美国威斯康星大学麦迪逊分校Feng, Dawei团队报道了卤化物液流电池用软硬两性离子添加剂。相关研究成果发表在2024年10月23日出版的《自然》。

具有卤化物基阴极电解液（卤素原子（X）为Br或I）的水性氧化还原液流电池有望实现可持续的电网储能。然而，在电化学充电过程中多卤化物的形成以及相关的X2相分离限制了可运行的充电状态（SoC），导致汽化和自放电效率低下，并引发了整个器件的故障。

该文中，研究人员介绍软硬两性离子捕获剂（SH-ZITs）作为络合剂，其由聚卤化物络合“软”阳离子基序和水溶性“硬”阴离子基序组成，以实现均匀的卤化物循环。设计了300多个结构，并对13个结构进行了表征，展示了在均相水溶液中络合多卤化物、阻止阳离子交换膜交叉和改变电化学电极机制的能力。

在标准阴极电解液SoC为66.6%（化学计量为X3-）的液流电池循环中，在2个月内进行1000多次循环后，在40mA/cm²时观察到平均库仑效率超过99.9%，没有明显的衰减，在高温下也表现出稳定性。

有趣的是，SH ZITs能够使卤化物阴极电解液在2ml/L（47.7Ah/L）的条件下实现高达90%的SoC的稳定循环，从而揭示了以前未知的有待研究的多卤化物体系。最终，SH-ZITs能够在80%的SoC下实现超高阴极电解液容量利用率，高达120Ah/L以上，具有稳定循环以及与混合液流电池中的锌阳极配对的能力。

附：英文原文

Title: Soft–hard zwitterionic additives for aqueous halide flow batteries

Author: Choi, Gyohun, Sullivan, Patrick, Lv, Xiu-Liang, Li, Wenjie, Lee, Kwanpyung, Kong, Haoyu, Gessler, Sam, Schmidt, J. R., Feng, Dawei

Issue&Volume: 2024-10-23

Abstract: Aqueous redox flow batteries with halide-based catholytes (where the halogen atom (X) is Br or I) are promising for sustainable grid energy storage. However, the formation of polyhalides during electrochemical charging and the associated phase separation into X2 limits the operable state of charge (SoC), results in vaporization and self-discharge inefficiencies, and spurs complete device failure1,2,3. Here we introduce soft–hard zwitterionic trappers (SH-ZITs) as complexing agents composed of a polyhalide-complexing ‘soft’ cationic motif and a water-soluble ‘hard’ anionic motif to enable homogeneous halide cycling. More than 300 structures were designed and 13 were characterized, showcasing the ability to complex polyhalides in homogeneous aqueous solution, to deter cation-exchange membrane crossover and to alter the electrochemical electrode mechanism. In flow battery cycling at a standard catholyte SoC of 66.6per cent (stoichiometrically X3–), an average coulombic efficiency of more than 99.9per cent at 40milliamperes per square centimetre with no apparent decay was observed after more than 1,000cycles over 2months, with stability at elevated temperatures also demonstrated. Interestingly, SH-ZITs enable homogeneous cycling of the halide catholyte up to 90per cent SoC at 2moles per litre (47.7ampere-hours per litre) for bromide, revealing previously unknown polyhalide regimes to be studied. Ultimately, SH-ZIT enables ultrahigh catholyte capacity utilization up to over 120 ampere-hours per litre at 80per cent SoC with homogeneous cycling as well as the ability to pair with a zinc anode in a hybrid flow battery.

DOI: 10.1038/s41586-024-08079-4

Source: https://www.nature.com/articles/s41586-024-08079-4