Engineering Stress‐Potential Coupled Interface on Ultrathin Lithium Anodes Toward 450 Wh Kg −1 ‐Level Long‐Cycling Lithium Metal Batteries

Dendrite-free lithium anodes are crucial for developing practical high-energy-density batteries (>400 Wh/kg) with extended cycle life, but conventional interface design lack self-adaptive adjustment against dendrite growth during Li plating. Herein, we obtain a dendrite-free ultrathin Li@FcCHO anode by engineering a stress-responsive nano-interface on lithium strips via a mechanochemical reaction between ferrocene carboxaldehyde (FcCHO) and metallic Li. As proved by in situ Kelvin probe force microscopy and scanning electrochemical microscopy tests, the Li@FcCHO anode shows local potential response to the Li plating stress. Furthermore, density functional theory calculations show that the local surface potential change originates from stress-induced redistribution of anion-pair coordination. The stress-potential coupled interface layers induce uniform and dendrite-free Li deposition beneath the interface by suppressing dendritic Li from capturing Li⁺ with the extra electric field. As a result, the Li@FcCHO anode exhibits ultralong cycling life over 5000 h under high areal capacity conditions, whilst a practical 452 Wh/kg pouch cell (9 Ah) based on the Li@FcCHO anode can survive over 470 cycles with capacity retention of 85.20%. This work pioneers a stress-potential coupled interface design to advance practical ultrathin Li anodes for next-generation high-energy-density batteries.