Unlocking Intrinsic Voltage Plateaus of Conversion-Type Fluoride Cathodes via Sulfur-Mediated Dynamic Charge...

Conversion-type transition-metal fluoride cathodes, renowned for their multielectron redox capacity, hold great promise for next-generation high-energy-density rechargeable batteries. However, their practical implementation has historically been hampered by the large overpotentials that deviate from the intrinsic voltage profiles, resulting in severe voltage hysteresis and ultralow round-trip efficiency of the battery. Herein, we demonstrate a sulfur-mediated dynamic charge redistribution strategy that unlocks the near-theoretical voltage plateaus of 2.73 V for the FeF₃ cathode, achieving a remarkable enhancement in the energy efficiency from 71.9% to 81.9%. The intrinsically multivalent nature of sulfur enables dynamic charge redistribution at the sulfur-fluoride interface during electrochemical charge/discharge, significantly enhancing lithium diffusion kinetics while constructing M-F-S intermediate states to mitigate phase and valence state heterogeneity on the surface of fluoride active particles. This synergistic mechanism substantially improves the reversibility of the conversion reactions. Extensive validation across diverse metal fluorides (e.g., CuF₂, FeF₂, CoF₂, NiF₂, MnF₃, and CrF₃) demonstrates the universality of this approach for mitigating voltage hysteresis in conversion-type fluoride cathodes, paving a critical advancement toward their practical deployment.