Bromine-based flow batteries (Br-FBs) are appealing for stationary energy storage because of their high energy density and low cost. However, the wider application of Br-FBs is hindered by the sluggish reaction kinetics of the Br₂/Br⁻ redox couple and serious bromine crossover. Adding bromine complexing agents (BCAs) into electrolytes can inhibit bromine crossover effectively, but it generally deteriorates the reaction kinetics. Here, we use hexadecyl trimethyl ammonium bromide (CTAB) to intercalate Ti₃C₂T_x MXene as electrodes for Br-FBs. In this design, CTAB acts as the BCA to form robust solid bromine complexes, which are accompanied by highly active Ti₃C₂T_x MXene carriers. Soluble bromine species diffusion is perfectly suppressed based on such a strong and reversible solid complexation effect, while the adverse effect of solid complexes on reaction kinetics is well overcome. Thus, the assembled zinc-bromine flow battery delivered a remarkable improvement in suppressing self-discharge, achieving an unprecedently high capacity retention rate of 82.93% after standing for 24 h at 80 mA cm⁻². At a high current density of 180 mA cm⁻², this battery exhibited the highest voltage efficiency of 66.76% and energy efficiency of 66.06% ever reported, and also showed an outstanding long-term durability for 580 cycles with a high coulombic efficiency of 99.30%. This work provides a new strategy for designing electrodes with ultralow self-discharge, high power density and long cycle life for Br-FBs.

中文翻译：

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可逆固体溴络合到 Ti3C2TX MXene 载体中：用于溴基液流电池的高活性电极，具有超低自放电

溴基液流电池（Br-FB）因其高能量密度和低成本而对于固定储能很有吸引力。然而，Br-FBs的更广泛应用受到Br ₂ /Br ^-氧化还原对缓慢的反应动力学和严重的溴交叉的阻碍。在电解质中添加溴络合剂（BCA）可以有效抑制溴渗透，但通常会恶化反应动力学。在这里，我们使用十六烷基三甲基溴化铵（CTAB）来插入 Ti ₃ C ₂ T _x MXene 作为 Br-FB 的电极。在此设计中，CTAB 充当 BCA，形成坚固的固体溴络合物，并伴有高活性 Ti ₃ C ₂ T _x MXene 载体。基于这种强而可逆的固体络合效应，可溶性溴物质的扩散得到了完美的抑制，同时也很好地克服了固体络合物对反应动力学的不利影响。因此，组装的锌溴液流电池在抑制自放电方面具有显着的改善，在80 mA cm ^-2下静置24小时后实现了82.93%的前所未有的高容量保持率。在180 mA cm ^-2的高电流密度下，该电池表现出迄今为止报道的最高电压效率66.76%和能量效率66.06%，并且还表现出出色的580次循环的长期耐久性，库仑效率高达99.30 %。这项工作为设计具有超低自放电、高功率密度和长循环寿命的 Br-FB 电极提供了新策略。