Efficient and stable cycling of lithium metal enabled by a conductive carbon primer layer

Two requirements must be met for efficient and stable cycling of Li metal: (1) intimate and uniform nucleation of Li metal on an electrode substrate for constant current distribution throughout the electrode surface and (2) chemical and electrochemical stability of electrolyte components for high coulombic efficiency. With a focus on the electrode substrate, in this work, we coat a very thin and highly conductive carbon layer as the Li plating primer onto the surface of an existing Cu substrate. It is shown that the carbon primer layer greatly increases coulombic efficiency and cycling stability of Li metal. Microstructural characterization and ac-impedance analysis reveal that the improvement is due to the preferential nucleation of Li metal on the surface of carbon granules, which results in low contact resistance between the plated Li and the electrode substrate. The results of this work indicate that applying a conductive carbon primer layer is a simple and cost-effective approach for the efficient and stable cycling of Li metal.