Br2/Br- redox couple has the advantage of higher electrode potential and lower cost, thus the bromine-based flow batteries have attracted lots of attention. However, the relatively low reactivity of Br2/Br-and crossover of Br2are the key challenges limiting the application of bromine-based flow batteries.

Energy Storage Division led by Prof. ZHANG Huamin and Prof. LI Xianfeng in Dalian Institute of Chemical Physics has made significant progress in electrode materials of bromine-based flow batteries. This group proposed the idea of using "pore size exclusion" to entrapping Br2complex, for the first time. The cage-like porous carbon with super high activity to Br2/Br- and Br2complex entrapping capability was designed and applied in zinc bromine flow battery.

Figure. Principle of cage-like porous carbon applied in bromine-based batteries (Image by WANG Chenhui)

In this work, cage-like porous carbon material is designed, whose pore size on the shell is between Br- and Br2complex. And the Br- can freely enter into the cage and be oxidized to Br2, which easily combines with complexing agent and further be entrapped in the cage due to the pore size exclusion. In this way, the crossover problem is efficiently suppressed and the zinc bromine flow battery assembled with the cage-like porous carbon achieves the coulombic efficiency of 98% and energy efficiency of 81% at 80 mA/cm2. This work has put forward a new idea for the design of the electrode material for the bromine-based flow batteries.(Text and Image by WANG Chenhui)

2017.4.11