Surface condition changes in lithium metal deposited in nonaqueous electrolyte containing HF by dissolution-deposition cycles

The dissolution-deposition cycle behavior of Li metal electrodeposited in n onaqueous electrolyte containing a small amount of HF was investigated. In the first deposition process, Li particles with a smooth hemispherical shap e were deposited on Ni in 1.0 M LiCF3SO3/propylene carbonate containing HE The morphology of these fine Li particles is due to electrodeposition via m igration of Li+ ions through a thin and compact surface film consisting of a LiF/Li2O bilayer, which was produced via surface modification by HE After the first dissolution process, a residual film was observed on the entire surface of the Ni substrate. This' residual film is derived from the surfac e film on the Li particles. Moreover, the residual film continuously accumu lated on the electrode during the cycling. On the other hand, it was found that the coulombic efficiency of Li deposition-dissolution during cycling w as much improved by the addition of HE Unfortunately, the formation of dend ritic Li was observed after the 45th cycle, suggesting that the accumulated thick residual film on the Li surface inhibits the supply of KF to the Li surface during the deposition process. (C) 1999 The Electrochemical Society . S0013-4651(98)08-106-3. All rights reserved.