Method for recycling solid electrolyte and cathode materials from lithium solid-state batteries

Abstract

The present invention relates to a method for recycling cathode material and solid electrolyte from a solid lithium battery, the method comprising the steps of: a) separating the lithium solid-state battery into a solid mixture, the mixture comprising a lithium anode, a cathode material and a solid electrolyte; b) mixing the solid mixture with an aprotic solvent to form a solution of the solid electrolyte in the aprotic solvent and an insoluble component comprising the lithium anode and cathode materials; c) separating the solution of the solid electrolyte from the insoluble component; d) contacting the insoluble component with a protic solvent to form a solution of a lithium salt of general formula LiX in the protic solvent and an undissolved cathode material, where X represents an alcoholate or hydroxide ion, whereby the lithium anode reacts with the protic solvent to form hydrogen and the lithium salt LiX, whereby the lithium salt LiX dissolves in the protic solvent; e) separating the solution of the lithium salt LiX from the undissolved cathode material; and f) adding a lithium compound to the separated cathode material and calcining.

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates to a method for recycling cathode materials and solid electrolytes from lithium solid-state batteries. [Background technology]

[0002] Technical background In the following, the term "lithium solid-state battery" is used synonymously with all common names in the technical field of lithium-containing galvanic elements and cells that use at least one solid electrolyte as a lithium-ion conductive connection between the cathode and the anode, such as lithium metal solid-state battery, lithium metal solid-state accumulator, all-solid-state battery (ASSB), lithium cell, lithium-ion solid-state battery, lithium polymer cell, lithium-ion accumulator, etc. In particular, it includes secondary batteries (secondary batteries). Also, the terms "battery", "cell", and "electrochemical cell" are used synonymously with the term "lithium solid-state battery". Furthermore, the term "lithium solid-state battery" also includes used batteries and used accumulators.

[0003] Lithium solid-state batteries have at least two distinct electrodes: a cathode (positive electrode) and an anode (negative electrode). In lithium solid-state batteries, the anode contains metallic lithium or a lithium-containing alloy. The cathode contains at least one cathode material, optionally with additives such as electrode binders and conductive additives.

[0004] The cathode material must be capable of reversibly absorbing and releasing lithium ions.

[0005] The two electrodes are connected to each other via a solid electrolyte, which ensures the transport of ions, especially lithium ions, during the charging and discharging process. Solid electrolytes can therefore carry electric current by ion transport in the solid. Solid electrolytes are divided into sulfide-based solid electrolytes, oxide-based solid electrolytes, and polymer-based solid electrolytes. While oxide-based and polymer-based solid electrolytes are already in industrial use, e.g. as solid electrolytes in sodium-sulfur storage batteries, fuel cells, and capacitors, sulfide-based solid electrolytes are still in the development stage. However, sulfide-based solid electrolytes are considered to have great potential for the development and industrialization of battery systems, especially lithium solid-state batteries.

[0006] In contrast to conventional lithium-ion batteries, which contain a liquid electrolyte to transport the lithium ions, lithium solid-state batteries are essentially composed of solid components, which gives them several advantages over lithium-ion batteries that use a liquid electrolyte.

[0007] In particular, lithium solid-state batteries can achieve higher energy densities than conventional lithium-ion batteries, making them promising candidates for use in at least partial electric vehicles. Replacing the liquid electrolyte, which in conventional batteries partly contains fluorine compounds, with a solid electrolyte can also stabilize the charging and discharging process of the battery.

[0008] A prerequisite for the success of electromobility is the long-term availability of the materials used in the batteries through efficient recycling methods. Compared to the recovery of raw materials from used lithium-ion batteries with liquid electrolytes, battery concepts based on lithium solid-state batteries could in principle also open up new avenues for the development of recycling methods.

[0009] Current recycling methods for conventional lithium-ion batteries mainly only process the cathode materials, especially the frequently used lithium nickel cobalt oxide (NMC). Recycling is carried out by a hydrothermal process. Valuable metals such as nickel and cobalt are dissolved and concentrated by digestion with acids such as hydrochloric and sulfuric acid. The hydrothermal process must be carried out under controlled conditions for safety reasons and is not environmentally friendly or resource-saving. An alternative method is pyrometallurgical recycling, in which lithium-ion batteries are thermally melted. In the pyrometallurgical process, a slag and a molten alloy are produced. The slag can be further hydrometallurgically processed to chemically dissolve and concentrate the valuable metals in the slag. The molten alloy contains a mixture of valuable metals and can be fed to further processing steps to separate the elements and recover them as pure metals.

[0010] However, the two described processes only provide the starting elements as pure metals such as nickel, cobalt, copper, chromium or aluminum. Therefore, the individual battery components such as cathode material, electrolyte and anode material need to be resynthesized in order to produce a new battery. This means that another resource-intensive and energy-consuming step is required before a battery can be obtained from the recycled parts. Furthermore, some components, especially the newly synthesized cathode material, need to be chemically relithiated in order to be reused in the battery system. Relithiation can be done, for example, with lithium carbonate. It is possible to transfer the described processes to a recycling method for lithium solid-state batteries. However, this does not fully exploit the potential of the new battery concept of solid-state batteries.

[0011] A scientific paper by Tan et al. (MRS Energy & Sustainability: A Review Journal, 2020) reveals a method for recycling solid-state lithium sulfide batteries with metallic lithium as the anode, Li6PS5Cl as the solid electrolyte, and LiCoO2 as the cathode material. The process includes five steps to recycle the battery components separately. However, this recycling process requires the complete consumption of the metallic lithium anode. As a result, only the Li6PS5Cl and LiCoO2 components are recycled. As a first step, the cell stack is separated to make the battery interior more accessible for further processing. It is then reprocessed with a protic solvent, such as ethanol, to form a solution of the solid electrolyte and insoluble components, including the cathode material. The cathode material is separated from the solution of the solid electrolyte by filtration or centrifugation in the third step. The solid electrolyte and the cathode material are obtained separately by drying in the fourth step. The final step of recycling is the regeneration of the solid electrolyte and the cathode material. Annealing the solid electrolyte regenerates it into a solid electrolyte that can be used again in lithium solid-state batteries. Chemical relithiation allows the cathode material to be reused in lithium solid-state batteries.

[0012] The process described here requires the complete consumption of metallic lithium. This requires, for example, a complete discharge of the battery. However, the choice of the anode material and the amount of lithium present limits the lithium absorption capacity of the cathode active material, so that the complete consumption of metallic lithium present in the battery cannot be achieved for some types of batteries. For this reason, in the routine recycling process, batteries in different states of discharge are introduced into the recycling circuit. Batteries in different states of discharge are therefore not suitable for recycling with the described process. The metallic lithium remaining in the battery may react with the protic solvent in the first step of the process, resulting in a highly reactive mixture that is difficult to separate. The known processes are therefore not suitable for recycling lithium solid-state batteries that contain unused amounts of metallic lithium. [Prior art documents] [Non-patent literature]

[0013] [Non-Patent Document 1] MRS Energy & Sustainability: A Review Journal, 2020 Summary of the Invention [Problem to be solved by the invention]

[0014] Summary of the Invention It is an object of the present invention to provide a recycling method for separately recycling solid electrolyte and cathode materials from a lithium solid-state battery in the presence of a metallic lithium anode. [Means for solving the problem]

[0015] This problem is solved according to the invention by a method for recycling cathode material and solid electrolyte from lithium solid-state batteries according to claim 1.

[0016] According to the present invention, a method for recycling cathode materials and solid electrolytes from lithium solid-state batteries includes the following steps: a) isolating a lithium solid-state battery into a solid mixture, the mixture including a lithium anode, a cathode material and a solid electrolyte; b) mixing the solid mixture with an aprotic solvent to form a solution of the solid electrolyte in the aprotic solvent and insoluble components including lithium anode and cathode materials; c) separating the solution of solid electrolyte from the insoluble components; d) contacting the insoluble components with a protic solvent to form a solution of a lithium salt of general formula LiX in the protic solvent and undissolved cathode material, where X represents an alcoholate or hydroxide ion, whereby the lithium anode reacts with the protic solvent to form hydrogen and the lithium salt LiX, whereby the lithium salt LiX dissolves in the protic solvent; e) separating the solution of lithium salt LiX from the undissolved cathode material; f) adding a lithium compound to the separated cathode material and calcining.

[0017] To carry out the method according to the invention, the components of the lithium solid-state battery are mixed stepwise with aprotic and protic solvents, respectively. In particular, the use of costly hydrothermal processes for disassembly of the cell stack, as described in the prior art, can be omitted. By using a protic solvent for disassembly of the cell stack, a controllable heterogeneous mixture can be formed, comprising a solution of the solid electrolyte in the protic solvent and insoluble components, including the lithium anode and cathode materials. Compared to the protic disassembly of the prior art, the mixture is easier to process.

[0018] The lithium present in the cell can also be used in the recycling process. By selectively adding a protic solvent in step d), the lithium is converted in a controlled manner into the soluble and easily manageable form of the lithium salt LiX, without obtaining a poorly soluble and reactive mixture. The solution of the lithium salt LiX thus obtained can be used directly to relithiate the separated cathode material for reuse in the battery system. Furthermore, it is also possible to first convert the lithium salt into a solid form and store it in the meantime, or alternatively to use all or part of the lithium salt in solid or concentrated form in the calcination step f). Finally, the lithium salt LiX can also be converted into another lithium compound, such as lithium carbonate, which allows it to be stored more easily. The lithium salt LiX obtained in step d) can thus be directly or indirectly available for the new production of lithiated cathode materials or can be used as a lithium source in other processes. Thus, the method according to the invention can not only be carried out in the presence of lithium metal in used / in-use lithium batteries, but it is even possible to recycle the lithium metal contained therein for further processing of the cathode material. The described recycling method is therefore particularly resource-saving, since no external lithium source is required for the relithiation of the cathode material. This design of the recycling method allows for particularly efficient recycling of the components of lithium solid-state batteries. The batteries can be recycled regardless of their discharge state, making further process steps such as pretreatment or testing of the batteries unnecessary.

[0019] Advantageous embodiments of the method according to the invention for recycling cathode material and solid electrolyte from lithium solid-state batteries are set out in the dependent claims, which can be optionally combined with one another. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The present invention will now be described in detail and illustratively with reference to preferred embodiments, which should not be construed in a limiting sense.

[0021] "Recycling" means here and below the reprocessing of waste or used materials for their original purpose or for other purposes in a manufacturing process, but excluding energy recovery.

[0022] The cathode material suitable for the recycling process may be or may consist of all cathode materials known in the prior art.

[0023] Preferred cathode materials for the recycling method according to the present invention include, for example, lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium-nickel-cobalt-aluminum oxide (NCA), lithium-nickel-manganese-cobalt oxide (NMC), lithium-manganese oxide (LMO), lithium iron phosphate (LFP), lithium-nickel-manganese oxide (LMR), lithium-nickel-manganese oxide spinel (LNMO), and combinations thereof.

[0024] Lithium-nickel-manganese-cobalt compounds are also known by the abbreviation NMC, and sometimes by the technical abbreviation NCM. NMC-based cathode materials are used in particular in automotive lithium-ion batteries. NMC as a cathode material has an advantageous combination of desirable properties, such as high specific capacity, reduced cobalt content, high high current capability, and high inherent safety, which is manifested, for example, by sufficient stability during overcharging.

[0025] NMC is the general formula unit, Li α Ni x Mn y Co zO2 (where x+y+z=1), where α represents the lithium stoichiometric ratio, which is usually between 0.8 and 1.15. Certain stoichiometries are designated in the literature by triple numbers, e.g. NMC811, NMC622, NMC532, NMC111, etc. The triple numbers indicate the relative contents of nickel:manganese:cobalt in each case, i.e. NMC811, for example, has the general formula units LiNi 0.8 Mn 0.1 Co 0.1 O2, i.e., α=1. Furthermore, the general formula unit Li 1+ε (Ni x Mn y Co z ) 1-ε So-called lithium- and manganese-rich NMCs of O2 can also be used, where in particular ε is between 0.1 and 0.6, preferably between 0.2 and 0.4. These lithium-rich layered oxides are also known as overlithiated (layered) oxides (OLO).

[0026] The method according to the invention is particularly suitable for recycling sulfide solid electrolytes. In general, all solid electrolytes based on sulfides known in the prior art are suitable.

[0027] Preferably, the process according to the invention comprises a compound of the general formula Li 1-a-b-c-d P a T b A c S d where T is phosphorus, arsenic, silicon, germanium, aluminum or boron, A is a halogen or nitrogen, and S is sulfur, and is suitable for recycling sulfide solid electrolytes containing compounds with 0≦a≦0.129, 0≦b≦0.096, 0.316≦c≦0.484, and 0.012≦d≦0.125. Such compounds are known from WO2018 / 183365A1.

[0028] Also suitable for the method are compounds of the general formula Li x T y S z R q(wherein T is boron or phosphorus, R is a halogen, and 2≦x≦7, 1≦y≦7, 3≦z≦13, and 0≦q≦1) are sulfide solid electrolytes such as lithium phosphate sulfide and lithium boron sulfide.

[0029] Lithium sulfide is a PS4 3- -It is a compound whose structural unit is a tetrahedron.

[0030] Particularly preferred are compounds of the general formula Li x P y S z R q where R is a halogen and 3≦x≦7, 1≦y≦3, 4≦z≦11, 0≦q≦1. Such lithium phosphosulfides are known from WO2020 / 153973A1.

[0031] Examples of lithium phosphorus sulfides are: Li3PS4, Li7P3S 11 , Li6PS5Cl, Li7PS6, Li6PS5Cl 0.5 Br 0.5 , Li6PS5I, Li6PS5Br.

[0032] Also suitable as sulfide solid electrolyte for the method according to the invention is lithium phosphorus sulfide Li 10 GeP2S 12 (LGPS).

[0033] Furthermore, the general formula Li x B y S z can be recycled using the method according to the invention, where 2≦x≦5, 1≦y≦7, and 3≦z≦13. Such lithium boron sulfides are known from WO 2019 / 051305 A1.

[0034] An example of lithium boron sulfide is the compound Li5B7S 13 , Li2B2B5, and Li3BS3.

[0035] In the sulfide solid electrolytes mentioned above, the sulfur can be completely or partially replaced by selenium.

[0036] The lithium anode for the method according to the invention can be or include lithium metal or a lithium alloy, where the lithium alloy preferably includes components including manganese, zinc, silver, lithium, silicon, germanium, antimony and combinations thereof.

[0037] The lithium anode may also be a composite electrode, such as a metallic current conductor coated with a thin lithium layer, the conductor and optionally other coating components of the electrode being mechanically removable during the separation of the lithium solid-state battery.

[0038] In one embodiment, the separation of the lithium solid state battery can be carried out in a closed system, preferably in an inert gas atmosphere. The separation of the lithium solid state battery can include a prior stripping of the cell, for example, separation of the can or pouch. After this, the electrochemical cell may be crushed to form a solid mixture. The solid mixture includes the anode lithium, the solid electrolyte, and the cathode material. The crushing of the stripped cell is preferably carried out mechanically. The particle size of the solid mixture is preferably 1-5 mm.

[0039] Examples of inert gases include argon, nitrogen, and sulfur hexafluoride. Isolation of lithium solid-state batteries in a closed system under an inert gas atmosphere allows the exclusion of atmospheric oxygen and moisture, which would react undesirably with the metallic lithium anode. In this way, it is possible to avoid that the lithium anode reacts before the actual recycling and becomes unavailable for the relithiation of the cathode material. In particular, the addition of aprotic solvents in the presence of atmospheric oxygen and moisture can lead to the formation of poorly soluble precipitates, which makes it possible to separate the individual battery components by type only under difficult conditions. At the same time, the separation of the cells is carried out in a controlled environment, allowing a controllable process control with associated advantages, such as the containment of any harmful gases that may be generated.

[0040] Aprotic solvents may be selected from the group consisting of dimethyl carbonate, acetonyl, cyclohexane, toluene, p-xylene, anisole, pyridine, propylene carbonate, tetrahydrofuran, naphthalene and ethyl methyl carbonate, and mixtures thereof. Aprotic solvents are understood here to mean compounds that do not split or absorb protons in the presence of lithium. Thus, the compounds in question are not chemically reactive towards lithium.

[0041] In general, all aprotic solvents known from the prior art which are chemically inert towards lithium are suitable for the process according to the invention.

[0042] The aprotic solvent serves to absorb and dissolve the solid electrolyte from the solid mixture. The solution of the solid electrolyte in the aprotic solvent can then be separated from the insoluble components in a convenient manner. The inventors have found that, in particular, PS4 3- It was found that solid electrolytes with tetrahedral units show particularly good solubility in aprotic solvents. Furthermore, when an aprotic solvent is used for dissolving and separating the solid electrolyte, there is no deterioration in the physical properties (such as the lithium ion conductivity) that affect the performance of the regenerated lithium solid-state battery.

[0043] The mixing of the aprotic solvent with the solid mixture results in a heterogeneous mixture containing the solid electrolyte dissolved in the aprotic solvent as a liquid component and undissolved solids including the cathode material and the lithium anode. The solids content in the heterogeneous mixture is preferably up to 70% by weight, preferably 30-70% by weight, more preferably 40-70% by weight or 50-70% by weight, based on the total weight of the mixture. Heterogeneous mixtures with solids content of more than 70% by weight are not flowable and therefore difficult to separate. Preferably, only the amount of aprotic solvent required to bring the solid electrolyte into solution is used. Addition of the aprotic solvent to the solid mixture includes the use of known extraction and filtration processes.

[0044] After separating the solid electrolyte solution, the solid electrolyte dissolved in the aprotic solvent can be isolated and recrystallized, for example, with another solvent to prepare the electrolyte. Preferred solvents include tetrahydrofuran, toluene dimethyl carbonate, acetonitrile, p-xylene, anisole, pyridine, propylene carbonate, naphthalene, and ethyl methyl carbonate, and mixtures thereof.

[0045] The solid electrolyte can also be obtained by simply drying the solvent. Drying can be carried out at room temperature. Drying can also be accelerated by heating. In particular, drying can be carried out under the effect of vacuum (reduced pressure) or under an inert gas atmosphere such as nitrogen or argon. Drying under vacuum or inert gas atmosphere can also be combined with heating of the wet solid electrolyte.

[0046] The recycled solid electrolyte can be fed to further process steps. In addition, the solid electrolyte can be mechanically ground, for example, by ball milling the solid electrolyte. In particular, the recycled solid electrolyte can be annealed (annealed, tempered) at a predetermined temperature for a predetermined time. This annealing is performed to improve the crystallinity of the solid electrolyte and remove crystal defects, and can be performed, for example, by heating in vacuum to a temperature of 350 to 600 ° C, preferably 550 ° C. However, the temperature used for annealing is not limited to the described temperature range, but depends on the particular solid electrolyte, in particular the crystallization temperature of the particular solid electrolyte at which the desired crystal phase of the solid electrolyte is obtained. The duration of annealing is also not constant, and is performed until the desired phase and composition of the solid electrolyte is obtained. For example, the annealing time can be from 1 minute to 48 hours. The annealing of the solid electrolyte can be performed in an air atmosphere, in an inert gas atmosphere, or under vacuum (reduced pressure).

[0047] After separation of the solution of the solid electrolyte in the aprotic solvent, the remaining insoluble components, especially those from the lithium anode and cathode materials, are contacted with a protic solvent, preferably water. This forms a mixture of a solution of the lithium salt LiX in the protic solvent and the undissolved cathode material. The protic solvent has hydrogen atoms active towards lithium. Thus, the lithium metal from the lithium anode reacts with the protic solvent to form hydrogen and a lithium salt of the general formula LiX, where X is an alcoholate or hydroxide ion, and the lithium salt LiX dissolves in the protic solvent.

[0048] In one embodiment of the present invention, hydrogen formed during the reaction of lithium metal with a protic solvent is recovered and potentially utilized energetically as hydrogen is a valuable, high energy resource.

[0049] The reaction of metallic lithium with a protic solvent to produce hydrogen and the lithium salt LiX is exothermic. Various measures can be taken to control this exothermic reaction that converts lithium to its salt in a controlled chemical reaction. On the one hand, the kinetics of the exothermic reaction can be controlled by the specific selection and mixture of protic solvents. On the other hand, control of the exothermic reaction is also possible by process control.

[0050] For control of the reaction by selection of the protic solvent, the protic solvent can be selected from the group consisting of water and alkanols and mixtures thereof.

[0051] By alkanol is understood the group of substances having at least one functional hydroxyl group and an aliphatic alkyl group. The aliphatic alkyl group may optionally be branched, cyclic or linear. The alkanol according to the invention may be a primary, secondary or tertiary alcohol.

[0052] Examples of primary alkanols include methanol, ethanol, propanol, butan-1-ol, pentan-1-ol, hexane-1-ol, heptan-1-ol, octan-1-ol, decan-1-ol, dodecan-1-ol, tetradecan-1-ol, hexadecan-1-ol, and octadecane-1-ol.

[0053] Examples of secondary alkanols include propan-2-ol, butan-2-ol, pentan-2-ol, pentan-3-ol, 3-methylbutan-2-ol, and the like.

[0054] Examples of higher alkanols include propane-1,2,3-triol, ethane-1,2-diol, propane-1,2-diol, propane-1,3-diol, butane-1,2-diol, butane-1,3-diol, butane-1,4-diol, butane-2,3-diol, pentane-1,5-diol, hexane-1,6-diol, octane-1,8-diol, nonane-1,9-diol, decane-1,10-diol.

[0055] Preferred alkanols are methanol, ethanol, propanol, and combinations thereof.

[0056] The rate of the chemical reaction can be controlled by the length of the aliphatic alkyl residue. Alkanols with longer alkyl chain lengths react more slowly with the lithium anode than alkanols with shorter alkyl chain lengths to produce lithium alcoholates and hydrogen. This process can be controlled by the choice of the particular alkanol.

[0057] In particular, in one embodiment, water can be mixed with at least one alkanol. The resulting mixture of water and at least one alkanol can be combined with insoluble components, including lithium anode and cathode materials. The kinetics of the reaction can be influenced by the mixing ratio of water and alkanol. The higher the water content, the higher the reactivity of the mixture. Water is preferably present in the water-alkanol mixture in a proportion of at least 80% or 85% by weight, particularly preferably at least 90% by weight, based on the total weight of the mixture.

[0058] In addition to the mixing ratio of water and alkanol, the reaction kinetics is also influenced by the chain length of the alkanol added to the mixture with water. Longer chain length alkanols in the mixture react slower with the lithium anode, while shorter chain length alkanols are converted faster. Examples of preferred water-alkanol mixtures for slowing the reaction rate include combinations of water with at least one of methanol, ethanol, propanol, and combinations thereof, with the water being preferably present in an amount of at least 80% or 85% by weight, more preferably at least 90% by weight, based on the total weight of the mixture.

[0059] The control of the reaction of the lithium anode with the protic solvent can be further achieved by process control. When the insoluble components are combined with the protic solvent, the solvent can be in liquid phase and can be optionally cooled. In another embodiment of the present invention, the protic solvent can be converted into a gas phase and contacted in a gas phase with the insoluble components, including the lithium anode. In this embodiment, the amount of protic solvent in the reaction atmosphere can be gradually increased. By slowly increasing the protic solvent in the atmosphere, the reaction with the insoluble components can be particularly controlled. A combination of liquid phase and gas phase contact can also be carried out. The protic solvent is an alkanol, water or a water-alkanol mixed solvent. Preferably, water is used as the protic solvent in the gas phase.

[0060] In this embodiment, the chemical rate of the reaction is reduced through process control, and lithium reacts with the protic solvent in the gas phase in a delayed manner to form the corresponding lithium salt and hydrogen. In particular, the addition of the protic solvent in the gaseous state can be easily and targeted by specific selection of pressure and temperature. This allows the introduction of further reaction parameters to control the reaction, such as temperature, pressure, and reactant concentration.

[0061] After contacting the protic solvent with the insoluble components of the lithium anode and cathode materials, a solution of the lithium salt LiX is present in the protic quencher. Separation of the solution of LiX and the undissolved cathode materials can be accomplished by centrifugation, filtration or precipitation.

[0062] The solution of the lithium salt LiX can be isolated and recovered. In particular, the solution of the lithium salt LiX can be concentrated or temporarily stored in solid form. The lithium salt LiX can also be converted into another compound that can be used as an easily accessible Li source for relithiation in a further step. Thus, in contrast to the prior art, the lithium from the lithium anode can be used in whole or in part for the relithiation of the cathode material, either directly in the form of the lithium salt LiX obtained from the contacting step or their solutions in a protic solvent, or indirectly after conversion to other lithium compounds such as lithium carbonate, which can then be easily stored.

[0063] A further advantage of the method according to the invention is that surplus lithium can be recovered in the form of LiX with respect to the amount required for the relithiation of the cathode material. This method therefore allows the construction of a lithium storage device. The recovered LiX can therefore be used ad-hoc in a subsequent process or can be added to the method depending on the amount of Li required. This makes the method according to the invention particularly resource-saving and sustainable, since no external Li source is required for the relithiation or for the new production of the cathode material.

[0064] The cathode material separated from the solution of LiX is then calcined, preferably by heating to a temperature between 600 ° C. and 1000 ° C., particularly preferably by heating to a temperature between 700 ° C. and 900 ° C. In one embodiment, the lithium compound can be added already during the calcination of the cathode material for relithiation. Preferably, the lithium compound is a lithium salt of general formula LiX. Particularly preferably, a solution of the lithium salt LiX obtained from step e) of the above-mentioned process can be used. The addition of the lithium compound can be stoichiometric. In particular, the concentration of the lithium salt LiX in the solution of the lithium salt LiX can be measured before the addition, which allows a stoichiometric addition of the lithium salt LiX to the cathode material during the recycling process. The stoichiometric addition allows a cost-effective and resource-saving handling of the valuable raw lithium.

[0065] Additionally, it is possible to convert all or a portion of the lithium salt LiX to a lithium compound such as lithium carbonate, which is easier to add and store, and which can be used in the calcination process or a downstream step to relithiate the cathode material.

[0066] The calcination of the cathode material can be carried out in a continuous reactor or a rotary kiln. In particular, the calcination process requires low energy because the cathode material is already in a crystalline state. The lower amount of energy allows for shorter calcination times or lower temperatures.

[0067] The method according to the invention is suitable for the production of recycled cathode materials and solid electrolytes. Recycling of cathode materials and solid electrolytes using the method according to the invention therefore represents an important sustainability aspect in the new concept of lithium solid-state batteries.

[0068] The recycled cathode material and solid electrolyte obtained from the method according to the invention are suitable as components for use in electrochemical cells. In particular, the recycled cathode material and solid electrolyte are suitable for use in lithium solid-state batteries, preferably lithium solid-state batteries for use in at least partially electrically driven vehicles. Thus, the lithium solid-state batteries according to the invention are produced from recycled materials and are produced in an environmentally friendly and sustainable manner compared to freshly synthesized batteries. [Brief description of the drawings]

[0069] Further advantages and characteristics of the present invention emerge from the following description of preferred embodiments in conjunction with the referenced drawings, in which:

[0070] FIG. 1 shows a schematic flow diagram illustrating the steps of a method according to the present invention for recycling cathode materials and solid electrolytes from lithium-ion solid-state batteries. First, the lithium solid-state battery is separated into a solid mixture, which includes a lithium anode, a cathode material, and a solid electrolyte (step S1).

[0071] An aprotic solvent is added to the solid mixture to form a solution of the solid electrolyte in the aprotic solvent and a mixture of insoluble components including the lithium anode material and the cathode material (step S2).

[0072] In a next step, the solution of solid electrolyte is separated from the insoluble components (step S3), for example by suitable filtration or extraction techniques.

[0073] Finally, the solid electrolyte dissolved in the aprotic solvent is isolated from the aprotic solvent and preferably annealed, more preferably recrystallized with another solvent (step S4). The solid electrolyte thus obtained can be used to manufacture new lithium-ion solid-state batteries. Examples of solvents suitable for recrystallization include tetrahydrofuran, toluene, cyclohexane, and mixtures thereof.

[0074] The insoluble components are then contacted with a protic solvent to form a mixture of a solution of a lithium salt of general formula LiX in the protic solvent and the undissolved cathode material, whereby the lithium anode reacts with the protic solvent to form hydrogen and the lithium salt LiX, whereby the lithium salt LiX dissolves in the protic solvent (step S5), where X represents an alcoholate or hydroxide ion.

[0075] The hydrogen evolved when the protic solvent is contacted with the insoluble components of the lithium anode and cathode materials can be simultaneously collected and stored (step S6).

[0076] The LiX solution is then separated from the undissolved cathode material (step S7).

[0077] Finally, the solution of the lithium salt LiX can be isolated and recovered, or the lithium salt LiX can be converted into another lithium compound (step S8).

[0078] Finally, the isolated cathode material is calcined by adding a lithium compound, preferably the lithium salt LiX obtained from step S8, more preferably a solution of the lithium salt LiX in a protic solvent, or a lithium compound obtained from a lithium salt LiX such as lithium carbonate (step S9).

Claims

1. A method for recycling cathode materials and solid electrolytes from lithium solid-state batteries, comprising the steps of: a) isolating a lithium solid-state battery into a solid mixture, the mixture including a lithium anode, a cathode material and a solid electrolyte; b) mixing the solid mixture with an aprotic solvent to form a solution of the solid electrolyte in the aprotic solvent and insoluble components including lithium anode and cathode materials; c) separating the solid electrolyte solution from the insoluble components; d) contacting the insoluble components with a protic solvent to form a solution of a lithium salt of general formula LiX in the protic solvent and undissolved cathode material, where X represents an alcoholate or hydroxide ion, where the lithium anode reacts with the protic solvent to form hydrogen and the lithium salt LiX, where the lithium salt LiX dissolves in the protic solvent; e) separating the solution of lithium salt LiX from undissolved cathode material; and f) adding a lithium compound to the separated cathode material and calcining.

2. 2. The method of claim 1, wherein the cathode material is selected from the group consisting of lithium cobalt oxide (LCO), lithium nickel oxide (LNO), lithium nickel cobalt aluminum oxide (NCA), lithium nickel manganese cobalt oxide (NMC), lithium manganese oxide (LMO), lithium iron phosphate (LFP), lithium nickel manganese oxide (LMR), lithium nickel manganese oxide spinel (LNMO), and combinations thereof.

3. The solid electrolyte is a sulfide-based solid electrolyte, preferably of the general formula Li ｘ T ｙ S ｚ R ｑ 3. The method of claim 1 or 2, comprising the step of: (wherein T is boron or phosphorus, R is a halogen, and 2≦x≦7, 1≦y≦7, 3≦z≦13, 0≦q≦1) comprising lithium phosphorus sulfide and / or lithium boron sulfide.

4. 3. The method of claim 1 or 2, wherein the lithium anode comprises lithium metal or a lithium alloy, wherein the lithium alloy preferably comprises the components manganese, zinc, silver, lithium, silicon, germanium, antimony and combinations thereof.

5. 3. The method according to claim 1 or 2, characterized in that the separation of the lithium solid state battery is carried out in a closed system, preferably under an inert gas atmosphere.

6. 3. The process according to claim 1 or 2, characterized in that the aprotic solvent is selected from the group consisting of dimethyl carbonate, acetonitrile, cyclohexane, toluene, p-xylene, anisole, pyridine, propylene carbonate, tetrahydrofuran, naphthalene and ethyl methyl carbonate, and mixtures thereof.

7. 3. The method according to claim 1 or 2, characterized in that by mixing the solid mixture with the aprotic solvent, a heterogeneous mixture is obtained comprising the liquid component aprotic solvent and solids comprising the cathode material and the lithium anode, the content of solids in the heterogeneous mixture being at most 70 wt.-%, based on the total weight of the mixture.

8. 3. The method according to claim 1 or 2, characterized in that after separation of the solution of the solid electrolyte, the solid electrolyte dissolved in the aprotic solvent is isolated and prepared, preferably by annealing, particularly preferably by recrystallization with a further solvent selected from the group consisting of tetrahydrofuran, toluene, dimethyl carbonate, acetonitrile, p-xylene, anisole, pyridine, propylene carbonate, naphthalene, ethyl methyl carbonate and cyclohexane, and mixtures thereof.

9. 3. The method according to claim 1 or 2, characterized in that the protic solvent is selected from the group consisting of water and alkanols and mixtures thereof, and that the contacting of the protic solvent with the insoluble components comprises the addition of a protic solvent, preferably in the liquid and / or gas phase.

10. 3. The method according to claim 1 or 2, characterized in that in step f) a lithium compound is added during the calcination of the cathode material, wherein the lithium compound is preferably selected from the lithium salt LiX obtained from step e), a solution of the lithium salt LiX in a protic solvent, or a lithium compound obtained from a lithium salt, and combinations thereof.

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