Porphyrin‐Based Symmetric Redox‐Flow Batteries towards Cold‐Climate Energy Storage

Electrochemical energy storage with redox‐flow batteries (RFBs) under subzero temperature is of great significance for the use of renewable energy in cold regions. However, RFBs are generally used above 10 °C. Herein we present non‐aqueous organic RFBs based on 5,10,15,20‐tetraphenylporphyrin (H2TPP) as a bipolar redox‐active material (anode: [H2TPP]2−/H2TPP, cathode: H2TPP/[H2TPP]2+) and a Y‐zeolite–poly(vinylidene fluoride) (Y‐PVDF) ion‐selective membrane with high ionic conductivity as a separator. The constructed RFBs exhibit a high volumetric capacity of 8.72 Ah L−1 with a high voltage of 2.83 V and excellent cycling stability (capacity retention exceeding 99.98 % per cycle) in the temperature range between 20 and −40 °C. Our study highlights principles for the design of RFBs that operate at low temperatures, thus offering a promising approach to electrochemical energy storage under cold‐climate conditions.