Emerging Janus/gradient anode structures for high-performance lithium-metal batteries
Lithium (Li)-metal batteries (LMBs) are promising next-generation energy storage systems due to their high theoretical capacity (3860 mAh g−1) and low electrochemical potential (−3.04 V vs. standard hydrogen electrode). However, uncontrollable Li dendrite growth and volume fluctuations during cycling cause low Coulombic efficiency, safety hazards, and rapid capacity decay. Conventional 3D current collectors mitigate these issues by increasing surface area and providing void space, but they suffer from top-heavy deposition and underutilization of internal space. Emerging Janus/gradient anode structures, featuring asymmetric or gradient properties in lithiophilicity, conductivity, or porosity, enable bottom-up Li plating and efficient space utilization. This review systematically summarizes design principles, operational mechanisms, and recent progress in lithiophilic-lithiophobic Janus designs, conductivity-gradient frameworks, and dual-gradient configurations. These structures collectively improve Coulombic efficiency, cyclic longevity, and safety. The review concludes with future research directions, underscoring the potential of Janus/gradient anodes for high-energy-density and durable LMBs.