Emerging deposition–dissolution chemistry for next-generation metal-based hybrid flow batteries: progress and perspectives

As fossil fuels deplete and environmental pollution intensifies, the effective utilization of intermittent renewables calls for large-scale long-duration energy storage technologies. Metal-based hybrid flow batteries (MBHFBs) have considerable potential in energy density and cost efficiency, attributed to unique deposition-dissolution chemistry and abundant metal resources. However, the deployment and understanding of MBHFBs remain in their infancy. Moreover, the variation among metals leads to distinct challenges across various MBHFBs. To systematically address these challenges, this review adopts deposition-dissolution chemistry as a central theme and provides a comprehensive analysis of MBHFBs from an all-round perspective. Horizontally, MBHFBs are categorized into two groups based on non-aqueous/aqueous electrolyte, and further subdivided into eleven subcategories according to the anodic metals, evaluated in terms of principles, architectures, advantages, challenges, and corresponding strategies. Vertically, the advances and limitations of four core components (electrolytes, electrodes, membranes, and bipolar plates) are examined, aiming to reveal underlying interconnections and synergistic effects. Finally, we propose ten promising future research directions for MBHFBs. This review aims to improve the understanding of design principles and optimization strategies for MBHFBs, support the establishment of a unified theoretical framework for deposition-dissolution chemistry, and offer relevant insights for developing next-generation low-cost and high-energy-density energy storage technologies.