Enhanced Stability of Halide All-in-One Cathode via Anionic Redox Regulation for All-Solid-State Batteries

The integrated all-in-one cathodes have been demonstrated great potentials for all-solid-state batteries, which increases effective energy density by reducing solid-state electrolytes in the composite cathodes. However, such all-in-one cathode of Li1.3Fe1.2Cl4 undergoes irreversible anionic oxidation above 4.0 V, leading to structural damage and capacity fading. Herein, we propose a strategy of anionic redox regulation by partially substitution of Cl with Br in Li1.3Fe1.2Cl4 cathode. The introduced Br suppresses the Cl-oxidation by enhancing Fe-Cl bond strength via inducing the contraction of adjacent Fe-Cl bond lengths and simultaneously provides an additional reversible Br-based redox reaction. The optimized Li1.3Fe1.2Cl3.7Br0.3 cathode exhibits an enhanced ionic conductivity of 0.217 mS cm-1, a discharge capacity of 147.1 mAh g-1 at 0.1C, and a capacity retention of >97% after 100 cycles. This work demonstrates that anionic redox regulation effectively improves the high-voltage stability and cycle life of all-in-one cathodes, offering a new route toward high-energy-density all-solid-state batteries.