Interphasial Chemistry Design for Seamless Lithium Deposition in Anode-Free Lithium Metal Batteries.

Anode-free lithium metal batteries (AFLMBs) are promising due to ultrahigh energy density, reduced manufacturing costs, and enhanced safety through active lithium elimination. However, their practical implementation remains challenged by unstable electrode-electrolyte interfaces and the resulting rapid active species depletion. Herein, an ultrathin ion-conducting membrane (ICM) is designed, featuring uniformly distributed rigid benzenesulfonimide anionic groups and flexible lithiophilic groups containing ether oxygen groups. The constrained benzenesulfonimide anions enable exceptional charge separation and reduced spatial resistance, boosting lithium-ion mobility, while the integrated lithophilic network directs lateral lithium deposition through ionic nanochannels. This ICM layer effectively promotes the enrichment of anions at the interface and constructs stable anion-derived solid electrolyte interphases (SEI). Meanwhile, ICM layers with electron-insulating and ion-conducting properties can further prevent side reactions, and suppress dendritic Li growth acting as a natural shield, resulting in seamless lithium deposition. Specifically, the Li||Cu coin cells with ICM achieve 99.82% Coulombic efficiency. The AFLMBs assembled with ICM-coated copper foil (ICM Cu) and NCM811 deliver an energy density of 495 Wh kg with 80.72% capacity retention after 100 cycles. The interphasial chemistry design strategy provides insights into the precise interfacial engineering to realize high-performance, high-safety battery systems and facilitates their development for practical applications.