Fig. 4: Performance and cycling stability of the Fe-Ce DTPA RFB.

a Voltage-capacity diagram of 0.5 M Fe-Ce DTPA RFB at different current densities (from 40 to 120 mA cm⁻²) and (b) corresponding efficiency and current densities. c Discharge voltage and power density plots vs. current density. Power densities are shown for the 60%, 70%, 80%, 90%, and 100% SOC, respectively. d Partial characteristic charge and discharge curve in full battery test at 40 mA·cm⁻². e Efficiency and capacity data of the full battery test at 40 mA cm⁻² for 500 cycles. f Cycle test of 0.5 M Fe-Ce DTPA RFB at 80 mA cm⁻² under 70% SOC. In situ Raman spectra on (g) Fe-DTPA and (h) Ce-DTPA obtained from 0 to 100% SOC, with the real-time status of the corresponding electrolyte recorded. i Representative charge and discharge profiles and (j) performance of the·0.5 M Fe-Ce DTPA RFB stack at 80 mA cm⁻². k CV curves of 0.2 M Fe-CN, Fe-DTPA, and Ce-DTPA solutions. l Efficiency and capacity of K₃[Fe(CN)₆] / K₄[Fe(CN)₆] electrolyte in a 1031 h cycling test. The inset in (l) shows the charge-discharge curves at the first 10 cycles and the last 10 cycles of the test. All electrochemical tests were performed at 25 ± 1 °C. Source data are provided as a Source Data file.