Understanding of Electrochemical Oxidation Route of Electrically Isolated Li2S Particles

New insight into the oxidation mechanism of solid Li2S is presented by investigating a specially designed cell in which the Li2S particles are electrically isolated from the carbon cathode. Surprisingly, the cell containing the isolated Li2S particles delivered considerable charge and discharge capacities despite the prevention of any charge transfer process between the Li2S particles and the carbon cathode. This fact directly indicates that the electrochemical oxidation of Li2S occurs not through a direct charge (electron) transfer between solid Li2S and conducting materials but through chemical reactions coupled with the charge transfer process. We believe that these unexpected results will greatly contribute to a deep understanding of the exact working mechanism of Li-S batteries and Li2S cathodes as well as a paradigm shift toward an innovative and rational design of Li-S batteries. (C) 2014 The Electrochemical Society. All rights reserved.