, is applied to the current collector. This is achieved by mixing the binder components in a solvent, and polymerization takes place in the solvent without the current collector being present, or by subsequently mixing the previously formed polymer with the other components and a solvent. The binder polymer can then be applied to the current collector and dried.

[0043] One advantage of this process is that water can be used as a solvent. Other suitable solvents are organic solvents, such as short-chain alcohols. An advantage of this binder material is that it is fluorine-free.

[0044] A further advantage of the binder material in question is that it acts as an acid or proton scavenger (acid scavenger function), so that it can capture hydrofluoric acid, which can form as a result of an electrolyte degradation reaction during the operation of a rechargeable battery.

[0045] The advantage of this binder material is that it exhibits higher adhesion to the current collector than conventional PVDF. This higher adhesion counteracts delamination and powdering of the electrode, which is already evident during processing but especially during operation. The surface-active properties of this binder material result in improved compatibility with the active and / or conductive material in the form of carbon, Li-metal oxides, or Li-Fe phosphates.

[0046] A further advantage of the binder material in question is that it is ionically conductive.

[0047] Tests confirmed electrochemical stability up to 4.3 V (vs. Li / Li+).

[0048] The electrodes provided with the binder according to the invention can be used in lithium iron phosphate batteries (LFP batteries), lithium nickel manganese cobalt oxide batteries (NMC batteries), Li-ion accumulators, and Na batteries. The binder according to the invention is also particularly suitable for NMC batteries with a high nickel content, such as NMC 622.

[0049] The advantage of this binder material is its pH-dependent solubility. The polymer can be dissolved in a basic medium and precipitated in an acidic medium.

[0050] This is used in a preferred recycling process, which comprises removing the polymer from the current collectors of batteries or accumulators coated with the subject polymer in a neutral or weakly alkaline medium, thereby also releasing the active material and the conductive material from the polymer. This can be assisted by mechanical action or by using ultrasound.

[0051] The active material and the conductive material can be extracted from the medium, for example, by centrifugation or filtration. When the remaining medium is acidified, the binder precipitates and can be extracted.

[0052] The recovered active materials are in particular Li, Co, Ni and Mn. The recovered conductive material can be in the form of conductive carbon. The current collector consists of a metal, in particular

[0053] Aluminum.

[0054] The invention is illustrated by drawings:

[0055] Fig. 1: Shows the general structure of a monomer suitable for forming the subject binder.

[0056] Fig. 2: shows the monomer based on an acrylamide.

[0057] Fig. 3: shows the monomer based on a methacrylamide.

[0058] Fig. 4: shows the monomer based on an acrylate.

[0059] Fig. 5: shows the monomer based on a methacrylate.

[0060] Fig. 6: shows the general structure of a polymer formed from the monomers of Fig. 1.

[0061] Fig. 7: shows the general structure of a monomer carrying a lithium carboxylate.

[0062] Fig. 8: shows the general structure of a polymer bearing lithium carboxylate on the side chains.

[0063] Fig. 9: shows the general structure of a polymer formed from the monomers of Fig. 1 and a copolymer.

[0064] Fig. 10: illustrates two reaction schemes for the synthesis of an exemplary binder material as a homopolymer.

[0065] Fig. 11: shows exemplary structures of possible binder materials in the form of copolymers.

[0066] The general structure of a suitable monomer is shown in Fig. 1. Y represents either NH or 0. X represents a value between 4 and 22 inclusive. When Y represents NH, the carboxylate group is bonded to an acrylamide; when Y represents 0, the carboxylate group is bonded to an acrylate.

[0067] The dashed line on the inner C atom of the C double bond illustrates that either a hydrogen atom H or CH3 can be present at the fourth bonding site of the inner C atom of the C double bond.

[0068] In the case of CH3, the chemical name is preceded by the suffix "Meth". In the case of H, this suffix is ​​not present.

[0069] Due to these possible combinations, the structure carrying the carboxylate group can be acrylamide, methacrylamide, acrylate or methacrylate.

[0070] In Fig. 2 an acrylamide is illustrated which carries the carboxylate group.

[0071] In Fig. 3 a methacrylamide is illustrated which carries the carboxylate group.

[0072] In Fig. 4 an acrylate is illustrated which carries the carboxylate group.

[0073] In Fig. 5 a methacrylate is illustrated which carries the carboxylate group.

[0074] Preferably, Y is NH, so that the monomer preferably comprises an acrylamide or a methacrylamide carrying the carboxylate group.

[0075] Fig. 6 illustrates the general structure of a polymer made from one of the monomers in Figs. 1-5. Polymerization occurs by chain formation with dissolution of the C double bond. Depending on the starting monomer, an H atom or a CHs group remains at the respective bonding site on the chain, which is again shown here with a dashed line. Y stands for NH or O, depending on the starting monomer. Due to the possible combinations, the polymer can be polyacrylamide, polymethacrylamide, polyacrylate or polymethacrylate, with each of the side chains of the polymer having a carboxylate group on the carbon chain with a length of X, where X is at least 4 and a maximum of 22.

[0076] Fig. 7 illustrates that the carboxylate group of a monomer of Fig. 1-5 is a lithium carboxylate in one embodiment.

[0077] Fig. 8 illustrates that the carboxylate group of a polymer of Fig. 6 is a lithium carboxylate in one embodiment.

[0078] Fig. 9 illustrates the general structure of a polymer which is produced from one of the monomers of Fig. 1-5 and a comonomer. At the fourth bonding position of the C atom of the chain, at which the comonomer is present as a side chain, there can be an H atom or a CH3 group, as in the monomer, so that in the case of the CH3 group the designation of the comonomer is preceded by the suffix Meth. In order for the comonomer to be polymerizable by chain polymerization with the monomer, this also has a C double bond, which can be provided by a vinyl group, acrylic group or methacrylic group. The side group represented by the letter Z results from the selected comonomer or its structure adjoining the C double bond.

[0079] In contrast to the monomer, the comonomer preferably does not carry a carboxylate group.

[0080] For n and m it applies that these can be the same or different.

[0081] Contrary to what is shown, several different comonomers may be present in the chain.

[0082] Example 1 Synthesis of a polymer PI

[0083] The invention is explained using a specific example in Fig. 10. In this specific example, the monomer is based on 11-acrylamidoundecanoic acid (AAmUDA), where X is 10. Fig. 10 shows two reaction schemes for the synthesis of a binder polymer PI without copolymer. Fig. 10 includes the reaction scheme of a direct synthesis of AAmUDA and subsequent polymerization to Li +poly (AAmUD~) and in the lower part the reaction scheme of a two-step methyl ester synthesis of mAUD, mAAmUD and subsequent polymerization.

[0084] Fig. 11 includes exemplary chemical structures of the binder material polymers: Li + poly (AAmUD~-co-mPEGA) (P2), Li + poly (AAmUD~-co-DMA) (P3) , Li+poly (AAmUD~-co-DDAm ) (P4) , which are formed from the monomer and one comonomer each.

[0085] This section describes the direct reaction of AUDA with acryloyl chloride to form 11-acrylamidoundecanoic acid (AAmUDA) and the synthesis of methyl 11-acrylamidoundecanoate (mAAmUD) (Fig. 10). The direct synthesis provides 93% AAmUDA, and mAAmUD is synthesized in 65% yield over two steps at purities of more than 99% ( 1H-NMR). The reactions were optimized using known synthesis methods and scaled to 40 g per batch. Larger scales are also accessible due to straightforward workup procedures (without column chromatography) and affordable, readily available reagents.

[0086] The direct addition of the acryloyl group occurs in an aqueous solution. After acidification, the crude AAmUDA is simply removed by filtration, and the pure product is selectively dissolved with ethyl acetate. Furthermore, AAmUDA is neutralized with LiOH and can be polymerized with polar monomers in aqueous solutions to obtain the polymer binder Li+poly(AAmUD~) (PI).

[0087] In the methyl ester route shown in Fig. 10 below, AUDA is first reacted with methanol (MeOH) and thionyl chloride (SOCl2) under solvent-free conditions. Methyl 11-aminoundecanoate hydrochloride (mAUD) is obtained quantitatively. The excess SOCl2 and MeOH are removed under vacuum. Subsequent reaction with acryloyl chloride produces mAAmUD, which, in contrast to the unprotected monomer, is soluble in various organic solvents with polarities ranging from toluene to 1,4-dioxane. Thus, the use of the protecting group scheme opens up the possibility of copolymerization with nonpolar comonomers. The versatility of radical polymerization in water and organic solvents enables the development of specially designed and tailored materials.

[0088] 11-Aminoundecanoic acid (AUDA) can be produced from the renewable raw material castor oil and is an interesting bifunctional starting material useful beyond the synthesis of polyamide 11. The reaction of AUDA with acryloyl chloride yields stable, solid monomers that are readily polymerizable by free radical catalysis. These lithium hydroxide-neutralized polymers carry lithium carboxylate groups linked to a polymer backbone via an aliphatic spacer. The polymers exhibit a combination of functional groups that promise properties such as good adhesion, water solubility, electrochemical stability, and the ability to scavenge protons.These advantageous properties, coupled with the versatility of radical (co)polymerization, make the corresponding (co)polymers promising candidates for use as binder materials, especially for lithium-ion batteries.

[0089] Example 2 Copolymers based on PI

[0090] The three comonomers monomethyl ether poly(ethylene glycol) acrylate (mPEGA), N,N-dimethylacrylamide (DMA), and N-dodecylacrylamide (DDAm) are selected as examples in Fig. 11. The maximum influence on the properties of each comonomer is shown by a selected molar ratio of 1:1 of AAmUDA and one of the mentioned comonomers. The structures of the exemplary copolymer binder materials Li + poly (AAmUD~-co-mPEGA) (P2), Li + poly (AAmUD~-co-DMA) (P3) and Li + poly (AAmUD~-co-DDAm). ) (P4) are shown in Fig. 11 shown.

[0091] The introduction of mPEGA (P2) proves to be particularly interesting. The resulting changes in mechanical behavior from a brittle to a flexible material appear to simultaneously increase ionic conductivity. DMA (P3) proves to be a good comonomer for improving adhesion strength beyond the already excellent properties of PI.

[0092] All of the polymers P1-P4 prepared are water-soluble up to about 10 wt. %. However, due to the surfactant-like structure of AAmUDA, polymerization of AAmUDA in water produces polymers that lead to cloudy solutions. This can be attributed to the formation of polymeric micelles during polymerization. As expected, turbidity only occurs in polymers obtained by aqueous polymerization and not in polymers obtained by methyl ester polymerization in organic media. The surfactant-like nature of the materials in question can be advantageous for use as binder materials. Due to their amphoteric properties, the binder materials promise good distribution in the electrodes and good compatibility with all electrode materials and the aqueous processing medium.

[0093] The determined thermal stability of the polymers lies well within the processing window of the electrodes and the operating range of battery cells. Therefore, processability and safe application can be assumed.

[0094] In tests, the AAmUDA homopolymer PI showed an approximately six-fold increase in adhesive strength compared to a PVDF reference material. The addition of 50 mol% DMA (P3), an adhesion-promoting monomer, increases the adhesive strength of the electrodes by a factor of ten compared to the PVDF reference material. P2 and P4, as expected, show weaker adhesion, but still retain a three-fold and five-fold increase, respectively, compared to PVDF. Visual inspection of the electrodes after the peel tests shows predominantly cohesive failure of the manufactured materials, while PVDF detaches almost completely from the electrodes. These results demonstrate the effectiveness of the materials for use as electrode binders. Tests conducted with the subject polymers, in particular the AAmUDA homopolymer PI, confirmed that the subject polymers with surfactant-like side chains can be used as binder materials. The binder materials are also up to 4.3 V vs .Li / Li+, which opens up many additional applications, such as the established, less demanding LiFePCu cathodes or even sodium-ion batteries. Application in high-voltage LMNO spinel cathodes can also be considered. The tunability of the properties (adhesion, ionic conductivity, or mechanical stability) of PI through comonomer incorporation, demonstrated for the P2-P4 copolymers, opens the way to specially developed, tailor-made materials.

[0095] Example 3 Recycling of PI

[0096] The polymer PI without a copolymer is used as the main example in this subsection, but all other copolymers P2-P4 can be processed and recycled under the same conditions. The currently used processing solvent NMP has a high boiling point, is expensive, toxic and must be fully recovered to prevent release to the environment or harm to operators. This is where the advantage of water-soluble binder materials comes into play, as solvent recycling is not necessary. This leads to simpler and more cost-effective coating equipment, increased safety for workers in the production plant and lower energy consumption throughout the process. It is shown in this example that PI is processable and applicable as a water-soluble, fluorine-free alternative to PVDF.Water solubility is an advantage for processing, as is the recycling of electrodes from used accumulators or batteries. Electrodes processed with the binder material PI can be efficiently recycled by dissolving the polymer in neutral or weakly alkaline aqueous solutions. The active materials are released from the current collector and can then be easily removed by centrifugation or filtration. In this process, the current collector is directly recovered and the active mass is obtained without any bound fluoropolymers. The latter fact is a clear advantage for further hydrometallurgical treatment and recovery of the valuable metals Li, Co, Ni and Mn. Subsequently, the pH-dependent solubility of PI enables the recovery of the polymer. By acidifying the remaining aqueous recycling solution, the binder material is precipitated and recovered.PI and its copolymers are not only water-processable but also demonstrate significant improvements in binder material recycling. The results described demonstrate that a holistic approach to binder material design not only considers stability and performance, but also considers environmentally friendly processing and recycling of spent materials.

[0097] In addition to tailored binder material properties (mechanical flexibility, adhesion, ionic conductivity), the possibility of efficient recycling is a key feature of the polymers in question, which are based, for example, on AAmUDA. Not only can the polymers be processed under aqueous conditions, they also support the recycling process because the materials in question exhibit pH-dependent solubility. The binder can therefore be detached from the electrodes under neutral / alkaline conditions. The clean current collector is then directly recycled, and the valuable metals such as lithium, cobalt, nickel, and manganese can be recovered by filtration or centrifugation. Since no polymer, and especially no fluoropolymer, adheres to the metals, recycling these materials is made much easier.The binder material remaining in the solution can be recovered by acidifying the solution, which leads to immediate precipitation of the binder material.

Claims

Patent claims 1. Binder material of an electrode of a battery or an accumulator in the form of a polymer which is produced by polymerization of monomers, wherein the monomers comprise either acrylamides or methacrylamides carrying carboxylate groups, wherein the carboxylate group is bonded to the nitrogen atom of the acrylamide or methacrylamide via a carbon chain, or the monomers comprise acrylates or methacrylates carrying carboxylate groups, wherein the carboxylate group is bonded to the oxygen atom of the acrylate or methacrylate via a carbon chain, wherein in both cases the chain length of the carbon chain is at least 4 and at most 22 and the binder material is fluorine-free.

2. Binder material according to claim 1, characterized in that the monomer has the following structural formula, where X is at least 4 and at most 22 and Y is NH or 0:

3. Binder material according to claim 1, characterized in that the monomer has the following structural formula, where X is at least 4 and at most 22 and Y is NH or 0:

4. Binder material according to one of claims 1 to 3, characterized in that the carboxylate group is a lithium carboxylate.

5. Binder material according to one of claims 1 to 4, characterized in that the monomers comprise at least one type of comonomer, which comonomer comprises a vinyl group, acrylic group or methacrylic group.

6. Binder material according to one of claims 1 to 4, characterized in that the binder material is a homopolymer.

7. Binder material according to one of claims 1 to 6, characterized in that it is the binder material of the positive electrode. 8 . A method for producing an electrode for a battery or accumulator, characterized in that monomers or the already polymerized monomers, active material and conductive material are mixed and applied to a current collector, wherein before, during or after the mixing, a polymerization of the monomers to a polymer takes place, wherein the monomers comprise at least a first type of monomers in the form of carboxylate group-bearing acrylamides, methacrylamides, acrylates, or Methacrylates, wherein the carboxylate group is carbon chain, where the chain length of the Carbon chain is at least 4 and a maximum of 22 and the Binder material is fluorine-free.

9. Method according to claim 8, characterized in that the positive electrode of the battery or an accumulator is produced.

10. The method according to claim 8 or 9, characterized in that it comprises mixing the monomers, the active material and the conductive material with a solvent to form a slurry.

11. The method according to claim 10, characterized in that the crosslinking of the monomers to form a polymer takes place before the slurry is applied to the current collector.

12. The method according to claim 10, characterized in that the crosslinking of the monomers to form a polymer takes place during or after the slurry is applied to the current collector.

13. The method according to claim 8, characterized in that the already polymerized monomers, the active material and conductive material are applied to the current collector by powder coating after mixing in powder form.

14. The method according to any one of claims 8 to 13, characterized in that the monomers comprise at least a second type of monomers which are in the form of a comonomer, which comonomer comprises a vinyl group, acrylic group or methacrylic group.

15. The method according to any one of claims 8 to 13, characterized in that the monomers comprise only one type of monomer, so that the polymer is a homopolymer.

16. A process for recycling electrodes of batteries or accumulators, which electrodes comprise a current collector and a binder material according to any one of claims 1 to 7, characterized in that the polymer of the binder material is dissolved in a neutral or alkaline medium, whereby the current collectors are freed from the binder material and active material and conductive material are released from the polymer into the medium.

17. A process according to claim 16, characterized in that metals released into the medium, such as lithium, cobalt, nickel and manganese, are recovered by filtration or centrifugation.

18. A method according to claim 16 or 17, characterized in that the binder material dissolved in the medium is recovered by precipitation by acidifying the medium.

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