LAUSR

Battery designs are swiftly changing from metal‐ion to rechargeable metal batteries. Theoretically, metals can deliver maximum anode capacity and enable cells with improved energy density. In practice, these advantages are only possible if the parasitic surface reactions associated with metal anodes are controlled. These undesirable surface reactions are responsible for many troublesome issues, like dendrite formation and accelerated consumption of active materials, which leads to anodes with low cycle life or even battery runaway. Here, a facile and solvent‐free brushing method is reported to convert powders into films atop Li and Na metal foils. Benefiting from the reactivity of Li metal with these powder films, surface energy can be effectively tuned, thereby preventing parasitic reaction. In‐operando study of P2S5‐modified Li anodes in liquid electrolyte cells reveals a smoother electrode contour and more uniform metal electrodeposition and dissolution behavior. The P2S5‐modified Li anodes sustain ultralow polarization in symmetric cell for >4000 h, ≈8× longer than bare Li anodes. The capacity retention is ≈70% higher when P2S5‐modified Li anodes are paired with a practical LiFePO4 cathode (≈3.2 mAh cm−2) after 340 cycles. Brush coating opens a promising avenue to fabricate large‐scale artificial solid‐electrolyte‐interphase directly on metals without the need for organic solvent.