Trimethyl borate additive contained high-voltage functional electrolyte and preparation method and application therefor

Abstract

The invention discloses a trimethyl borate additive contained high-voltage functional electrolyte and a preparation method and an application therefor. The electrolyte is obtained by adding a functional additive to a common electrolyte; the common electrolyte is formed by a cyclic carbonate solvent, a linear carbonate solvent and a conductive lithium salt; and the functional additive adopts trimethyl borate. According to the functional electrolyte, the trimethyl borate additive is taken as the high-voltage film-forming additive for the lithium ion electrolyte; the additive is relatively low in oxidization and reduction potential, so that a compact and stable SEI film layer can be formed on the surfaces of a positive electrode and a negative electrode in the first charge-discharge process; therefore, the films on the surfaces of the positive electrode and the negative electrode are optimized, the resistance between the positive electrode and the electrolyte is lowered, and the surface activity of the electrodes is restrained, so that the further contact between the electrolyte and the electrode active material is restrained consequently, and the oxidization and decomposition of the electrolyte main body solvent on the electrode surface is lowered; and the cycling performance and the rate capability of the electrolyte additive contained lithium ion battery under 3-4.5V can be improved.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, and in particular relates to a high-voltage functional electrolytic solution containing trimethyl borate additive and its preparation method and application. Background technique [0002] Lithium-ion batteries have the advantages of high energy density, high operating voltage and long cycle life. At present, the positive electrode materials of commercial lithium-ion batteries include lithium manganese oxide, lithium cobalt oxide, lithium iron phosphate, and ternary materials. The charging cut-off voltage generally does not exceed 4.2V. With the advancement of technology and the continuous development of the market, It is increasingly important and urgent to increase the energy density of lithium batteries. In addition to the improvement of existing materials and battery production processes, high-voltage (>4.5V) cathode materials are one of the more popular research directions, mainly to ...

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Problems solved by technology

[0004] However, while increasing the voltage of the positive electrode material, the electrical performance of the battery such as charge and discharge cycles is declining. On the one hand, the reason is that the structure of the ternary material is not stable enough, and on the other hand, it is the matching problem of the electrolyte.

Conventional commercial electrolytes are easy to oxidize and decompose on the surface of the positive electrode of the battery under high voltage, and the oxidative decomposition reaction of the electrolyte itself will also promote vicious reactions such as morphology changes and structural collapse of the positive electrode material.

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