Electrochemical performance of all-solid-state lithium secondary batteries improved by the coating of Li2O–TiO2 films on LiCoO2 electrode

All-solid-state lithium secondary batteries using LiCoO2 particles coated with amorphous Li2O–TiO2 films as an active material and Li2S–P2S5 glass-ceramics as a solid electrolyte were fabricated; the electrochemical performance of the batteries was investigated. The interfacial resistance between LiCoO2 and solid electrolyte was decreased by the coating of Li2O–TiO2 films on LiCoO2 particles. The rate capability of the batteries using the LiCoO2 coated with Li2Ti2O5 (Li2O·2TiO2) film was improved because of the decrease of the interfacial resistance of the batteries. The cycle performance of the all-solid-state batteries under a high cutoff voltage of 4.6 V vs. Li was highly improved by using LiCoO2 coated with Li2Ti2O5 film. The oxide coatings are effective in suppressing the resistance increase between LiCoO2 and the solid electrolyte during cycling. The battery with the LiCoO2 coated with Li2Ti2O5 film showed a large initial discharge capacity of 130 mAh/g and good capacity retention without resistance increase after 50 cycles at the current density of 0.13 mA/cm2.