Lithium ion battery

Abstract

The invention relates to the field of electrochemistry, and particularly relates to a lithium ion battery. One aspect of the invention provides a lithium ion battery. The lithium ion battery comprisesa positive pole piece, a negative pole piece, an isolation membrane and an electrolyte, and is characterized in that the negative pole piece comprises a negative active material layer containing a negative active material, the electrolyte comprises an electrolyte lithium salt, the electrolyte lithium salt comprises a first lithium salt, the first lithium salt is selected from fluorine-containingsulfimide lithium salt, and the first lithium salt and the negative pole piece meet a relational expression (1). According to the invention, the fluorine-containing sulfimide lithium salt is used as the electrolyte of the first lithium salt, so that too fast impedance increase or too large concentration polarization of the battery can be effectively inhibited, the high-temperature advantage and the high-conductivity advantage of the fluorine-containing sulfimide lithium salt can be fully exerted, the formed battery is relatively low in floating charge physical resistance increase rate, the safety problems such as lithium precipitation in the middle and later periods of circulation are avoided, and finally the excellent properties of high safety performance, long cycle life and good high-temperature storage are achieved.

Description

technical field [0001] The invention relates to the field of electrochemistry, in particular to a lithium ion battery. Background technique [0002] Since the mass production of lithium-ion batteries at the end of the 20th century, they have been widely used in the field of consumer electronics due to their advantages such as high specific energy, no memory effect, and long cycle life. In recent years, the global environmental protection situation has become increasingly serious, and the shortage of fossil fuels has become more and more serious. Therefore, with the continuous maturity of materials and processes, lithium-ion batteries, as a clean energy source, have gradually become an important power source for automobiles. [0003] Commonly used power batteries mostly use lithium iron phosphate and nickel cobalt lithium manganate ternary materials as positive electrode active materials. Lithium iron phosphate has a stable structure and low activity, and can provide high sa...

AI Technical Summary

Problems solved by technology

Lithium iron phosphate has a stable structure and low activity, which can provide high safety and long cycle life, but its platform is low and specific energy is low, and its energy density often cannot meet the growing demand for electric vehicle cruising range

The nickel-cobalt lithium manganate ternary material combines the advantages of lithium nickelate, lithium cobaltate, and lithium manganate, and has obvious advantages in life and energy density. However, the structure of the ternary material itself is not stable enough, and it is alkaline. In the electrolyte with lithium hexafluorophosphate as the main salt, the safety performance is difficult to guarantee due to the influence of trace HF in it, and thermal runaway is very easy to occur during the thermal shock process

Compared with lithium hexafluorophosphate, lithium bisfluorosulfonyl imide (LiFSI) has lower content of F element and good thermal stability, which can provide excellent battery safety, but too high content of LiFSI can easily cause high voltage resistance of the battery become worse

Images