Electrolyte for promoting film formation of graphite cathode and battery using electrolyte

Abstract

The invention provides electrolyte for promoting film formation of a graphite cathode and a battery using the electrolyte. The electrolyte comprises an electrolyte lithium salt, difluoride ethylene carbonate (DFEC), propylene carbonate (PC) and a non-aqueous organic solvent, wherein a chemical structure of the DFEC is as shown in the formula (I); the formula (I) is as shown in the specification; a lithium secondary battery comprises a positive plate, a negative plate, a diaphragm and the electrolyte for promoting film formation of the graphite cathode provided by the invention. By the DFEC, a passivation film which is stable enough can be formed on the surface of a graphite material; when the PC is utilized by the electrolyte as a high dielectric constant solvent component, graphite powder is not stripped due to the fact that propylene carbonate molecules are embedded into a layered structure of the graphite material, and the lithium ion battery does not lose efficacy in the charging and discharging cycle processes of the lithium ion battery; and the service life of the lithium battery is prolonged.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to an electrolyte that can promote the film formation of a graphite negative electrode and a battery using the electrolyte. Background technique [0002] Lithium secondary batteries have the advantages of high working voltage, high specific energy density, long cycle life, low self-discharge rate, no memory effect, and low environmental pollution. Ideal power source for power tools. At present, in the technical market, the negative electrode materials are mainly monopolized by graphite negative electrodes. The electrolyte generally adopts a mixed ring and linear carbonate system to take into account properties such as viscosity, solubility, and conductivity, and various functional additives to meet the requirements. Comprehensive performance of lithium-ion batteries. [0003] The electroreduction product of ethylene carbonate on the surface of the graphite negative electrode i...

AI Technical Summary

Problems solved by technology

[0003] The electroreduction product of ethylene carbonate on the surface of the graphite negative electrode is relatively stable and is an essential component of the electrolyte solvent system, but the high melting point of ethylene carbonate is not conducive to the low temperature performance of the electrolyte

Propylene carbonate has a wide liquid range, and the dielectric constant and donor number are comparable to ethylene carbonate. It is widely used in primary lithium batteries. However, when propylene carbonate is used with graphite materials, propylene carbonate is easy to intercalate Into the layered structure of graphite, leading to graphite pulverization and destruction

The previous research work in academia hoped that by adding film-forming additives (including vinylene carbonate, fluoroethylene carbonate, dioxalate borate, difluorooxalate borate, vinyl sulfate, etc.) The co-embedding potential of propylene carbonate is formed into a film to inhibit the co-embedding behavior of propylene carbonate. This technical solution controls the destructive effect of propylene carbonate on graphite materials to a certain extent, but the currently developed negative electrode surface formation Membrane additives have limited functionality. In the electrolyte formula combination, propylene carbonate is only suitable for a small amount of addition, and the main component of high dielectric constant solvent can only use ethylene carbonate.

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