Electrochemical deposition of lithium metal in nonaqueous electrolyte containing (C 2H 5) 4NF(HF) 4 additive

Abstract

A new additive (C 2H 5) 4NF(HF) 4 to nonaquecus electrolytes was investigated in order to modify the surface state of lithium metal and to realize a superior discharge and charge cycle performance of lithium metal anodes in rechargeable lithium batteries. (C 2H 5) 4NF(HF) 4 created a new surface film consisting of a LiF/Li 2O bi-layer. This surface film was formed as a result of acid-base reactions of (C 2H 5) 4NF(HF) 4 with various basic lithium compounds produced by chemical reactions of nonaqueous electrolytes with lithium metal. Lithium deposited in these electrolytes exhibited particle forms suggesting a high degree of reversibility in lithium metal dissolution and deposition processes. Specifically, the dimethoxy ethane (DME) electrolyte with (C 2H 5) 4NF(HF) 4 added at a concentration of 2.5 × 10 −3 mol dm −3 yielded the highest reversibility for a lithium metal anode. This result can be explained by the reduced reactivity of DME with lithium metal and the larger particle size of lithium deposited in this electrolyte.