Bioderived Freestanding Film as a Robust Interfacial Protective Layer for Advanced Lithium Metal Anodes

Lithium metal is a potential candidate for anode material in next-generation rechargeable batteries with high energy and power densities. However, the huge volume change caused by the uneven deposition of metallic Li leads to the cracking of the solid electrolyte interphase (SEI), which cannot prevent the reaction of inner fresh Li with electrolyte, resulting in severe dendrite growth and electrochemical degradation. Herein, a freestanding protein film derived from eggshell is reported as the protective layer on the electrode surface to form a robust artificial SEI layer. Benefiting from its 3D interconnected fiber framework along with good mechanical stiffness and softness, the Li-ion flow is uniformly modulated, leading to the suppression of Li dendrite growth. The electrochemical performance of corresponding symmetric, asymmetric, and full cells is significantly enhanced. A high coulombic efficiency above 95% for nearly 700 cycles is achieved for the modified Cu/Li asymmetric cell at a current density of 3 mA cm(-2) (with a capacity of 1 mAh cm(-2)). This study indicates a SEI reinforcement approach for the stabilization of the Li metal anode based on the freestanding structure derived from biomaterials.