Cycle Performances of Si-flake-powder Anodes in Lithium Salt-tetraglyme Complex Electrolytes

Abstract

Charge and discharge properties of amorphous Si nano-flake powder (Si Leaf Powder^®, Si-LP) in lithium bis(trifluoromethanesulfonyl)amide-tetraglyme complex electrolyte, [Li(G4)][TFSA], were investigated for use as an anode in silicon-sulfur battery. Though a high reversible capacity (2,300–2,700 mAh g⁻¹) was obtained initially in [Li(G4)][TFSA], the overpotential gradually increased upon cycling. The increase in overpotential was reduced by dilution with 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether. The addition of fluoroethylene carbonate (FEC) further reduced the overpotential and improved cycleability. Electrochemical impedance spectroscopy analysis revealed that the observed improvements in charge and discharge characteristics are due to the formation of solid electrolyte interface layer with a high ionic-conductivity in the presence of FEC.