ELECTROCHEMICAL DEPOSITION OF LITHIUM METAL IN NONAQUEOUS ELECTROLYTECONTAINING (C2H5)(4)NF(HF)(4) ADDITIVE

A new additive (C2H5)(4)NF(HF)(4) to nonaqueous electrolytes was inves tigated in order to modify the surface state of lithium metal and to r ealize a superior discharge and charge cycle performance of lithium me tal anodes in rechargeable lithium batteries. (C2H5)(4)NF(HF)(4) creat ed a new surface film consisting of a LiF/Li2O bi-layer. This surface him was formed as a result of acid-base reactions of (C2H5)(4)NF(HF)(4 ) with various basic lithium compounds produced by chemical reactions of nonaqueous electrolytes with lithium metal. Lithium deposited in th ese electrolytes exhibited particle forms suggesting a high degree of reversibility in lithium metal dissolution and deposition processes. S pecifically, the dimethoxy ethane (DME) electrolyte with (C2H5)(4)NF(H F)(4) added at a concentration of 2.5 X 10(-3) mol dm(-3) yielded the highest reversibility for a lithium metal anode. This result can be ex plained by the reduced reactivity of DME with lithium metal and the la rger particle size of lithium deposited in this electrolyte. (C) 1998 Elsevier Science S.A.