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CN-122000466-A - Electrolyte containing organic nitrile additive and application thereof

CN122000466ACN 122000466 ACN122000466 ACN 122000466ACN-122000466-A

Abstract

The invention discloses electrolyte containing an organic nitrile additive and application thereof, and belongs to the field of lithium batteries. The organic nitrile electrolyte is suitable for a high-voltage system, and contains organic nitrile substances, wherein the molecular structural general formula of the nitrile substances is R-XC-CN, X is the number of hydrogen connected with carbon adjacent to a carbon-nitrogen triple bond, the number of the hydrogen is less than or equal to 1 (namely 0 or 1), and R-XC is a chain or annular organic group. The electrolyte containing the nitrile additive can obviously improve the cycle stability of the electrolyte under high voltage.

Inventors

  • LI XIANFENG
  • DU XINYU
  • QU CHAO

Assignees

  • 中国科学院大连化学物理研究所

Dates

Publication Date
20260508
Application Date
20241107

Claims (10)

  1. 1. An electrolyte containing an organic nitrile additive, characterized in that: the electrolyte contains organic nitrile substances, The molecular structural general formula of the organic nitrile substance is R-XC-CN, wherein X is the number of hydrogen connected with carbon adjacent to a carbon-nitrogen triple bond, the number of the hydrogen is 0 or 1, and R-XC is a chain or cyclic organic group.
  2. 2. The electrolyte of claim 1, wherein: The carbon adjacent to the carbon-nitrogen triple bond is carbon on a cyclic structure, and the cyclic structure is a cyclic structure within a six-membered ring; The cyclic structure has one or more than two of nitrogen atoms or carbon-carbon unsaturated bonds.
  3. 3. Electrolyte according to claim 1 or 2, characterized in that: The organic nitrile substance comprises one or more than two of trimethylacetonitrile, N-cyano-N' -methyl acetamidine, trichloroacetonitrile, dichloroacetonitrile, 2-bromopropionitrile, dibromoacetonitrile, 2-chloro-6-trifluoromethyl nicotinonitrile, 2-chloro-6-methyl-3-pyridine carbonitrile, 2-chloro-3-cyanopyridine and 3-cyano-6-trifluoromethyl pyridine.
  4. 4. Electrolyte according to claim 1 or 2, characterized in that: The organic nitrile substance is one or more than two of 2-chloro-6-trifluoromethyl nicotinonitrile, 2-chloro-6-methyl-3-pyridine carbonitrile, 2-chloro-3-cyanopyridine and 3-cyano-6-trifluoromethyl pyridine.
  5. 5. The electrolyte according to any one of claims 1 to 4, wherein: The organic nitrile material accounts for 0.1-10% of the electrolyte by weight, preferably 0.5-3%.
  6. 6. The electrolyte according to any one of claims 1 to 5, characterized in that: the electrolyte is a nonaqueous high-voltage lithium ion battery electrolyte, and also comprises a nonaqueous organic solvent and electrolyte lithium salt; the nonaqueous organic solvent comprises one or more of carbonate solvents or carboxylic ester solvents, wherein the carbonate solvents comprise one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate and methyl ethyl carbonate, and the carboxylic ester solvents comprise one or more of methyl acetate, ethyl acetate, methyl butyrate, ethyl butyrate and methyl propionate; The lithium salt comprises one or more than two of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisoxalato borate, lithium bistrifluoromethylsulfonyl imide, lithium bisoxalato borate and lithium bisfluoro sulfonyl imide, preferably lithium hexafluorophosphate; the concentration of the lithium salt in the electrolyte is 0.2mol/L to 3mol/L, preferably 0.8mol/L to 1.5mol/L.
  7. 7. The electrolyte according to claim 6, wherein the electrolyte further comprises an additive, the additive is one or more than two of ethylene sulfate, 1, 3-propane sultone, lithium difluorophosphate, ethylene carbonate, ethylene carbonate and fluoroethylene carbonate, and the weight percentage of the additive in the electrolyte is 0.1% -10%, preferably 0.5% -5%.
  8. 8. A lithium ion battery, characterized by comprising the electrolyte as claimed in any one of claims 1 to 7.
  9. 9. Use of the electrolyte according to any one of claims 1 to 7 in a lithium ion battery.
  10. 10. The method according to claim 9, wherein the operating voltage of the lithium ion battery is greater than or equal to 4.4V, preferably 4.4V-5V.

Description

Electrolyte containing organic nitrile additive and application thereof Technical Field The invention belongs to the field of lithium batteries, relates to electrolyte containing an organic nitrile additive and application thereof, and particularly relates to an organic nitrile electrolyte solvent suitable for a high-voltage system. Background Nowadays, rechargeable batteries (secondary batteries) are already ubiquitous in modern life. The lithium ion battery is widely applied to various fields such as mobile phones, unmanned aerial vehicles, electric vehicles and the like due to the characteristics of high conversion efficiency, long service life, flexible volume adjustment according to requirements and the like. The energy density and the power density of the battery are two critical performance parameters, which directly determine the application range. The high energy density means that longer endurance times can be achieved at limited masses, while the power density determines whether the battery can provide a large amount of electrical energy output in a short time. Therefore, increasing the energy density and power density of lithium ion batteries has been the goal of a broad practitioner and researcher effort. The method for improving the use voltage of the positive electrode material is an effective method, and not only can the specific capacity of the positive electrode material be improved, but also the power level of the whole battery can be improved. However, at high voltages (typically referred to as full cell voltages ∈4.4V), conventional organic electrolyte components undergo decomposition reactions such as Ethylene Carbonate (EC), propylene Carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethylmethyl carbonate (EMC), etc. Batteries using these solvents have poor cycle performance at high voltages, resulting in high voltage systems being limited in practical applications. In general, the nitrile is subjected to chemical adsorption on the surface of the cathode in preference to other solvents under high voltage to form a layer of oxidation-resistant organic compound, so that side reactions of other solvents and electrodes are prevented, meanwhile, similar to carbonate functional groups in alkyl carbonate solvents, the terminal electron-rich CN group of the nitrile is a high nucleophilic site of a coordination cation, can complex cobalt ions released by a positive electrode due to high potential, and can prevent cobalt ions from invading a negative electrode material. Therefore, the nitrile substance as an additive can effectively improve the cycle stability of the battery under high voltage. However, the stability of the anode and cathode of the electrolyte is generally opposite, and although nitrile has strong oxidation resistance, the compatibility with metallic lithium is extremely poor, and serious side reactions with materials such as metallic lithium with strong reducibility or lithium intercalation graphite (LiC 6) occur in the electrolyte, which limits their application in the electrolyte. Disclosure of Invention Aiming at the problems, the invention provides the organic nitrile additive with a special structure, and the electrolyte containing the organic nitrile additive can realize stable operation under high voltage and improve the cycle stability of the lithium ion battery under high voltage. The invention aims to provide a nitrile electrolyte additive which does not have side reaction with a high-reducibility cathode and can effectively play roles in inhibiting oxidative decomposition of electrolyte and dissolution of cathode transition metal. The electrolyte containing the additive can effectively improve the cycle performance of the lithium ion battery under high voltage. In order to achieve the above purpose, the technical scheme adopted by the invention comprises the following steps: In a first aspect, the present invention provides a class of electrolytes containing organic nitrile additives, the electrolytes containing organic nitrile species, The molecular structural general formula of the organic nitrile substance is R-XC-CN, wherein X is the number of hydrogen connected with carbon adjacent to a carbon-nitrogen triple bond, the number of the hydrogen is 0 or 1, and R-XC is a chain or cyclic organic group. Further, the carbon adjacent to the carbon-nitrogen triple bond is a carbon on a cyclic structure, the cyclic structure being a cyclic structure within a six-membered ring (i.e., a 3, 4, 5, or 6 membered ring); The cyclic structure has one or more than two of nitrogen atoms or carbon-carbon unsaturated bonds. The invention can effectively inhibit the side reaction of the nitrile substance and the battery cathode by controlling the number of the hydrocarbon bonds in the carbon adjacent to the carbon-nitrogen triple bond, and simultaneously, the carbon adjacent to the carbon-nitrogen triple bond in the additive is a characteristic structure of a cyclic s