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

Abstract

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 (i0) 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 i0 and ionic conductivity showed Arrhenius type dependence, and activation energies (Ea) for the charge transfer reactions and ionic conduction were evaluated. In the case of the organic liquid electrolyte, Ea 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 Ea for the Li/Li+ couple reactions was quite close to that for ionic conduction due to the lack of the solvation/desolvation.