Enhancing bromine redox conversion via electrochemical self-induced catalyst gel encapsulation strategy toward high energy efficiency bromine-based flow battery

Benefiting from features such as high-voltage platforms, superior energy density, and cost-effectiveness, Zinc-bromine flow batteries (ZBFBs) demonstrate significant potential for large-scale energy storage applications. However, their practical implementation faces critical challenges: sluggish Br 2 /Br − redox reactions and severe shuttle effects, which lead to diminished energy efficiency and self-discharge. Here, we develop an innovative electrochemical self-induced catalyst gel encapsulation strategy. Under electrochemical driving, the poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS, abbreviated as PES) catalyst spontaneously undergoes gelation and coating on carbon fibers, thereby forming a PES@C composite cathode with enhanced bromine conversion reversibility. This innovative strategy effectively addresses three critical challenges in existing ZBFBs: shuttle effect, low bromine utilization, and poor energy efficiency. PES@C with sulfur sites and C–O-C group enable efficient bromine/poly-bromide anchoring through strong polar interactions, effectively suppressing shuttling effects. Furthermore, the abundant active sites exhibit exceptional catalytic activity towards Br 2 /Br − redox reactions. This synergistic adsorption-catalysis mechanism significantly enhances the electrochemical performance of ZBFBs. The ZBFBs with PES@C achieve stable operation under ultrahigh current density (200 mA cm −2 ) and high areal capacity (40 mA h cm −2 ), delivering outstanding voltage efficiency (84.91%) and energy efficiency (81.78%). Notably, the proposed strategy demonstrates universal applicability for performance enhancement in various bromine-based battery systems, providing an efficient pathway to improve energy efficiency and cycling durability in bromine-based flow batteries.