Relationship between activity and structure of carbon materials for Br₂/Br⁻ in zinc bromine flow batteries

Abstract

The relationship between activity and structure of carbon materials for Br2/Br− in zinc bromine flow batteries.

Cage‐Like Porous Carbon with Superhigh Activity and Br2‐Complex‐Entrapping Capability for Bromine‐Based Flow Batteries

“…First, the diffusion of strong corrosive and oxidizing Br 2 will cause serious self‐discharge and irreversible capacity decay . Second, the high electrochemical polarization caused by the mismatch of the positive and negative redox couple kinetics hampers its wide application . On the one hand, enormous efforts have been devoted to complexing agents and separators to suppress the Br 2 crossover.…”

A Zinc–Bromine Flow Battery with Improved Design of Cell Structure and Electrodes

“…It can be observed that CV curves of the CP electrode obtained at the 500th cycle was almost the same as the first cycle, implying that CP shows a good stability and high durability in the Br 2 /Br − system. CVs at different scan rates were also investigated to understand the nature of the electrode reaction; the relationships between Br 2 reduction peak current ( I p ) and the square root of the scan rates ( v 1/2 ) are plotted in Figure c and d. As the scan rate increases, the onset oxidation potential and the reduction peak shifts toward more positive and negative values, respectively, suggesting that the redox reaction of Br 2 /Br − is quasi‐reversible . It is found that the I p of CP is linearly proportional to v 1/2 , which indicates that the Br 2 reduction on CP is mainly controlled by mass transfer …”

“…CVs at different scan rates were also investigated to understand the nature of the electroder eaction;t he relationshipsb etween Br 2 reduction peak current (I p )a nd the Figure 2c and d. As the scan rate increases,t he onset oxidation potential and the reduction peak shifts towardm ore positive and negative values,r espectively,s uggesting that the redox reaction of Br 2 /Br À is quasi-reversible. [23,24] It is found that the I p of CP is linearly proportional to v 1/2 ,w hich indicates that the Br 2 reduction on CP is mainly controlled by mass transfer. [34][35][36] Thep ractical application of CP as ap ositivee lectrode was evaluated for al ab-scale ZBFB.A st he CP is thin and cannot be used in af low-through mode,t he battery in this work features at hin positive electrode interfacing as erpentine flow-field structure,i nw hicht he electrolyte is fed through the flow field to electrodeb yacombination of diffusion and convection.…”

“…Therefore, to increase the power density of ZBFB, it is necessary to develop efficient electrode materials with high activity towards the Br 2 /Br − redox reaction; in addition, an effective strategy should be adopted to reduce the internal resistance. As for the former issue, carbon nanotubes (CNTs), active carbon, and carbon black have been proposed to enhance the kinetics of Br 2 /Br − redox reaction in ZBFB. For example, Munaiah et al .…”

“…Moreover, the use of thick electrodes will result in al arge internal resistance,e specially when operated at ah igh current density. [21,22] Therefore,t oi ncrease the power density of ZBFB,i t is necessary to develop efficient electrode materials with high activity towards the Br 2 /Br À redox reaction; in addition, an effective strategy should be adopted to reduce the internal resistance.A sf or the former issue,c arbon nanotubes (CNTs), [20,23] active carbon, [18] and carbon black [24] have been proposed to enhance the kinetics of Br 2 /Br À redox reaction Thez inc-brominef low battery (ZBFB) is regarded as one of the most promising candidatesf or large-scale energys torage owing to its high energyd ensity and low cost. However, because of the large internal resistance and poor electrocatalytic activity of graphite-or carbon-felt electrodes,c onventional ZBFBsu sually can only be operated at ar elatively low current density,w hich limits their widespread application.…”