Protecting lithium metal anode by magnetron sputtering a copper coating

We propose that the Li anode can be protected by a Cu coating via the technique of magnetron sputtering. Cu has high electrical conductivity, mechanical strength, and chemical stability. Li deposition on Cu coating with a porous structure disperses the local current density and produces a uniform Li-ion flux, greatly suppressing growth of Li dendrites and the layer prevents Li from directly contacting electrolyte while ensures Li-ion transport. The symmetric battery with the Cu-coated Li anode lasting for 140h presents stable Li deposition/dissolution and improved polarization. The full Li-S battery adopting this modified anode exhibits well-improved cycling stability and capacity retention. It delivers an initial discharge specific capacity of 1148mAh/g and obtains 526mAh/g after 300cycles with high Coulombic efficiency of 99.6% at 0.5 C (1 C=1675mAh/g), while the traditional Li-S battery only obtains 490mAh/g after 200cycles. Scanning electron microscopy images of the cycled Cu-coated Li anode presents favorable integrity. Electrochemical impedance spectra, cyclic voltammogram, and charge-discharge profiles were investigated to consolidate the function of the Cu coating. This simple and facile strategy provides an approach to protect the metal electrode applied in other metal batteries.