In Situ Vertically Aligned MoS2 Arrays Electrodes for Complexing Agent‐Free Bromine‐Based Flow Batteries with High Power Density and Long Lifespan

Abstract Bromine‐based flow batteries (Br‐FBs) are highly competitive for stationary energy storage due to their high energy density and cost‐effectiveness. However, adding bromine complexing agents (BCAs) to electrolytes slows down Br 2 /Br − reaction kinetics, causing higher polarization and lower power density of Br‐FBs. Herein, in situ vertically aligned MoS 2 nanosheet arrays on traditional carbon felt substrates as electrodes to construct high power–density BCA‐free Br‐FBs are proposed. MoS 2 arrays exhibit strong adsorption capacity to bromine, which helps the electrodes capture and retain bromine species. Even without BCAs, the battery self‐discharge caused by bromine diffusion is also inhibited. Moreover, the rate‐determining step of Br 2 /Br − reactions is boosted and the vertically aligned array structure provides sufficient sites, motivating Br 2 /Br − reaction kinetics and decreasing the battery polarization. The capacity retention rate of the BCA‐free Br‐FB based on MoS 2 arrays‐based electrodes reaches 46.34% after the 24‐h standing test at 80 mA cm −2 , meeting the requirements of practical applications. Most importantly, this BCA‐free Br‐FB exhibits a high Coulombic efficiency of 97.00% and an ultralong cycle life of 1000 cycles at a high current density of 200 mA cm −2 . This work provides an available approach to developing advanced electrode materials for high power–density and long‐lifespan Br‐FBs.