Cation–Anion Redox Co‐Modulation: Unlocking the Potential of All‐Electrochem‐Active Sulfur‐Based Solid‐State Batteries

ABSTRACT The capacity utilization of all‐solid‐state sulfur cathodes reveals a significant disparity between material and electrode levels due to the high proportion of inactive components required for electro‐ionic transport. While the all‐electrochem‐active (AEA) electrode concept seeks to bridge this gap, fully realizing the energy‐density potential of sulfur‐based cathodes remains challenging. Here, we report a new strategy for co‐modulating the redox of the transition‐metal cation/sulfur anion to unlock the potential of the sulfur‐based electrode. By carefully adjusting the coordination between S anions and Ti cations, we constructed the AEA electrode with S‐anion (TiS x , x > 2)/Ti‐cation (amorphous TiS 2 ) co‐redox, where TiS x activates the redox activity of sulfur‐rich phases with narrower bandgaps through the reversible cleavage and recombination of S–S bonds, thereby enhancing the capacity utilization of anion‐redox in the electrode level, and amorphous TiS 2 serves as an electrochemically active matrix facilitating mixed ionic‐electronic conduction. This design eliminates inactive components and enables synergistic anion‐cation redox chemistry. Consequently, this designed cathode achieves an unprecedented electrode‐level energy density of 1829 Wh/kg, sustains an areal capacity of 11.6 mAh/cm 2 , and exhibits long‐term stability over 10 000 h. Device‐level demonstrations validate this synergistic approach as an effective design principle for realizing high‐energy‐density, long‐life all‐solid‐state battery cathodes under practical conditions.