Effect of Li₃BO₃ addition to NASICON-type single-phase all-solid-state lithium battery based on Li_1.5Cr_0.5Ti_1.5(PO₄)₃

Abstract

All-solid-state Li-ion battery is expected as the post Li-ion battery because of its high reliability and safety. However, the biggest issue for the all-solid-state Li-ion battery is the interfacial resistance between electrode and electrolyte rather than the bulk ionic conductivity of the solid electrolyte. In order to reduce the interfacial resistance, we recently adopted a new concept, “single-phase all-solid-state battery”, which is made of a single material. In principle, single-phase all-solid-state battery has low interfacial resistance between the solid electrolyte and electrodes, because the solid electrolyte and electrodes are same material. Here, the electrochemical properties of single-phase all-solid-state battery based on Li_1.5Cr_0.5Ti_1.5(PO₄)₃ and the effect of Li₃BO₃ additive as flux to Li_1.5Cr_0.5Ti_1.5(PO₄)₃ are shown. The pellet of Li_1.5Cr_0.5Ti_1.5(PO₄)₃ with Li₃BO₃ additive showed higher density by filling the voids of Li_1.5Cr_0.5Ti_1.5(PO₄)₃. As the result of the low electronic conductivity of Li₃BO₃, the overpotential was increased. However, the electron leakage was suppressed. On the other hand, the operation voltage and the reversible capacity were improved due to the high lithium-ionic conductivity of Li₃BO₃. It was found that Li₃BO₃ additive is useful for the improvement of the single-phase battery.