Emerging Polyoxometalate Clusters-based Redox Flow Batteries: Performance Metrics, Application Prospects, and Development Strategies

Redox flow battery (RFB) technologies open a new era for large-scale energy storage systems, with the development of a new generation of polyoxometalate clusters-based redox flow batteries (POM-RFBs) enabling the high energy density RFBs to be possible. Looking back at the decade-long journey of POM-RFB research, it is evident that significant progress has been made in enhancing the RFB performance, yet several challenges still require resolution. Herein, firstly, the critical merits of POM clusters including their multi-electron redox properties, strong stability, and high solubility, are emphatically summarized as they significantly contribute to the superior performance metrics of POM-RFBs. Furthermore, applications of POM as electrolyte active materials in both aqueous and non-aqueous RFBs are systematically elaborated, considering both symmetric and asymmetric configurations, which highlight the adaptability of POMs across different setups and their RFB performance. Looking ahead, future development strategies for POM-RFBs are chiefly elucidated, focusing on advanced computational efforts, performance improvement and cost reduction of electrolyte-membrane-electrode, as well as forward-looking evaluations in commercial applications. Drawing from these discussions, this review is expected to furnish valuable insights for POM-RFBs both in-depth laboratory research and broad commercial deployment, concurrently laying a solid foundation for achieving the strategic goals in long-duration energy storage.