Surface/Interface Effects on High-Performance Thin-Film All-Solid-State Li-Ion Batteries.

The further development of all-solid-state batteries is still limited by the understanding/engineering of the interfaces formed upon cycling. Here, we correlate the morphological, chemical, and electrical changes of the surface of thin-film devices with Al negative electrodes. The stable Al-Li-O alloy formed at the stress-free surface of the electrode causes rapid capacity fade, from 48.0 to 41.5 μAh/cm(2) in two cycles. Surprisingly, the addition of a Cu capping layer is insufficient to prevent the device degradation. Nevertheless, Si electrodes present extremely stable cycling, maintaining >92% of its capacity after 100 cycles, with average Coulombic efficiency of 98%.