Electrolyte for lithium metal battery, lithium metal battery and recycling method thereof

Abstract

The present application discloses an electrolyte for a lithium metal battery, a lithium metal battery, and a recycling method thereof. The lithium metal battery includes a positive electrode and a negative electrode. The electrolyte is disposed between the positive electrode and the negative electrode. The negative electrode includes a lithium metal material or a lithium alloy material. The electrolyte includes a lithium salt and an additive. The additive includes chloroethylene carbonate. In this way, the lithium metal of the negative electrode reacts preferentially with chloroethylene carbonate, thereby improving the problem of the intrinsic electrolyte in the electrolyte reacting with the lithium metal, resulting in the consumption of the intrinsic electrolyte, thereby improving the stability of the electrolyte in the lithium metal battery. In addition, during the recycling process of the lithium metal battery, chloroethylene carbonate is used to reduce the temperature required for the decomposition of the positive electrode active material of the lithium metal battery to obtain the target decomposition product, thereby reducing the power consumption required for recycling the positive electrode active material.

Description

Technical Field

[0001] The present application relates to the field of electrolyte technology, and in particular to an electrolyte for a lithium metal battery, a lithium metal battery and a recovery method thereof. Background Art

[0002] With the continuous development of portable electronic devices, electric vehicles and large-scale energy storage markets, the demand for lithium metal batteries continues to grow. At present, the lithium metal anode of lithium metal batteries easily reacts with the electrolyte, resulting in poor stability of the electrolyte of lithium metal batteries. Summary of the invention

[0003] The present application provides an electrolyte for a lithium metal battery, a lithium metal battery and a recovery method thereof, so as to improve the stability of the electrolyte during the cycle of the lithium metal battery.

[0004] In a first aspect, the present application provides an electrolyte for a lithium metal battery. The lithium metal battery comprises a positive electrode and a negative electrode. The electrolyte is disposed between the positive electrode and the negative electrode. The negative electrode comprises a lithium metal material or a lithium alloy material. The electrolyte comprises a lithium salt and an additive. The additive comprises ethylene chloride carbonate.

[0005] In a second aspect, the present application further provides a lithium metal battery, the lithium metal battery comprising a positive electrode, a negative electrode and the above electrolyte, wherein the above electrolyte is arranged between the positive electrode and the negative electrode. The negative electrode comprises a lithium metal material or a lithium alloy material.

[0006] In a third aspect, the present application also provides a method for recycling a lithium metal battery. The lithium metal battery comprises a positive electrode, a negative electrode, and an electrolyte disposed between the positive electrode and the negative electrode. The positive electrode comprises a positive electrode active material. The negative electrode comprises a lithium metal material or a lithium alloy material. The method comprises:

[0007] Separating the positive electrode active material of the lithium metal battery;

[0008] mixing the positive electrode active material with an additive comprising chloroethylene carbonate to obtain a mixture; and

[0009] The mixture is heated until the positive electrode active material is decomposed to obtain a target decomposition product.

[0010] In the electrolyte and lithium metal battery of some embodiments of the present application, ethylene chloride is added to the electrolyte, and the lithium metal at the negative electrode reacts preferentially with the ethylene chloride, thereby improving the problem of the intrinsic electrolyte in the electrolyte reacting with the metallic lithium and consuming the intrinsic electrolyte, thereby improving the stability of the electrolyte and the cycle performance of the lithium metal battery.

[0011] In the lithium metal battery recycling method of some embodiments of the present application, ethylene chloride is used as an additive during the decomposition of the positive electrode active material to reduce the temperature required for the positive electrode active material to decompose to obtain the target decomposition product and reduce the power consumption required to recover the positive electrode active material. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 These are the XRD test results of the products obtained by heating a mixture of an electrolyte containing ethylene chloride carbonate and a nickel-cobalt-manganese lithium acid material at different temperatures. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present application.

[0014] With the continuous development of portable electronic devices, electric vehicles and large-scale energy storage markets, the demand for lithium metal batteries continues to grow. At present, the lithium metal anode of lithium metal batteries easily reacts with the electrolyte, resulting in poor stability of the electrolyte of lithium metal batteries.

[0015] In view of this, the present application provides an electrolyte for a lithium metal battery to improve the stability of the electrolyte in the lithium metal battery.

[0016] In a first aspect, the present application provides an electrolyte for a lithium metal battery. The lithium metal battery includes a positive electrode and a negative electrode. The electrolyte is disposed between the positive electrode and the negative electrode. The negative electrode includes a lithium metal material or a lithium alloy material. The electrolyte includes a lithium salt and an additive. The additive includes chloroethylene carbonate. In this way, when the electrolyte is used in a lithium metal battery, the negative electrode lithium metal preferentially reacts with chloroethylene carbonate to form LiCl, thereby improving the problem of the intrinsic electrolyte (including organic solvents and lithium salts) in the electrolyte reacting with the negative electrode metal lithium to consume the intrinsic electrolyte, thereby improving the stability of the electrolyte.

[0017] The lithium salt is used to provide lithium ions. In some embodiments, the lithium salt is selected from at least one of bis(trifluoromethylsulfonyl)amide lithium, bis(trifluoromethylsulfonyl) lithium salt, lithium perchlorate, lithium tetrafluoroborate, lithium trifluoromethylsulfonate, bis(trifluoromethylsulfonyl)amide lithium and lithium hexafluorophosphate. Optionally, the lithium salt is bis(trifluoromethylsulfonyl)amide lithium. Bis(trifluoromethylsulfonyl)amide lithium has better conductivity and higher stability when dissolved in an organic solvent, and has stronger performance such as anti-hydrolysis ability, which can further improve the stability of the electrolyte.

[0018] In some embodiments, the electrolyte further comprises an organic solvent, and the organic solvent is used to dissolve the lithium salt and the additive. The solubility of the lithium salt in the organic solvent is relatively high, thereby improving the ionic conductivity of the intrinsic electrolyte comprising the organic solvent and the lithium salt.

[0019] In some embodiments, the molar ratio of lithium salt to organic solvent is (0.8-1.2): (1.2-1.6). In this way, the lithium salt is fully dissolved in the ether solvent, the concentration of lithium salt in the electrolyte is increased, and the ionic conductivity of the electrolyte is further increased.

[0020] Illustratively, the molar ratio of the lithium salt to the organic solvent is 0.8:(1.2-1.6), 0.9:(1.2-1.6), 1.0:(1.2-1.6), 1.1:(1.2-1.6) or 1.2:(1.2-1.6).

[0021] Illustratively, the molar ratio of the lithium salt to the organic solvent is 0.8:1.2, 0.9:1.2, 1.0:1.2, 1.2:1.2, 0.8:1.4, 0.9:1.4, 1.0:1.4, 1.2:1.4, 0.8:1.6, 0.9:1.6, 1.0:1.6 or 1.2:1.6.

[0022] In some embodiments, the molar ratio of ethylene chlorocarbonate to the organic solvent is less than or equal to 0.22. In this way, while ensuring that ethylene chlorocarbonate reacts preferentially with the negative electrode lithium metal, the risk of shuttle effect caused by excessive concentration of ethylene chlorocarbonate is reduced.

[0023] In some embodiments, the molar ratio of ethylene carbonate to organic solvent is greater than or equal to 0.007, so as to ensure that the concentration of ethylene carbonate is large enough to ensure that ethylene carbonate reacts preferentially with the negative electrode lithium metal of the lithium metal battery.

[0024] Optionally, the molar ratio of ethylene chlorocarbonate to the organic solvent may be 0.03 to 0.15. In this way, while ensuring that ethylene chlorocarbonate preferentially reacts with the negative electrode lithium metal, the risk of shuttle effect caused by excessive concentration of ethylene chlorocarbonate is reduced.

[0025] Optionally, the molar ratio of chloroethylene carbonate to the organic solvent may be 0.05-0.08, 0.01-0.2, 0.03-0.18, 0.06-0.15 or 0.065-0.12.

[0026] Illustratively, the molar ratio of ethylene chlorocarbonate to the organic solvent can be selected from any one of the following values: 0.008, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1, 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2, 0.21 or 0.22.

[0027] In some embodiments, the molar ratio of the organic solvent to the ethylene carbonate can be (1.2-1.6): (0.01-0.3). In this way, the concentration of the ethylene carbonate is ensured to be sufficiently large, thereby ensuring that the ethylene carbonate reacts preferentially with the negative electrode lithium metal of the lithium metal battery, and improving the problem of the shuttle effect caused by the excessive concentration of ethylene carbonate.

[0028] In some embodiments, the molar ratio of the organic solvent to the ethylene carbonate can be (1.2-1.6): (0.06-0.14). In this way, the ethylene carbonate is ensured to have a suitable concentration to ensure that the ethylene carbonate reacts preferentially with the negative electrode lithium metal of the lithium metal battery while reducing the risk of the shuttle effect caused by the excessive concentration of ethylene carbonate.

[0029] Optionally, the molar ratio of the organic solvent to ethylene chloride is (1.2-1.6):(0.02-0.28), (1.2-1.6):(0.05-0.25), (1.2-1.6):(0.07-0.2), (1.2-1.6):(0.075-0.16), (1.25-1.55):(0.08-0.12) or (1.35-1.55):(0.095-0.115).

[0030] Exemplarily, the molar ratio of the organic solvent to the ethylene carbonate is 1.2: (0.01-0.3), 1.4: (0.01-0.3), 1.6: (0.01-0.3), 1.2: (0.03-0.25), 1.4: (0.03-0.25), 1.6: (0.03-0.25), 1.2: (0.05-0.2), 1.4: (0.05-0.2), 1.6: (0. 05~0.2), 1.2: (0.07~0.18), 1.4: (0.07~0.18), 1.6: (0.07~0.18), 1.2: (0.08~0.15), 1.4: (0.08~0.15), 1.6: (0.08~0.15), 1.2: (0.09~0.12), 1.4: (0.09~0.12) or 1.6: (0.09~0.12).

[0031] Illustratively, the molar ratio of the organic solvent to the chloroethylene carbonate is 1.2:0.03, 1.2:0.06, 1.2:0.08, 1.2:0.1, 1.2:0.12, 1.2:0.14, 1.2:0.16, 1.2:0.18, 1.2:0.2, 1.2:0.22, 1.2:0.24, 1.2:0.26, 1.2:0.28, 1.2:0.30, 1.4:0.03, 1.4:0.06, 1.4:0.08, 1.4:0.1, 1.4:0.12, 1.4:0.1 4. 1.4: 0.16, 1.4: 0.18, 1.4: 0.2, 1.4: 0.22, 1.4: 0.24, 1.4: 0.26, 1.4: 0.28, 1.4: 0.30, 1.6: 0.03, 1.6: 0.06, 1.6: 0.08, 1.6: 0.1, 1.6: 0.12, 1.6: 0.14, 1.6: 0.16, 1.6: 0.18, 1.6: 0.2, 1.6: 0.22, 1.6: 0.24, 1.6: 0.26, 1.6: 0.28 or 1.6: 0.30.

[0032] In some embodiments, the organic solvent includes an ether solvent. Compared with other solvents, ether solvents have better stability in lithium metal batteries and improve the cyclability of lithium metal batteries.

[0033] In some embodiments, the ether solvent is selected from at least one of ethylene glycol dimethyl ether (DME), ethylene glycol methyl ethyl ether (EME), diethylene glycol dimethyl ether (G2), triethylene glycol dimethyl ether (G3), tetraethylene glycol dimethyl ether (G4), ethylene glycol diethyl ether (DEE), diethylene glycol methyl ethyl ether (DGEME), 1,3-dioxolane (DOL), 1,3-dioxane (1,3-DX), 1,4-dioxane (1,4-DX), 2-methyl-1,4-dioxane (2-Me-1,4-DX), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), and tetrahydropyran (THP). Optionally, the organic solvent is selected from ethylene glycol dimethyl ether to improve the solubility of the lithium salt in the solvent, thereby improving the ionic conductivity of the intrinsic electrolyte, and at the same time better improve the stability of the organic solvent in the lithium metal battery, thereby improving the cycle performance of the lithium metal battery.

[0034] In some embodiments, the electrolyte also includes a fluoroether diluent, which plays a diluting role. The concentration of lithium salt in ether solvents is relatively high. By introducing a fluoroether diluent that does not dissolve lithium salts and is poorly soluble in ether solvents, a local high-concentration system of lithium salts can be formed in the electrolyte. Compared with a high-concentration electrolyte without a diluent, the local high-concentration system has a lower viscosity, higher ion conductivity, and lower battery internal resistance, making it more stable during the cycle of the lithium metal battery.

[0035] In some embodiments, the molar ratio of the ether solvent to the fluoroether diluent is (1.2-1.6): (1.5-5). In this way, a local high-concentration system with suitable viscosity is formed to ensure that the electrolyte has a higher ion conductivity and a lower battery internal resistance, while also ensuring that the concentration of ethylene chloride in the electrolyte is sufficient to allow ethylene chloride to react with lithium metal. Too much fluoroether diluent will result in a low concentration of ethylene chloride, which is not conducive to the reaction of ethylene chloride with the negative electrode lithium metal. Too little fluoroether diluent is not conducive to the formation of a local high-concentration system, and makes the concentration of ethylene chloride high, which is not conducive to reducing the risk of the shuttle effect.

[0036] In some embodiments, the molar ratio of the ether solvent to the fluoroether diluent is (1.2-1.6): (2.8-4.0). In this way, a local high-concentration system with appropriate viscosity is formed to ensure that the electrolyte has higher ion conductivity and lower battery internal resistance, while also ensuring that the concentration of chloroethylene carbonate in the electrolyte is appropriate, so that the reaction rate of chloroethylene carbonate and lithium metal is moderate, while protecting the intrinsic electrolyte and suppressing the shuttle effect.

[0037] Optionally, the molar ratio of the ether solvent to the fluoroether diluent is (1.2~1.6):(1.8~4.8), (1.2~1.6):(2.0~4.5), (1.2~1.6):(2.2~4.2), (1.2~1.6):(2.5~4.0), (1.2~1.6):(2.8~4.0), (1.2~1.6):(3.2~3.8), (1.2~1.6):(3.3~3.6) or (1.2~1.6):(3.45~3.55).

[0038] Illustratively, the molar ratio of the ether solvent to the fluoroether diluent is 1.2: (1.5-5), 1.2: (1.8-4.8), 1.2: (2.0-4.6), 1.2: (2.2-4.4), 1.2: (2.4-4.2), 1.2: (2.6-4.0), 1.2: (2.8-3.8), 1.2: (3.0-3.6), 1.4: (1.5-5), 1.4: (1.8-4.8), 1.4: (2.0-4.6), 1.4: (2.2~4.4), 1.4: (2.4~4.2), 1.4: (2.6~4.0), 1.4: (2.8~3.8), 1.4: (3.0~3.6), 1.6: (1.5~5), 1.6: (1.8~4.8), 1.6: (2.0~4.6), 1.6: (2.2~4.4), 1.6: (2.4~4.2), 1.6: (2.6~4.0), 1.6: (2.8~3.8) or 1.6: (3.0~3.6).

[0039] Illustratively, the molar ratio of the ether solvent to is 1.2:1.5, 1.2:1.6, 1.2:1.8, 1.2:2.0, 1.2:2.2, 1.2:2.4, 1.2:2.6, 1.2:2.8, 1.2:3.0, 1.2:3.2, 1.2:3.4, 1.2:3.6, 1.2:3.8, 1.2:4.0, 1.2:4.2, 1.2:4.4, 1.2:4.6, 1.2:4.8, 1.2:5.0, 1.4:1.5, 1.4:1.6, 1.4:1.8, 1.4:2.0, 1.4:2.2, 1.4:2.4, 1.4:2.6, 1.4:2.8, 1.4: 3.0, 1.4:3.2, 1.4:3.4, 1.4:3.6, 1.4:3.8, 1.4:4.0, 1.4:4.2, 1.4:4.4, 1.4:4.6, 1.4:4.8, 1.4:5.0, 1.6:1.5, 1.6:1.6, 1.6:1.8, 1.6:2.0, 1.6:2.2, 1.6:2.4, 1.6:2.6, 1.6:2.8, 1.6:3.0, 1.6:3.2, 1.6:3.4, 1.6:3.6, 1.6:3.8, 1.6:4.0, 1.6:4.2, 1.6:4.4, 1.6:4.6, 1.6:4.81.6:5.0.

[0040] In some embodiments, the fluoroether diluent is selected from at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,2-trifluoroethyl-1,1,2,2-tetrafluoroethyl ether, bis(2,2,2-trifluoroethyl) ether, 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether, 1,1,2,3,3,3-hexafluoropropyl-2,2,2-trifluoroethyl ether, 1H,1H,5H-octylfluoropentyl-1,1,2,2-tetrafluoroethyl ether and bis(2,2,3,3-tetrafluoropropyl) ether. Alternatively, the fluoroether diluent is selected from at least one of 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether.

[0041] In some embodiments, the electrolyte further includes a polymer, which is obtained by polymerization reaction of a polymerized monomer under the action of a polymerization initiator, and the polymerized monomer includes at least one of an acrylamide monomer and an acrylate monomer. In this way, lithium salt, organic solvent, and additives are dispersed in the polymer to form a gel polymer electrolyte, thereby improving the safety of the electrolyte. In addition, the polymer obtained by polymerization of the polymerized monomer has good flexibility, so that the electrolyte forms good contact with the electrode of the lithium metal battery.

[0042] In some embodiments, the polymerized monomer includes an acrylamide monomer. Thus, the polymer also includes an amide group to improve the ionic conductivity of the electrolyte and enhance the cycle performance of the lithium metal battery.

[0043] In some embodiments, the acrylamide monomer may include at least two acrylamide groups, so as to significantly improve the ionic conductivity of the electrolyte and enhance the cycle performance of the lithium metal battery.

[0044] In some embodiments, the acrylamide monomer includes at least one of acrylamide, methacrylamide, isopropyl acrylamide, N,N-diethyl acrylamide, isobutyloxymethyl acrylamide, diacetone acrylamide and N,N-methylenebisacrylamide. Optionally, the polymerizable monomer includes N,N-methylenebisacrylamide to more significantly improve the ionic conductivity of the electrolyte and enhance the cycle performance of the lithium metal battery.

[0045] In some embodiments, the acrylate monomer includes at least one of methyl acrylate, ethyl acrylate, butyl acrylate, and methacrylate.

[0046] In the electrolyte, the mass percentage of polymer is 2.5%~5%. In this way, the consistency of the polymer monomer during the in-situ curing process is improved, thereby ensuring the mechanical properties of the polymer. At the same time, the interface impedance between the polymer and the electrode is reduced, and the electrical performance of the lithium metal battery is improved.

[0047] Optionally, in the electrolyte, the mass percentage of the polymer is 2.8% to 4.8%, 3.0% to 4.5%, 3.2% to 4.3% or 3.3% to 3.8%.

[0048] Illustratively, in the electrolyte, the mass percentage of the polymer is 2.5%, 2.7%, 2.9%, 3.1%, 3.3%, 3.5%, 3.7%, 3.9%, 4.1%, 4.3%, 4.5%, 4.7%, 4.9% or 5.0%.

[0049] In some embodiments, the polymerization initiator is selected from at least one of ammonium persulfate, benzoyl peroxide, tetramethylethylenediamine, benzoyl peroxide, azobisisobutyronitrile, and azobisisoheptyl. In this way, the polymerization initiator can initiate polymerization of the polymerization monomer at low temperature. Optionally, the polymerization initiator is azobisisobutyronitrile.

[0050] In other embodiments, the electrolyte may be a liquid electrolyte.

[0051] In some embodiments, the lithium salt is lithium bis(trifluoromethylsulfonyl)amide, the organic solvent is ethylene glycol dimethyl ether, the fluoroether diluent is 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, the polymerization monomer is N,N-methylenebisacrylamide, and the polymerization initiator is azobisisobutyronitrile. In this way, the polymer of the electrolyte has good mechanical properties, can form good contact with the electrodes of the lithium metal battery, and the interface impedance between the polymer and the electrode is small. In addition, the electrolyte also has high ionic conductivity and lower battery internal resistance, which is beneficial to improving the cycle performance of the lithium battery.

[0052] In some embodiments, the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene chloride carbonate and 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether is 1: (1.35-1.55): (0.095-0.115): (3.2-3.8). In this way, the mechanical properties and ionic conductivity of the electrolyte are further improved, the internal resistance of the battery is reduced, and the concentration of ethylene chloride carbonate in the electrolyte is ensured to be appropriate, so that the reaction rate of ethylene chloride carbonate and lithium metal is moderate, while protecting the intrinsic electrolyte, the shuttle effect is also suppressed.

[0053] In a second aspect, the present application also provides a method for preparing an electrolyte for a lithium metal battery, the preparation method comprising the following steps:

[0054] Step S101: providing multiple components of a composition, wherein the multiple components of the composition include a lithium salt and an additive, wherein the additive includes chloroethylene carbonate; and

[0055] Step S102: Mix the various components of the composition evenly to obtain a mixture of the composition.

[0056] In the preparation method of the electrolyte of some embodiments of the present application, ethylene chloride is added to the electrolyte so that the negative electrode lithium metal of the lithium metal battery preferentially reacts with ethylene chloride to form LiCl, thereby improving the problem of the intrinsic electrolyte in the electrolyte reacting with the negative electrode metal lithium and consuming the intrinsic electrolyte, thereby improving the stability of the electrolyte.

[0057] In some embodiments, in step S101, the various components of the composition may further include an organic solvent, which is used to dissolve the lithium salt and the additive.

[0058] In some embodiments, in step S101, the various components of the composition may further include a fluoroether diluent. The fluoroether diluent is insoluble in an organic solvent, and the lithium salt and the additive are insoluble in the fluoroether diluent.

[0059] In some embodiments, in step S101, the multiple components of the composition may further include a polymerizable monomer and a polymerization initiator. Thus, the polymerizable monomer is polymerized under the action of the polymerization initiator to form a polymer, and the lithium salt and the additive are dispersed in the polymer to form a gel electrolyte, thereby improving the safety of the electrolyte.

[0060] In some embodiments, in the composition, the mass percentage of the polymerized monomer is 2.5% to 5%. In this way, the consistency of the polymerized monomer during the in-situ curing process is improved, thereby ensuring the mechanical properties of the polymer. At the same time, the interface impedance between the polymer and the electrode is reduced, and the electrical properties of the lithium metal battery are improved.

[0061] Optionally, in the composition, the mass percentage of the polymerized monomer is 2.8% to 4.8%, 3.0% to 4.5%, 3.2% to 4.3% or 3.3% to 3.8%.

[0062] Illustratively, in the composition, the mass percentage of polymerized monomers is 2.5%, 2.7%, 2.9%, 3.1%, 3.3%, 3.5%, 3.7%, 3.9%, 4.1%, 4.3%, 4.5%, 4.7%, 4.9% or 5.0%.

[0063] In some embodiments, in the composition, the mass percentage of the polymerization initiator is 0.002% to 0.004%, so as to ensure that the polymerization initiator can initiate the polymerization of the polymerization monomer.

[0064] The process of preparing the electrolyte from the above composition mainly involves the polymerization reaction of the polymerized monomer under the action of the polymerization initiator, and the lithium salt, organic solvent, additive and fluoroether diluent hardly participate in the chemical reaction. Therefore, the proportion of lithium salt, organic solvent, additive and fluoroether diluent in the composition is basically the same as the proportion of these components in the electrolyte. For relevant content, please refer to the relevant content in the electrolyte, which will not be repeated here.

[0065] In other embodiments, the mixture of the composition obtained in the above step S102 can be directly used as a liquid electrolyte.

[0066] In some embodiments, the various components of the composition are mixed uniformly, including:

[0067] Step S1021: dissolving the lithium salt and the additive in an organic solvent to obtain a first mixed solution;

[0068] Step S1022: adding a fluoroether diluent to the first mixed solution and stirring the mixture to obtain a second mixed solution;

[0069] Step S1023: adding the polymerizable monomer to the second mixed solution and stirring evenly to obtain a third mixed solution; and

[0070] Step S1024: adding a polymerization initiator to the third mixed solution and stirring the mixture to obtain a mixture of the composition.

[0071] In some embodiments, in step S1021, the molar ratio of lithium salt, additive and organic solvent may be (0.08-1.2): (0.06-0.14): (1.2-1.6). The first mixed solution is a transparent solution.

[0072] In some embodiments, in step S1022, the fluoroether diluent reduces the viscosity of the first mixed solution to form a local high concentration system of lithium salt. In some embodiments, in step S1022, the molar ratio of the organic solvent to the fluoroether diluent is (1.2-1.6): (1.5-5).

[0073] In some embodiments, in step S1023, after obtaining the third mixed solution, the third mixed solution is stored at a low temperature, thereby reducing the risk of polymerization of the polymerizable monomers.

[0074] In some embodiments, the method for preparing the electrolyte further includes: Step S103: heating the mixture of the composition to allow the polymerization initiator to initiate polymerization of the polymerization monomer to obtain the electrolyte.

[0075] In some embodiments, heating the mixture of the composition includes: heating the mixture of the composition at 55° C. to 65° C. for 1.5 h to 2.5 h.

[0076] In a third aspect, the present application also provides a lithium metal battery, which includes the above-mentioned electrolyte. In this way, the negative electrode lithium metal of the lithium metal battery preferentially reacts with chloroethylene carbonate to form LiCl, thereby improving the problem of the intrinsic electrolyte in the electrolyte reacting with metallic lithium to consume the intrinsic electrolyte, thereby improving the stability of the electrolyte in the lithium metal battery and improving the cycle performance of the lithium metal battery.

[0077] The selection of relevant contents of electrolytes in lithium metal batteries refers to the relevant contents of the above-mentioned electrolytes, which will not be repeated here.

[0078] The lithium metal battery also includes a positive electrode and a negative electrode, and the electrolyte is located between the positive electrode and the negative electrode. The positive electrode includes a positive electrode current collector and a positive electrode active material located on the positive electrode current collector. The positive electrode active material may include a nickel cobalt manganese lithium acid material. The positive electrode current collector may include a metal foil such as aluminum foil. The negative electrode includes a negative electrode current collector and a negative electrode active material located on the negative electrode current collector. The negative electrode active material includes a lithium metal material or a lithium alloy material. The negative electrode current collector may include a metal foil such as copper foil.

[0079] In some embodiments, the lithium metal battery may further include a diaphragm, which is located between the positive electrode and the negative electrode. The diaphragm includes an organic film such as polyethylene. In the case where the electrolyte is a gel electrolyte, the electrolyte is located on both surfaces of the diaphragm facing the positive electrode and the negative electrode. In the case where the electrolyte is a liquid electrolyte or a solid electrolyte, the electrolyte is located between the surfaces of the negative electrode, the positive electrode and the diaphragm and the gaps between the three.

[0080] In a fourth aspect, the present application also provides a method for recycling a lithium metal battery. The lithium metal battery may be a lithium metal battery that has failed after long-term use, or may be another lithium metal battery that has failed and needs to recover the positive electrode active material. The lithium metal battery includes a positive electrode, a negative electrode and an electrolyte, the electrolyte is located between the positive electrode and the negative electrode, and the positive electrode includes a positive electrode active material. The negative electrode includes a lithium metal material or a lithium alloy material. The recycling method includes:

[0081] Step S201: separating the positive electrode active material of the lithium metal battery;

[0082] Step S202: mixing the positive electrode active material with an additive comprising chloroethylene carbonate to obtain a mixture; and

[0083] Step S203: heating the mixture until the positive electrode active material is decomposed to obtain a target decomposition product.

[0084] In the related art, when there is no chloroethylene carbonate in the electrolyte, the temperature of the nickel-cobalt-manganese lithium acid material decomposing under the action of C is greater than or equal to 800°C, which requires a large amount of energy. In some embodiments of the present application, chloroethylene carbonate is used to reduce the temperature required for the decomposition of the positive electrode active material of the lithium metal battery to obtain the target decomposition product, thereby reducing the power consumption required for recovering the positive electrode active material.

[0085] In some embodiments, the above step S201, i.e. separating the positive electrode active material of the lithium metal battery, includes:

[0086] Disassemble the lithium metal battery and separate the positive electrode;

[0087] Treating the positive electrode with an eluent to obtain a positive electrode current collector and an eluent; and

[0088] The eluate is filtered to obtain positive electrode material powder, which includes positive electrode active material.

[0089] In some embodiments, the eluent includes a solvent such as N-methylpyrrolidone (NMP).

[0090] In some embodiments, the positive electrode active material includes a nickel-cobalt-manganese lithium acid material, but is not limited thereto. In this way, the raw materials of the nickel-cobalt-manganese lithium acid material are recycled.

[0091] In some embodiments, in some embodiments, the above recycling method further includes: separating the electrolyte of the lithium metal battery, the electrolyte including an additive including chloroethylene carbonate; and / or; providing additional additives independently of the lithium metal battery. In this way, the decomposition temperature of the positive electrode active material is reduced by using at least one of the additive in the electrolyte and the additionally introduced additive. In addition, by using the additive in the electrolyte, the discarded electrolyte can be fully utilized to achieve waste treatment.

[0092] In some embodiments, in the above step S202, the positive electrode active material of the lithium metal battery is mixed with ethylene carbonate, including: mixing ethylene carbonate with the positive electrode active material in a mass ratio of 1: (5-8). In this way, ethylene carbonate and the positive electrode active material are mixed in a suitable ratio to reduce the decomposition temperature of the nickel-cobalt-manganese lithium acid material. In addition, when the additive comes from the electrolyte, the content of ethylene carbonate in the lithium metal battery is also ensured to be moderate, thereby ensuring the performance of the lithium metal battery during operation.

[0093] For example, the mass ratio of chloroethylene carbonate to the positive electrode active material may be 1:5, 1:6, 1:7 or 1:8.

[0094] In some embodiments, in the above step S203, heating the mixture until the positive electrode active material decomposes to obtain the target decomposition product includes: heating the mixture to a temperature greater than or equal to 500° C. and less than 800° C. In this way, heating decomposes the positive electrode active material while lowering its decomposition temperature.

[0095] Optionally, the mixture is heated to 500° C. to 650° C. In this way, the positive electrode active material is decomposed while the decomposition temperature of the positive electrode active material is reduced.

[0096] Optionally, the mixture is heated to 600° C. to 650° C., so that the target decomposition products are converted into multiple independent components, making it easier to subsequently process the target decomposition products.

[0097] Illustratively, the mixture can be heated to any of the following temperatures: 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C, 650°C, 660°C, 670°C, 680°C, 690°C, 700°C, 710°C, 720°C, 730°C, 740°C, 750°C, 760°C, 770°C, 780°C or 790°C.

[0098] In some embodiments, heating the mixture to 500°C or more and less than 800°C comprises: heating the mixture to 500°C or more and less than 800°C at a heating rate of 8°C / min to 12°C / min in an inert gas for 1.5h to 2.5h.

[0099] In some embodiments, the inert gas includes, but is not limited to, nitrogen.

[0100] In some embodiments, in the above step S203, the target decomposition product is selected from at least one of nickel-cobalt alloy, MnO and lithium carbonate. Exemplarily, the target decomposition product includes nickel-cobalt alloy, MnO and lithium carbonate.

[0101] In summary, in the lithium metal battery of some embodiments of the present application, the introduction of chloroethylene carbonate into the electrolyte can not only improve the stability of the electrolyte, but also improve the cycle characteristics of the lithium metal battery. Moreover, in the recycling process of the positive electrode active material of the lithium metal battery, the chloroethylene carbonate in the discarded electrolyte can reduce the temperature required for the decomposition of the positive electrode active material to obtain the target decomposition product, thereby reducing the difficulty of recycling the nickel-cobalt-manganese lithium acid material and achieving waste treatment with waste.

[0102] The technical solution of the present application is described in detail below in combination with the examples and comparative examples. The raw materials used in the following examples are all commercially available products unless otherwise specified.

[0103] Example 1

[0104] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0105] (1) The electrolyte of this embodiment is prepared from a composition, which includes N,N-methylenebisacrylamide (polymerization monomer), azobisisobutyronitrile (polymerization initiator), lithium bis(trifluoromethylsulfonyl)amide (lithium salt), ethylene glycol dimethyl ether (solvent), 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (fluoroether diluent) and ethylene carbonate (additive).

[0106] The molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.1:3.5. The sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0107] (2) The preparation method of the lithium metal battery of this embodiment includes:

[0108] According to the above ratio, lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether and ethylene chloride carbonate are mixed evenly to obtain a first mixed solution;

[0109] Add 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether to the first mixed solution according to the above ratio, and stir until completely uniform to obtain a second mixed solution;

[0110] Add 3.5%m of N,N-methylenebisacrylamide to the second mixed solution, stir evenly to obtain a third mixed solution, and then store the third mixed solution at low temperature;

[0111] Adding 0.0035% m of azobisisobutyronitrile to the third mixed solution, stirring evenly, to obtain a mixture of the composition;

[0112] The mixture of the composition is coated on both surfaces of the separator, and the separator is then disposed between the positive electrode and the negative electrode; wherein the positive electrode comprises an aluminum foil and a positive electrode active material on the aluminum foil, the negative electrode comprises a copper foil and a negative electrode material on the copper foil, the positive electrode active material comprises NCM811 (nickel cobalt manganese lithium acid material), the negative electrode material comprises lithium metal, and the separator is a polyethylene film coated with Al2O3 layers on both sides, and the thickness of the Al2O3 layer on each side is 2 μm; and

[0113] The mixture of the composition was heated at 60° C. for 2 hours to obtain a lithium metal battery including a gel polymer electrolyte.

[0114] Example 2

[0115] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0116] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.05:3.5. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0117] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0118] Example 3

[0119] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0120] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.06:3.5. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0121] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0122] Example 4

[0123] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0124] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.14:3.5. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0125] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0126] Example 5

[0127] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0128] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.08:3.5. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0129] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0130] Example 6

[0131] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0132] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.12:3.5. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0133] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0134] Example 7

[0135] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0136] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.1:2.5. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0137] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0138] Example 8

[0139] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0140] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.1:2.8. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0141] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0142] Example 9

[0143] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0144] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.1:4.0. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0145] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0146] Example 10

[0147] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0148] The composition in this embodiment is substantially similar to the composition in Example 1, except that the molar ratio of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether is 1:1.4:0.1:4.5. In addition, in this embodiment, the sum of the masses of lithium bis(trifluoromethylsulfonyl)amide, ethylene glycol dimethyl ether, ethylene carbonate chloride and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether in the above ratio is m, the mass of N,N-methylenebisacrylamide is 3.5%m, and the mass of azobisisobutyronitrile is 0.0035%m.

[0149] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0150] Embodiment 11

[0151] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium metal battery.

[0152] The composition of this embodiment is substantially similar to the composition of embodiment 1, except that the polymerizable monomer N,N-methylenebisacrylamide is replaced by "butyl acrylate".

[0153] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0154] Example 12

[0155] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium battery.

[0156] The composition of this embodiment is substantially similar to the composition of embodiment 1, except that the mass of N,N-methylenebisacrylamide is 4.5%m.

[0157] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0158] Example 13

[0159] This embodiment provides a composition for preparing an electrolyte and a method for preparing a lithium battery.

[0160] The composition of this embodiment is substantially similar to the composition of embodiment 1, except that the mass of N,N-methylenebisacrylamide is 2.5%m.

[0161] The preparation method of the lithium battery in this embodiment is the same as that in Embodiment 1, except that the composition is the composition of this embodiment.

[0162] Comparative Example 1

[0163] This comparative example provides a composition for preparing an electrolyte and a method for preparing a lithium battery.

[0164] The composition of this comparative example is substantially similar to the composition of Example 1, except that chloroethylene carbonate is not included in the composition.

[0165] The preparation method of the lithium battery in this comparative example is the same as that in Example 1, except that the composition is the composition of this comparative example.

[0166] The following performance tests were performed on the lithium metal batteries of Examples 1 to 13 and Comparative Example 1, respectively.

[0167] Cycle test: The lithium battery was charged at a constant current of 0.33C at 25°C to a voltage of 4.2 V, and then discharged at a constant current of 0.5C until the voltage reached 3V. The above charge and discharge cycles were repeated 300 times, with a time interval of 10 min between two adjacent cycles, and the capacity retention rate after 150 cycles at 25°C was obtained.

[0168] Table 1

[0169]

[0170] It can be seen from Table 1 that, compared with Comparative Example 1, the capacity retention rate of the lithium metal battery of some embodiments of the present application at 25° C. for 150 cycles is greater. Therefore, the introduction of chloroethylene carbonate into the electrolyte of the lithium metal battery can better improve the stability of the electrolyte in the lithium metal battery and enhance the cycle performance of the lithium metal battery.

[0171] Moreover, compared with Example 11, the capacity retention rate of the lithium metal batteries of Examples 1 to 10 and Examples 12 to 13 after 150 cycles at 25°C is greater, indicating that using N,N-methylenebisacrylamide as a polymerization monomer can improve the cycle performance of lithium metal batteries.

[0172] Decomposition temperature test of nickel-cobalt-manganese lithium acid materials for lithium metal batteries

[0173] The test method includes: mixing ethylene chloride carbonate and nickel cobalt manganese lithium acid material in a mass ratio of 1:7 to obtain a mixture; heating the mixture to a temperature between 400°C and 650°C at a heating rate of 10°C / min, and continuously heating for 2 hours to obtain products at different temperatures. The products at different temperatures are analyzed by X-ray diffraction spectrum test.

[0174] Combination Figure 1 It can be seen that when the temperature is 500℃ and above, the nickel-cobalt-manganese lithium acid material decomposes into nickel-cobalt alloy (Ni x Co1-x ), MnO and lithium carbonate (Li2CO3). It can be seen that chloroethylene carbonate can reduce the decomposition temperature of nickel-cobalt-manganese lithium acid materials.

[0175] The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present application. Ordinary technical personnel in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for recycling lithium metal batteries, characterized in that: The lithium metal battery comprises a positive electrode, a negative electrode and an electrolyte disposed between the positive electrode and the negative electrode, the positive electrode comprises a positive electrode active material, the negative electrode comprises a lithium metal material or a lithium alloy material, and the method comprises: Separating the positive electrode active material of the lithium metal battery, wherein the positive electrode active material comprises a nickel-cobalt-manganese lithium acid material; mixing the positive electrode active material with an additive comprising chloroethylene carbonate to obtain a mixture; and The mixture is heated until the positive electrode active material is decomposed to obtain a target decomposition product.

2. The method for recycling lithium metal batteries according to claim 1, characterized in that: The method further comprises: separating the electrolyte of the lithium metal battery, wherein the electrolyte includes the additive comprising chloroethylene carbonate; and / or; The additive is additionally provided independently of the lithium metal battery.

3. The method for recycling lithium metal batteries according to claim 1, characterized in that: The target decomposition product is selected from at least one of the following compounds: nickel-cobalt alloy, MnO and lithium carbonate.

4. The method for recycling lithium metal batteries according to claim 1, characterized in that: The method of mixing the positive electrode active material of the lithium metal battery with chloroethylene carbonate comprises: The chloroethylene carbonate and the positive electrode active material are mixed in a mass ratio of 1:(5-8).

5. The method for recycling lithium metal batteries according to claim 1, characterized in that: The step of heating the mixture until the positive electrode active material is decomposed to obtain a target decomposition product comprises: heating the mixture to a temperature greater than or equal to 500° C. and less than 800° C. to obtain the target decomposition product.

6. The method for recycling lithium metal batteries according to claim 1, characterized in that: The step of heating the mixture until the positive electrode active material is decomposed to obtain a target decomposition product comprises: The mixture is heated to 500° C. to 650° C. to obtain the target decomposition product.

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