CN-121983665-A - Inert electrolyte and preparation method and application thereof

Abstract

The invention discloses an inert electrolyte and a preparation method and application thereof, wherein the inert electrolyte comprises alkali metal salt and organic solvent, the organic solvent comprises a first solvent, the first solvent is a methylation inert solvent, and the methylation inert solvent is at least one selected from a first organic ester compound, an organic ether compound, an organic fluoro compound and an organic nitrile compound. Through methylation molecular engineering transformation of the first solvent molecules, the inert methyl groups can increase the inertia of the solvent molecules and the coordination of anions, so that the oxidative decomposition of the positive electrode and the reductive decomposition of the negative electrode under high voltage are effectively inhibited, a stable and uniform interface film is formed on the surfaces of the positive electrode and the negative electrode, and the cycle stability of the battery under high voltage is remarkably improved. Meanwhile, the electrolyte has a wide electrochemical window, high-efficiency lithium ion transmission capacity and strong wide temperature adaptability, and the battery can keep stable cycle performance in a low-temperature and 60-temperature environment of-20 ℃.

Inventors

• CHANG JIAN
• QIU YANBIN

Assignees

• 大湾区大学

Dates

Publication Date

20260505

Application Date

20260127

Claims (10)

1. 1. The inert electrolyte is characterized by comprising an alkali metal salt and an organic solvent, wherein the organic solvent comprises a first solvent, the first solvent is a methylation inert solvent, and the methylation inert solvent is at least one selected from a first organic ester compound, an organic ether compound, an organic fluoro compound and an organic nitrile compound.
2. 2. The inert electrolyte of claim 1, wherein the first organic ester compound has a structural formula selected from any one of formulas A1 to A6: ; And/or the structural formula of the organic ether compound is selected from any one of the formulas B1-B17: ; And/or the structural formula of the organic fluoro compound is selected from any one of the formulas C1-C29: ; and/or the structural formula of the organic nitrile compound is selected from any one of the formulas D1-D17: 。
3. 3. the inert electrolyte according to claim 1 or 2, wherein the alkali metal salt comprises a lithium salt, a concentration of the alkali metal salt in the inert electrolyte is 0.5 to 5mol/L, and/or a content of the first solvent in an organic solvent is not less than 10wt%.
4. 4. The inert electrolyte according to claim 1, wherein the organic solvent further comprises a second solvent selected from at least one of a second organic ester compound, a fluoroether compound, an aromatic hydrocarbon compound, and a cyclic ether compound.
5. 5. The inert electrolyte of claim 4, wherein the structural formula of the second organic ester compound is selected from any one of formulas E1 to E9: ; and/or the structural formula of the fluoroether compound is selected from any one of the formulas F1-F6: ; and/or the structural formula of the aromatic hydrocarbon compound is selected from any one of the formulas G1-G9: ; And/or the structural formula of the cyclic ether compound is selected from any one of the formulas H1-H6: 。
6. 6. An inert electrolyte according to claim 4 or 5, characterized in that the content of the second solvent in the organic solvent is not more than 70wt%.
7. 7. The inert electrolyte of claim 1, wherein the organic solvent further comprises a third component selected from at least one of vinylene carbonate, fluoroethylene carbonate, ethylene carbonate, propane sultone, trimethyl phosphate, trifluoro methyl ethylene carbonate, ethoxy (pentafluoro) cyclotriphosphazene, ethylene sulfate, methylene methane disulfonate, p-toluenesulfonyl isocyanate, dimethyl dimethoxy silane, N-dimethyl formamide, perfluoro hexanone, triethyl phosphate.
8. 8. The inert electrolyte of claim 7, wherein the third component is present in the organic solvent in an amount of no more than 30wt%.
9. 9. A method for preparing an inert electrolyte according to any one of claims 1 to 8, comprising the steps of: the inert electrolyte is prepared by dissolving an alkali metal salt in an organic solvent.
10. 10. A secondary battery comprising the inert electrolyte according to any one of claims 1 to 8.

Description

Inert electrolyte and preparation method and application thereof Technical Field The invention belongs to the technical field of batteries, and particularly relates to an inert electrolyte, a preparation method and application thereof. Background In order to meet urgent requirements of electric automobiles, large-scale energy storage, aerospace and other fields on high energy density, positive and negative electrode materials of secondary lithium-based batteries (including lithium ion batteries and lithium metal batteries) are evolving in a synergistic way, positive electrodes are developed towards high-pressure high-capacity nickel-rich layered oxides, spinel oxides, lithium-rich manganese-based layered oxides and high-pressure polyanion compounds, and negative electrodes are accelerated from traditional graphite to silicon-carbon composite materials and lithium metal negative electrodes. However, the core bottleneck of the transformation of high energy density is that the chemical and electrochemical stability of the widely used lithium hexafluorophosphate/carbonate electrolyte system cannot be matched with the requirements of the new generation of batteries under the extreme working conditions of high voltage, fast charge, high temperature, low temperature and the like. Therefore, innovative development of a novel electrolyte system capable of stably running for a long time under extreme conditions has become a key breakthrough point for promoting the commercialization application of next-generation high-performance lithium batteries. In order to break through the development bottleneck of the next generation of high energy density lithium-based batteries (covering lithium ion and lithium metal systems), the development of a high voltage electrolyte matching with the development bottleneck has become key. The core aim is to construct an electrolyte system with a wide electrochemical window, high ionic conductivity and excellent interface compatibility. The ideal electrolyte needs to keep high chemical inertness under extreme working conditions of high pressure, quick charge, high and low temperature and the like, so as to fundamentally inhibit continuous interface side reaction and gas production and ensure the performance and safety of the battery. High-voltage electrolytic liquid systems represented by organic esters, ethers, nitriles and halogenated (fluoro, chloro, bromo) compounds have been widely explored, however, the high-activity hydrogen atoms attached to carbon atoms near the ionic groups (e.g. c=o, C-O-C, c≡n, etc.) in these solvent molecules are fundamental sources of electrochemical and chemical instability of the electrolyte. These hydrogen atoms are easily oxidized at the positive electrode under high pressure, and a severe decomposition reaction is induced on the surface of the strongly reducing negative electrode, and the solid electrolyte interface film (SEI) and the positive electrode electrolyte interface film (CEI) formed in situ thereof tend to have poor mechanical strength and poor chemical stability. The sustained interfacial side reactions lead to degradation of battery cycling performance, bulging gassing, and a significant increase in thermal runaway risk. Disclosure of Invention The present invention aims to solve at least one of the technical problems in the prior art described above. Therefore, the invention provides an inert electrolyte, a preparation method and application thereof, wherein the inert electrolyte can stabilize an anode and a cathode simultaneously and improve the energy density and the cycle performance of a battery. In order to solve the technical problem, a first aspect of the present invention provides an inert electrolyte, which comprises an alkali metal salt and an organic solvent, wherein the organic solvent comprises a first solvent, the first solvent is a methylated inert solvent, and the methylated inert solvent is at least one selected from a first organic ester compound, an organic ether compound, an organic fluoro compound and an organic nitrile compound. The methylation inert solvent refers to a methylation inert solvent formed by systematically substituting a high-activity hydrogen atom connected with a carbon atom near an electron withdrawing group (such as C=O, C-O-C, C≡N, F and the like) in solvent molecules in a high-voltage electrolyte system such as organic esters, ethers, nitriles and fluoro compounds with a chemically stable inert functional group methyl (-CH 3). According to the invention, through methylation molecular engineering modification of the first solvent molecules, the coordination of inertia and anions of the solvent molecules is increased, so that the oxidation resistance and reduction resistance of an electrolyte body and an interface film derived from the electrolyte body under high voltage are improved, the oxidation-reduction stability of the electrolyte is further improved, a stable interface film is generated at the