Relaxation of the Interface Resistance between Solid Electrolyte and 5 V-Class Positive Electrode.

Solid-state Li batteries using 5 V-class positive electrode materials display a higher energy density. However, the high resistance at the interface of the electrolyte and positive electrode (interface resistance, ) hinders their practical applications. Here, we report the relaxation of between a solid electrolyte (LiPO) and a 5 V-class electrode (LiCoMnO). Although is small at the Mn redox voltage of 4.0 V vs Li/Li (11 Ω cm), it rapidly increases by more than 2 orders of magnitude as the voltage increases above the Co redox voltage of 5.2 V vs Li/Li. After the applied voltage is reduced to 4.0 V vs Li/Li, decays to the original value after 3 h. The relaxation of after exposure to high voltages suggests that the increase in above 5 V vs Li/Li is attributable to the formation of an interfacial layer at the LPO/LCMO interface.