Tailoring a Fast Ion‐Conducting Substrate with Competitive Adsorption for Dendrite‐Free Lithium/Potassium Metal Batteries

Abstract The desolvation behavior of Li + is widely regarded as primarily governed by the electrolyte composition, while the dynamic decoupling mechanism between the electrode interface and solvation structure has received limited attention. Herein, a competitive adsorption‐driven, fast‐ion‐conducting host was innovatively developed based on the Li 15 Si 4 /Li 3 N microrods. Guided by density functional theory (DFT) calculations and molecular dynamics (MD) simulations, it was revealed for the first time that the dual‐phase interface exhibits competitive adsorption interactions with solvent molecules and anions within the solvation sheath. This unique interfacial interaction triggers dynamic reconstruction of the solvation structure at the interface, significantly reducing the Li + desolvation barrier by 33%. Benefiting from the integration of these multifunctional advantages, the symmetric cell delivers an ultra‐long cycle lifespan of over 5000 h at 1 mA cm −2 with an exceptionally low overpotential of 13 mV. Moreover, the full cell coupled with LiFePO 4 cathodes achieves an impressive cycling stability of 2000 cycles at 5 C, with a capacity retention of 107%. This work unveils a substrate‐mediated solvation structure decoupling mechanism, offering a new paradigm for the rational design of dendrite‐free Li metal anodes with 3D architectures.