A lithium ion battery

Abstract

The invention relates to the field of electrochemistry, in particular to a lithium ion battery. One aspect of the present invention provides a lithium ion battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, the negative electrode sheet includes a negative active material layer containing a negative active material, and the electrolyte includes an electrolyte lithium salt , the electrolyte lithium salt includes a first lithium salt, the first lithium salt is selected from fluorine-containing sulfonimide lithium salts, and the first lithium salt and the negative electrode sheet satisfy the relational formula (1). The present invention adopts fluorine-containing sulfonyl imide lithium salt as the electrolyte solution of the first lithium salt, which can effectively prevent the impedance of the battery from increasing too fast or the concentration polarization is too large, and can give full play to the high temperature advantage of fluorine-containing sulfonyl imide lithium salt And the advantages of high conductivity, the formed battery has a low increase rate of floating charge physical resistance, avoiding safety problems such as lithium precipitation in the middle and late stages of the cycle, and finally achieves excellent performance of high safety performance, long cycle life, and good high-temperature storage.

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 in the late 20th century, they have been widely used in the field of consumer electronics due to their high specific energy, no memory effect, and long cycle life. In recent years, the global environmental protection situation has become increasingly severe, 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 source of power for automobiles. [0003] Commonly used power batteries mostly use lithium iron phosphate and nickel cobalt lithium manganate ternary materials as positive active materials. Lithium iron phosphate has a stable structure and low activity, which can provide high safety and long cycle life, but i...

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