A kind of electrolytic solution, preparation method and lithium-ion battery containing same

Abstract

The present invention relates to an electrolytic solution, a preparation method and a lithium ion battery containing the same. The electrolytic solution is a non-aqueous lithium ion battery electrolytic solution, which contains a mixed solvent, a fluorine-containing additive and a lithium salt; the solvent includes a first A solvent and a second solvent; the relative strength of the solvation ability of the first solvent to lithium ions is not less than 1.8; the contact angle of the second solvent to the diaphragm is less than 90°. The electrolytic solution provided by the application improves the mechanical properties of the SEI film on the one hand, so that it can adapt to the volume expansion of the silicon negative electrode material, and has a certain elastic deformation, so that the SEI film is less likely to rupture and has a certain shrinkage; on the other hand On the one hand, the wettability between the electrolyte solution and the diaphragm is improved by cooperating with the second solvent, so as to avoid mass transfer obstruction and reduce impedance; the two aspects cooperate with each other to improve the electrical performance of the battery.

Description

technical field [0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to an electrolyte solution of a non-aqueous lithium ion battery, a preparation method and a lithium ion battery containing the same. Background technique [0002] The development of lithium-ion batteries with high energy density, long cycle life and low cost has important practical value. Lithium-ion batteries using graphite anode materials occupy a pivotal market position in the current consumer electronics and electric vehicles. With the deepening of these applications and the upgrading of social needs, people have put forward higher requirements on all aspects of lithium-ion batteries, especially energy density. [0003] It is proposed to use silicon-based anode materials with higher theoretical specific capacity instead of traditional graphite anode materials (the theoretical capacity of silicon at room temperature is 3579mAh / g, while graphite is 372mA...

AI Technical Summary

Problems solved by technology

On the one hand, the volume expansion of silicon-based anode materials leads to poor contact between the anode active material and the current collector; on the other hand, it also causes the solid electrolyte layer (SEI) on the surface of the anode to crack and re-grow during the process of alloying and expansion. , resulting in a decrease in Coulombic efficiency, which seriously reduces the cycle performance of silicon-based negative electrodes

[0004] For lithium-ion batteries with silicon negative electrodes, most of the main electrolyte solvents used are from graphite-based negative electrode carbonate electrolytes. For example, the SEI formed by ethylene carbonate (EC)-based electrolytes is completely unable to adapt to silicon-based negative electrodes. The volume expands and the performance decays rapidly

In the prior art, the addition of fluorine-containing substances such as fluoroethylene carbonate as additives to carbonate electrolyte can improve the compatibility of traditional ester electrolytes with silicon negative electrodes to a certain extent, but it still cannot meet the needs of practical use.

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