Electrolyte, positive electrode, lithium ion battery and vehicle

Abstract

The invention discloses an electrolyte, a positive electrode, a lithium ion battery and a vehicle. The electrolyte comprises a lithium salt, an organic solvent and an additive, the additive comprises a first additive, the first additive is an alkyl thiomorpholine ring compound, the structural formula of the alkyl thiomorpholine ring compound is as follows: R is selected from at least one of C1-C10 alkyl, C2-C10 alkenyl, C2-C10 alkynyl, C3-C10 cycloalkyl, C6-C30 aryl, C3-C10 thiazinyl and C4-C10 thienyl; hydrogen atoms in C1-C10 alkyl groups, C2-C10 alkenyl groups, C2-C10 alkynyl groups, C3-C10 cycloalkyl groups, C6-C30 aryl groups, C3-C10 thiazinyl groups and C4-C10 thienyl groups can be partially or completely substituted by substituent groups. The additive of the electrolyte has more substituent groups and complexing sites, is high in reduction potential, is favorable for forming an interface protection film on a negative electrode, and meanwhile, complexes metal ions dissolved out from a positive electrode, so that the cycling stability of the battery under high voltage is improved.

Description

Technical field [0001] The present invention relates generally to the field of new energy, specifically to an electrolyte, a cathode, a lithium-ion battery and a vehicle. Background [0002] Lithium-ion batteries have the advantages of high working voltage, large specific capacity, long cycle life, no memory effect and environmental friendliness, and have been widely used in electronic products such as communication tools and notebook computers. With the application of lithium-ion batteries in electric vehicles and hybrid vehicles, people have put forward higher requirements for the energy density of lithium-ion batteries, especially the mass energy density, and high nickel ternary cathode materials are widely used as cathode materials due to their higher energy density and specific capacity (especially when the charging cut-off voltage reaches 4.5V). [0003] However, the existing electrolyte system composed of carbonate and lithium hexafluorophosphate is unstable at high voltag...

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Problems solved by technology

[0003] However, the existing electrolyte system composed of carbonate and lithium hexafluorophosphate is unstable at high voltage (4.5V), prone to oxidative decomposition, and the generated by-products will also accelerate the metal dissolution and structural collapse of the positive electrode material, and increase the surface of the positive electrode. Impedance, and high-nickel materials will undergo oxygen evolution at high potentials, which accelerates the oxidation and decomposition of carbonate electrolytes to produce gas, resulting in rapid consumption and deterioration of the electrolyte, and eventually leads to battery expansion, poor battery interface stability, and impedance increase and decrease in battery performance

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