Modification of Interface Between LiCoO2 Electrode and Li2S-P2S5 Solid Electrolyte Using Li2O-SiO2 Glassy Layers

Effects of modification of the electrode/electrolyte interface with Li2O-SiO2 thin films on impedance profiles and rate capabilities of all-solid-state In/80Li(2)S center dot 20P(2)S(5) glass ceramic/LiCoO2 cells were investigated. Large resistance was observed at the LiCoO2-electrode/sulfide-electrolyte interface in all-solid-state cells. The interfacial resistance was decreased by 0.06 wt % oxide coatings on LiCoO2; the effective coatings were a lithium-ion conductive Li2SiO3 glassy film and an insulative SiO2 film. The Li2SiO3 coating film decreased the interfacial resistance more effectively when the coating amounts increased from 0.06 to 0.6 wt % (film thickness was ca. 10 nm). However, 0.6 wt % of SiO2 coating exhibited higher interfacial resistance than noncoating because the thick SiO2 coating film acted as a high-resistance layer. Temperature dependence of the interfacial resistance suggests that the resistance decrease was achieved mainly by an increase of pre-exponential factor rather than by a decrease of activation energy for ion conduction at the interface. At room temperature, all-solid-state cells with Li2SiO3-coated LiCoO2 were discharged even under the high current density, 6.4 mA cm(-2).