Lithium-ion secondary battery and its electrolyte

Abstract

The invention provides a lithium ion secondary battery and electrolyte thereof. The electrolyte of the lithium ion secondary battery comprises lithium salt, a non-aqueous organic solvent and an additive, wherein the additive contains at least one of compounds with the structure as shown in a general formula (1), R1 and R2 in the general formula (1) are respectively and independently expressed as a general formula (2), and R3 is hydrogen or alkyl groups of C1-C3; R4 and R5 in the general formula (2) are respectively and independently expressed as hydrogen or alkyl groups of C1-C3, and n is a natural number in the range from 0-2; the additive can also contain vinylene carbonate (VC). The lithium ion secondary battery comprises a positive plate, a negative plate, an isolating membrane for isolating the adjacent positive plate and negative plate, and the electrolyte. The lithium ion secondary battery provided by the invention has good first coulombic efficiency, cycle performance and good low-temperature charging property.

Description

technical field [0001] The invention relates to the field of batteries, in particular to a lithium-ion secondary battery and its electrolyte. Background technique [0002] Lithium-ion secondary batteries have the advantages of high working voltage, long life and fast charging speed, and are gradually expanding to the fields of electric bicycles and electric vehicles. With the continuous deepening of the marketization of lithium-ion secondary batteries, people's expectations for lithium-ion secondary batteries are getting higher and higher. The current commercial lithium-ion secondary batteries have been difficult to meet the needs of practical applications. [0003] Studies have shown that there are some irregular structures on the surface of graphite materials, which catalyze the irreversible decomposition of the electrolyte, resulting in the degradation of the electrochemical performance of graphite materials and seriously affecting the performance of lithium-ion secondar...

AI Technical Summary

Problems solved by technology

However, when these compounds are applied to the electrolyte of lithium-ion secondary batteries, there are still the following disadvantages: the SEI film formed at the graphite negative electrode interface has poor stability, and as the number of cycles increases, the electrode interface resistance gradually increases. The resistance polarization of the electrode becomes more and more serious, which leads to a rapid decrease in the reversible capacity of the electrode

However, the addition of VC will form a dense SEI film on the surface of the negative electrode, which has a large impedance and will deteriorate the charging performance of lithium-ion secondary batteries at low temperatures.

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