Microelectrode Studies on Kinetics of Charge Transfer at an Interface of Li Metal and Li2S-P2S5 Solid Electrolytes

Charge transfer kinetics at the Li metal electrode/electrolyte interface for three inorganic solid electrolytes and an organic liquid electrolyte were elucidated with two parameters, exchange current density (i(0)) for Li/Li+ couple reactions and ionic conductivity in electrolyte. The former was evaluated by potential step method with a microelectrode, while the latter was done by electrochemical impedance spectroscopy. Both i(0) and ionic conductivity showed Arrhenius type dependence, and activation energies (E-a) for the charge transfer reactions and ionic conduction were evaluated. In the case of the organic liquid electrolyte, E-a for the Li/Li+ couple reactions was higher than that for ionic conduction because of the solvation/desolvation of Li+ ion. However, for the Li2S-P2S5 solid solid electrolytes, the E-a for the Li/Li+ couple reactions was quite close to that for ionic conduction due to the lack of the solvation/desolvation. (C) The Electrochemical Society of Japan, All rights reserved.