Lithium ion battery and electrolyte thereof

Abstract

The invention discloses electrolyte of a lithium ion battery. The electrolyte comprises lithium salt, an anhydrous organic solvent and an adding agent, wherein the adding agent contains fluoroethylene carbonate being 0.5-9 percent of the total mass of the electrolyte, nitrile compounds being 1-8 percent of the total mass of the electrolyte and o-benzoyl sulfonyl imide salt being 0.3-5 percent of the total mass of the electrolyte, and the o-benzoyl sulfonyl imide salt has a structural formula as shown in the specification, wherein M is alkali metal, and R1, R2, R3 and R4 are respectively hydrogen or alkyl group or alkyl halide group. In the electrolyte of the lithium ion battery, the o-benzoyl sulfonyl imide salt can overcome a destructive effect of FEC anodic film by-products on cathode; the nitrile compounds are combined with the cathode in a coordination mode, the degree of reaction of the o-benzoyl sulfonyl imide salt and a cathode material is reduced, the o-benzoyl sulfonyl imide salt forms a film at cathode to protect cathode, and the impedance on the cathode is seldom increased; the high-temperature storage performance is improved, and meanwhile the multiplying power and the cycle performance can be kept at an acceptable level.

Description

technical field [0001] The invention belongs to the field of lithium ion batteries, and more specifically, the invention relates to a lithium ion battery and an electrolyte thereof. Background technique [0002] Compared with other rechargeable batteries, lithium-ion batteries have the advantages of high energy density, high operating voltage, long cycle life and low self-discharge. At present, small-capacity lithium-ion batteries have been successfully used in mobile phones, digital cameras and notebook computers, and large-capacity and high-power lithium-ion power batteries also have good application prospects. However, when the existing lithium-ion batteries are used in a high-temperature environment, side reactions are prone to generate gas, which causes the battery to expand and increase in thickness, affecting normal use. [0003] With the continuous deepening of practical applications, the demand for lithium-ion batteries with high energy density is becoming more and...

AI Technical Summary

Problems solved by technology

This patent applies the electrolyte to coin-type batteries and steel-case batteries, and there is no problem of thickness expansion. However, for soft-pack liquid electrolyte batteries, due to the existence of DMC, the battery will produce a large amount of gas during high-temperature storage, resulting in obvious thickness expansion.

[0005] However, in high-voltage applications, due to the relative increase in the cathode potential, the reactivity of the cathode material is enhanced, and the electrolyte is prone to oxidation reactions, especially in high-temperature applications.

By using some additives, the storage performance of the battery can be improved, but the impedance of the battery is greatly increased, and its rate performance and cycle performance are deteriorated.

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