Method for recovering perfluorinated lithium compounds from lithium-ion batteries

Abstract

The invention relates to a method for recovering a perfluorinated lithium compound from an electrolyte of a lithium-ion battery. The method comprises the steps of: (a) thermally treating the electrolyte such that the perfluorinated lithium compound is decomposed to obtain a first compound as a gaseous reaction product and a second compound as a solid reaction product; (b) providing an electrolyte matrix which contains the second compound; and (c) leading the first compound obtained in step (a) to the electrolyte matrix, the first compound obtained in step (a) being reacted with the second compound contained in the electrolyte matrix provided in step (b), to form the perfluorinated lithium compound.

Description

Description Process for the recovery of perfluorinated lithium compounds from lithium-ion batteries

[0001] The invention relates to a process for recovering perfluorinated lithium compounds from lithium-ion batteries. It also relates to a process for producing a conductive salt-containing electrolyte matrix for a lithium-ion battery.

[0002] Lithium-ion batteries (LIBs) are secondary batteries, also known as accumulators. They consist of several interconnected cells, each of which essentially has a negative electrode (also known as the anode), a positive electrode (also known as the cathode), and an ion-conducting electrolyte. The electrolyte contains a conducting salt containing lithium ions. The conducting salt can be a perfluorinated lithium compound, such as lithium hexafluorophosphate (LiPFe) or lithium tetrafluoroborate (LiBF4). The conducting salt is dissolved in an electrolyte matrix, which is usually a mixture of organic carbonates and various additives, and enables the transport of current between the anode and cathode of a LIB cell. The conducting salt is therefore essential for the production of LIB cells.

[0003] The recovery of valuable materials from used lithium-ion batteries is of enormous economic interest. This is primarily due to the ongoing trend toward societal electrification, which is reflected, among other things, in the widespread expansion of global e-mobility. As a result, securing the LIB raw material base is of corresponding importance. This is reflected, among other things, in current legal requirements, which stipulate a recycling rate of 65% for the net recovery of valuable materials from an entire LIB cell by 2025 and 70% by 2030. Considering only lithium, which is essential for LIB production, a 35% recycling rate is required by 2026 and a 70% recycling rate by 2030. [1]

[0004] Already established recycling processes address this challenge by processing the solid electrode material into LIB black mass. This represents the non-magnetic fraction of the coating and electrode materials resulting from mechanical processing. During the generation of LIB black mass, which forms the starting material for LIB recycling processes, the electrolyte of a LIB cell is destroyed at the beginning of the process chain.

[0005] The prior art LIB recycling process (100) shown in Fig. 1 begins with the preparation of the used LIB cells (101) to obtain a LIB material. This preparation can involve comminution, optionally under inert gas or aqueous conditions, of the LIB cells. In the next step, thermal pretreatment of the optionally comminuted LIB material (104) is carried out. The electrolyte is removed by decomposing the conductive salt. The electrolyte does not participate in the further processing of the LIB cells. After the optional comminution (101) and thermal pretreatment of the LIB cells (104), the LIB black mass (105) is obtained. This contains all LIB components that were not removed by the thermal pretreatment. This therefore includes housing part residues that could not be separated during mechanical processing, electrode material, and collector foils.Therefore, the original conducting salt, i.e., the perfluorinated lithium compound, and (depending on the process parameters of the thermal pretreatment) the organic components of the electrolyte are excluded. The LIB black mass undergoes hydrometallurgical processing (107). For this purpose, one of the following processes can be used, for example: Accurec process [16-20], Duesenfeld process [21-23], Primobius process

[0024] , or COOL process

[0025] . These processes develop secondary lithium sources (108), which can be used together with primary lithium sources (109) for LIB production (110). For this purpose, the primary and secondary lithium sources (109, 108) can first be converted into lithium carbonate (111), which can then be used in LIB production (110). The use of lithium from secondary lithium sources (108) is associated with a reduction in greenhouse gas emissions (112).Those obtained with the addition of elements such as Mn, Fe, Co and Ni (113) in LIB production (110). Lithium-ion batteries are recycled (100) after their use (114), for example, for the electrification of vehicles, as storage for renewable energy, etc. (arrow A). The electrolyte is destroyed again.

[0006] However, the electrolyte contains valuable lithium compounds, which make up to 2% by weight of an entire LIB cell of a battery electric vehicle (EV), and which are pyrolyzed or hydrolyzed during removal. [2] In the process, the valuable lithium compounds mentioned above are lost in their original form. This product devaluation in the form of waste generation therefore does not realize any recovery of the electrolyte's lithium compounds. Overall, this results in a continuous deficit in the accounting of lithium recovery for all established LIB recycling processes. Achieving the previously formulated recycling targets is made more difficult, and complete lithium recovery is impossible.

[0007] The approaches described so far for the recovery of perfluorinated lithium compounds such as LiPFe do not provide for the actual recovery of these compounds. Recovery requires that, at the end of a process chain, the valuable material used is recovered in a usable form, ideally as a previously used valuable material. This lack of recovery of perfluorinated lithium compounds such as LiPFe is evident, for example, in the extraction with ionic liquids known from EP 2 410 603 A1 [3]. Apart from the fact that such extraction agents and thus the resulting process are generally correlated with high costs, this only results in the generation of lithium chloride LiCl, which has a low market value, and the binding of the perfluorinated PFe anion in the ionic liquid. Recovery of these ionic species as previously used lithium salt is not possible.

[0008] This misunderstanding of the concept of recovery of perfluorinated lithium compounds such as LiPFe is also evident in recent publications. For example, these claim 100% recovery through reaction with sodium salts, although the product is sodium hexafluorophosphate (NaPFe). and not LiPFe. [4] This compound has neither potential application in the LIB sector, nor does it represent a compound with a higher value than LiPFe. Nevertheless, successful LiPFe recovery is incorrectly postulated in the course of this work.

[0009] Furthermore, processes for handling LiPFe are known from the prior art. One such process is described, for example, in US 2015 / 0013499 A1 [5]. However, the intention of these processes is the removal of LiPFe rather than its recovery, as already shown in Fig. 1. Such processes for LiPFe removal have not yet achieved any technical significance, since simple hydrolysis / pyrolysis is the most cost-effective and therefore industrially applied method.

[0010] The object of the invention is to eliminate the disadvantages of the prior art. In particular, it is intended to provide a process that enables the recovery of perfluorinated lithium compounds from lithium-ion batteries. Furthermore, it is intended to provide a process for producing a conductive salt-containing electrolyte matrix for a lithium-ion battery.

[0011] This object is achieved by the features of claims 1 and 15. Advantageous embodiments of the inventions emerge from the features of the subclaims.

[0012] According to the invention, a process is provided for recovering a perfluorinated lithium compound from an electrolyte of a lithium-ion battery. The process comprises the steps (a) thermal treatment of the electrolyte to decompose the perfluorinated lithium compound to obtain a first compound as a gaseous reaction product and a second compound as a solid reaction product; (b) providing an electrolyte matrix containing the second compound; and (c) introducing the first compound obtained in step (a) into the electrolyte matrix by reacting the first compound obtained in step (a) with the second compound contained in the electrolyte matrix provided in step (b) to form the perfluorinated lithium compound.

[0013] The process according to the invention enables the recovery of a perfluorinated lithium compound from the electrolyte of a lithium-ion battery (LIB). The perfluorinated lithium compound can be, for example, lithium hexafluorophosphate (LiPFe) or lithium tetrafluoroborate (LiBF4). Preferably, the perfluorinated lithium compound is lithium hexafluorophosphate. The perfluorinated lithium compound is the conducting salt of the lithium-ion battery. The perfluorinated lithium compound can thus be a salt of a cation and an anion, where the cation is Li + and the anion is a perfluorinated anion.

[0014] Step (a) involves the thermal treatment of an electrolyte originating from one or more lithium-ion batteries. Preferably, a plurality of lithium-ion batteries are used to obtain the electrolyte. The term "electrolyte" refers to the material containing the conducting salt, including the conducting salt itself. In other words, the electrolyte used in step (a) comprises the conducting salt and the material containing the conducting salt. This material is the electrolyte matrix. The electrolyte used in step (a) can be obtained by disassembling and / or comminuting one or more lithium-ion batteries. The disassembly and / or comminution is known per se from the prior art (see Fig. 1, reference numeral 101) and can be carried out as described, for example, in [16, 21, 22]. The electrolyte is separated from the remaining components of the lithium-ion battery by opening the LIB cells.The electrolyte is produced as a liquid. To obtain the electrolyte, the lithium-ion batteries may first be completely discharged. The lithium-ion batteries can then be disassembled by removing components that are not part of the LIB cells, such as the casing, electronic circuits (such as the battery management system), as well as cables, busbars, and screws. removed. The remaining LIB cells can then be crushed. This can be done, for example, by shredding, producing shredded material. The shredded material preferably has a particle size of 10 to 50 pm. If necessary, the shredded material can be sieved. The liquid components can then be separated from the solid components. The liquid components are the electrolyte, while the solid components can be thermally untreated black mass.

[0015] The thermal treatment provided in step (a) is preferably carried out at a temperature of 40°C or more, more preferably at a temperature in a range from 40°C to 200°C, and particularly preferably at a temperature greater than 40°C and less than 200°C. This heating of the electrolyte can be regarded as the basis for the process according to the invention. During the thermal treatment, thermal decomposition of the conducting salt, i.e. the perfluorinated lithium compound, takes place. The thermal treatment can be carried out at ambient pressure, for example 101325 Pa. At ambient pressure, the first compound is a gas, the second compound a solid. It can be provided that step (a) is carried out in an inert gas. The inert gas can be, for example, nitrogen or argon, with nitrogen being preferred. The inert gas used must be anhydrous.

[0016] The first compound is obtained as a gaseous reaction product in step (a). The second compound, obtained as a solid reaction product in step (a), is preferably lithium fluoride (LiF). The term "first compound" refers to a chemical compound, and the term "second compound" refers to a chemical compound. The first compound is a different chemical compound than the second chemical compound.

[0017] The thermal decomposition of lithium hexafluorophosphate (LiPFe), which is known from the state of the art [6-10], is described in equation (1). LiPF6PF5f + LiFf (1) During the thermal decomposition of LiPFe, the first compound formed is phosphorus pentafluoride (PF5), which is released as a gas, and the second compound formed is lithium fluoride (LiF), which is released as a solid. PF5 is thus a gaseous reaction product of the thermal treatment, while LiF is a solid reaction product. During the thermal decomposition of lithium tetrafluoroborate (LiBF4), the first compound formed is boron trifluoride (BF3), which is released as a gas, and the second compound formed is lithium fluoride (LiF), which is released as a solid. BF3 is a gaseous reaction product of the thermal treatment, while LiF is a solid reaction product.

[0018] Step (b) involves providing an electrolyte matrix containing the second compound. The second compound may be the solid reaction product obtained in step (a) by the thermal treatment, for example LiF. However, it may be provided that, instead of or in addition to the solid reaction product obtained in step (a), another second compound, for example LiF, originating from a different source is used. The other second compound is chemically identical to the second compound obtained in step (a), but differs from it in that it originates from a different source. The term "other" in the term "other source" refers to the fact that the solid reaction product obtained in step (a) is a first source of the second compound. If the second compound originates wholly or partially from a different source, this means that it does not originate from the first source, i.e., not from step (a).The other source can be LIB black mass itself. This is characterized by a LiF content of 1 to 2 wt.%, based on the weight of the LIB black mass. This content is due to the currently established removal of the conductive salt by hydrolysis and / or thermolysis, depending on the process for LIB black mass generation. In step (b), the solid reaction product obtained in step (a) is preferably used.

[0019] It may be provided that instead of or in addition to the second compound obtained in step (a) as the second reaction product, a second chemical compound originating from a different source is used. However, it may be provided that in step (c) only the first chemical compound obtained in step (a) is used. Compound is used. Preferably, only the first compound obtained as a gaseous reaction product in step (a) is used in the entire process according to the invention.

[0020] The first compound is thus the first compound obtained in step (a) as a gaseous reaction product, while the second compound was either obtained as a solid reaction product in step (a) or originates from another source or is a mixture of the solid reaction product obtained in step (a) as a first part and a second part of the second compound originating from another source.

[0021] The electrolyte matrix is ​​the electrolyte material that, together with the conducting salt, is intended to form the electrolyte. The electrolyte matrix can be viewed as a solvent for the conducting salt, meaning that in step (c) a solution of the conducting salt can be obtained in the matrix. This solution is also referred to below as the electrolyte solution. Step (b) provides one of the starting materials, for example LiF, for forming the conducting salt in step (c). In step (c), the second starting material, for example PF5 or BF3, which is required for forming the conducting salt, is added to the electrolyte matrix. The electrolyte matrix is ​​usually a mixture of one or more organic carbonates and one or more additives. The organic carbonates are, for example, selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and mixtures thereof.The composition of the electrolyte matrix depends on the type of lithium-ion battery for which the electrolyte matrix is ​​to be used after formation of the conducting salt, i.e., the perfluorinated lithium compound. The electrolyte matrix is ​​preferably dried before its provision in step (b) by distilling its individual components and / or using one or more molecular sieves. It may be provided that the distillation of the individual components takes place under an inert gas atmosphere. Drying using molecular sieve(s) is preferably carried out using a 3 A or 4 A molecular sieve, preferably using a 4 A molecular sieve.

[0022] Preferably, the electrolyte matrix containing the second compound is provided in a reactor. This reactor is also referred to below as an absorption reactor because it is intended to enable the absorption of the gaseous reaction product obtained in step (a). Provision may be made for the second compound obtained in step (a) to be fed to the absorption reactor in which the electrolyte matrix is ​​located, thereby obtaining the electrolyte matrix containing the second compound.It can be provided that (i) the second compound is provided together with the electrolyte matrix in the absorption reactor, that (ii) the electrolyte matrix is ​​first provided in the absorption reactor and then the second compound is introduced into the absorption reactor, or that (iii) a first portion of the second compound is provided together with the electrolyte matrix in the absorption reactor and then a second portion of the second compound is introduced into the absorption reactor. The second portion of the second compound can be the second compound obtained in step (a).

[0023] In a preferred embodiment, the absorption reactor consists of a perfluoroalkoxy copolymer (PFA) and / or polytetrafluoroethylene (PTFE). The use of an absorption reactor made of, for example, glass or Monel is also possible. However, the use of glass correlates with lower recovery yields and time-dependent damage to the reactor material.

[0024] It can be provided that the first compound obtained in step (a) is fed into the absorption reactor in which the electrolyte matrix containing the second compound is located. For this purpose, it can be provided that the first compound is fed to the electrolyte matrix by means of an inert gas. The inert gas can be, for example, nitrogen or argon, with nitrogen being preferred. The inert gas used must be anhydrous. The first compound obtained in step (a) can thus be fed to the absorption reactor by means of an inert gas stream. The inert gas serves as a transport gas. The inert gas stream can dilute the first compound.

[0025] Preferably, in step (c), the second compound is present in excess of the first compound. Preferably, in step (c), the first compound is introduced into the electrolyte matrix in an amount corresponding to a molar ratio of 1:1 to 1:15, particularly preferably 1:1 to 1:10, to the molar ratio of the second compound contained in the electrolyte matrix provided in step (b). This molar ratio is established in step (c). In other words, the ratio of the molar ratio m of the first compound to the molar ratio of the second compound is preferably 1:1 to 1:10, with an excess of the second compound being preferred.

[0026] Preferably, the reaction in step (c) is carried out at a temperature in a range between 0 and 25°C, particularly preferably at a temperature greater than 5°C and less than 10°C. For this purpose, the absorption reactor can be cooled to this temperature. In other words, the first compound can be added to the electrolyte matrix containing the second compound while cooling. Cooling is preferred because the reaction of the first compound with the second compound occurs with the evolution of heat.

[0027] Equation (2) illustrates the preparation of the perfluorinated lithium compound LiPFe from PH and LiF. PH is the first compound obtained in step (a) as a gaseous reaction product, and LiF is the second compound, which is either obtained as a solid reaction product in step (a) or originates from another source, or is a mixture of the solid reaction product obtained in step (a) as the first part and a second part of the second compound originating from another source. PF5+ LiF LiPF6(2)

[0028] The process according to the invention uses exclusively the first compound obtained in step (a). This first compound is the decomposition product of the conducting salt of a lithium-ion battery. The first compound thus originates from a secondary raw material source, namely the electrolyte. used LIB cells. The process according to the invention thus envisages the use and utilization of secondary raw material sources, namely the electrolyte of used LIB cells. In contrast, the LiPFe synthesis methods already known from the prior art require the use of PF> as a pure substance [11-13].

[0029] Furthermore, the process according to the invention is characterized by the direct generation of the perfluorinated lithium compound, e.g., LiPFe, in one of its application forms. This means that the perfluorinated lithium compound is formed in an electrolyte matrix, yielding an electrolyte that can be used to produce lithium-ion batteries. The process according to the invention thus makes it possible to obtain an electrolyte matrix in which the perfluorinated lithium compound is dissolved. The process according to the invention avoids the otherwise usual, additional process step of externally dissolving the perfluorinated lithium compound, e.g., LiPFe, in the electrolyte matrix. This not only results in cost savings but also in improved process reliability. The latter is due to the stabilization of the perfluorinated lithium compound, e.g., LiPFe, by the electrolyte matrix compared to the pure substance.While the perfluorinated lithium compound, e.g., LiPFe, hydrolyzes explosively upon contact with air as a pure solid, an electrolyte solution in which the perfluorinated lithium compound is dissolved exhibits temporary hydrolytic stability [7, 8, 14]. The electrolyte solution in which the perfluorinated lithium compound is dissolved can, for example, be a LiPFe electrolyte solution. The process according to the invention therefore excludes the handling of an explosive hazardous substance, such as LiPFe as a solid. The risk of explosion remains for the resulting electrolyte solution in which the perfluorinated lithium compound is dissolved, such as LiPFe electrolyte solutions.

[0030] It may be provided that, following step (c), a purification of the electrolyte matrix containing the perfluorinated lithium compound is carried out. The purification may be carried out using an anion exchanger. For this purpose, it may be provided that the anion exchanger is treated with a salt having a perfluorinated anion that is identical to the anion of the perfluorinated lithium compound. compound. Such purification is expedient in order to achieve complete, or at least as complete as possible, removal of anionic impurities that may be present in the crude electrolyte obtained in step (c). The term “crude electrolyte” refers to the electrolyte matrix obtained in step (c), which contains the perfluorinated lithium compound. If water is present within the electrolyte matrix, even in trace amounts, the stepwise hydrolysis of the first compound, for example a PF5 hydrolysis, is observed according to equations (3) to (6) [8, 14]. With regard to the large-scale implementation of the process according to the invention, this represents a problem, since it is practically difficult to achieve complete freedom from water from the electrolyte matrix provided in step (b). PF5+ H2O 2 HF + POF3(3) POF3+ H2O HF + HPO2F2(4) HPO2F2 + H2O HF + H2PO3F (5) H2PO3F + H20HF + H3PO4 (6)

[0031] The formation of the byproducts described above results in a reduction in product purity. However, in order to reuse the perfluorinated lithium compound for the production of lithium-ion batteries, the highest possible product purity is required. This can be achieved by purifying the electrolyte matrix containing the perfluorinated lithium compound obtained in step (c).

[0032] The purification of the electrolyte matrix containing the perfluorinated lithium compound is preferably carried out using a weakly or strongly basic anion exchanger, with a strongly basic anion exchanger being particularly preferred. A strongly basic anion exchanger is an anion exchanger that preferably contains quaternary ammonium groups. The anion exchanger is preferably treated with an aqueous salt solution containing a perfluorinated anion. This perfluorinated anion is preferably the anion of the perfluorinated lithium compound, in the case of LiPFe, PFe'. If the process according to the invention is used to recover LiPFe, the anion exchanger is preferably treated with aqueous, Treated with a PFe'-containing salt solution. Treatment is preferably carried out with an aqueous solution of a potassium and sodium salt of the perfluorinated anion. If LiPFe is to be recovered, the treatment is preferably carried out using potassium hexafluorophosphate (KPFe), as this is a stable and inexpensive compound. The use of the much more expensive NaPFe, for example, would also be possible.

[0033] After loading the anion exchanger with the perfluorinated anion, for example, a PFe' loading, the prepared anion exchanger is preferably completely, or at least as completely, freed of water as possible. Vacuum drying may also be used to remove the residual moisture typically found in anion exchangers. The drying temperature is preferably below the hydrolysis temperature of the perfluorinated anion salt. For example, if the KPFe salt is used, the drying temperature should be below 90 °C, otherwise hydrolysis of the KPFe will occur. Hydrolysis of the salt would not only prevent the successful loading of the anion exchanger with the perfluorinated anion, for example, a PFe' loading of the anion exchanger. The HF released during hydrolysis would also pose a safety risk.Vacuum drying is therefore preferably carried out at a temperature in the range of 20 to 80 °C, particularly preferably at a temperature greater than 20 °C and less than 80 °C. Vacuum drying can be carried out at a pressure of 3 mbar or less. The water collected during vacuum drying can be used to prepare a new solution of a salt of the perfluorinated anion, for example, a KPFe solution.

[0034] By loading the anion exchanger with perfluorinated anions, such as PFe' ions, and exchanging these with the impurities contained in the raw electrolyte according to equations (3) to (6), the introduction of foreign ions into the electrolyte is prevented. As a result, maximum purity of the recovered electrolyte matrix containing the perfluorinated lithium compound is achieved. For example, a LiPFe electrolyte solution of maximum purity is obtained. This maximization of product purity is particularly advantageous for Recycling of the recovered electrolyte matrix containing the perfluorinated lithium compound in the production of lithium-ion batteries. If the product purity is based on the content of the main impurity, hydrofluoric acid (HF), this purification can increase it from approximately 50% to at least 98%. The residual fluoride content of the electrolyte matrix containing the perfluorinated lithium compound can be attributed to the solubility of the LiF used in the electrolyte matrix, which is why the product is free of HF after purification.

[0035] The process according to the invention is fully compatible with existing LIB recycling processes, such as the Duesenfeld or Accurec processes. As already described in connection with Fig. 1, one of the first process steps in the process of LIB black mass generation is the thermal treatment of the LIB cells. Accordingly, with regard to the design of the process according to the invention, this step of thermal LIB treatment was chosen as the basis. Therefore, the process according to the invention represents an advantageous addition to existing recycling processes, which is associated with hardly any additional costs compared to the overall process of recycling lithium-ion batteries.

[0036] By means of the process according to the invention, in particular through this extension of existing process chains, the Li recovery rate is improved. Furthermore, the range of recoverable Li-containing components of the lithium-ion battery is completed for the first time. Furthermore, the preservation of the perfluorinated anions of the perfluorinated lithium compounds results in cost savings in the LIB production sector, since the generally required amount of perfluorinated lithium compound, for example the amount of LiPFe, which previously resulted from the cost-intensive synthesis from primary raw materials

[0015] , is greatly reduced. This results from the achieved recovery yields of perfluorinated lithium compound by means of the process according to the invention of more than 93%. The purity is preferably at least 95%, more preferably at least 97%, and particularly preferably more than 98%.

[0037] Due to the increasing demand for LIB cells and therefore for perfluorinated lithium compounds as conductive salts, for example, LiPFe, the process according to the invention is of great economic importance. It is possible to also use the first compound obtained in step (a), for example, PFs, which results from the thermal treatment of the LIB material, as a fluorination reagent. However, since LiPFe represents the compound of greatest economic interest due to its high demand, any use of PF5 for fluorination correlates with a devaluation of the product.

[0038] According to the invention, a method for producing a conductive salt-containing electrolyte matrix for a lithium-ion battery, wherein the conductive salt is a perfluorinated lithium compound, is further provided. The method comprises the steps (a) thermally treating the electrolyte of a lithium-ion battery containing the conducting salt to decompose the conducting salt to obtain a first compound as a gaseous reaction product and a second compound as a solid reaction product; (b) providing an electrolyte matrix containing the second compound; and (c) feeding the first compound obtained in step (a) to the electrolyte matrix, reacting the first compound obtained in step (a) with the second compound contained in the electrolyte matrix provided in step (b), to obtain the electrolyte matrix containing conducting salt.

[0039] Details of the inventive method for producing a conductive salt-containing electrolyte matrix have already been explained in connection with the inventive method for recovering a perfluorinated lithium compound from an electrolyte of a lithium-ion battery. Reference is made to this explanation. The inventive method for producing a conductive salt-containing electrolyte matrix differs from the The inventive method for recovering a perfluorinated lithium compound from an electrolyte of a lithium-ion battery. The aim of the inventive method for producing a conductive salt-containing electrolyte matrix is ​​to produce a conductive salt-containing electrolyte matrix for a lithium-ion battery, while the aim of the inventive method for recovering a perfluorinated lithium compound from an electrolyte of a lithium-ion battery is to recover a perfluorinated lithium compound. Both objectives can be achieved in both inventive methods.

[0040] The invention will be explained in more detail below using exemplary embodiments, which are not intended to limit the invention, with reference to the drawings. Fig. 1 is a flow diagram illustrating the recycling of lithium-ion batteries according to the state of the art; and Fig. 2 is a flow diagram illustrating an embodiment of the process according to the invention. Abbreviations used DMC dimethyl carbonate EC ethylene carbonate sccm standard cubic centimeters per minute PF A perfluoroalkoxy copolymer PTFE Polytetrafluoroethylene Example 1

[0041] Fig. 2 illustrates an embodiment of the method according to the invention for recovering a perfluorinated lithium compound from an electrolyte of a lithium-ion battery. For this purpose, LIB cells are provided which have an electrolyte containing a perfluorinated lithium compound, in this case Embodiment contains LiPFe. In a step (a) preceding the process according to the invention, the LIB cells are disassembled and crushed (2).

[0042] Following the disassembly and comminution of the LIB cells, the thermal treatment according to step (a) is carried out (3), which results in decomposition of the conductive salt LiPFe (Box 91). In this embodiment, the thermal treatment is carried out at a temperature greater than 40 °C and less than 200 °C. PF5 is obtained as the first compound (4). Furthermore, LiF is obtained as the second compound (5). Steps (2) and (3), which are located in Box 91, are compatible with established LIB recycling processes.

[0043] The LiF obtained as the second compound is then used to prepare the electrolyte matrix (Box 92). The components (11) used to prepare the electrolyte matrix (12) are first dried (13), for example, using a 4 A molecular sieve or distillation. Components (11) include, for example, organic carbonates such as ethylene carbonate and dimethyl carbonate. Mixing the dried components produces the electrolyte matrix (12), which is also subjected to drying (14), for example, using a 4 A molecular sieve. The dried electrolyte matrix (15) thus obtained is then admixed with the LiF obtained in step (a) (arrow A), resulting in a LiF-containing electrolyte matrix (16). The LiF-containing electrolyte matrix is ​​the electrolyte matrix prepared in step (b) containing the second compound. LiF is used in excess of Pü, which is introduced into the LiF-containing electrolyte matrix in step (c).The excess LiF may come from the LIB black mass or from another source.

[0044] The LiF-containing electrolyte matrix obtained in step (b) can now be used to carry out step (c) (arrow B, box 93). For this purpose, the Pu obtained in step (a) is fed to the LiF-containing electrolyte matrix (arrow C), whereby absorption of PF> in the LiF-containing electrolyte matrix is ​​achieved (31). In this embodiment, the absorption takes place at a temperature greater than 5 °C and less than 10 °C. The absorbed Pu reacts with LiF to form LiPFe, thus obtaining a LiPFe-containing raw electrolyte (32). The LiPFe- The LiPFe-containing raw electrolyte is then subjected to purification with an anion exchanger (33) to remove impurities from the LiPFe-containing raw electrolyte by exchange with PFe' ions. The preparation of the anion exchanger is described below in connection with Box 94. Purification converts the LiPFe-containing raw electrolyte into a LiPFe-containing electrolyte (34), which in this embodiment has a purity of more than 98%. The resulting LiPFe-containing electrolyte can now be used to produce LIB cells (arrow D).

[0045] The preparation of the anion exchanger, shown in Box 94, involves the preparation of a strongly basic anion exchanger (21) and the preparation of KPFe (22). The anion exchanger is treated with KPFe in the presence of water (24), thereby loading the anion exchanger with PFe' (23). The PFe'-loaded anion exchanger is then subjected to vacuum drying (25) at a drying temperature greater than 20 °C and less than 80 °C. The pressure was 3 mbar. The water obtained during drying can be used to treat the anion exchanger in step (23) (26). The dried, PFe'-loaded anion exchanger (27) can be used to purify the crude LiPFe electrolyte in step (32) (arrow E). Example 2

[0046] Example 2 focuses on the recovery of LiPFe from an electrolyte consisting of a LiPFe-EC-DMC solution. The electrolyte is thus a solution of LiPFe in a mixture of EC and DMC. Such an electrolyte is an example of an electrolyte used in LIB cells.

[0047] The system was purged with a dry N2 stream at room temperature for at least 1 h (flow rate: 100 sccm). 2 mL to 4 mL of a 1 mol / L LiPFe-EC-DMC solution (EC:DMC, 50:50 v / v) was heated to 200 °C in a tube furnace (heating rate: 15 K / min). Dry N2 was flushed through the ceramic furnace tube (flow rate: 200 sccm).

[0048] In a N2-operated glove box, approximately 0.22 g of LiF was dissolved in 30 mL of a dried (4 A molecular sieve) EC-DMC mixture (EC:DMC, 50:50 v / v). This was done in a PFA-PTFE reactor (50 mL). The generated PF5 was introduced into this absorption mixture. The absorption mixture was cooled to 10 °C and homogenized using a magnetic stirrer. The generated PF5 was introduced for 160 min, yielding LiPFe as the crude product. A LiPFe recovery yield of 93% was achieved.

[0049] The crude product was purified using anion exchangers outside the reactor under inert gas. For practical application, various anion exchangers were investigated for their PFe' loading (Table 1).

[0050] The anion exchangers were in the Cl' form. For the preparation of the PFe-loaded anion exchangers, they were first conditioned with sodium hydroxide solution (approx. 1.5 mol / L) in an overhead shaker at 20 revolutions per minute and room temperature. For the PFe' loading, KPFe was added to the respective anion exchanger in a mass ratio of 1:1 by dissolving it in a sufficient amount of water (solubility of 83.5 g / L KPFe in EEO at 25 °C).

[0025] The PFe' loading was carried out in an overhead shaker at 20 revolutions per minute and room temperature. After complete PFe' loading, the anion exchangers were dried overnight in a vacuum drying oven at room temperature and < 3 mbar.

[0051] Regarding the PFe' loading, it was observed that only strongly basic anion exchangers are suitable for purifying the LiPFe solution. Therefore, any strongly basic anion exchanger, regardless of its pore structure, is suitable for LiPFe purification. Lewatit M500 was initially used for the purification experiments. Table 1 : Technical data and PFe' loading of the investigated anion exchangers [27-30]

[0052] The cleaning was carried out in batch or continuous operation. An example of the cleaning results in batch operation, which allows for better comparability of the data, is given in Table 2. The contact time for the c / v cleaning was 30 minutes. The solid:liquid weight ratio (anion exchanger: product solution) was 1:1. Table 2: Anion chromatographic data of the crude LiPFe solution and the PFe-loaded product solution purified with M500. literature [1] European Commission, Proposals for a Regulation of the European Parliament and of the Council on batteries and waste batteries, repealing Directive 2006 / 66 / EC and amending Regulation (EU) 2019 / 1020, 2020. [2] DL Thompson, JM Hartley, SM Lambert, M Shiref, GDJ Harper, E Kendrick, P Anderson, KS Ryder, L Gaines, AP Abbott, Green Chem. 2020, 22, 7585. [3] B. Thijs, J. Pelgrims, EP 2410603 Al. [4] K. He, Z.-Y. Zhang, L. Alai, F.-S. Zhang, J. Hazard. Mater. 2019, 375, 43. [5] S. Asano, H. Ishida, T. Nakai, US 2015 / 0013499 Al. [6] CL Campion, W. Li, BL Lucht, J. Electrochem. Soc. 2005, 152, A2327. [7] AV Plakhotnyk, L. Ernst, R. Schmutzler, J. Fluorine Chem. 2005, 126, 27. [8] T. Kawamura, S. Okada, J. Yamaki, J. Power Sources 2006, 156, 547. [9] U. Heider, R. Oesten, M. Jungnitz, J. Power Sources 1999, 81-82, 119.

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[0019] A. Vezzini in Lithium-Ion Batteries, Elsevier, 2014, P. 529-551.

[0020] E. Worrell, MA Reuter, Handbook of recycling. State-of-the-art for practitioners, analysts, and scientists, Elsevier, Waltham, Mass, 2014.

[0021] J. Diekmann, J. Hanisch, L. Froböse, G. Schälicke, T. Loellhoeffel, A.-S. Folster, A. Kwade, J. Electrochem. Soc. 2017, 164, A6184-A6191.

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[0027] LANXESS Deutschland GmbH, Technical Data Sheet: LEWATIT K6362, 2017.

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Claims

Patent claims 1. Method for recovering a perfluorinated lithium compound from an electrolyte of a lithium-ion battery, comprising the steps (a) thermal treatment of the electrolyte with decomposition of the perfluorinated lithium compound to obtain a first compound as a gaseous reaction product and a second compound as a solid reaction product; (b) Providing an electrolyte matrix containing the second compound; and (c) Adding the first compound obtained in step (a) to the electrolyte matrix, reacting the first compound obtained in step (a) with the second compound contained in the electrolyte matrix provided in step (b) to give the perfluorinated lithium compound.

2. The method according to claim 1, characterized in that the perfluorinated lithium compound is lithium hexafluorophosphate or lithium tetrafluoroborate.

3. Method according to claim 1 or claim 2, characterized in that the electrolyte used in step (a) is obtained by dismantling and / or comminuting one or more lithium-ion batteries.

4. Method according to one of the preceding claims, characterized in that in step (a) the thermal treatment is carried out at a temperature of 40 °C or more.

5. Method according to one of the preceding claims, characterized in that the second compound contained in the electrolyte matrix provided in step (b) is the solid reaction product obtained in step (a) and / or is derived from another source.

6. Method according to one of the preceding claims, characterized in that the second compound obtained in step (a) is fed to a reactor in which an electrolyte matrix is ​​located, thereby obtaining the electrolyte matrix containing the second compound.

7. Method according to one of the preceding claims, characterized in that in step (c) the first compound is introduced to the electrolyte matrix by means of an inert gas.

8. Method according to claim 6 or claim 7, characterized in that the first compound is introduced into the reactor in which the electrolyte matrix containing the second compound is located.

9. Method according to one of the preceding claims, characterized in that the electrolyte matrix provided in step (b) is dried by distillation of its components and / or using a molecular sieve.

10. Method according to one of the preceding claims, characterized in that in step (c) the first compound is supplied in an amount m corresponding to an amount of substance of 1 : 1 to 1 : 15 to the amount of substance of the second compound contained in the electrolyte matrix provided in step (b).

11. Method according to one of the preceding claims, characterized in that in step (c) the reaction is carried out at a temperature in a range between 0 and 25 °C.

12. Method according to one of the preceding claims, characterized in that, following step (c), the electrolyte matrix containing the perfluorinated lithium compound is purified.

13. Method according to claim 12, characterized in that the purification is carried out using an anion exchanger.

14. Method according to claim 13, characterized in that the anion exchanger is treated with a salt having a perfluorinated anion corresponding to the anion of the perfluorinated lithium compound.

15. Method for producing a conducting salt-containing electrolyte matrix for a lithium-ion battery, wherein the conducting salt is a perfluorinated lithium compound, comprising the steps (a) thermal treatment of the electrolyte of a lithium-ion battery containing the conducting salt, decomposing the conducting salt to obtain a first compound as a gaseous reaction product and a second compound as a solid reaction product; (b) Providing an electrolyte matrix containing the second compound; and (c) Leading the first compound obtained in step (a) to the electrolyte matrix, reacting the first compound obtained in step (a) with the second compound contained in the electrolyte matrix provided in step (b), obtaining the conducting salt-containing electrolyte matrix.

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