High-throughput exploration of Li-alloy protection layers for high-performance lithium metal batteries

In order to realize high specific capacity Li-metal batteries, a protection layer for the Li-metal anode is needed. We are carrying out combinatorial screening of Li-alloy thin films as the protection layer which can undergo significant lithiation with minimum change in volume and crystal structure. Here, we have fabricated lithium-free binary alloy thin film composition spreads of Co1-xSnx on Cu layers on Si substrates. The crystallinity of the thin films was tuned by varying the deposition temperature followed by electrochemical lithiation to form Li-alloy ternary thin films. Synchrotron diffraction is used as the main tool to investigate the crystallinity of the films before and after lithiation. Nano-grained Co3Sn2 alloy thin films are found to exhibit significant lithium uptake capacity (Li atomic concentration up to ≈ 40 %) while maintaining its structural integrity, and are thus a good candidate of the Li-metal protection layer.