Effects of Lithium Salt Concentration in Ionic Liquid Electrolytes on Battery Performance of LiNi0.5Mn0.3Co0.2O2/Graphite Cells

Autor: Takuya TAKAHASHI, Masashi ISHIKAWA, Yosuke UGATA, Kaoru DOKKO, Masayoshi WATANABE
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: Electrochemistry, Vol 89, Iss 5, Pp 455-460 (2021)
Druh dokumentu: article
ISSN: 2186-2451
DOI: 10.5796/electrochemistry.21-00075
Popis: Ionic liquids (ILs) possess low volatility and low flammability and are promising electrolytes for thermally stable Li-ion batteries (LIBs). Among ILs, bis(fluorosulfonyl)imide (FSI−) anion-based ILs have low viscosity and high ionic conductivity and FSI-based electrolytes are useful for achieving a high power density LIB. In this study, we investigated the effects of LiFSI concentration in IL electrolytes on the performance of LIBs. We prepared electrolytes composed of 1-ethyl-3-methyl imidazolium bis(fluorosulfonyl)imide (EMImFSI) and LiFSI. The ionic conductivity of the electrolyte decreased with increasing LiFSI concentration due to an increase in viscosity; however, the Li+ transference number increased with increasing LiFSI concentration. The IL electrolyte was tested in a LiNi0.5Mn0.3Co0.2O2/graphite pouch cell. The discharge rate capability of the cell was improved by increasing the LiFSI concentration. The higher LiFSI concentration was effective in suppressing the depletion of Li+ in the vicinity of the cathode during the high current discharge. Furthermore, we demonstrated that cells with IL electrolytes can be stably operated over 500 charge-discharge cycles at 25 °C and 60 °C.
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