Water‐Stable Lithium Metal Anodes with Ultrahigh‐Rate Capability Enabled by a Hydrophobic Graphene Architecture

Implementing the utilization of lithium metal in actual processing and application conditions is essential for next-generation high-energy batteries at a practical level. However, the air/water instability of the high-reactive Li metal remains unsolved. Here, a water-stable Li metal anode with ultrahigh-rate capability enabled by a rationally designed architecture is reported. A hydrophobic graphene framework, consists of an array of vertically aligned sheets and a roof of sloping-aligned sheets, is utilized to fully host lithium metal. As a result, it is first demonstrated that the composite Li metal anode can run stably even after it directly contacts with water. In addition, both the arrays and the roof in the framework are directional graphene microsheets that can provide fast charge transport kinetics in the anode without tortuosity. Therefore, the anode can operate at an extremely high current density of 50 mA cm-2 with long-term cycling stability. Importantly, the composite Li anodes in Li||LiFePO4 and Li||NCM-811 cells also show much improved performances than Li metal foil under crucial conditions of lean electrolyte and low negative/positive capacity ratio. This design provides a significant stride in the safety toward the practicability of low air/water tolerance materials.