Impact of annealing on the resistance of Li₃PO₄ electrolyte–LiNi_0.5Mn_1.5O₄ electrode interfaces Available to Purchase

The operation of solid-state Li batteries, which are promising power supplies for portable electronic devices and electric vehicles, is accompanied by heating. Therefore, investigating the thermal stability of battery systems is essential. In this study, we report the impact of annealing on the interface of a Li₃PO₄ electrolyte and LiNi_0.5Mn_1.5O₄ electrode in thin-film batteries. The batteries with the interface annealed at 200 °C show low Li₃PO₄–LiNi_0.5Mn_1.5O₄ interface resistance of 7.2 Ω cm². Furthermore, the batteries exhibit stable charge–discharge characteristics with high current density up to 1170 μA cm⁻², similar to those of batteries with the non-annealing interface. The batteries with the interface annealed at 450 °C show high Li₃PO₄–LiNi_0.5Mn_1.5O₄ interface resistance of 490 Ω cm², resulting in low battery performance. X-ray photoemission spectroscopy indicates that the P in Li₃PO₄ is reduced by high-temperature annealing, possibly causing the performance degradation of batteries. This study provides an in-depth understanding of the interfaces of solid-state batteries and is expected to facilitate the development of thermally stable batteries.