Melting lithium alloying to improve the affinity of Cu foil for ultra-thin lithium metal anode

Before lithium (Li) metal can be formally used as the anode material of Li-ion battery, the key technical defects of Li metal electrode, such as low active Li metal proportion and low mechanical strength, must be solved. Herein, the surface affinity of molten lithium-copper (LiCu) alloy with Cu foil is improved by alloying Cu and Li in a molten state. The surface of Cu foil naturally adsorbs an ultra-thin (∼30 μm) composite Li metal layer. The ultra-thin composite Li metal layer can greatly reduce the amount of inactive Li, and the Cu foil improves the mechanical strength and engineering workability of Li metal anode. In addition, the enhanced Young's modulus facilitates the uniform Li plating/stripping process. As a result, the stable cycle stability of up to 600 h and the average overpotential of 13 mV (area specific capacity is 1 mAh cm−2 and current density is 1 mA cm−2) are achieved. The cycle life is higher than 150 h even though the maximum utilization rate of Li is greater than 50%. The Li metal full battery assembled with the commercial NCM811 cathode shows more stable cycle performance and Coulombic efficiency. Such strategy can effectively pave the way for the practical application of Li metal anode.