A novel tin-bromine redox flow battery for large-scale energy storage

[Display omitted] •A tin-bromine redox flow battery with the Br-mixed electrolyte is proposed.•The current density is up to 200 mA cm−2 with the energy efficiency of 82.6%.•A Sn reverse-electrodeposition method achieves in-situ capacity recovery.•The battery cost is estimated to be $148 kWh−1 at the optimistic scenario. The redox flow battery (RFB) is among the most promising large-scale energy storage technologies for intermittent renewables, but its cost and cycle life still remain challenging for commercialization. This work proposes and demonstrates a high-performance, low-cost and long-life tin-bromine redox flow battery (Sn/Br RFB) with the Br-mixed electrolyte. The coulombic efficiency and energy efficiency of the Sn/Br RFB reach 97.6% and 82.6% at a high operating current density of 200 mA cm−2, respectively. The peak power density at 50% state-of-charge achieves 673 and 824 mW cm−2 at 15 and 35 °C, respectively, which is among the highest performance of hybrid RFBs. To address the Sn cross-contamination issue, a Sn reverse-electrodeposition method is demonstrated, and achieves in-situ capacity recovery as well as long cycle life. Moreover, the active material cost of the Br-mixed electrolyte is merely $54 kWh−1, while capital cost of the Sn/Br RFB is estimated to be as low as $193 kWh−1 for 4-hour electricity discharge, and expected to reduce to $148 kWh−1 at the optimistic scenario in the future. With high cell performance, in-situ capacity recovery and inexpensive active materials, the Sn/Br RFB is believed to offer a promising solution for massive electricity storage.