Energy storage systems are crucial in the deployment of renewable energies. As one of the most promising solutions, redox flow batteries (RFBs) are still hindered for practical applications by low energy density, high cost, and environmental concerns. To breakthrough the fundamental solubility limit that restricts boosting energy density of the cell, we here demonstrate a new RFB system employing polysulfide and high concentrated ferricyanide (up to 1.6 M) species as reactants. The RFB cell exhibits high cell performances with capacity retention of 96.9% after 1,500 cycles and low reactant cost of $32.47/kWh. Moreover, neutral aqueous electrolytes are environmentally benign and cost-effective. A cell stack is assembled and exhibits low capacity fade rate of 0.021% per cycle over 642 charging-discharging steps (spans 60 days). This neutral polysulfide/ferricyanide RFB technology with high safety, long-duration, low cost, and feasibility of scale-up is an innovative design for storing massive energy.

储能系统对于可再生能源的部署至关重要。作为最有前途的解决方案之一，氧化还原液流电池（RFBs）仍然受到低能量密度、高成本和环境问题的实际应用的阻碍。为了突破限制提高电池能量密度的基本溶解度极限，我们在这里展示了一种新的 RFB 系统，该系统采用多硫化物和高浓度铁氰化物（高达 1.6 M）物种作为反应物。RFB 电池表现出高电池性能，1,500 次循环后容量保持率为 96.9%，反应物成本低，仅为 32.47 美元/千瓦时。此外，中性水性电解质对环境无害且具有成本效益。电池组组装完成，在 642 次充放电步骤（跨度 60 天）中显示出每个循环 0.021% 的低容量衰减率。