Clean Solid–Electrolyte/Electrode Interfaces Double the Capacity of Solid-State Lithium Batteries

Solid-state lithium (Li) batteries using spinel-oxide electrode materials such as LiNi 0.5 Mn 1.5 O 4 are promising power supplies for mobile devices and electric vehicles. Here, we demonstrate stable battery cycling between the Li 0 Ni 0.5 Mn 1.5 O 4 and Li 2 Ni 0.5 Mn 1.5 O 4 phases with working voltages of approximately 2.9 and 4.7 V versus Li/Li + in solid-state Li batteries with contamination-free clean Li 3 PO 4 /LiNi 0.5 Mn 1.5 O 4 interfaces. This clean interface has the effect of doubling the capacity of conventional battery cycling between the Li 0 Ni 0.5 Mn 1.5 O 4 and Li 1 Ni 0.5 Mn 1.5 O 4 phases. We also investigated the structural changes between the Li 0 Ni 0.5 Mn 1.5 O 4 and Li 2 Ni 0.5 Mn 1.5 O 4 phases during battery cycling. Furthermore, we found an inhomogeneous distribution of the Li 2 Ni 0.5 Mn 1.5 O 4 phase in the LiNi 0.5 Mn 1.5 O 4 electrode, induced by spontaneous Li migration after the formation of the Li 3 PO 4 /LiNi 0.5 Mn 1.5 O 4 interface. These results indicate that the formation of a contamination-free clean Li 3 PO 4 /LiNi 0.5 Mn 1.5 O 4 interface is key to increase the battery capacity.