Lithium bis(fluorosulfonyl)imide (LiFSI) as conducting salt for nonaqueous liquid electrolytes for lithium-ion batteries: Physicochemical and electrochemical properties

摘要

Lithium bis(fluorosulfonyl)imide (LiFSI) has been studied as conducting salt for lithium-ion batteries, in terms of the physicochemical and electrochemical properties of the neat LiFSI salt and its non-aqueous liquid electrolytes. Our pure LiFSI salt shows a melting point at 145℃, and is thermally stable up to 200℃ It exhibits far superior stability towards hydrolysis than LiPF_6. Among the various lithium salts studied at the concentration of 1.0 M (=moldm~(-3)) in a mixture of ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (3:7, v/v), LiFSI shows the highest conductivity in the order of LiFSI>LiPF_6>Li[N(SO_2CF_3)_2] (LiTFSl)>LiCIO_4>LiBF_4. The stability of Al in the high potential region (3.0-5.0V vs. Li~+/Li) has been confirmed for high purity LiFSI-based electrolytes using cyclic voltamme-try, SEM morphology, and chronoamperometry, whereas Al corrosion indeed occurs in the LiFSI-based electrolytes tainted with trace amounts of LiCl (50ppm). With high purity, LiFSI outperforms LiPF_6 in both Li/LiCoO_2 and graphite/LiCoO_2 cells.