Bipolar Polymeric Protective Layer for Dendrite‐Free and Corrosion‐Resistant Lithium Metal Anode in Ethylene Carbonate Electrolyte

The unstable interface between Li metal and ethylene carbonate (EC)‐based electrolytes triggers continuous side reactions and uncontrolled dendrite growth, significantly impacting the lifespan of Li metal batteries (LMBs). Herein, a bipolar polymeric protective layer (BPPL) is developed using cyanoethyl (−CH 2 CH 2 C≡N) and hydroxyl (−OH) polar groups, aiming to prevent EC‐induced corrosion and facilitating rapid, uniform Li + ion transport. Hydrogen‐bonding interactions between −OH and EC facilitates the Li + desolvation process and effectively traps free EC molecules, thereby eliminating parasitic reactions. Meanwhile, the −CH 2 CH 2 C≡N group anchors TFSI − anions through ion‐dipole interactions, enhancing Li + transport and eliminating concentration polarization, ultimately suppressing the growth of Li dendrite. This BPPL enabling Li|Li cell stable cycling over 750 cycles at 10 mA cm −2 for 2 mAh cm −2 . The Li|LiNi 0.8 Mn 0.1 Co 0.1 O 2 and Li|LiFePO 4 full cells display superior electrochemical performance. The BPPL provides a practical strategy to enhanced stability and performance in LMBs application.