Enhancing Longevity and Efficiency of Iron-Chromium Flow Batteries through Bromide-Bridged by Solvation Restructuring under Wide-Temperature Operation.

Iron-chromium flow batteries (ICFBs) are a promising large-scale energy storage technology characterized by cost-effectiveness and scalability. However, their practical deployment is often limited by low energy density, kinetic inefficiencies, and high temperature dependence. This work engineers a bromine-bridged solvation architecture to overcome the identified limitations. The reconstructed Cr3+ solvation sheath featuring bromine-bridged coordination accelerates redox kinetics and suppresses degradation, enhancing operational stability of the ICFB. Concurrently, the analogous solvation restructuring of iron species expands the electrochemical potential window, boosting volumetric energy density. Notably, this solvent-mediated reconstruction enhances electrolyte ionic conductivity through optimized ion transport channels, which synergistically improve the voltage efficiency. Critically, the bromine-bridged surface anchoring of Cr3+ on electrode interfaces facilitates ultrafast interfacial electron transfer. Consequently, the HBr-modified ICFB achieves an energy efficiency (EE) of 81.93% at 100 mA cm-2 under 65°C, along with an energy density of 18.65 Wh/L and EE of 81.25% at the same current density but 25°C, exhibiting stable cycling over 200 cycles. This work proposes a high-efficiency ICFB that can operate over a wide temperature range for the first time, offering a scalable pathway for developing next-generation ICFB electrolytes with enhanced efficiency, durability, and energy storage performance.