Boosting the Power Characteristics of All‐Solid‐State Batteries Through Improved Electrochemical Stability: Site‐Specific Nb Doping in Argyrodite

ABSTRACT Enhancing the energy density of all‐solid‐state batteries (ASSBs) with lithium metal anodes is crucial, but lithium dendrite‐induced short circuits limit fast‐charging capability. This study presents a high‐power ASSB employing a novel, robust solid electrolyte (SE) with exceptionally high stability at the lithium metal/SE interface, achieved via site‐specific Nb doping in the argyrodite structure. Pentavalent Nb incorporation into Wyckoff 48 h sites enhances structural stability, as confirmed by neutron diffraction, X‐ray absorption spectroscopy, magic angle spinning nuclear magnetic resonance, and density functional theory calculations. While Nb doping slightly reduces ionic conductivity, it significantly improves interfacial stability, suppressing dendrite formation and enabling a full cell capable of charging in just 6 min (10‐C rate, 16 mA cm −2 ). This study highlights, for the first time, that electrochemical stability, rather than ionic conductivity, is key to achieving high‐power performance, advancing the commercialization of lithium metal‐based ASSBs.