Electrolyte solution and preparation method for improving performance of solid electrolyte membrane on graphite electrode surface

Abstract

The invention provides an electrolyte capable of improving performance of a solid electrolyte membrane on the surface of a graphite electrode and a preparation method of the electrolyte. The electrolyte comprises an organic solvent and a solute salt; the organic solvent is a cyclic carbonic acid solvent; the solute salt is a lithium salt or mixed by a lithium salt and an ionic liquid; and the lithium salt accounts for 50-100 molar% of the whole solute. The invention also relates to an application of the electrolyte in preparation of a graphite-lithium half battery. The electrolyte disclosed inthe invention is stable in performance and simple in preparation; and when the electrolyte is applied to the battery, a more compact, stable and thinner SEI membrane can be formed on the surface of the graphite electrode, so that the capacity retention ratio of the battery can be improved, and cycle performance of the battery is improved.

Description

technical field [0001] The invention belongs to the technical field of lithium-ion battery electrolytes, and in particular relates to the preparation and application of electrolytes for improving the performance of solid electrolyte membranes on the graphite electrodes of lithium-ion batteries. Background technique [0002] Graphite is a commonly used negative electrode active material in commercial lithium-ion batteries. However, the interlayer lithium intercalation characteristics of graphite make it encounter many problems in the application process. One of the most important problems is the solvated lithium in the electrolyte. Ions intercalate into the graphite layer and decompose between the graphite layers to generate gas, which causes the destruction of the graphite layered structure, reduces the initial efficiency of the battery, and rapidly reduces the cycle capacity. Therefore, the formation of an interface film between graphite and electrolyte is of great importanc...

AI Technical Summary

Problems solved by technology

[0002] Graphite is a commonly used negative electrode active material in commercial lithium-ion batteries. However, the interlayer lithium intercalation characteristics of graphite make it encounter many problems in the application process. One of the most important problems is the solvated lithium in the electrolyte. Ions intercalate into the graphite layer and decompose between the graphite layers to generate gas, which causes the destruction of the graphite layered structure, reduces the initial efficiency of the battery, and rapidly reduces the cycle capacity. Therefore, the formation of an interface film between graphite and electrolyte is of great importance to improve battery performance. special meaning

[0003] So far, the addition of film-forming additives such as VC and FEC to the electrolyte of lithium-ion batteries has been widely studied. Due to the presence of polymer components in the reduction product of VC, the formed solid electrolyte film is denser. However, using too much VC will affect the cycle efficiency of the battery and increase the self-discharge rate of the battery

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