Five-Membered-Heterocycle Bridged Viologen with High Voltage and Superior Stability for Flow Battery

作者：Huang, Mingbao; Hu, Shuzhi; Yuan, Xianzhi; Huang, Jinghua; Li, Wenjin; Xiang, Zhipeng; Fu, Zhiyong^*; Liang, Zhenxing^*

来源：Advanced Functional Materials, 2022, 32(16): 2111744.

DOI：10.1002/adfm.202111744

• pi-bridge
• aqueous flow batteries
• high voltage
• thiophene
• viologen

Viologen and its derivatives have been widely investigated as the electroactive materials in aqueous flow batteries (AFBs). The high redox potential of viologen poses a challenge to the AFB's energy density when used as the negative electrolyte. A molecular engineering strategy is developed by inserting an electron-rich pi-bridge unit (viz. thiophene, furan) between the two pyridiniums to lower the redox potential. The resultant 1,1'-bis[3-(trimethylamonium)propyl]-4,4'-(2,5-thiophenediyl)bispyridinium tetrachloride ((ATBPy)Cl-4) and 1,1'-bis[3-(trimethylamonium)propyl]-4,4 '-(2,5-furandiyl)bispyridinium tetrachloride ((AFBPy)Cl-4) are investigated by a variety of physiochemical methods to track the structure of the molecule and its evolution during the electrochemical reaction. A flow battery is assembled to verify the applicability of (ATBPy)Cl-4 with 1-(1-oxyl-2,2,6,6-tetramethylpiperidin-4-yl)-1'-(3-(trimethylammonio)propyl)-4,4'-bipyridinium trichloride as the positive electrolyte. Run at the concentration of 1.0 m, the battery achieves a standard cell voltage of 1.51 V, capacity of 23.6 Ah L-1, energy efficiency of 85.7% at 60 mA cm(-2), and a record peak power density of 302 mW cm(-2), which outperform the reported viologen-AFBs in literature. This work provides an effective strategy to develop electrochemically active compounds with tunable redox potential and superior chemical stability by molecule engineering.

• 单位
  中山大学