Lithium ion battery non-aqueous electrolyte and lithium ion battery

Abstract

The invention belongs to the technical field of lithium ion batteries, and discloses a lithium ion battery non-aqueous electrolyte and a lithium ion battery. The non-aqueous electrolyte of the lithiumion battery comprises an electrolyte lithium salt, a non-aqueous organic solvent and a film-forming additive, wherein the film-forming additive comprises a compound with a structure shown in a formula (I), and the formula (I) is shown in the description. The chalcogenide additive with the structure shown in the formula (I) can form a passivation film on a negative electrode interface better, so that the cracking of the passivation film caused by the expansion of graphite or a silicon-based material in the charging and discharging process is inhibited. Meanwhile, the increase of alternating-current impedance of the battery in the cycle process can be reduced, and the battery cycle performance is improved. Besides, novel conductive lithium salt lithium difluorophosphate and lithium bis(fluorosulfonyl)imide with good film-forming characteristics are added, and compared with single use of LiPF6, multiple novel film-forming lithium salts are combined for use, so that the high and low temperature performance, the rate capability and the long cycle performance of the power battery are improved.

Description

technical field [0001] The invention relates to the field of lithium ion batteries, in particular to a lithium ion battery non-aqueous electrolyte and a lithium ion battery. Background technique [0002] Lithium-ion batteries are widely used in 3C digital products, power tools, electric vehicles and other fields due to their advantages such as high working voltage, high energy density, long life, wide working temperature range and environmental friendliness. Among them, the field of electric vehicles has higher and higher requirements on the energy density of power batteries. [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 positive electrode materials, such as NCM622 and NCM...

AI Technical Summary

Problems solved by technology

[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 positive electrode materials, such as NCM622 and NCM811, etc., and high energy density negative electrode materials, such as silicon-based negative electrodes

[0004] The increase of the charge cut-off voltage, although it can bring higher specific capacity, will make it easier for some additives or solvents to undergo oxidation reactions on the interface of the positive electrode material, resulting in gas production and capacity fading of the battery

With the increase of Ni content in the positive electrode material with high energy density, the specific capacity of the ternary material also increases accordingly, but the increase of Ni content also leads to a decrease in the stability of the ternary material, and the high-nickel ternary material from layer to layer during the cycle like structure to disordered spinel structure and rock-salt structure, resulting in an increase in interfacial impedance and a decline in reversible capacity

Negative electrode silicon-based materials such as silicon carbon have higher energy density, but they are easy to expand during charging and discharging, which leads to the cracking and reorganization of the passivation film on the negative electrode interface, and the continuous consumption of lithium ions, resulting in rapid decline in battery capacity.

[0005] At present, high content of fluorocarbonate is generally used in the industry to improve the cycle performance of the battery at room temperature, but high content of fluorocarbonate will cause the battery to generate gas and expand

The technical difficulty of high-nickel ternary materials lies in the poor high-temperature cycle performance and the problem of high-temperature storage and gas production. Conventional film-forming additives cannot well inhibit the dissolution of metal ions of ternary positive electrode materials, the destruction of the structure, and the oxidation and catalysis of the positive electrode after separation.

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