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.