CuO Nanofilm-Covered Cu Microcone Coating for a Long Cycle Li Metal Anode by In Situ Formed Li2O

Despite the high theoretical specific capacity and ultralow reduction potential advantages of Li anodes, dendrite growth in Li metal batteries leads to many problems. Realizing uniform Li deposition is the key to solving these problems, but it is usually difficult for traditional Li metal electrodes. In this study, CuO nanofilm-covered Cu microcones (NFMCs) on a Cu foil are prepared as current collectors to suppress Li dendrite growth and improve the electrochemical performance of the batteries. Li2O is in situ formed during the course of Li deposition according to the conversion reaction between CuO and Li. The nucleation energy barrier of Li is decreased due to high affinity between Li2O and Li. In addition, we found that Li2O also decreases the elastic strain energy at the interface between the deposited Li and the Li2O film, leading to uniform coverage of Li metal on microcones. The Li2O/Cu NFMCs show a coral-like structure instead of the sharp cone structure in Cu microcones. Thus, they can effectively mitigate the tip-charge effect, which will cause the continuous reduction of the Li ion at the tip. As a result, uniform and stable Li deposition without observation of the Li dendrite up to 1000 cycles at a current density of 5 mA cm-2 is achieved using this Li2O/ Cu NFMC substrate. A full cell upon pairing with LiFePO4 achieves a high Coulombic efficiency of 96.7% for over 100 cycles at 0.2 C with a capacity retention over 92.7%.