N,O-Bis(trimethylsilyl)trifluoroacetamide as an Effective Interface Film Additive on Lithium Anodes.

ABSTRACT

Lithium anodes have attracted much attention because of their high energy density, but the existence of lithium dendrites tremendously limits their practical application. Herein, it is creatively proposed to employ N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) as an electrolyte additive to stabilize the solid electrolyte interface. BSTFA is reduced on the lithium anode surface prior to other components to form a passivation layer composed of LiF, Li3N, and SiOx, which not only significantly prevents the continuous consumption of the electrolyte and reduces side reactions but also effectively promotes the uniform deposition of lithium ions with fast Li+ transmission, thereby solving the problem of lithium dendrites. Electrochemical results indicate that BSTFA can obviously reduce polarization in a Li||Li battery at a current density of 1 mA cm-2. Besides, an excellent cycling performance (107 mA h g-1) and Coulombic efficiency (99%) can be obtained for a Li||LiNi0.6Co0.2Mn0.2O2 (NCM622) battery with 0.5 wt % BSTFA at 2 C after 200 cycles, even at a high NCM622 loading of 6 mg cm-2.