Lithium ion battery electrolyte suitable for NCM811 and SiO-C material system and preparation method

Abstract

The invention discloses a lithium ion battery electrolyte suitable for a NCM811 and SiO-C material system and a preparation method. In the electrolyte of the present invention, an organic solvent composed of ethyl methyl carbonate, diethyl carbonate, and ethylene carbonate, a lithium salt composed of lithium hexafluorophosphate and lithium difluorophosphate, and an additive composed of vinylene carbonate, fluoroethylene carbonate, ethylene sulfate, and 1,3-propane sultone are compounded in a certain proportion, and cooperate to react, during a lithium ion battery cycle, on the surface of NCM811 and SiO-C and form a stable solid electrolyte protective film to prevent direct contact between the electrolyte and NCM811 and SiO, thereby reducing the side reactions between the electrode and theelectrolyte, and reducing the phase transition and volume change of the material, and further improving the cycling performance of the lithium ion battery. Experimental results show that by using theelectrolyte of the present invention, the lithium ions of the NCM811 and SiO-C material system has a capacity retention rate of more than 90% after 500 cycles of 1C/1C at room temperature, and has excellent cycle performance.

Description

technical field [0001] The invention relates to the technical field of lithium ion batteries, in particular to a lithium ion battery electrolyte suitable for NCM811 and SiO-C material systems and a preparation method. Background technique [0002] With the rapid development of electric vehicles, the market places higher requirements on the energy density and cycle performance of lithium-ion batteries. The traditional lithium cobalt dioxide (LCO) and graphite (C) lithium-ion battery system has low energy density and high cost, which can no longer meet the market demand of electric vehicles. [0003] To increase the energy density of lithium-ion batteries, the common measure is to increase the charge cut-off voltage of the battery, but the battery is under high voltage, and the positive electrode material will have certain defects, such as structural collapse, ion mixing and metal ion dissolution; the second is to use High-energy-density ternary cathode materials are combined...

AI Technical Summary

Problems solved by technology

The inventor of the present application found in the process of realizing the embodiment of the present application that the existing lithium-ion battery electrolyte has at least the following technical problems: the lithium-ion battery with NCM811 as the positive electrode and SiO-C as the negative electrode, the existing electrolyte and The compatibility of electrode materials is poor. NCM811 is a positive electrode material, which is prone to phase transition and oxygen evolution during the cycle of lithium-ion batteries. NCM811 reacts with the electrolyte and produces gas, which leads to rapid capacity decay and low cycle stability; SiO -C is the negative electrode material. A stable solid electrolyte film cannot be formed on the surface of the material. The electrolyte directly contacts and reacts with the electrode, which leads to the failure of the electrode and the rapid decline in capacity, which leads to further improvement in the cycle performance of the corresponding lithium-ion battery.

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