With the increasing penetration of renewable energy sources in the past decades, stationary energy storage technologies are critically desired for storing electricity generated by non-dispatchable energy sources to mitigate its impact on power grids. Redox flow batteries (RFBs) stand out among these technologies due to their salient features for large-scale energy storage. The primary obstacle to the successful industrialization and broad deployment of RFBs is now their high capital costs. A feasible route to cost reduction is to develop high-power RFBs, since the increase in power performance has a pronounced impact on the cost of RFB systems. In this review, an in-depth inspection of the power performance of RFBs is presented. Perspectives for the future development of high-power RFBs along with implementable strategies addressing both the intrinsic and extrinsic limiting factors are summarized, which are expected to provide useful references steering the further improvement in the power density of RFBs.

Large-scale electrical energy storage with high energy density and round-trip efficiency is important to the resilience of power grids and the effective use of intermittent renewable energy such as solar and wind. Lithium-oxygen battery, due to its high energy density, is believed to be one of the most promising energy storage systems for the future. However, large overpotentials, poor cycling stability, and degradation of electrolytes and cathodes have been hindering the development of lithium-oxygen batteries. Numerous heterogeneous oxygen electrocatalysts have been investigated to lower the overpotentials and enhance the cycling stability of lithium-oxygen batteries. Unfortunately, the prevailing issues of electrode passivation and clogging remain. Over the past few years, redox mediators were explored as homogenous catalysts to address the issues, while only limited success has been achieved for these soluble catalysts. In conjunction with a flowing electrolyte system, a new redox flow lithium-oxygen battery (RFLOB) has been devised to tackle the aforementioned issues. The working mechanism and schematic processes will be elaborated in this review. In addition, the performance gap of RFLOB with respect to practical requirements will be analysed. With the above, we anticipate RFLOB would be a credible solution for the implementation of lithium-oxygen battery chemistry for the next generation energy storage.