Advances and prospects of flow batteries under the “Dual Carbon” goals

Against the backdrop of China’s carbon peaking and neutrality targets, the accelerated transition toward clean and low-carbon energy systems has driven substantial increases in renewable energy penetration, particularly photovoltaic and wind power generation. However, renewable energy sources exhibit significant intermittency and volatility. The increasing penetration of renewable energy generation will exacerbate challenges in power system accommodation, grid peak shaving, and frequency regulation. Energy storage technologies, capable of effectively balancing load demands in power systems, represent an essential pathway for achieving the “dual carbon” objectives.Compared with conventional pumped hydro storage, emerging energy storage technologies represented by electrochemical systems demonstrate bidirectional millisecond-level rapid regulation capabilities. These technologies play crucial roles in enhancing power system flexibility, emergency power support, and contingency reserves, serving as effective solutions to address power balance and grid stability challenges. They are progressively becoming a pivotal direction in energy storage development. Among various electrochemical energy storage technologies, flow batteries stand out with their unique advantage of decoupled power and capacity, coupled with inherent safety, exceptional cycle longevity, and environmental friendliness, gradually emerging as one of the most promising electrochemical energy storage candidates for long-duration storage applications. In recent years, China has witnessed vigorous development across multiple flow battery technological routes, including iron-chromium, all-vanadium, zinc-iron, all-iron, and aqueous organic systems. Flow battery technology has now entered a phase of full-speed advancement in both production capacity and technological innovation. However, current flow battery technology accounts for no more than 2% of the electrochemical energy storage market, with high initial installation costs remaining a key factor constraining its industrialization. The levelized costs of flow batteries are closely tied to their efficiency and lifespan. Components such as battery membranes, electrodes, and bipolar plates form critical elements of the stack (power module), while the electrolyte constitutes the capacity module. These materials represent the core components of flow batteries, whose quality directly impacts the operational efficiency and stability. Consequently, researchers are currently conducting cutting-edge studies on these key materials to break through performance bottlenecks. Regarding the stack, developing high-power-density and low-cost stacks represents a critical future direction and a key prerequisite for achieving large-scale applications of flow batteries, which entails advancing membranes with high selectivity, conductivity, and stability; electrodes with high activity, conductivity, and low resistance; and novel bipolar plates featuring high conductivity, mechanical strength, stability, and cost-effectiveness. Additionally, optimizing flow field configurations, stack architectures, and assembly processes can further promote cost reduction and efficiency improvement for flow battery stacks. For the electrolyte, exploring novel electrolyte systems characterized by low cost, high stability, and high energy density constitutes a strategic pathway toward achieving affordable long-duration energy storage. Through the innovation of key materials, the improvement of flow battery performance and the reduction of comprehensive cost can be realized, hence promoting the rapid development of flow battery energy storage technology.In this review, we will systematically outline prevailing flow battery technological pathways and their developmental milestones, critically analyze persistent material-level bottlenecks, and synthesize cutting-edge research advancements focusing on core components, including ion-exchange membranes, porous electrodes, bipolar plates, and redox-active electrolytes. Furthermore, strategic trajectories for next-generation flow battery system optimization and scale-up deployment will be delineated.