High-voltage lithium ion battery capacity compensation type electrolyte with slow release effect

Abstract

The invention discloses a high-voltage lithium ion battery capacity compensation type electrolyte with a slow release effect, and relates to the technical field of electrolyte preparation. The electrolyte comprises a lithium salt, an organic solvent, a cosolvent and a lithium supplement agent, the cosolvent is a compound containing a nitrogen-containing heteroaromatic ring, and the nitrogen-containing heteroaromatic ring is modified with a boron group and / or a strong electron withdrawing group. According to the cosolvent, the solubility of the lithium supplement agent in an electrolyte solvent can be remarkably improved, meanwhile, the cosolvent and the lithium supplement agent can jointly participate in CEI forming an organic-inorganic hybrid component, and higher Young modulus, ion diffusion rate and interface stability are achieved, so that the interface side reaction between the electrolyte and an electrode can be effectively inhibited, and the service life of the electrolyte is prolonged. And the interface impedance is reduced, so that the capacity attenuation caused by the fracture of the electrode material structure is slowed down, and the cycling stability of the battery under high voltage is comprehensively improved. According to the invention, the problems of poor capacity compensation performance and poor interface stability under high voltage of the existing electrolyte are solved.

Description

Technical Field

[0001] This invention relates to the field of electrolyte preparation technology, and specifically to a high-voltage lithium-ion battery capacity compensation electrolyte with a slow-release effect. Background Technology

[0002] The ongoing energy transition and the rapid development of the electric vehicle industry have placed higher demands on power batteries, urgently requiring the development of new lithium-ion battery systems with high energy density, long cycle life, and low cost. Lithium-rich manganese (LRM) cathodes, as emerging high-energy-density cathodes, have attracted widespread attention due to their extremely high operating voltage (4.6-4.8 V) and reversible specific capacity (250-300 mAh / g). Matching LRM cathodes with graphite or silicon-based anodes holds promise for breaking through the energy density limitations of existing battery systems. However, in practical applications, LRM cathodes suffer from severe interfacial side reactions at high voltages, leading to the continuous decomposition of electrolyte solvents (such as EC and EMC), forming a thick and unstable cathode-electrolyte interphase (CEI) film. This further results in problems such as active lithium loss, manganese dissolution, and oxygen release during cycling, affecting the battery's energy density and long-term stability. To address the aforementioned issues, electrolyte film-forming additives preferentially oxidize on the positive electrode side to form a stable CEI, which can improve the high-voltage cycling stability of LRMs. However, this cannot compensate for the loss of active lithium during cycling. Therefore, further combining this with lithium replenishment technology involves introducing high-capacity lithium replenishment additives to pre-replenish a certain amount of active lithium in the battery system to compensate for lithium consumption during the first cycle and subsequent cycles. Among various lithium replenishment methods, electrolyte lithium replenishment has the advantages of simple process, high safety, and compatibility with existing production equipment. However, the solubility of lithium replenishment additives in electrolytes is low, which cannot provide sufficient capacity compensation during long-term battery cycling. Therefore, there is an urgent need for a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect, combining the advantages of film formation and lithium replenishment to achieve long-term stable cycling of high-energy-density batteries at high voltages. Summary of the Invention

[0003] To address the aforementioned technical problems, the present invention aims to provide a high-voltage lithium-ion battery capacity compensation electrolyte with a slow-release effect, thereby solving the problems of poor capacity compensation performance and poor interface stability under high voltage in existing electrolytes.

[0004] The technical solution of this invention to solve the above-mentioned technical problems is as follows: A high-voltage lithium-ion battery capacity-compensating electrolyte with a sustained-release effect is provided, comprising a lithium salt, an organic solvent, a co-solvent, and a lithium replenishing agent; the co-solvent is a nitrogen-containing heteroaromatic ring compound, wherein the nitrogen-containing heteroaromatic ring is modified with a boron group and / or a strong electron-withdrawing group; the lithium replenishing agent is LiP, Li3P, LiP5, LiP7, Li3P7, or LiP... 10 At least one of Li3N, LiN3, Li2S and Li2Se.

[0005] The beneficial effects of this invention are as follows: the cosolvent of this invention can significantly improve the solubility of the lithium replenishing agent in the electrolyte solvent, thereby enhancing its capacity compensation effect on the battery; at the same time, the cosolvent and lithium replenishing agent of this invention can jointly participate in the formation of an organic-inorganic hybrid positive electrode electrolyte interphase (CEI) film, which has higher Young's modulus, ion diffusion rate and interfacial stability. Therefore, it can effectively suppress interfacial side reactions between the electrolyte and the electrode, reduce interfacial impedance, thereby slowing down the capacity decay caused by the cracking of the electrode material structure, and comprehensively improving the cycle stability of the battery under high voltage.

[0006] Based on the above technical solution, the present invention can be further improved as follows: Furthermore, the aza-aryl ring is pyridine, pyrimidine, pyridazine, pyrazine, or quinoline; the boron group is a borate ester group, borate group, or alkylborane group; and the strong electron-withdrawing group is a cyano group, a halogen atom, a trifluoromethyl group, a nitro group, or a carboxyl group.

[0007] Furthermore, when the nitrogen-containing heteroaromatic ring of the cosolvent is modified with a boron group and a strong electron-withdrawing group, the cosolvent is 2-cyano-3-fluoropyridine-5-boronic acid pinacol ester, 2-cyano-3-fluoropyridine-4-boronic acid pinacol ester, 4-cyano-3-fluoropyridine-2-boronic acid pinacol ester, 2-cyano-3-fluoropyridine-5-boronic acid, 2-cyano-3-fluoropyridine-4-boronic acid, 4-cyano-3-fluoropyridine-2-boronic acid, 2-cyanopyridine-5-boronic acid pinacol ester, 2 -Cyanopyridine-4-boronic acid pinacol ester, 3-cyanopyridine-4-boronic acid pinacol ester, 4-cyanopyridine-3-boronic acid pinacol ester, 2-cyanopyridine-5-boronic acid, 2-cyanopyridine-4-boronic acid, 3-cyanopyridine-4-boronic acid, 4-cyanopyridine-3-boronic acid, 2-cyanopyrimidine-5-boronic acid pinacol ester, 2-cyanopyrimidine-4-boronic acid pinacol ester, 3-cyanopyrimidine-4-boronic acid pinacol ester, 4-cyanopyrimidine-3-boronic acid pinacol Esters, 2-cyanopyrimidine-5-boronic acid, 2-cyanopyrimidine-4-boronic acid, 3-cyanopyrimidine-4-boronic acid, 4-cyanopyrimidine-3-boronic acid, 2-fluoropyridine-5-boronic acid pinacol ester, 2-fluoropyridine-4-boronic acid pinacol ester, 3-fluoropyridine-4-boronic acid pinacol ester, 4-fluoropyridine-3-boronic acid pinacol ester, 2-trifluoromethyl-3-fluoropyrimidine-5-boronic acid pinacol ester and their structural isomers, 2-trifluoromethylpyrimidine-5-boronic acid and its structure The isomers, 2-fluoro-3-carboxypyridine-5-boronic acid and its structural isomers, pinacol ester of 2,6-difluoropyridine-3-boronic acid and its structural isomers, 2-fluoro-5-chloropyridine-4-boronic acid and its structural isomers, pinacol ester of 2-nitro-5-pyridineboronic acid and its structural isomers, 2-cyano-3-fluoropyridine-5-difluoroborane and its structural isomers, and 2-cyano-3-fluoropyridine-5-bis(trifluoromethyl)borane and its structural isomers.

[0008] Furthermore, when the nitrogen-containing heteroaromatic ring of the cosolvent is modified with a boron group, the cosolvent is 2-pyridine-boronic acid pinacol ester, 3-pyridine-boronic acid pinacol ester, 4-pyridine-boronic acid pinacol ester, 2-pyrimidine-boronic acid pinacol ester, 3-pyrimidine-boronic acid pinacol ester, 4-pyrimidine-boronic acid pinacol ester, 2-pyridine-boric acid, 3-pyridine-boric acid, 4-pyridine-boric acid, pyrimidine-2-boric acid, (pyrimidine-3-boric acid, pyrimidine-4-boric acid, pyrimidine-5-boric acid) At least one of the following: 2-pyrazine-boronic acid, 2-pyrazine-boronic acid and its structural isomers, 2-pyrazine-boronic acid and its structural isomers, 2-pyrazine-boronic acid and its structural isomers, 2-quinoline-boronic acid and its structural isomers, 2-quinoline-boronic acid and its structural isomers, 2-pyridine-difluoroborane and its structural isomers, and 2-pyridine-bis(trifluoromethyl)borane and its structural isomers. Furthermore, when the nitrogen-containing heteroaromatic ring of the cosolvent is modified with a strong electron-withdrawing group, the cosolvent can be 2-cyano-3-fluoropyridine, 2-cyano-5-fluoropyridine, 3-cyano-2-fluoropyridine, 4-cyano-2-fluoropyridine, 4-cyano-3-fluoropyridine, 2-cyano-3-fluoropyrimidine, 2-cyano-5-fluoropyrimidine, 3-cyano-2-fluoropyrimidine, 4-cyano-2-fluoropyrimidine, 4-cyano-3-fluoropyrimidine, 2-cyano-5-trifluoromethylpyridine and its structural isomers, 2-cyano-5-nitropyridine and its structural isomers, 2-cyano-3-bromopyridine and its structural isomers, 5-bromo-2-cyano-3-nitropyridine and its structural isomers. At least one of the following: 6-chloro-2-cyano-3-nitropyridine and its structural isomers; 2,4-dichloro-5-fluoropyrimidine and its structural isomers; 6-nitro-2-carboxylic acid pyridine and its structural isomers; 3-trifluoromethylpyridine and its structural isomers; 5-(trifluoromethyl)pyridine and its structural isomers; 5-(trifluoromethyl)pyrimidine and its structural isomers; 2-nitropyridine and its structural isomers; 2-carboxylic acid pyrimidine and its structural isomers; 3-cyanopyridazine and its structural isomers; 2-chloro-3-cyanopyridazine and its structural isomers; 2-cyanopyridazine and its structural isomers; and 3-cyanoquinoline and its structural isomers.

[0009] Furthermore, the co-solvent is at least one selected from 2-cyano-3-fluoropyridine-5-boronic acid pinacol ester (FTDP), 2-cyano-3-fluoropyridine (CFP), 2-pyridineboronic acid pinacol ester (PBP), 2-cyanopyridine-5-boronic acid (CPB), 2-trifluoromethylpyridine-5-boronic acid (TMPB), 2-cyano-5-nitropyridine (CNP), 2-cyano-5-fluoropyrimidine (FPMB), and 2-pyridazine-boronic acid (PDB).

[0010] Furthermore, the mass fraction of the co-solvent in the electrolyte is 0.1-10%. Furthermore, the mass fraction of the co-solvent in the electrolyte is 0.5%.

[0011] Furthermore, the mass fraction of the co-solvent in the electrolyte is 5%.

[0012] Furthermore, the mass fraction of the lithium supplement in the electrolyte is 0.01-15%.

[0013] Furthermore, the mass fraction of the lithium replenishing agent in the electrolyte is 0.5%.

[0014] Furthermore, the mass fraction of the lithium replenishing agent in the electrolyte is 1%.

[0015] Furthermore, the lithium salt is at least one selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium trifluoromethanesulfonate, lithium fluoroborate, lithium hexafluoroaluminate, lithium hexafluoroarsenate, lithium perchlorate, lithium bis(oxalateborate), and lithium difluorophosphate.

[0016] Furthermore, the concentration of lithium salt in the electrolyte is 0.8-5 mol / L.

[0017] Furthermore, the concentration of lithium salt in the electrolyte is 1 mol / L.

[0018] Furthermore, the organic solvent is at least one of ester, ether, sulfone, and nitrile.

[0019] Furthermore, the ester is at least one selected from dimethyl carbonate, diethyl carbonate, 1,4-butylpropyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate, ethyl acetate, vinylene carbonate, and fluoroethylene carbonate.

[0020] Furthermore, the ester is at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), 1,4-butyropropyl carbonate (GBL), ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), ethyl acetate (EA), vinylene carbonate (VC), and fluoroethylene carbonate (FEC).

[0021] Furthermore, the ether is at least one of ethylene glycol dimethyl ether, tetrahydrofuran, and 1,3-dioxolane.

[0022] Furthermore, the ether is at least one of ethylene glycol dimethyl ether (DME), tetrahydrofuran (THF), and 1,3-dioxolane (DOL).

[0023] Furthermore, the sulfone is at least one selected from sulfolane, dimethyl sulfoxide, thionyl chloride, and diphenyl sulfoxide.

[0024] Further, the sulfone is at least one of sulfolane (SL), dimethyl sulfoxide (DMSO), thionyl chloride, and diphenyl sulfoxide.

[0025] Further, the nitrile is at least one of succinonitrile, adiponitrile, 1,3,6-hexanetricarbonitrile, and glutaronitrile.

[0026] Further, the nitrile is at least one of succinonitrile (SN), adiponitrile (ADN), 1,3,6-hexanetricarbonitrile (HTCN), and glutaronitrile.

[0027] Further, the organic solvent is DME and THF.

[0028] Further, the organic solvent is EC and DEC.

[0029] Further, the organic solvent is EC and EMC.

[0030] The present invention also provides a method for preparing the high-voltage lithium-ion battery capacity compensation type electrolyte with a slow-release effect, including the following steps: under an inert gas environment, mixing a lithium salt and an organic solvent to obtain a mixed solution, adding a co-solvent and a lithium supplement agent to a part of the mixed solution, stirring, then adding the remaining mixed solution, and stirring again to prepare a high-voltage lithium-ion battery capacity compensation type electrolyte with a slow-release effect. The present invention also provides an application of the high-voltage lithium-ion battery capacity compensation type electrolyte with a slow-release effect in the preparation of lithium-ion batteries.

[0031] The present invention also provides a lithium-ion battery as described above, including a positive electrode, a negative electrode, a separator, and the high-voltage lithium-ion battery capacity compensation type electrolyte with a slow-release effect according to any one of claims 1-7. Further, the positive electrode is at least one of LiCoO2, LiNiO2, LiMn2O4, LiNi 0 .5 Mn 1.5 O4, LiNi a Co b Mn 1-a-b O2, and LiNi c Co d Al 1-c-d O2; where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1; the negative electrode is graphite, hard carbon, silicon, silicon alloy, phosphorus-based negative electrode, lithium, or Li4Ti5O 12 .

[0032] Further, the silicon alloy is an alloy of silicon and germanium, tin, or iron.

[0033] The present invention has the following beneficial effects: 1. Achieve efficient dissolution of the lithium supplement agent based on the molecular design of the co-solvent Although the lithium supplements of this invention (such as Li3P, Li3N, etc.) are rich in active lithium, their solubility in conventional electrolytes is extremely low, limiting their functionality. Therefore, this invention introduces a uniquely structured co-solvent (such as pinacol 2-cyano-3-fluoropyridine-5-boronic acid), which can significantly improve the solubility and reactivity of the lithium supplement in the electrolyte. Its mechanism of action (see...) Figure 1 The key lies in the fact that the pyridine ring and borate ester groups directly bonded to strong electron-withdrawing groups (such as -CN, -F) in the cosolvent molecule possess highly electron-deficient characteristics. This electron-deficient center can react with electron-rich anions of lithium-replenishing agents (such as P...). 3- This process involves highly efficient nucleophilic reactions; simultaneously, the strong electron-withdrawing groups coordinate with lithium ions on the surface of the lithium replenisher. This multi-site synergistic mechanism effectively disrupts the crystal or aggregated structure of the lithium replenisher, thereby greatly improving its solubility in the electrolyte.

[0034] 2. Composite additives construct a highly efficient "slow-release lithium library" with intelligent response. The lithium supplement of the present invention, after activation by a co-solvent, has an active component (such as Li) x P, P x n- Li + Through chemical bonding or strong intermolecular interactions, it tightly binds to the organic framework or network structure derived from the cosolvent. This unique structure significantly increases the steric hindrance at the contact between the lithium replenishing agent's active component and the electrode, and raises the electrochemical energy barrier for its oxidative decomposition, thus transforming it into a "reserve lithium source" mainly stored near the interface, rather than being rapidly depleted in the first cycle. During long-term battery cycling, this "lithium reservoir" can respond to changes in electrode volume, interface reconstruction, or changes in external operating conditions (such as increased voltage and temperature), continuously exposing new active sites and stimulating their oxidation reactions, thereby achieving durable and intelligent capacity compensation and effectively compensating for the continuous loss of active lithium during cycling.

[0035] 3. Composite additives synergistically construct a stable electrode interface with high ionic conductivity. In this invention, the co-solvent and lithium replenishing agent play synergistic and complementary roles in interface construction. The co-solvent, as a source of the organic molecular framework, preferentially oxidizes at the positive electrode and dominates the construction of a flexible, dense, and elastic organic CEI film. Meanwhile, the lithium replenishing agent and its interaction products with the co-solvent participate in the formation of an SEI film rich in high ionic conductivity components such as Li3P and Li3N at the negative electrode. The two mutually promote each other, constructing a hybrid interface structure in situ at both the positive and negative electrodes that is uniformly composited and synergistically enhanced by organic and inorganic phases. This structure combines the flexibility and density of organic films with the high ionic conductivity and mechanical strength of inorganic components, effectively adapting to volume changes during cycling, inhibiting continuous electrolyte decomposition, and reducing interfacial impedance, thereby comprehensively improving the high-voltage stability and long-cycle performance of the battery.

[0036] 4. Achieving comprehensive improvement in electrolyte performance through simplified formulation. This invention integrates three functions—solubilization and activation, capacity compensation, and interfacial synergistic regulation—into a streamlined composite additive system through ingenious molecular design. The co-solvent simultaneously plays multiple roles as a solubilizer, activator, and film-forming agent, while the lithium replenisher serves as the core active lithium source, directly providing capacity compensation and contributing key inorganic components. This formulation not only solves the problem of low lithium replenisher solubility but also achieves synergistic optimization of electrolyte solubility characteristics, electrode interface properties, battery capacity compensation, and electrochemical stability through the synergistic effect of the two components. The process is simple and highly compatible with existing battery manufacturing processes, providing an efficient and reliable solution for developing high-performance lithium-ion batteries with long cycle life. Attached Figure Description

[0037] Figure 1 A schematic diagram illustrating the mechanism of action of the cosolvent and lithium supplementer; Figure 2 This is a comparison chart of the performance of the electrolytes in Examples 1-2 and Comparative Example 1; Figure 3 This is a performance comparison chart of the electrolytes in Examples 5-6 and Comparative Example 3; Figure 4 This is a comparison chart of the discharge curve performance of the electrolytes in Examples 7-8 and Comparative Example 2 after the first activation cycle. Figure 5 This is a comparison chart of the transition metal element content on the graphite negative electrode side after electrolyte cycling in Example 5 and Comparative Example 3. Detailed Implementation

[0038] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0039] Example 1: A high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC and EMC in a volume ratio of 3:7), a co-solvent (FTDP, 0.5 wt%), and a lithium replenishing agent (Li3P, 0.5 wt%).

[0040] A method for preparing a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes the following steps: mixing lithium salt and organic solvent in an inert gas environment to obtain a mixed solution; adding a co-solvent and a lithium supplement agent to a portion of the mixed solution and stirring; then adding the remaining mixed solution and stirring again to obtain a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect.

[0041] Example 2: A high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes a lithium salt (LiFSI, 1 mol / L), an organic solvent (DME and THF in a volume ratio of 1:1), a co-solvent (CFP, 1 wt%), and a lithium replenishing agent (Li3P7, 1 wt%).

[0042] A method for preparing a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes the following steps: mixing lithium salt and organic solvent in an inert gas environment to obtain a mixed solution; adding a co-solvent and a lithium supplement agent to a portion of the mixed solution and stirring; then adding the remaining mixed solution and stirring again to obtain a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect.

[0043] Example 3: A high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes a lithium salt (LiPF6, 0.8 mol / L), an organic solvent (EC, DEC and DMC in a volume ratio of 1:1:1), a co-solvent (PBP, 0.1 wt%), and a lithium replenishing agent (LiP, 0.01 wt%).

[0044] A method for preparing a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes the following steps: mixing lithium salt and organic solvent in an inert gas environment to obtain a mixed solution; adding a co-solvent and a lithium supplement agent to a portion of the mixed solution and stirring; then adding the remaining mixed solution and stirring again to obtain a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect.

[0045] Example 4: A high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes a lithium salt (LiDFOB, 5 mol / L), an organic solvent (EC and EMC in a volume ratio of 3:7), a co-solvent (CPB, 10 wt%), and a lithium replenishing agent (Li2S, 15 wt%).

[0046] A method for preparing a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes the following steps: mixing lithium salt and organic solvent in an inert gas environment to obtain a mixed solution; adding a co-solvent and a lithium supplement agent to a portion of the mixed solution and stirring; then adding the remaining mixed solution and stirring again to obtain a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect.

[0047] Example 5: A high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC and EMC in a volume ratio of 3:7), a co-solvent (TMPB, 1 wt%), and a lithium replenishing agent (Li3N, 2 wt%).

[0048] A method for preparing a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes the following steps: mixing lithium salt and organic solvent in an inert gas environment to obtain a mixed solution; adding a co-solvent and a lithium supplement agent to a portion of the mixed solution and stirring; then adding the remaining mixed solution and stirring again to obtain a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect.

[0049] Example 6: A high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC and EMC in a volume ratio of 3:7), a co-solvent (CNP, 2 wt%), and a lithium replenishing agent (Li3P, 1 wt%).

[0050] A method for preparing a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes the following steps: mixing lithium salt and organic solvent in an inert gas environment to obtain a mixed solution; adding a co-solvent and a lithium supplement agent to a portion of the mixed solution and stirring; then adding the remaining mixed solution and stirring again to obtain a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect.

[0051] Example 7: A high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC, EMC and DMC in a volume ratio of 1:1:1), a co-solvent (FPMB, 3 wt%), and a lithium replenishing agent (LiN3, 6 wt%).

[0052] A method for preparing a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes the following steps: mixing lithium salt and organic solvent in an inert gas environment to obtain a mixed solution; adding a co-solvent and a lithium supplement agent to a portion of the mixed solution and stirring; then adding the remaining mixed solution and stirring again to obtain a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect.

[0053] Example 8: A capacity-compensating electrolyte for high-voltage lithium-ion batteries with a sustained-release effect comprises a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC and EMC volume ratio of 3:7), a co-solvent (PDB, 2 wt%), and a lithium replenishing agent (LiP). 10 (5wt%).

[0054] A method for preparing a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect includes the following steps: mixing lithium salt and organic solvent in an inert gas environment to obtain a mixed solution; adding a co-solvent and a lithium supplement agent to a portion of the mixed solution and stirring; then adding the remaining mixed solution and stirring again to obtain a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect.

[0055] Comparative Example 1: A high-voltage lithium-ion battery electrolyte with a sustained-release effect comprises a lithium salt (LiPF6, 1 mol / L) and an organic solvent (EC and EMC in a volume ratio of 3:7).

[0056] A method for preparing a high-voltage lithium-ion battery electrolyte with a sustained-release effect includes the following steps: Same as Example 1.

[0057] Comparative Example 2: A high-voltage lithium-ion battery electrolyte with a sustained-release effect includes a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC and EMC in a volume ratio of 3:7) and a co-solvent (FTDP, 0.5 wt%).

[0058] A method for preparing a high-voltage lithium-ion battery electrolyte with a sustained-release effect includes the following steps: Same as Example 1.

[0059] Comparative Example 3: A high-voltage lithium-ion battery electrolyte with a slow-release effect includes a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC and EMC volume ratio of 3:7), and a lithium replenishing agent (Li3N, 2 wt%).

[0060] A method for preparing a high-voltage lithium-ion battery electrolyte with a sustained-release effect includes the following steps: Same as Example 1.

[0061] Comparative Example 4: A high-voltage lithium-ion battery electrolyte with a slow-release effect includes a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC and EMC in a volume ratio of 3:7), a co-solvent (DMC, 2 wt%), and a lithium replenishing agent (Li3P, 1 wt%).

[0062] A method for preparing a high-voltage lithium-ion battery electrolyte with a sustained-release effect includes the following steps: Same as Example 1.

[0063] Comparative Example 5: A high-voltage lithium-ion battery electrolyte with a slow-release effect includes a lithium salt (LiPF6, 1 mol / L), an organic solvent (EC and EMC in a volume ratio of 3:7), a co-solvent (CNP, 11 wt%), and a lithium replenishing agent (Li3P, 1 wt%).

[0064] A method for preparing a high-voltage lithium-ion battery electrolyte with a sustained-release effect includes the following steps: Same as Example 1.

[0065] Test case I. The electrolytes prepared in Examples 1-8 and Comparative Examples 1-5 were subjected to performance testing. The specific testing methods were as follows: The electrolytes prepared in Examples 1-4 and Comparative Example 1 were tested in LRM|| lithium metal batteries under the following conditions: initial activation at 0.1 C, cycling at 0.33 C, and voltage of 2-4.45 V.

[0066] The electrolytes prepared in Examples 5-8 and Comparative Examples 2-5 were tested in LRM||graphite full cells under the following conditions: initial activation at 0.1 C, followed by 1 C cycling. Specifically, the voltage range was 2-4.6 V for cycles 1-39, the high cutoff voltage was increased to 4.7 V for cycle 40, and the voltage returned to 2-4.6 V for continued cycling in cycle 41.

[0067] The electrolytes prepared in Example 5 and Comparative Example 3 were tested in LRM|| graphite full cells, and the transition metal element content on the graphite anode side was tested after cycling.

[0068] See results Figure 2-5 See Table 1-2.

[0069] Table 1 Electrolyte performance of Examples 1-4 and Comparative Example 1

[0070] Table 2 Electrolyte performance of Examples 5-8 and Comparative Examples 2-5

[0071] Depend on Figure 2 As shown in Table 1, in the LRM|| lithium metal battery system, the first-cycle discharge specific capacity of Examples 1-4 is close to or exceeds 205 mAh / g, while that of Comparative Example 1 (without the two additives) is only 202.6 mAh / g. With increasing cycle number, the discharge specific capacity of Examples 1-4 gradually increases, while that of Comparative Example 1 gradually decreases. This indicates that the electrolyte combination can slowly release active lithium during battery cycling, thereby significantly reducing lithium loss during cycling. Therefore, the capacity retention rate of Examples 1-4 after 100 cycles is close to or exceeds 99.5%, significantly better than Comparative Example 1 (96.0%), demonstrating the capacity compensation and interface stabilization effects of the composite components.

[0072] Depend on Figure 3-5 As shown in Table 2, in the LRM||graphite full cell, after increasing the cutoff voltage at the 40th cycle, the discharge capacity of Examples 5 and 6 significantly increased, and after restoring the original voltage, they stabilized at a new capacity plateau for cycling, proving that their "slow-release lithium library" can be effectively activated and release capacity under high voltage. In contrast, the capacity of Comparative Example 3 did not show a leap, proving that there is no beneficial lithium source in its system that can be activated by high voltage. In addition, Examples 5 and 6 exhibited excellent cycle stability, with retention rates of 87.5% and 84.0% at the 100th cycle, respectively, which were much higher than those of Comparative Example 3 (73.3%). The retention rate of Comparative Example 5 (with 11wt% excess co-solvent added) was only 69.4%, indicating that the co-solvent concentration exceeding the critical point degrades battery performance.

[0073] The results show that the two additives have a synergistic effect. Cosolvents with multiple functional groups (such as FTDP and CFP) are typically used as film-forming aids, forming a stable electrolytic interfacial film (CEI) on the positive electrode surface under high voltage, thus inhibiting the continuous decomposition of the electrolyte. Lithium replenishing agents (such as Li3P, Li3N, and Li2S) are lithium-rich compounds that replenish lithium, continuously compensating for the loss of active lithium caused by side reactions and interfacial reconstruction during long battery cycles, thereby improving cycle retention.

[0074] Comparative Example 4 shows that replacing the co-solvent with ordinary DMC (a conventional solvent) results in the loss of the synergistic effect and a significant decrease in retention. Comparative Example 5 shows that more co-solvent is not necessarily better. Excessively high concentrations may lead to increased interfacial resistance or the formation of an excessively thick passivation layer on the electrode surface, hindering lithium-ion migration.

[0075] from Figure 5It can be seen that the composite component can effectively suppress the dissolution of transition metals on the positive electrode side during cycling, especially significantly reducing manganese dissolution. This indicates that the stable interface film formed by the composite component effectively protects the structure of the positive electrode material and is beneficial to the long-term cycling stability of the battery.

[0076] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect, characterized in that, Including lithium salts, organic solvents, cosolvents, and lithium supplements; The cosolvent is a nitrogen-containing heteroaromatic ring compound, wherein the nitrogen-containing heteroaromatic ring is modified with a boron group and / or a strong electron-withdrawing group; The lithium supplement is LiP, Li3P, LiP5, LiP7, Li3P7, LiP 10 At least one of Li3N, LiN3, Li2S and Li2Se.

2. The high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect according to claim 1, characterized in that, The aza-aryl ring is pyridine, pyrimidine, pyridazine, pyrazine, or quinoline; The boron group is a borate ester group, a borate group, or an alkylborane group; The strong electron-withdrawing group is a cyano, halogen atom, trifluoromethyl, nitro or carboxyl group.

3. The high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect according to claim 1, characterized in that, When the nitrogen-containing heteroaromatic ring of the cosolvent is modified with a boron group and a strong electron-withdrawing group, the cosolvent is 2-cyano-3-fluoropyridine-5-boronic acid pinacol ester, 2-cyano-3-fluoropyridine-4-boronic acid pinacol ester, 4-cyano-3-fluoropyridine-2-boronic acid pinacol ester, 2-cyano-3-fluoropyridine-5-boronic acid, 2-cyano-3-fluoropyridine-4-boronic acid, 4-cyano-3-fluoropyridine-2-boronic acid, 2-cyanopyridine-5-boronic acid pinacol ester, 2- Pinacol ester of cyanopyridine-4-boronic acid, Pinacol ester of 3-cyanopyridine-4-boronic acid, Pinacol ester of 4-cyanopyridine-3-boronic acid, Pinacol ester of 2-cyanopyridine-5-boronic acid, Pinacol ester of 2-cyanopyridine-4-boronic acid, Pinacol ester of 3-cyanopyridine-4-boronic acid, Pinacol ester of 4-cyanopyridine-3-boronic acid, Pinacol ester of 2-cyanopyrimidine-5-boronic acid, Pinacol ester of 2-cyanopyrimidine-4-boronic acid, Pinacol ester of 3-cyanopyrimidine-4-boronic acid, Pinacol ester of 4-cyanopyrimidine-3-boronic acid 2-Cyanopyrimidine-5-boronic acid, 2-Cyanopyrimidine-4-boronic acid, 3-Cyanopyrimidine-4-boronic acid, 4-Cyanopyrimidine-3-boronic acid, 2-Fluoropyridine-5-boronic acid pinacol ester, 2-Fluoropyridine-4-boronic acid pinacol ester, 3-Fluoropyridine-4-boronic acid pinacol ester, 4-Fluoropyridine-3-boronic acid pinacol ester, 2-Trifluoromethyl-3-fluoropyrimidine-5-boronic acid pinacol ester and their structural isomers, 2-Trifluoromethylpyrimidine-5-boronic acid and its structure The isomers, 2-fluoro-3-carboxypyridine-5-boronic acid and its structural isomers, pinacol ester of 2,6-difluoropyridine-3-boronic acid and its structural isomers, 2-fluoro-5-chloropyridine-4-boronic acid and its structural isomers, pinacol ester of 2-nitro-5-pyridineboronic acid and its structural isomers, 2-cyano-3-fluoropyridine-5-difluoroborane and its structural isomers, and 2-cyano-3-fluoropyridine-5-bis(trifluoromethyl)borane and its structural isomers.

4. The high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect according to claim 1, characterized in that, When the nitrogen-containing heteroaromatic ring of the cosolvent is modified with a boron group, the cosolvent is 2-pyridine-boronic acid pinacol ester, 3-pyridine-boronic acid pinacol ester, 4-pyridine-boronic acid pinacol ester, 2-pyrimidine-boronic acid pinacol ester, 3-pyrimidine-boronic acid pinacol ester, 4-pyrimidine-boronic acid pinacol ester, 2-pyridine-boric acid, 3-pyridine-boric acid, 4-pyridine-boric acid, pyrimidine-2-boric acid, pyrimidine-3-boric acid, pyrimidine-4-boric acid, pyrimidine-5- At least one of the following: boric acid, 2-pyridazine-boronic acid pinacol ester and its structural isomers, 2-pyridazine-boronic acid and its structural isomers, 2-pyrazine-boronic acid pinacol ester and its structural isomers, 2-quinoline-boronic acid pinacol ester and its structural isomers, 2-quinoline-boronic acid and its structural isomers, 2-pyridine-difluoroborane and its structural isomers, and 2-pyridine-bis(trifluoromethyl)borane and its structural isomers.

5. The high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect according to claim 1, characterized in that, When the nitrogen-containing heteroaromatic ring of the cosolvent is modified with a strong electron-withdrawing group, the cosolvent is 2-cyano-3-fluoropyridine, 2-cyano-5-fluoropyridine, 3-cyano-2-fluoropyridine, 4-cyano-2-fluoropyridine, 4-cyano-3-fluoropyridine, 2-cyano-3-fluoropyrimidine, 2-cyano-5-fluoropyrimidine, 3-cyano-2-fluoropyrimidine, 4-cyano-2-fluoropyrimidine, 4-cyano-3-fluoropyrimidine, 2-cyano-5-trifluoromethylpyridine and its structural isomers, 2-cyano-5-nitropyridine and its structural isomers, 2-cyano-3-bromopyridine and its structural isomers, 5-bromo-2-cyano-3-nitropyridine and its structural isomers, 6 At least one of the following: 2-chloro-2-cyano-3-nitropyridine and its structural isomers; 2,4-dichloro-5-fluoropyrimidine and its structural isomers; 6-nitro-2-carboxylic acid pyridine and its structural isomers; 3-trifluoromethylpyridine and its structural isomers; 5-(trifluoromethyl)pyridine and its structural isomers; 5-(trifluoromethyl)pyrimidine and its structural isomers; 2-nitropyridine and its structural isomers; 2-carboxylic acid pyrimidine and its structural isomers; 3-cyanopyridazine and its structural isomers; 2-chloro-3-cyanopyridazine and its structural isomers; 2-cyanopyridazine and its structural isomers; and 3-cyanoquinoline and its structural isomers.

6. The high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect according to claim 1, characterized in that, The mass fraction of the co-solvent in the electrolyte is 0.1-10%.

7. The high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect according to claim 1, characterized in that, The lithium replenishing agent has a mass fraction of 0.01-15% in the electrolyte.

8. The method for preparing the high-voltage lithium-ion battery capacity-compensating electrolyte with a sustained-release effect according to any one of claims 1-7, characterized in that, Includes the following steps: In an inert gas environment, lithium salt and organic solvent are mixed to obtain a mixed solution. A co-solvent and lithium replenishing agent are added to a portion of the mixed solution and stirred. Then, the remaining mixed solution is added and stirred again to obtain a high-voltage lithium-ion battery capacity compensation electrolyte with a slow-release effect.

9. The application of the high-voltage lithium-ion battery capacity-compensating electrolyte with sustained-release effect as described in any one of claims 1-7 in the preparation of lithium-ion batteries.

10. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and a high-voltage lithium-ion battery capacity-compensating electrolyte with a slow-release effect as described in any one of claims 1-7.

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