Extremely Low Resistance of Li3PO4 Electrolyte/Li(Ni0.5Mn1.5)O4 Electrode Interfaces.

Solid-state Li batteries containing Li(Ni0.5Mn1.5)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(Ni0.5Mn1.5)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.