Extremely Low Resistance of Li₃PO₄ Electrolyte/Li(Ni_0.5Mn_1.5)O₄ Electrode Interfaces

Solid-state Li batteries containing Li­(Ni_0.5Mn_1.5)­O₄ as a 5 V-class positive electrode are expected to revolutionize mobile devices and electric vehicles. However, practical applications of such batteries are hampered by the high resistance at their solid electrolyte/electrode interfaces. Here, we achieved an extremely low electrolyte/electrode interface resistance of 7.6 Ω cm² in solid-state Li batteries with Li­(Ni_0.5Mn_1.5)­O₄. Furthermore, we observed spontaneous migration of Li ions from the solid electrolyte to the positive electrode after the formation of the electrolyte/electrode interface. Finally, we demonstrated stable fast charging and discharging of the solid-state Li batteries at a current density of 14 mA/cm². These results provide a solid foundation to understand and fabricate low-resistance electrolyte/electrode interfaces.