Affiliation:
1. Department of Chemistry Zhejiang University Hangzhou Zhejiang 310058 China
2. Key Laboratory of Precise Synthesis of Functional Molecules of Zhejiang Province Department of Chemistry School of Science and Research Center for Industries of the Future Westlake University Hangzhou 310030 China Institute of Natural Sciences Westlake Institute for Advanced Study Hangzhou 310024 China
3. School of Chemistry and Materials Science Hangzhou Institute for Advanced Study University of Chinese Academy of Sciences 1 Sub-lane Xiangshan Hangzhou 310024 China
Abstract
AbstractThe rising energy demand driven by human activity has posed pressing challenges in embracing renewable energy, necessitating advances in energy storage technologies to maximize their utilization efficiency. Recent studies in aqueous organic redox flow batteries have focused primarily on the development of organic negative electrolytes, while the progress in organic positive electrolytes remains constrained by limitations in their redox potentials and effective electron concentrations. Herein, we report a spatially twisted chlorinated spirobifluorene ammonium salts (CSFAs), created through an unexpected green chlorination‐protection pathway during the initial cycling in the flow battery cell, utilizing chloride ions from counterions in aqueous solution. The chlorinated, nonplanar spiral structure of CSFAs possesses a one‐step four‐electron transfer electrochemical property and offers exceptional resistance to nucleophilic attacks, exhibiting an unprecedented redox potential as high as 1.05 V (vs. SHE). A full redox flow battery based on CSFA‐Cl (chloride ions as the counter ions) with 1.4 M electron concentration achieved an average coulombic efficiency exceeding 99.4 % and a capacity utilization reaching 95 % of the four‐electron capacity for a stable cycling over 250 cycles (~22 days). The present work exemplifies the use of side reactions to develop new redox species, which can be extended to create more structurally versatile energy storage materials.