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LiFSI improvement of high-temperature performance of graphite anodes for Li-ion battery

2022-02-15 10:41:57

Currently, LiPF6-containing electrolytes are widely used for Li-ion battery dute to good ion conductivity and reasonable safety. However, LiPF6 electrolytes are inevitably contaminated by a detrimental byproduct, hydrogen fluoride (HF), which causes fatal metal dissolution of cathode materials.


Researchers have developed a variety of new lithium salts, such as LiBOB, LiODFB, LiFSI, to overcome LiPF6 electrolyte defect. LiFSI is considered a promising alternative to LiPF6 because of its higher ionic conductivity to LiPF6, high thermal stability, and innate HF-free nature.


Recently, Lee et al. [1] systematically compared LiFSI and LiPF6 electrolytes to explain the effect of LiFSI on the performance of graphite anodes. The researchers identified the effects of LiFSI electrolyte on graphite and Li electrodes by comparing graphite / Li half-cells and graphite / graphite symmetric cells. The results show that LiFSI and LiPF6 exhibit similar cycling performance for graphite anodes at 25 °C, but LiFSI shows better cycling and storage performance at elevated temperature (60 °C)


In order to understand superior high temperature performance of LiFSI in depth, the researchers found by DSC and XPS measurements that a thin, inorganic-rich SEI film was formed on the graphite anodes for LiFSI electrolyte. For LiPF6 electrolyte, the SEI film formed is organic-rich, thermally unstable.


In a word, the superior high temperature performance of LiFSI electrolyte is mainly due to its high thermal stability, HF-free nature, and the formation of a unique SEI film on the graphite anode.


References:

[1] SJ Kang, K. Park, S. Park, H. Lee, Unraveling the role of LiFSI electrolyte in the superior performance of graphite anodes for Li- ion batteries, Electrochimica Acta, 2018, 259 (1), 949-954.


Edited by Suzhou Yacoo Science Co., Ltd.

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