Solid-state electrolyte composition for lithium metal secondary battery and method of preparation

Abstract

The present application relates to a solid-state electrolyte composition and preparation method for lithium metal secondary batteries; the composition components and content are: 1000 parts of butanedinitrile; 0-10000 parts of boron-free lithium salt; 1-10000 parts of boron-containing lithium salt; 100-10000 parts of cyanoacrylate; 0-10000 parts of acrylate; 1-5000 parts of azobisisobutyronitrile; under an inert atmosphere, butanedinitrile, boron-free lithium salt and boron-containing lithium salt are mixed together, heated and dissolved to form a eutectic solvent, cyanoacrylate, acrylate and azobisisobutyronitrile are added to the eutectic solvent and stirred to form a mixed solution; under an inert atmosphere, the glass fiber filter membrane is soaked in the prepared solution, then heated and solidified on a heating table to obtain a solid-state electrolyte suitable for CR2032 type button cell, cylindrical battery and soft package battery; simple preparation, green and environmentally friendly, suitable for large-scale production.

Description

Technical Field

[0001] This invention relates to a solid electrolyte composition and preparation method for lithium metal secondary batteries, specifically a method for preparing a polymer solid electrolyte for lithium metal secondary batteries. Background Technology

[0002] Lithium-ion batteries are widely used in transportation, energy storage, and 3C digital products due to their high energy density, long cycle life, and low self-discharge rate. Graphite remains the primary anode material in commercially available lithium-ion batteries. However, its relatively low theoretical specific capacity (372 mAh / g) makes it difficult to continue meeting the demand for high-energy rechargeable batteries. Among the various anodes currently being studied, lithium metal anodes possess the highest theoretical specific capacity (3860 mAh / g) and the lowest electrode potential (-3.04 V relative to the standard hydrogen electrode). Compared to traditional lithium-ion batteries, lithium metal batteries using lithium metal as the anode can achieve three to five times higher energy density. The use of lithium metal as the anode is of great significance for the development of high-energy-density lithium metal batteries.

[0003] Due to the high reactivity of lithium metal, using commercially available electrolytes as the electrolyte layer easily promotes the reaction between lithium metal and the electrolyte, leading to the formation of an unstable solid-state electrolyte interface (SEI) and lithium dendrites. Furthermore, the formation of lithium dendrites can penetrate the separator, causing short circuits in the battery. Therefore, using a stable electrolyte is an effective solution. When using a polymer electrolyte instead of a commercially available liquid electrolyte, not only can the growth of lithium dendrites be effectively suppressed, but a more stable SEI layer can also be formed. To improve the energy density of lithium metal batteries, lithium nickel cobalt manganese oxide (LiMC) ternary materials are commonly used as cathode materials. However, due to the high voltage of LiMC ternary materials, the development of high-voltage resistant polymer electrolytes is urgent. Cyano and fluorine groups are typical electron-withdrawing groups; therefore, fluoropolymers and cyanopolymers typically have high oxidation resistance and thus hold promise for matching LiMC ternary cathodes.

[0004] Cyanoacrylate molecules contain two electron-withdrawing groups, namely a cyano group and an ester group, which makes them highly activated and capable of efficient polymerization. Therefore, cyanoacrylates are characterized by easy polymerization, rapid polymerization, room-temperature polymerization, and catalyst-free polymerization. It is well known that cyanoacrylate monomers can readily undergo anionic polymerization, even under the initiation of small amounts of weak bases, such as water, alcohols, and ammonia. *Applied Materials & Interfaces* reported a poly(ethyl cyanoacrylate) gel electrolyte, using poly(ethyl cyanoacrylate) as the polymer, a commercially available electrolyte as the liquid component, and water from the air as the initiator. The study also demonstrated that the addition of poly(ethyl cyanoacrylate) significantly improves the electrochemical stability window and enhances its electrochemical performance (ACS Appli. Mater. Interfaces 7 (2015) 4720-4727). Meanwhile, the *Chinese Journal of Electrochemistry* reported a method using ethyl cyanoacrylate as a binder and coating agent for the positive electrode material, demonstrating that ethyl cyanoacrylate exhibits good high-voltage stability (Electrochim. Acta 236(2017)221-227). *Materials Chemistry* reported a method using lithium metal to catalyze the polymerization of ethyl cyanoacrylate to prepare an artificial solid electrolyte protective layer, similarly demonstrating the stability of ethyl cyanoacrylate (Chem. Mater. 29(2017)4682-4689). However, all the ethyl cyanoacrylates reported above are used as gel electrolytes, which have lower safety compared to solid electrolytes. This is mainly due to the rapid polymerization of ethyl cyanoacrylate, making it difficult to prepare solid electrolytes. If the polymerization rate of ethyl cyanoacrylate can be reduced, then solid electrolytes can be prepared. *Polymer* reported that acidified methanol (a mixture of methanol and hydrochloric acid) can act as an inhibitor of ethyl cyanoacrylate. Meanwhile, it can undergo free radical polymerization with methyl methacrylate (Polymer 50 (2009) 1270-1280). However, the presence of hydrochloric acid readily reacts with lithium metal, making acidified methanol unsuitable for use in lithium batteries. Therefore, finding a mild inhibitor is urgently needed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a polymer solid electrolyte for lithium metal secondary batteries. Cyanoacrylate undergoes free radical polymerization under the action of an inhibitor and an initiator to form polycyanoacrylate. Simultaneously, under the action of an inhibitor, cyanoacrylate undergoes free radical polymerization with other monomers in an initiator to form a polycyanoacrylate copolymer. This method facilitates its application in practical production. Polycyanoacrylate and its copolymer exhibit good antioxidant properties, effectively matching high-voltage cathode materials. Furthermore, the polymer possesses good mechanical properties and adhesion, thus effectively inhibiting lithium dendrite growth and improving interfacial stability. The solid electrolyte provided by this invention utilizes widely available raw materials, has a simple and easy preparation process, is environmentally friendly, suitable for large-scale production, and can be applied to lithium metal secondary batteries.

[0006] The technical solution of the present invention is as follows:

[0007] A solid electrolyte composition for lithium metal secondary batteries; the composition and content are as follows:

[0008] The mass of succinic anion is 1000 parts;

[0009] The weight of boron-free lithium salt is 0-10000 parts;

[0010] The boron-containing lithium salt has a mass of 1-10,000 parts;

[0011] The mass of cyanoacrylate is 100-10000 parts;

[0012] The mass of acrylate is 0-10000 parts;

[0013] The mass of azobisisobutyronitrile is 1-5000 parts.

[0014] The boron-containing lithium salt monomer is lithium tetrafluoroborate, lithium difluorooxalate borate, or lithium dioxalate borate.

[0015] The boron-free lithium salt is lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, or lithium bis(fluorosulfonyl)imide.

[0016] The cyanoacrylate monomers are: methyl 2-cyanoacrylate, ethyl cyanoacrylate, octyl α-cyanoacrylate, or isopropyl 2-cyanoacrylate.

[0017] The acrylate monomers are: methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, octyl acrylate, 2-ethoxyethyl acrylate; and isopropyl methacrylate.

[0018] The acrylate monomers include all acrylate monomers containing CH2-CH2-O, -CN, -CF, or -OH groups; acrylate monomers containing CH2-CH2-O groups include poly(ethylene glycol) ethyl ether methacrylate, 2-methoxyethyl acrylate, ethyl allyl propionate, or 2-methyl-2-acrylate-2-(2-methoxyethoxy)ethyl ester; acrylate monomers containing -CN groups include 2-ethyl cyanoacrylate or 1,2-isopropylglycerol 2-cyanoacrylate; acrylate monomers containing -CF groups include 2,2,2-trifluoroethyl acrylate, hexafluorobutyl methacrylate, perfluorobutyl acrylate, or heptafluorobutyl acrylate; acrylate monomers containing -OH groups include 3-hydroxypropyl acrylate or 2,3-dihydroxypropyl acrylate.

[0019] The method for preparing a solid electrolyte for a lithium metal secondary battery using the composition of the present invention includes the following steps:

[0020] 1) Under an inert atmosphere, succinic anion, boron-free lithium salt, and boron-containing lithium salt are first mixed together and heated at 30-100℃ to dissolve and form...

[0021] 1) To form a eutectic solvent, cyanoacrylate, acrylate, and azobisisobutyronitrile are added to the eutectic solvent and stirred to form a mixed solution; 2) Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in step 1), and then cured by heating on a heating stage.

[0022] The heating temperature is 50-100℃, and the heating time is 0.5-14h.

[0023] The inert atmosphere includes nitrogen, argon, or helium.

[0024] The solid electrolyte for lithium metal secondary batteries prepared by this invention is suitable for use in CR2032 coin cells, cylindrical cells, and pouch cells.

[0025] This invention provides a solid electrolyte composition and a method for preparing a solid electrolyte for lithium metal secondary batteries. The preferred chemical composition of the polymer solid electrolyte for lithium metal secondary batteries is as follows:

[0026] (1) A eutectic solvent is formed by mixing succinic acid and boron-containing lithium salt, and cyanoacrylate is used as the polymer body after polymerization;

[0027] (2) A eutectic solvent is formed by mixing succinic acid, boron-free lithium salt and boron-containing lithium salt, and cyanoacrylate is used as the polymer body after polymerization;

[0028] (3) A eutectic solvent is formed by mixing succinic acid and boron-containing lithium salt, and a copolymer is formed by polymerizing cyanoacrylate and comonomer acrylate.

[0029] (4) A eutectic solvent is formed by mixing succinate, boron-free lithium salt and boron-containing lithium salt, and a copolymer is formed by polymerizing cyanoacrylate and copolymer monomer acrylate.

[0030] Lithium tetrafluoroborate, lithium difluorooxalate borate, and lithium bis(oxalate borate) borate are all inhibitors of anionic polymerization of cyanoacrylates, while simultaneously undergoing free radical polymerization under the action of azobisisobutyronitrile.

[0031] The beneficial technical effects of this invention are mainly reflected in:

[0032] The boron-containing lithium salts (difluorooxalatoborate, tetrafluorooxalatoborate, and lithium bis(oxalatoborate)) provided by this invention can all act as inhibitors of cyanoacrylate, effectively suppressing the anionic polymerization of cyanoacrylate. Simultaneously, they can undergo free radical polymerization in the presence of azobisisobutyronitrile (AIBN). The eutectic solvent formed by AIBN and boron-free lithium salts effectively improves the ionic conductivity of the electrolyte. However, boron-free lithium salts alone (such as lithium bis(trifluoromethanesulfonylimide)) do not inhibit the anionic polymerization of cyanoacrylate. Due to the presence of cyano groups, the polymerized product of cyanoacrylate exhibits a high electrochemical stability window. Furthermore, introducing other copolymers, such as acrylates and carbonates, can further improve the ionic conductivity and electrochemical stability window of the material. It is noteworthy that although AIBN and lithium salts form a solvent when mixed, both AIBN and lithium salts are solids at room temperature; therefore, the electrolyte prepared from the polymer and eutectic solution is generally considered a solid electrolyte, not a gel electrolyte. The solid electrolyte provided by this invention has widely available raw materials, a simple preparation process, low cost, is environmentally friendly, and suitable for large-scale production. It can be applied to lithium metal secondary batteries. Attached Figure Description

[0033] Figure 1 The NMR characterization of the poly(cyanoacrylate) polymer prepared in Example 1.

[0034] Figure 2 The NMR characterization of the poly(ethyl cyanoacrylate)-poly(methyl methacrylate) copolymer prepared in Example 17.

[0035] Figure 3 This is a SEM image of the glass fiber filter membrane in Example 17.

[0036] Figure 4 This is a SEM image of a glass fiber filter membrane filled with ethyl cyanoacrylate-methyl methacrylate copolymer, as shown in Example 17.

[0037] Figure 5 The impedance spectrum is shown for the poly(ethyl cyanoacrylate)-poly(methacrylate) copolymer prepared in Example 17.

[0038] Figure 6 The graph shows the full-cell cycle performance of the poly(ethyl cyanoacrylate)-poly(methyl methacrylate) copolymer prepared in Example 17. Detailed Implementation

[0039] The present invention will be further described in detail below with reference to specific embodiments. Experimental methods not specifically described in the embodiments are generally performed under conventional conditions and conditions described in the manual, or under conditions recommended by the manufacturer; the general equipment, materials, reagents, etc. used are commercially available unless otherwise specified.

[0040] Example 1

[0041] Under an inert atmosphere, 1000g of succinic anionyl and 100g of lithium difluorooxalate borate were mixed together and heated at 30°C to dissolve them into a eutectic solvent. 100g of ethyl cyanoacrylate and 1g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0042] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 50°C for 0.5 hours.

[0043] Specific steps for preparing a full cell:

[0044] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0045] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0046] Figure 1 The NMR characterization of the polycyanoacrylate solid electrolyte prepared in Example 1 shows that it can undergo free radical polymerization in the presence of azobisisobutyronitrile (AIBN).

[0047] Example 2

[0048] Under an inert atmosphere, 1000g of succinic anionyl nitrile and 1000g of lithium tetrafluoroborate were mixed together and heated at 50°C to dissolve them and form a eutectic solvent. 1000g of methyl 2-cyanoacrylate and 200g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0049] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 70°C for 8 hours.

[0050] Specific steps for preparing a full cell:

[0051] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0052] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0053] Example 3

[0054] Under an inert atmosphere, 1000g of succinic anion and 10000g of lithium bis(oxalato)borate were mixed together and heated at 100°C to dissolve and form a eutectic solvent. 10000g of 2-octyl α-cyanoacrylate and 5000g of azobisisobutyronitrile were added to the eutectic solvent in sequence and stirred to form a mixed solution.

[0055] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 100°C for 14 hours.

[0056] Specific steps for preparing a full cell:

[0057] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0058] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0059] Example 4

[0060] Under an inert atmosphere, 1000g of succinate, 100g of lithium bis(trifluoromethanesulfonyl)imide and 1g of lithium bis(oxalato)borate were mixed together and heated at 30°C to dissolve and form a eutectic solvent. 100g of cyanoacrylate and 1g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0061] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 50°C for 0.5 hours.

[0062] Specific steps for preparing a full cell:

[0063] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0064] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0065] Example 5

[0066] Under an inert atmosphere, 1000g of succinic anionyl nitrile, 1000g of lithium perchlorate and 1000g of lithium difluorooxalate borate were mixed together and heated at 50°C to dissolve and form a eutectic solvent. 1000g of isopropyl 2-cyanoacrylate and 100g of azobisisobutyronitrile were added to the eutectic solvent in sequence and stirred to form a mixed solution.

[0067] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 80°C for 8 hours.

[0068] Specific steps for preparing a full cell:

[0069] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0070] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0071] Example 6

[0072] Under an inert atmosphere, 1000g of succinic acid, 10000g of lithium hexafluoroarsenate and 10000g of lithium tetrafluoroborate were mixed together and heated at 100°C to dissolve and form a eutectic solvent. 10000g of 2-octyl α-cyanoacrylate and 5000g of azobisisobutyronitrile were added to the eutectic solvent in sequence and stirred to form a mixed solution.

[0073] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 100°C for 14 hours.

[0074] Specific steps for preparing a full cell:

[0075] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0076] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0077] Example 7

[0078] Under an inert atmosphere, 1000g of succinic acid and 100g of lithium tetrafluoroborate are first mixed together and heated at 30°C to dissolve and form a eutectic solvent. 100g of methyl 2-cyanoacrylate, 10g of methyl acrylate and 1g of azobisisobutyronitrile are then added to the eutectic solvent and stirred to form a mixed solution.

[0079] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 50°C for 0.5 hours.

[0080] Specific steps for preparing a full cell:

[0081] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0082] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0083] Example 8

[0084] Under an inert atmosphere, 1000g of succinic acid and 125g of lithium difluorooxalate borate were first mixed together and heated at 50°C to dissolve them and form a eutectic solvent. 100g of ethyl cyanoacrylate, 100g of ethyl acrylate and 2g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0085] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 55°C for 2 hours.

[0086] Specific steps for preparing a full cell:

[0087] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0088] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0089] Example 9

[0090] Under an inert atmosphere, 1000g of succinic acid and 167g of lithium bis(oxalato)borate were first mixed together and heated at 40°C to dissolve them and form a eutectic solvent. 200g of 2-octyl α-cyanoacrylate, 150g of propyl acrylate and 20g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0091] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then cured by heating on a heating table at a temperature of 60°C for 3.5 hours.

[0092] Specific steps for preparing a full cell:

[0093] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0094] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0095] Example 10

[0096] Under an inert atmosphere, 1000g of succinic acid and 250g of lithium bis(oxalato)borate were first mixed together and heated at 50°C to dissolve them and form a eutectic solvent. 300g of isopropyl 2-cyanoacrylate, 500g of butyl acrylate and 16g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0097] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 65°C for 5 hours.

[0098] Specific steps for preparing a full cell:

[0099] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0100] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0101] Example 11

[0102] Under an inert atmosphere, 1000g of succinic anionyl and 500g of lithium difluorooxalate borate were first mixed together and heated at 60°C to dissolve them and form a eutectic solvent. 700g of isopropyl 2-cyanoacrylate, 1000g of 2-methoxyethyl acrylate and 17g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0103] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then cured by heating on a heating table at a temperature of 70°C for 6.5 hours.

[0104] Specific steps for preparing a full cell:

[0105] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0106] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0107] Example 12

[0108] Under an inert atmosphere, 1000g of succinic anionyl and 2000g of lithium difluorooxalate borate were first mixed together and heated at 70°C to dissolve and form a eutectic solvent. 2000g of ethyl cyanoacrylate, 5000g of octyl acrylate and 100g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0109] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 75°C for 8 hours.

[0110] Specific steps for preparing a full cell:

[0111] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0112] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0113] Example 13

[0114] Under an inert atmosphere, 1000g of succinic anion and 4000g of lithium bis(oxalato)borate were first mixed together and heated at 50°C to dissolve and form a eutectic solvent. 2000g of 2-octyl α-cyanoacrylate, 8000g of 2-ethoxyethyl acrylate and 900g of azobisisobutyronitrile were added to the eutectic solvent and stirred to form a mixed solution.

[0115] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 80°C for 9.5 hours.

[0116] Specific steps for preparing a full cell:

[0117] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0118] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0119] Example 14

[0120] Under an inert atmosphere, 1000g of succinic anionyl and 6000g of lithium difluorooxalate borate were first mixed together and heated at 70°C to dissolve them and form a eutectic solvent. 8000g of ethyl cyanoacrylate, 1000g of isopropyl methacrylate and 2000g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0121] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 85°C for 11 hours.

[0122] Specific steps for preparing a full cell:

[0123] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0124] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0125] Example 15

[0126] Under an inert atmosphere, 1000g of succinic anion and 8000g of lithium tetrafluoroborate are first mixed together and heated at 50°C to dissolve and form a eutectic solvent. 9000g of ethyl cyanoacrylate, 6000g of poly(ethylene glycol) ethyl ether methacrylate and 4000g of azobisisobutyronitrile are added to the eutectic solvent and stirred to form a mixed solution.

[0127] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 90°C for 12.5 hours.

[0128] Specific steps for preparing a full cell:

[0129] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0130] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0131] Example 16

[0132] Under an inert atmosphere, 1000g of succinic anionyl and 10000g of lithium difluorooxalate borate were first mixed together and heated at 100°C to dissolve them and form a eutectic solvent. 10000g of 2-octyl α-cyanoacrylate, 10000g of 2-methoxyethyl acrylate and 5000g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0133] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 100°C for 14 hours.

[0134] Specific steps for preparing a full cell:

[0135] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0136] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0137] Example 17

[0138] Under an inert atmosphere, 1000g of succinate, 100g of lithium bis(trifluoromethanesulfonyl)imide and 1g of lithium tetrafluoroborate are first mixed together and heated at 30°C to dissolve and form a eutectic solvent. Then, 100g of ethyl cyanoacrylate, 100g of methyl methacrylate and 1g of azobisisobutyronitrile are added to the eutectic solvent and stirred to form a mixed solution.

[0139] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 50°C for 0.5 hours.

[0140] Specific steps for preparing a full cell:

[0141] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0142] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0143] Figure 2 The NMR characterization of the poly(ethyl cyanoacrylate)-poly(methyl methacrylate) copolymer prepared in Example 17 shows a high degree of reaction. Figure 3 The image shows an SEM image of the glass fiber filter membrane used in Example 17, which has obvious pores. Figure 4The image shows an SEM image of the copolymer used in Example 17 after it has been filled into a glass fiber filter membrane. It can be seen that the polymer is clearly filled into the glass fiber filter membrane. Figure 5 The impedance spectrum of the poly(ethyl cyanoacrylate)-poly(methyl methacrylate) copolymer in Example 17 is shown, with an ionic conductivity of 0.35 mS / cm at room temperature. -1 It has high ionic conductivity. Figure 6 The diagram shows the full-cell cycle of the poly(ethyl cyanoacrylate)-poly(methyl methacrylate) copolymer in Example 17. The nickel-cobalt-manganese ternary material used is the positive electrode (NCM811), which has good cycle stability at 1C.

[0144] Example 18

[0145] Under an inert atmosphere, 1000g of succinic anionyl nitrile, 125g of boron-free lithium salt and 10g of boron-containing lithium salt were first mixed together and heated at 50°C to dissolve them and form a eutectic solvent. 300g of ethyl cyanoacrylate, 100g of 2-methyl-2-acrylate-2-(2-methoxyethoxy)ethyl ester and 50g of azobisisobutyronitrile were added to the eutectic solvent and stirred to form a mixed solution.

[0146] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 55°C for 2 hours.

[0147] Specific steps for preparing a full cell:

[0148] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0149] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0150] Example 19

[0151] Under an inert atmosphere, 1000g of succinic anion, 180g of lithium perchlorate and 2g of lithium bis(oxalato)borate were first mixed together and heated at 50°C to dissolve and form a eutectic solvent. 300g of methyl 2-cyanoacrylate, 200g of 2-ethyl cyanoacrylate and 50g of azobisisobutyronitrile were added to the eutectic solvent and stirred to form a mixed solution.

[0152] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then cured by heating on a heating table at a temperature of 60°C for 3.5 hours.

[0153] Specific steps for preparing a full cell:

[0154] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0155] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0156] Example 20

[0157] Under an inert atmosphere, 1000g of succinic anionyl, 250g of lithium hexafluoroarsenate and 20g of lithium difluorooxalate borate were first mixed together and heated at 60°C to dissolve and form a eutectic solvent. 500g of methyl 2-cyanoacrylate, 200g of 1,2-isopropylidene glycerol 2-cyanoacrylate and 80g of azobisisobutyronitrile were added to the eutectic solvent and stirred to form a mixed solution.

[0158] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 65°C for 5 hours.

[0159] Specific steps for preparing a full cell:

[0160] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0161] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0162] Example 21

[0163] Under an inert atmosphere, 1000g of succinic acid, 500g of lithium hexafluorophosphate and 20g of lithium tetrafluoroborate were first mixed together and heated at 50°C to dissolve and form a eutectic solvent. 750g of ethyl cyanoacrylate, 1000g of 2,2,2-trifluoroethyl acrylate and 100g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0164] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then cured by heating on a heating table at a temperature of 70°C for 6.5 hours.

[0165] Specific steps for preparing a full cell:

[0166] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0167] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0168] Example 22

[0169] Under an inert atmosphere, 1000g of succinate, 2000g of lithium difluorosulfonylimide and 40g of lithium difluorooxalate borate were first mixed together and heated at 80°C to dissolve and form a eutectic solvent. 4000g of 2-octyl α-cyanoacrylate, 500g of hexafluorobutyl methacrylate and 1000g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0170] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 75°C for 8 hours.

[0171] Specific steps for preparing a full cell:

[0172] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0173] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0174] Example 23

[0175] Under an inert atmosphere, 1000g of succinate, 4000g of lithium bis(trifluoromethanesulfonyl)imide and 1000g of lithium tetrafluoroborate were first mixed together and heated at 50°C to dissolve and form a eutectic solvent. 2000g of 2-octyl α-cyanoacrylate, 8000g of butyl perfluoroacrylate and 500g of azobisisobutyronitrile were then added to the eutectic solvent and stirred to form a mixed solution.

[0176] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 80°C for 9.5 hours.

[0177] Specific steps for preparing a full cell:

[0178] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0179] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0180] Example 24

[0181] Under an inert atmosphere, 1000g of succinic acid, 6000g of lithium perchlorate and 200g of lithium tetrafluoroborate were first mixed together and heated at 50°C to dissolve them and form a eutectic solvent. Then, 8000g of isopropyl 2-cyanoacrylate, 1000g of heptafluorobutyl acrylate and 3000g of azobisisobutyronitrile were added to the eutectic solvent and stirred to form a mixed solution.

[0182] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 85°C for 11 hours.

[0183] Specific steps for preparing a full cell:

[0184] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0185] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0186] Example 25

[0187] Under an inert atmosphere, 1000g of succinic anionyl, 8000g of lithium perchlorate and 4000g of lithium bis(oxalato)borate were first mixed together and heated at 80°C to dissolve and form a eutectic solvent. Then, 9000g of ethyl cyanoacrylate, 9000g of 3-hydroxypropyl acrylate and 4000g of azobisisobutyronitrile were added to the eutectic solvent and stirred to form a mixed solution.

[0188] Under an inert atmosphere, the glass fiber filter membrane was immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 90°C for 12.5 hours.

[0189] Specific steps for preparing a full cell:

[0190] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0191] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0192] Example 26

[0193] Under an inert atmosphere, 1000g of succinic anionyl, 10000g of lithium hexafluorophosphate and 10000g of lithium difluorooxalate borate were first mixed together and heated at 100°C to dissolve and form a eutectic solvent. Then, 10000g of 2,3-dihydroxyacrylate, 10000g of propyl 2,3-dihydroxyacrylate and 5000g of azobisisobutyronitrile were added to the eutectic solvent and stirred to form a mixed solution.

[0194] Under an inert atmosphere, the glass fiber filter membrane is immersed in the solution prepared in the previous step, and then heated and cured on a heating table at a temperature of 100°C for 14 hours.

[0195] Specific steps for preparing a full cell:

[0196] The assembly of the full cell uses lithium metal sheets as the negative electrode, lithium nickel cobalt manganese oxide (NCM811) as the positive electrode, and a prepared polymer as the solid electrolyte to assemble a CR2032 coin cell.

[0197] The assembled coin cells were placed in a 25°C constant temperature chamber, and their electrochemical performance was tested using a charge-discharge tester with constant current. The test current density was 1C, corresponding to a theoretical capacity of 200mAh / g for NCM811, and a voltage window of 2.5-4.8V.

[0198] The technical solutions disclosed and proposed in this invention can be implemented by those skilled in the art by appropriately modifying the conditions and routes, etc. Although the methods and preparation techniques of this invention have been described through preferred embodiments, those skilled in the art can obviously modify or recombine the methods and technical routes described herein without departing from the content, spirit, and scope of this invention to achieve the final preparation technique. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included within the spirit, scope, and content of this invention.

Claims

1. A solid electrolyte for lithium metal secondary batteries, characterized in that, The raw materials and contents of the solid electrolyte are as follows: The mass of succinic anion is 1000 parts; The weight of boron-free lithium salt is 0-10000 parts; The mass of boron-containing lithium salt monomers ranges from 1 to 10,000 parts; The mass of cyanoacrylate monomer is 100-10000 parts; The mass of the acrylate monomer is 0-10000 parts; The mass of azobisisobutyronitrile is 1-5000 parts; The boron-containing lithium salt monomer is lithium tetrafluoroborate, lithium difluorooxalate borate, or lithium bis(oxalate borate); the boron-free lithium salt is lithium bis(trifluoromethanesulfonyl)imide, lithium perchlorate, lithium hexafluoroarsenate, lithium hexafluorophosphate, or lithium bis(fluorosulfonyl)imide; the cyanoacrylate monomer is methyl 2-cyanoacrylate, ethyl cyanoacrylate, octyl α-cyanoacrylate, or isopropyl 2-cyanoacrylate; the acrylate monomer is methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, methyl methacrylate, octyl acrylate, 2-ethoxyethyl acrylate, or isopropyl methacrylate; the solid electrolyte is prepared by mixing succinate with boron-containing lithium salt monomers and boron-free lithium salts to form a eutectic solvent, then adding cyanoacrylate monomers, acrylate monomers, and azobisisobutyronitrile to the eutectic solvent, stirring until uniform to obtain a mixed solution, heating and curing the mixed solution, and polymerizing to obtain the solid electrolyte.

2. A method for preparing a solid electrolyte for lithium metal secondary batteries as described in claim 1, characterized in that, Includes the following steps: 1) Under an inert atmosphere, succinic acid, boron-free lithium salt and boron-containing lithium salt monomers are first mixed together and heated at 30-100℃ to dissolve and form a eutectic solvent. Cyanoacrylate monomer, acrylate monomer and azobisisobutyronitrile are then added to the eutectic solvent and stirred to form a mixed solution. 2) Immerse the glass fiber filter membrane in the solution prepared in step 1) under an inert atmosphere, and then heat it on a heating table for curing at a temperature of 50-100℃ for 0.5-14 h.

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