Improvement of lithium-metal electrode performance of all-solid-state batteries by shot peening on solid-electrolyte surface

Abstract

The anode interface resistance and the critical current density of an all-solid-state lithium metal battery with oxide solid electrolyte needs improvement to obtain a suitable high-performance battery. In this study, surface processing of an oxide solid electrolyte by shot peening is achieved. The experimental results show that shot peening decreases the interface resistance to 1/24 of the interface resistance before this treatment and increases the critical current density by a factor of 7. This improvement in performance is comparable to that obtained by the conventional gold thin-film insertion method. Moreover, there is a synergistic effect between shot peening and gold thin-film insertion: lower interface resistances and higher critical current densities are obtained when using the two techniques together than when either method is used alone. The results of measurements of surface structural and mechanical characteristics suggest two reasons for the increase in the electrode performance with shot peening. One is that the surface roughness caused by shot peening increases the contact between the solid electrolyte and the lithium metal with inhomogeneous mechanical stress. The other is that shot peening increases the fracture toughness by applying a compressive residual stress, thus suppressing the growth of lithium dendrite.