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Lithium (Li) metal anode is a promising candidate for next-generation high capacity energy storage systems. Unfortunately, the uneven deposition/dissolution of Li metal hinders its wide applications. Herein, a robust and deformable polymer electrolyte film as the advanced protective layer on Li metal is developed by a simple tape-casting method, in which the polymer endows a comfortable interfacial contact as well as membrane flexibility to adapt the volume change, while the coordination between the polymer and Li salt provides fast Li + ion diffusion channels. The modified Li metal anodes deliver a stable cycling over 1000 cycles under a high current density of 3 mA cm −2 in the ether-based electrolyte. The enhanced cycling performance at high current densities are mainly attributed to the Li plating occurred beneath the ion-conducting protective layer, which facilitates Li + ion uniform distribution and further suppresses Li dendrite growth. Accordingly, constructing a polymer electrolyte protective film onto the Li metal anodes is a facile and low-cost methodology to drive the Li metal anode toward practical application.

Li alloy film has been developed as an advanced artificial protection layer on Li metal anode, attributed to its tight contact with Li metal and unique transportation capability of mixed ion/electron. Li+ diffusion coefficient of the alloy interphase layer is crucial for Li dendrite growth and rate performance. Here, Zn thin film is sputtered on the surface of Li foil, and Li−Zn alloy buffer layer is spontaneously formed via an alloying reaction. In the process of electrochemical cycling, while Li+ ions are reduced on the interface of the electrolyte and the anode, the fresh Li atoms rapidly diffuse into the alloy layer via fast ion transport channels of the mixed conductor, resulting in the formation of Li metal free surface. As a consequence, Li−Zn layer protected Li electrode can effectively suppress Li dendrite growth and mitigate the deterioration of Li metal, demonstrating the greatly promoted performance at high current density in both the liquid electrolyte and all solid‐state electrolyte systems.

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