This paper describes the design and synthesis of a series of terpyridine-based complexes of the first-row transition metals Cr, Mn, Fe, and Co for non-aqueous redox flow batteries (NARFBs). Electrochemical studies reveal that these complexes can undergo multi-electron transfer redox reactions. In particular, the Mn and Fe-based complexes exhibit both low negative redox potentials and high positive redox potential, permitting them to serve as a bipolar electrolyte for symmetric RFBs with a cell voltage of more than 2 V. The solubility of these complexes can be effectively improved by incorporating a polyether substituent on the terpyridine ligand and counter anion optimization. The iron complex [Fe(tpy-O(CH₂CH₂O)₃CH₃)₂][TFSI]₂ shows a high solubility of 0.76 M in MeCN. The fabricated iron-based symmetric NARFB demonstrates a superior battery performance with a high cell voltage of 2.3 V, columbic efficiency of 97%, energy efficiency as high as 88%, and stable charge-discharge capacity retention of 60% after 160 cycles, corresponding to 99.75 % capacity retention per cycle. The post-cycling cyclic voltammetry (CV), UV-Vis, and ¹H-NMR characterizations indicate only minor chemical decomposition of the cycled complex, confirming its good charging-discharging stability.

本文描述了一系列用于非水氧化还原液流电池 (NARFB) 的第一排过渡金属 Cr、Mn、Fe 和 Co 的三联吡啶基配合物的设计和合成。电化学研究表明，这些配合物可以进行多电子转移氧化还原反应。特别是，基于 Mn 和 Fe 的配合物表现出低负氧化还原电位和高正氧化还原电位，使它们可以用作电池电压超过 2 V 的对称 RFB 的双极电解质。这些配合物的溶解度可以是通过在三联吡啶配体上加入聚醚取代基和抗衡阴离子优化，有效改善了性能。铁配合物[Fe(tpy-O(CH ₂ CH ₂ O) ₃ CH ₃ ) ₂][TFSI] ₂在 MeCN 中显示出 0.76 M 的高溶解度。制备的铁基对称NARFB表现出优异的电池性能，电池电压高达2.3 V，库伦效率为97%，能量效率高达88%，160次循环后稳定的充放电容量保持率为60%，相应每个循环的容量保持率为 99.75%。循环后循环伏安法 (CV)、UV-Vis 和¹ H-NMR 表征表明循环配合物仅发生轻微的化学分解，证实了其良好的充放电稳定性。