Rational design of robust-flexible protective layer for safe lithium metal battery

Rational design of artificial protective layers with low resistance, high mechanical strength and good compliance is desirable to suppress dendritic lithium growth, thus realizing the superiority of Li metal anode for high-energy devices such as large electric grids and electrical vehicles. Here, a 2.5 μm-thick lithiated Nafion/LiCl interface (NLI) is fabricated by a simple dip-casting method, in which soft lithiated Nafion polymer can provide a fast ionic pathway as well as comfortable interfacial contact, meanwhile robust LiCl salts act as a mechanical modulus enhancer against severe interface fluctuation and dendrite growth upon cell cycling. Due to its sufficient ionic conductivity and stability, the as-prepared robust-flexible NLI layer enables lithium metal anode to operate at high current density of 8 mA cm−2 in Li/Li symmetrical cells and shows longer lifespan in Li/Cu half cells as well as full cells paired with Li4Ti5O12, LiFePO4, or sulfur cathode. This work proposes a design principle of combining robust inorganic enhancer with flexible polymer matrix to construct stable lithium metal interface and opens a new opportunity to achieve next-generation power-intensive Li metal batteries under safe operation.