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

ABSTRACT 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.