Interfacial Chemistry Regulation via a Skin-Grafting Strategy Enables High-Performance Lithium-Metal Batteries.

The lithium (Li) metal anode suffers severe interfacial instability from its high reactivity toward liquid electrolytes, especially carbonate-based electrolytes, resulting in poor electrochemical performance of batteries that use 4 V high-capacity cathodes. We report a new skin-grafting strategy that stabilizes the Li metal-liquid electrolyte interface by coating the Li metal surface with poly((N-2,2-dimethyl-1,3-dioxolane-4-methyl)-5-norbornene-exo-2,3-dicarboximide), a chemically and electrochemically active polymer layer. This layer, composed of cyclic ether groups with a stiff polycyclic main chain, serves as a grafted polymer skin on the Li metal anode not only to incorporate ether-based polymeric components into the solid-electrolyte interphase (SEI) but also to accommodate Li deposition/dissolution under the skin in a dendrite/moss-free manner. Consequently, a Li-metal battery employing a Li metal anode with the grafted skin paired with LiNi0.5 Co0.2 Mn0.3 O2 cathode has a 90.0% capacity retention after 400 charge/discharge cycles and a capacity of 1.2 mAh/cm2 in a carbonate-based electrolyte. This proof-of-concept study provides a new direction for regulating the interfacial chemistry of Li metal anodes and for enabling high-performance Li-metal batteries.