Positive and Negative Aspects of Interfaces in Solid-State Batteries

Solid-state lithium batteries are regarded as promising energy storage devices that meet the requirements for realizing a low-carbon society. Although solid-state batteries have been suffering from low power density, the power density has become comparable to or greater than that of liquid systems in a recently developed battery, which has been achieved not only by the high ionic conductivity of the used sulfide solid electrolyte. This Perspective presents anomalous transport properties appearing at the interfaces in solid-state batteries to highlight the importance of controlling the interface phenomena in achieving the high performance. The battery employs not only the highly conductive sulfide but also some oxides in spite of their low conductivity. LiNbO3 interposed to the cathode interface effectively reduces the cathode impedance by suppressing lithium depletion at the interface. Li4Ti5O12 used as the anode becomes a good conductor in its two-phase region because of enhanced transport properties at the phase boundaries.