Separators with reactive metal oxide coatings for dendrite-free lithium metal anodes

Lithium metal anodes with their high theoretical capacity and low redox potential attract considerable attention, however, practical use of lithium metal batteries is limited by uneven lithium deposition and dendrites formation. Lithium dendrites in the anode side pierce the separator and reach the cathode, leading to short circuit, thermal runaway of the batteries and the associated safety hazards. Herein, we develop separators with reactive metal oxide coatings to alleviate the problem of lithium dendrites formation. It is identified that the reactive metal oxide coatings (e.g., Mg(OH)2@MgO coating) interact with the lithium metal anode and facilitate uniform lithium deposition especially when the coatings are used together with a fluorinated electrolyte. The synergistic effect enables dendrite-free lithium deposition and fast charging capability of lithium metal batteries, which is attributed to the unique lithium metal/separator interface that effectively redistributes Li+ ions. Use of separators with the reactive metal oxide coatings proves to be a facile strategy to regulate lithium deposition and is a universal method to protect alkali metal anodes in rechargeable batteries. Using reactive separator also revolutionizes separator design and manufacturing for alkali metal batteries.