Solid electrolyte for high-temperature stable lithium ion battery and application of solid electrolyte in high-nickel lithium ion battery

Abstract

The invention relates to a solid electrolyte for a high-temperature stable lithium ion battery and application of the solid electrolyte in a high-nickel lithium ion battery, and the solid electrolyte is formed by polymerizing a solid electrolyte prepolymerization solution for the high-temperature stable lithium ion battery. The solid electrolyte prepolymerization liquid for the high-temperature stable lithium ion battery comprises a three-salt synergistic basic electrolyte, a polymerizable polymer monomer and an initiator, according to the composite electrolyte system, the high-temperature performance is improved through a multi-component synergistic effect, a thermally stable ion transmission network is constructed through an innovative lithium salt compounding strategy, and a wide-temperature-range stable medium is formed in cooperation with a multi-solvent system; the prepared solid electrolyte can ensure the junction integrity under a high-temperature condition, reduce the interface micro-damage generated by high-temperature circulation, inhibit the safety problems of short circuit, overcharge and the like caused by lithium dendrites and non-uniform current distribution of the battery, and realize double breakthrough of electrochemical performance and safety under a high-temperature environment.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and in particular relates to a high-temperature stable solid electrolyte for lithium-ion batteries and its application in high-nickel lithium-ion batteries. Background Technology

[0002] With the rapid development of the global new energy vehicle industry, the demand for power battery energy density is growing exponentially. 9-series high-nickel ternary cathode materials (LiNi) 0.9 Co 0.05 Mn 0.05 O2 and other similar materials have become the most promising cathode material systems due to their ultra-high specific capacity (≥220mAh / g) and relatively high operating voltage (3.6-4.4V). However, these materials face severe challenges under high-temperature conditions: firstly, their high residual alkali content on the surface accelerates electrolyte decomposition at 80℃; secondly, the release of lattice oxygen in the deep delithiation state intensifies, leading to a significant increase in the risk of thermal runaway. Traditional liquid electrolyte systems lack thermal stability at high temperatures and are flammable and volatile, completely failing to meet the high-temperature requirements of 9-series high-nickel batteries and posing serious safety hazards. Solid electrolytes have become an ideal solution due to their non-flammability and good thermal stability. Among them, in-situ solidification solid electrolyte technology, by directly injecting liquid precursors into the battery and initiating polymerization, can achieve molecular-level contact at the electrode / electrolyte interface, combining good interfacial contact performance with the safety characteristics of solid electrolytes, making it one of the most promising technologies for industrialization.

[0003] Patent CN113363415B discloses a lithium-ion battery with a high-nickel ternary composite cathode containing a solid electrolyte, wherein the cathode is coated with Li 2.5 C 0.5 B 0.5 The coating with O3 and magnesium oxide mitigates the dissolution of metal ions in the electrolyte and their deposition on the negative electrode surface. At 45°C, when the capacity reaches 80% of the initial capacity, the cycle life is as high as 1100 cycles. Although the cycle life is relatively long, it deviates significantly from the high-temperature resistance (≥80°C) required for power battery energy storage systems, lacking high-temperature cycling data above 80°C.

[0004] Patent CN115911574A discloses an in-situ cured solid-liquid hybrid electrolyte and a lithium-ion battery. By optimizing the electrolyte's raw material formulation, using PEGDA and / or PEGMEA as polymer monomers, and through a simple mixture of polymer monomers, crosslinking agents, thermal initiators, and liquid electrolyte, the electrolyte is directly injected into commercial batteries and cured in situ to obtain the lithium-ion battery, exhibiting excellent room-temperature and high-temperature cycling performance. However, the in-situ cured solid-liquid hybrid electrolyte in this patent contains up to 20% polymer monomers and 0.1% initiators. Practical experience has shown that high polymer monomer and initiator contents negatively impact battery capacity performance. Furthermore, this patent lacks high-temperature cycling data above 80°C. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a high-temperature stable solid electrolyte for lithium-ion batteries and its application in high-nickel lithium-ion batteries.

[0006] The technical solution adopted in this invention is: a method for preparing a solid electrolyte for high-temperature stable lithium-ion batteries, which is formed by polymerization of a solid electrolyte prepolymer for high-temperature stable lithium-ion batteries. The solid electrolyte prepolymer for high-temperature stable lithium-ion batteries includes a three-salt synergistic basic electrolyte, a polymerizable polymer monomer, and an initiator.

[0007] The tri-salt synergistic basic electrolyte includes any three of the following: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium bis(oxalateborate)borate (LiBOB), lithium difluorooxalateborate (LiDFOB), lithium difluorophosphate (LiPO2F2), and lithium trifluoromethanesulfonate (LiCF3SO3); the total lithium salt concentration is 1.0 mol / L to 1.25 mol / L.

[0008] It also includes a first solvent formed by a high dielectric constant solvent, a second solvent formed by a highly stable solvent, and a third solvent formed by a universal solvent.

[0009] Preferably, the volume ratio of the first solvent, the second solvent, and the third solvent is 1:1:2; the first solvent is one of propylene carbonate (PC), acetonitrile (AN), and ethylene carbonate (EC); the second solvent is one of diethyl carbonate (DEC), triethyl phosphate (TEP), and sulfolane (TMS); and the third solvent is ethyl methyl carbonate (EMC) or fluoroethyl methyl carbonate (F-EMC).

[0010] Preferably, the three-salt synergistic basic electrolyte also includes additives, including film-forming additives, low-temperature additives, and high-temperature additives.

[0011] Preferably, the mass ratio of film-forming additive, low-temperature additive, and high-temperature additive is 2:1:1; the film-forming additive is one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), and adiponitrile (ADN); the low-temperature additive is one of vinyl sulfate (DTD), ethyl acetate (EA), and vinylene carbonate (VC); and the high-temperature additive is one of propylene sulfite (PS), lithium difluorophosphate (LiPO2F2), ionic liquid (such as EMIM-TFSI), and 1,3-propenesulfonyl lactone (PST).

[0012] Preferably, the polymerizable monomer is an acrylate monomer, an ether monomer, or an ionic liquid monomer.

[0013] Preferably, when the polymerizable polymer is an acrylate monomer, specifically any two of isoprene tetraacrylate, ethylene glycol dimethacrylate, triethylene dimethacrylate, cyclohexyl acrylate, and methyl isobutylene acrylate; and the initiator is an azo-based azobisisobutyronitrile (AIBN).

[0014] When the polymerizable polymer is an ether monomer, specifically one of poly(1,3-dioxolane), bisphenol A diglycidyl ether, various crown ethers, and polyethylene glycol diglycidyl ether; the initiator is a Lewis acid lithium salt in the tri-salt synergistic basic electrolyte;

[0015] When the polymerizable polymer is an ionic liquid monomer, it is specifically one of 1-cyanopropyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide, 1-allyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide, and 1-(2,3-epoxypropyl)-3-methylimidazolium bis(trifluoromethanesulfonyl)imide.

[0016] Preferably, when the polymerizable polymer is an acrylate monomer, the prepolymerized liquid for high-temperature stable lithium-ion batteries comprises, by mass parts, 97.07-99.00% of a three-salt synergistic basic electrolyte, 0.99-2.91% of an acrylate monomer, and 0.01-0.02% of an initiator;

[0017] When the polymerizable polymer is an ether monomer, the prepolymerized liquid for solid electrolytes used in high-temperature stable lithium-ion batteries contains 75.0-87.5% by mass of a three-salt synergistic basic electrolyte and 12.5-25.0% by mass of small molecule ether monomers.

[0018] A high-temperature stable solid electrolyte for lithium-ion batteries is prepared by a method for preparing solid electrolytes for high-temperature stable lithium-ion batteries.

[0019] A high-nickel lithium-ion battery is prepared by manufacturing a battery cell comprising a high-nickel positive electrode with a Ni content of more than 90%, a silicon-carbon negative electrode with a silicon content of more than 5%, and a battery separator with a double-sided ceramic coating. A high-temperature stable lithium-ion battery solid electrolyte prepolymer is injected into the battery cell and polymerized to form a high-temperature stable lithium-ion battery solid electrolyte.

[0020] Preferably, the thermal initiation temperature is 50℃-80℃, and the thermal initiation time is 4-7h; the electrical performance testing steps of the battery are carried out at 80℃.

[0021] The advantages and positive effects of this invention are as follows: the composite electrolyte system improves high-temperature performance through the synergistic effect of multiple components; the innovative lithium salt compounding strategy constructs a thermally stable ion transport network, which, together with the multi-solvent system, forms a stable medium with a wide temperature range; the unique "viscoelasticity" of the solidified electrolyte can ensure the integrity of the structure under high-temperature conditions, reduce interfacial micro-damage caused by high-temperature cycling, and at the same time suppress the occurrence of safety problems such as short circuits and overcharging caused by lithium dendrites and uneven current distribution in the battery, thus achieving a dual breakthrough in electrochemical performance and safety under high-temperature conditions;

[0022] Tests showed that the solid electrolyte for high-temperature stable lithium-ion batteries operates stably at 80℃ and exhibits high lithium-ion conductivity (8.3 × 10⁻⁶). -4 It has a high energy density of 345 Wh / kg and a capacity retention of 90.6% after 60 cycles. Attached Figure Description

[0023] Figure 1 Linear scan curves of the electrolytes listed in Examples 1-6 and Comparative Examples 1-3;

[0024] Figure 2 Comparison chart of discharge capacity and capacity retention rate of Examples 1 and 2 and Comparative Example 1;

[0025] Figure 3 Comparison chart of discharge capacity and capacity retention rate of Examples 3 and 4 and Comparative Example 2;

[0026] Figure 4 Comparison chart of discharge capacity and capacity retention rate of Examples 5 and 6 and Comparative Example 3. Detailed Implementation

[0027] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0028] This invention relates to a high-temperature stable solid electrolyte for lithium-ion batteries and its application in high-nickel lithium-ion batteries. Addressing the poor stability and safety issues of 9-series high-nickel lithium-ion batteries under high-temperature conditions, this invention provides a high-temperature stable solid electrolyte for lithium-ion batteries. This composite electrolyte system achieves breakthroughs in high-temperature performance through the synergistic effect of multiple components. A thermally stable ion transport network is constructed through a lithium salt compounding strategy, and a wide-temperature-range stable medium is formed in conjunction with a multi-solvent system. The unique "viscoelasticity" of the solidified electrolyte ensures structural integrity under high-temperature conditions, reduces interfacial micro-damage caused by high-temperature cycling, and simultaneously suppresses safety issues such as short circuits and overcharging caused by lithium dendrites and uneven current distribution, achieving a dual breakthrough in electrochemical performance and safety under high-temperature conditions.

[0029] The solid electrolyte for high-temperature stable lithium-ion batteries is formed by polymerization of a solid electrolyte prepolymer for high-temperature stable lithium-ion batteries. The solid electrolyte prepolymer is composed of a three-salt synergistic basic electrolyte, polymerizable polymer monomers, and an initiator.

[0030] The three-salt synergistic basic electrolyte consists of three lithium salts, a first solvent, a second solvent, a universal solvent, and additives; the additives account for 4% of the solvent mass; the total lithium salt solute concentration is 1.0 mol / L-1.25 mol / L, based on the volume of the solvent.

[0031] The lithium salt in the tri-salt synergistic basic electrolyte is selected from three of the following lithium salts: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium bis(oxalateborate)borate (LiBOB), lithium difluorooxalateborate (LiDFOB), lithium difluorophosphate (LiPO2F2), and lithium trifluoromethanesulfonate (LiCF3SO3). Preferably, it is selected from three of the following: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium difluorooxalateborate (LiDFOB), and lithium difluorophosphate (LiPO2F2).

[0032] The solvent of the three-salt synergistic basic electrolyte is composed of a first solvent, a second solvent, and a universal solvent, in a volume ratio of 1:1:2. The first solvent is a high dielectric constant solvent, such as one of propylene carbonate (PC), acetonitrile (AN), or ethylene carbonate (EC); the second solvent is a highly stable solvent, such as one of diethyl carbonate (DEC), triethyl phosphate (TEP), or sulfolane (TMS); and the third solvent is a universal solvent, such as one of ethyl methyl carbonate (EMC) or fluoroethyl methyl carbonate (F-EMC).

[0033] The additives include film-forming additives, high-temperature additives, and low-temperature additives in a mass ratio of 2:1:1. The film-forming additive is one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), adiponitrile (ADN), etc.; the high-temperature additive is one of propylene sulfite (PS), lithium difluorophosphate (LiPO2F2), ionic liquids (such as EMIM-TFSI), 1,3-propenesulfonate lactone (PST), etc.; the low-temperature additive is one of vinyl sulfate (DTD), ethyl acetate (EA), vinylene carbonate (VC), etc.; preferably, the film-forming additive is fluoroethylene carbonate (FEC) or vinylene carbonate (VC); the high-temperature additive is lithium difluorophosphate (LiPO2F2) or 1,3-propenesulfonate lactone (PST); and the low-temperature additive is vinyl sulfate (DTD) or vinylene carbonate (VC). The synergistic effect of the film-forming additives and the high- and low-temperature additives promotes the formation of a gradient interface protective layer, significantly improving the structural stability of the high-nickel cathode under high temperature and high pressure.

[0034] The polymerizable monomers in the solid electrolyte prepolymer are high-temperature resistant polymerizable monomers, such as one or more combinations of acrylate monomers, ether monomers, and ionic liquid monomers.

[0035] When the polymerizable monomer is a high-temperature resistant acrylate monomer, specifically two of the following: isoprene tetraacrylate, ethylene glycol dimethacrylate, triethylene dimethacrylate, cyclohexyl acrylate, and methyl isobutylene acrylate; the two polymerizable monomers can be mixed in a mass ratio of 1:0.5-2; when the polymerizable monomer is an acrylate containing multiple C=C atoms and exhibiting high reactivity, the initiator is an azo-based azobisisobutyronitrile (AIBN); by mass fraction, the prepolymer solution includes 97.07-99.00% of a tri-salt synergistic basic electrolyte, 0.99-2.91% of the acrylate monomer, and 0.01-0.02% of the initiator.

[0036] When the polymerizable monomer is an ether monomer, specifically one of poly(1,3-dioxolane), bisphenol A diglycidyl ether, various crown ethers, and polyethylene glycol diglycidyl ether; when the polymerizable monomer is a small molecule ether monomer, the initiator is a Lewis acid lithium salt (which exists in the base solution as the main salt solute), and the Lewis acid lithium salt is lithium hexafluorophosphate (LiPF6); by mass fraction, the prepolymer solution includes 75.0-87.5% of the three-salt synergistic base electrolyte and 12.5-25.0% of the small molecule ether monomer.

[0037] The solid electrolyte prepolymer is polymerized via thermal initiation at a temperature of 50°C-80°C for 4-7 hours. Preferably, the thermal initiation temperature is 60°C-70°C for 5-6 hours. Specifically, the mixed solid electrolyte prepolymer is injected into the constructed cell structure, followed by thermal initiation to form a solid-state lithium-ion battery.

[0038] The high-nickel lithium-ion battery comprises a high-nickel cathode with a Ni content exceeding 90%, a silicon-carbon anode with a silicon content exceeding 5%, a battery separator with double-sided ceramic coating, and a high-temperature stable solid electrolyte for lithium-ion batteries. A prepolymer solution consisting of an unpolymerized three-salt synergistic basic electrolyte and a polymerizable monomer mixture is first injected into a high-nickel, high-silicon lithium-ion battery cell, and then the solid-state lithium-ion battery is prepared via thermal initiation. In some embodiments of this invention, the high-nickel lithium-ion battery consists of 29 cells with an area of ​​39.6 cm². 2 Double-sided high-nickel cathode, 30 pieces with an area of ​​42.18 cm² 2 The high-nickel lithium-ion battery was prepared by using a double-sided silicon-carbon anode and a double-sided Al2O3-coated separator; the prepared battery has a capacity of 9.8 Ah (area capacity of 4.3 mAh / cm²). 2 ).

[0039] The high-temperature stable solid electrolyte for lithium-ion batteries comprises three lithium salts. A three-salt synergistic base solution is thermally cured with acrylate monomers. The dense cross-linked network formed by the multifunctional acrylates exhibits excellent high-temperature dimensional stability and mechanical strength. Simultaneously, the unique interaction between the lithium salts and the polymer matrix constructs stable ion transport channels, effectively enhancing electrochemical stability at high temperatures, giving the three-salt synergistic electrolyte an excellent electrochemical window. In the ether-based curing system, the ring-opening polymerization of monomers such as polyDOL ethers constructs a polyether-based three-dimensional network structure that combines flexibility and thermal stability. This architecture achieves a perfect balance between dimensional stability at high temperatures and segment mobility at low temperatures by precisely controlling the cross-linking density and chain segment flexibility. This intelligent polymer network maintains excellent mechanical strength and interfacial stability at high temperatures while maintaining excellent ion conductivity at low temperatures, demonstrating outstanding wide-temperature adaptability.

[0040] The solid electrolyte for high-temperature stable lithium-ion batteries also includes three solvents. The first solvent is a high-dielectric-constant solvent such as propylene carbonate, which reduces the association energy between Li+ and anions through strong polarity, facilitating the dissolution of lithium salts and ion conduction, while also helping to form a stable flexible interface film on the silicon-based anode surface. The second solvent is a highly stable solvent such as diethyl carbonate, which has stable thermodynamic properties, can alleviate electrolyte decomposition at high temperatures, and reduce the formation of byproducts detrimental to the battery. The third solvent is a universal solvent such as ethyl methyl carbonate, which does not easily volatilize or decompose at high temperatures, and can form a dynamic electrochemical passivation layer on the high-voltage cathode surface, reducing "lattice stress cracks" in high-nickel materials, inhibiting transition metal dissolution and electrolyte oxidative decomposition, and especially reducing battery gas expansion at high temperatures. Regarding the anode, the ethyl groups in the molecule can capture "reactive oxygen free radicals" (such as ·O⁻) generated during high-temperature cycling, blocking the "chain thermal degradation" reaction of the SEI film and improving the high-temperature cycle life of the silicon-based anode. The prepared high-temperature, high-nickel lithium-ion battery has a high energy density of 345Wh / kg at 80℃ and a capacity retention of 90.6% after 60 cycles.

[0041] The present invention will now be described with reference to the accompanying drawings. Experimental methods not specifically described in terms of operation steps are performed in accordance with the corresponding product manuals. Unless otherwise specified, the instruments, reagents, and consumables used in the embodiments can be purchased from commercial companies.

[0042] Example 1

[0043] A high-temperature stable solid electrolyte prepolymer solution for lithium-ion batteries was prepared. The prepolymer solution was formulated from a three-salt synergistic base electrolyte, polymerizable polymer monomers, and an initiator.

[0044] PC, DEC, and EMC were mixed in a volume ratio of 1:1:2 to prepare a mixed solvent. 0.4 mol / L LiFSI, 0.4 mol / L LiTFSI, and 0.45 mol / L LiPF6 lithium salt were successively dissolved in the mixed solvent. Then, 4% by mass of FEC, DTD, and LiPO2F2 (mass ratio 2:1:1) additives were added to obtain a colorless, clear solution. The solution was stirred until homogeneous to obtain the three-salt synergistic basic electrolyte.

[0045] Add 1.5% by total mass of the polymerizable monomers isoprene tetraacrylate and triethylene dimethacrylate to the tri-salt synergistic basic electrolyte. The mass ratio of isoprene tetraacrylate is 1% of the tri-salt synergistic basic electrolyte, and the mass ratio of triethylene dimethacrylate is 0.5% of the tri-salt synergistic basic electrolyte. After stirring for 6 hours, add 0.015% by mass of azobisisobutyronitrile (AIBN) and stir for 1 hour to obtain a high-temperature stable solid electrolyte prepolymer solution a for lithium-ion batteries.

[0046] Example 2

[0047] A high-temperature stable solid electrolyte prepolymer for lithium-ion batteries. The prepolymer is prepared from a tri-salt synergistic basic electrolyte, polymerizable monomers, and an initiator. The preparation process of the tri-salt synergistic basic electrolyte is basically the same as in Example 1, except that 2% by mass of the polymerizable monomer poly1,3-dioxolane is added to the tri-salt synergistic basic electrolyte, and after stirring for 4 hours, the high-temperature stable solid electrolyte prepolymer for lithium-ion batteries, b, is obtained.

[0048] Example 3

[0049] A high-temperature stable solid electrolyte prepolymer for lithium-ion batteries. The prepolymer is prepared from a three-salt synergistic basic electrolyte, polymerizable polymer monomers, and an initiator. The preparation of the three-salt synergistic basic electrolyte is basically the same as in Example 1, except that PC is replaced with EC to obtain the high-temperature stable solid electrolyte prepolymer c for lithium-ion batteries.

[0050] Example 4

[0051] A high-temperature stable solid electrolyte prepolymer for lithium-ion batteries. The prepolymer is prepared from a three-salt synergistic basic electrolyte, polymerizable polymer monomers, and an initiator. The preparation of the three-salt synergistic basic electrolyte is basically the same as in Example 2, except that PC is replaced with EC to obtain the high-temperature stable solid electrolyte prepolymer d for lithium-ion batteries.

[0052] Example 5

[0053] A solid electrolyte prepolymer for high-temperature stable lithium-ion batteries. The prepolymer is formulated from a dual-salt synergistic base electrolyte, polymerizable monomers, and an initiator.

[0054] PC, DEC, and EMC were mixed in a volume ratio of 1:1:2 to prepare a mixed solvent. 0.8 mol / L LiFSI and 0.2 mol / L LiPF6 were successively dissolved in the mixed solvent, followed by the addition of 4% (2:1:1) of FEC, DTD, and PST additives to obtain a colorless, clear solution. The solution was stirred until homogeneous to obtain the dual-salt synergistic basic electrolyte.

[0055] Polymerizable monomers isoprene tetraacrylate and triethylene dimethacrylate were added to a dual-salt synergistic base electrolyte at a total mass ratio of 1.5%, wherein the mass ratio of isoprene tetraacrylate was 1% of the dual-salt synergistic base electrolyte and the mass ratio of triethylene dimethacrylate was 0.5% of the dual-salt synergistic base electrolyte; after stirring for 6 hours, azobisisobutyronitrile (AIBN) was added at a mass ratio of 0.015%, and after stirring for 1 hour, a high-temperature stable solid electrolyte prepolymer e for lithium-ion batteries was obtained.

[0056] Example 6

[0057] A high-temperature stable solid electrolyte prepolymer for lithium-ion batteries. The prepolymer is prepared from a dual-salt synergistic base electrolyte, polymerizable monomers, and an initiator. The preparation process of the dual-salt synergistic base electrolyte is basically the same as in Example 3, except that 2% by mass of the polymerizable monomer poly1,3-dioxolane is added to the prepared dual-salt synergistic base electrolyte, and after stirring for 4 hours, the high-temperature stable solid electrolyte prepolymer for lithium-ion batteries is obtained.

[0058] Comparative Example 1

[0059] The high-temperature stable lithium-ion electrolyte is the three-salt synergistic basic liquid electrolyte of Example 1.

[0060] Comparative Example 2

[0061] The high-temperature stable lithium-ion electrolyte is the three-salt synergistic basic liquid electrolyte of Example 3.

[0062] Comparative Example 3

[0063] The high-temperature stable lithium-ion electrolyte is the dual-salt synergistic basic liquid electrolyte of Example 5.

[0064] Example 7: Fabrication of a high-temperature, high-nickel lithium-ion solid-state battery

[0065] The preparation process for high-nickel lithium-ion battery cells is consistent and is as follows:

[0066] Positive electrode: The positive electrode active material layer is LiNi 0.95 Co 0.03 Mn 0.02 O2 ternary material. The positive electrode active material layer, conductive agent acetylene black, and binder polyvinylidene fluoride-hexafluoropropylene are mixed at a solid content ratio of 96.2:2.6:1.2 by mass. An appropriate amount of NMP is added to dilute to a certain viscosity. After stirring evenly, the mixture is uniformly coated on both sides of a 9μm aluminum foil. After drying and rolling, a surface density of 24 mg / cm³ is obtained. 2 The positive electrode sheet was then slit and punched to obtain an area of ​​39.6 cm². 2 The positive electrode sheet.

[0067] Negative electrode layer: The negative electrode active material layer is made of silicon-carbon material. The negative electrode active material layer, graphite, conductive agent single-arm carbon nanotubes, and aqueous carboxymethyl cellulose are mixed at a solid content ratio of 32.5:60.5:2.5:4.5. An appropriate amount of deionized water is added to dilute to a certain viscosity, and after stirring evenly, the mixture is uniformly coated on both sides of a 6μm aluminum foil. After drying and rolling, an areal density of 8 mg / cm³ is obtained. 2 The negative electrode sheet was then slit and punched to obtain an area of ​​42.18 cm². 2 The negative electrode sheet.

[0068] The lithium-ion battery cells with 29 positive and 30 negative cells are obtained by stacking the cells using a semi-automatic stacking machine. After welding the tabs and sealing with an aluminum shell, a 10.1Ah high-nickel lithium-ion dry cell is obtained.

[0069] The high-temperature stable lithium-ion battery prepolymer solution prepared in Examples 1-6 was added to the above-mentioned dry cell at an injection rate of 1.9 g / Ah, and then vacuum-sealed. The cell was then immersed at 25°C for 36 h to obtain a 10.1 Ah high-nickel lithium-ion battery. The 10.1 Ah high-nickel lithium-ion battery was then placed in a 60°C forced-air oven without clamps for 5-6 h of thermal initiation. After being removed and cooled to room temperature, a high-temperature high-nickel lithium-ion solid-state battery was obtained. The prepared high-temperature high-nickel lithium-ion solid-state battery was placed in a fixture with a pre-tightening force of 1.0 N / m for subsequent formation, capacity determination, and cycle testing.

[0070] The high-temperature stable lithium-ion battery liquid electrolyte prepolymer prepared in Comparative Examples 1-3 was added to the above-mentioned dry cell at an injection rate of 1.9 g / Ah. After vacuum sealing, the cell was immersed at 40°C for 24 h to obtain a 10.1 Ah high-nickel lithium-ion liquid battery. The prepared high-nickel lithium-ion liquid battery was placed in a fixture with a pre-tightening force of 1.0 N / m for subsequent formation, volume determination, and cycle testing.

[0071] The prepared batteries were tested, and the electrochemical stability window test results and conductivity test results at different temperatures for the solid electrolyte and liquid electrolyte of the high-temperature stable lithium-ion batteries prepared in Examples 1-6 and Comparative Examples 1-3 are shown in Table 1.

[0072] Table 1

[0073]

[0074] Table 2 shows the specific energy values ​​of the high-temperature, high-nickel lithium-ion batteries prepared in Examples 1-6 and Comparative Examples 1-3 at constant capacity at 80°C.

[0075] Table 2

[0076]

[0077] Table 3 shows the cycle performance (voltage range 2.7-4.0V) of the high-temperature, high-nickel lithium-ion batteries prepared in Examples 1-6 and Comparative Examples 1-3 at 80°C.

[0078] Table 3

[0079]

[0080] According to Tables 2 and 3, and Figure 2 , 3A comparison of specific energy and capacity retention revealed that the specific energy of high-temperature, high-nickel lithium-ion solid-state batteries all exceeded 340Wh / kg. High-temperature, high-nickel lithium-ion solid-state batteries prepared from poly(1,3-dioxolane) monomers exhibited superior cycle performance at 80℃ compared to a mixture of isoprene tetraacrylate and triethylene glycol dimethacrylate monomers. Among these, the poly(1,3-dioxolane) solid electrolyte lithium-ion battery, composed of LiFSI, LiTFSi, LiPF6, PC, DEC, EMC, FEC, DTD, and LiPO2F2, demonstrated the best cycle performance, retaining over 92% of its capacity after 51 cycles and 90.6% after 60 cycles. Compared to dual-salt synergistic electrolytes, LiFSI and LiTFSi became dominant in the tri-salt system, significantly reducing the overall electrolyte system's dependence on the thermally unstable LiPF6. Introducing the more antioxidant LiTFSi into the LiFSI (with an oxidation resistance of approximately 4.5V) effectively increased the electrolyte's "voltage limit." This can more effectively suppress the oxidative decomposition of the electrolyte on the surface of the high-voltage positive electrode, reduce the dissolution of transition metals, and form a more stable positive electrode electrolyte interface film (CEI), thereby improving the cycle life under high voltage.

[0081] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method for preparing a solid electrolyte for high-temperature stable lithium-ion batteries, characterized in that: It is formed by polymerization of a high-temperature stable lithium-ion battery solid electrolyte prepolymer, which includes a three-salt synergistic basic electrolyte, polymerizable polymer monomers and initiators; The tri-salt synergistic basic electrolyte includes any three of the following: lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium bis(oxalateborate)borate (LiBOB), lithium difluorooxalateborate (LiDFOB), lithium difluorophosphate (LiPO2F2), and lithium trifluoromethanesulfonate (LiCF3SO3); the total lithium salt concentration is 1.0 mol / L to 1.25 mol / L. It also includes a first solvent formed by a high dielectric constant solvent, a second solvent formed by a highly stable solvent, and a third solvent formed by a universal solvent.

2. The method for preparing a high-temperature stable solid electrolyte for lithium-ion batteries according to claim 1, characterized in that: The volume ratio of the first solvent, the second solvent, and the third solvent is 1:1:2; the first solvent is one of propylene carbonate (PC), acetonitrile (AN), and ethylene carbonate (EC); the second solvent is one of diethyl carbonate (DEC), triethyl phosphate (TEP), and sulfolane (TMS); and the third solvent is ethyl methyl carbonate (EMC) or fluoroethyl methyl carbonate (F-EMC).

3. The method for preparing a high-temperature stable solid electrolyte for lithium-ion batteries according to claim 1, characterized in that: The basic electrolyte with three salts also includes additives, including film-forming additives, low-temperature additives, and high-temperature additives.

4. The method for preparing a high-temperature stable solid electrolyte for lithium-ion batteries according to claim 3, characterized in that: The mass ratio of film-forming additive, low-temperature additive, and high-temperature additive is 2:1:1; the film-forming additive is one of fluoroethylene carbonate (FEC), vinylene carbonate (VC), and adiponitrile (ADN); the low-temperature additive is one of vinyl sulfate (DTD), ethyl acetate (EA), and vinylene carbonate (VC); the high-temperature additive is one of propylene sulfite (PS), lithium difluorophosphate (LiPO2F2), ionic liquid (such as EMIM-TFSI), and 1,3-propenesulfonyl lactone (PST).

5. The method for preparing a high-temperature stable solid electrolyte for lithium-ion batteries according to any one of claims 1-4, characterized in that: Polymerizable monomers include acrylate monomers, ether monomers, or ionic liquid monomers.

6. The method for preparing a high-temperature stable solid electrolyte for lithium-ion batteries according to claim 5, characterized in that: When the polymerizable polymer is an acrylate monomer, specifically any two of isoprene tetraacrylate, ethylene glycol dimethacrylate, triethylene dimethacrylate, cyclohexyl acrylate, and methyl isobutylene acrylate; and the initiator is an azo-based azobisisobutyronitrile (AIBN). When the polymerizable polymer is an ether monomer, specifically one of poly(1,3-dioxolane), bisphenol A diglycidyl ether, and polyethylene glycol diglycidyl ether; the initiator is a Lewis acid lithium salt in the tri-salt synergistic basic electrolyte.

7. The method for preparing a high-temperature stable solid electrolyte for lithium-ion batteries according to claim 6, characterized in that: When the polymerizable polymer is an acrylate monomer, the prepolymerized liquid for solid electrolyte of high-temperature stable lithium-ion battery includes 97.07-99.00% of the three-salt synergistic basic electrolyte, 0.99-2.91% of the acrylate monomer, and 0.01-0.02% of the initiator by mass. When the polymerizable polymer is an ether monomer, the prepolymerized liquid for solid electrolytes used in high-temperature stable lithium-ion batteries contains 75.0-87.5% by mass of a three-salt synergistic basic electrolyte and 12.5-25.0% by mass of small molecule ether monomers.

8. The high-temperature stable solid electrolyte for lithium-ion batteries prepared by the method for preparing high-temperature stable solid electrolyte for lithium-ion batteries according to any one of claims 1-7.

9. A high-nickel lithium-ion battery, characterized in that: A battery cell comprising a high-nickel cathode with a Ni content greater than 90%, a silicon-carbon anode with a silicon content greater than 5%, and a battery separator with a double-sided ceramic coating is prepared. A high-temperature stable lithium-ion battery solid electrolyte prepolymer is injected into the battery cell and polymerized to form the high-temperature stable lithium-ion battery solid electrolyte as described in claim 8.

10. The high-nickel lithium-ion battery according to claim 9, characterized in that: The thermal initiation temperature is 50℃-80℃, and the thermal initiation time is 4-7h; the electrical performance test of the battery is carried out at 80℃.

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