Cation-Anion Redox Co-Modulation: Unlocking the Potential of All-Electrochem-Active Sulfur-Based Solid-State...

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 TiS₂) 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 TiS₂ 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/cm², 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.