All-Vanadium Flow Battery(VRFB): A Key Long-Duration Energy Storage Technology Supporting the Energy Transition

The world is now at a critical stage of transitioning from traditional fossil fuels to renewable energy. The continuous growth in installed capacity and power generation share of wind and solar power is an inevitable trend. However, the weather-dependent nature of renewable energy poses new challenges to power grid stability and supply reliability.

China’s goals of carbon peaking and carbon neutrality have further driven the deep decarbonization of the energy system. In this process, the traditional energy supply model has come under mounting pressure. Although the new energy industry has emerged as a new growth engine, it also faces difficulties in grid connection and accommodation. Improper handling may not only jeopardize energy security but also hinder steady economic and social development.

Flow Batteries: A Rising Star in Long-Duration Energy Storage

Long-duration energy storage generally refers to technologies that can discharge continuously for 4 hours to several days or even weeks. In the energy system, it can smooth fluctuations of renewable energy, realize peak shaving and valley filling, provide reserve capacity, and enhance grid resilience. It plays an irreplaceable role in building a new power system dominated by renewable energy, raising the share of renewable energy accommodation, and safeguarding national energy security. From a broader perspective, long-duration energy storage is also key infrastructure for unlocking the full potential of renewable energy, lowering the overall cost of the power system, creating green jobs, and enhancing national scientific, technological and industrial competitiveness.

Flow batteries convert electrical energy and chemical energy via the circulation of electrolyte between external tanks and stacks. Their defining feature is the decoupling of power and capacity — power is determined by stack size, while energy capacity depends on the volume of electrolyte.

This gives flow batteries the advantages of high safety (mostly aqueous electrolytes), ultra-long cycle life (over 10,000 cycles), easy capacity expansion, environmental friendliness and flexible siting. They are highly suitable for long-duration energy storage scenarios such as large‑scale grid‑side storage, renewable power plant integration, microgrids and off‑grid power supply.

Research Progress in Flow Battery Technology

Continuous innovation in electrolytes, ion exchange membranes, electrodes and stacks is pushing flow batteries toward higher efficiency, lower cost and wider application. As a key long‑duration energy storage technology, flow batteries are playing an increasingly important role in the global energy transition thanks to their high safety, ultra‑long lifespan and flexible scalability.

Industrial Chain Takes Shape! All‑Vanadium Flow Battery Technology Matures

01 Electrolyte Material Innovation: High Concentration, High Stability & Low Cost in ParallelThe electrolyte is the core of the energy storage system, directly affecting battery energy density and cycle life. In recent years, research has focused on developing high‑concentration, high‑stability electrolytes to boost energy density and suppress side reactions.

For inorganic systems such as vanadium‑based and iron‑based chemistries, the key is to improve the solubility and chemical stability of active materials. In organic systems, researchers are designing active molecules with suitable potentials and actively exploring abundant, lower‑cost materials like iron and zinc.

Short‑process manufacturing has become a breakthrough for cost reduction. For example, Sichuan Development Xingxin Vanadium Energy developed a direct liquid‑phase conversion process that bypasses traditional high‑purity vanadium oxide production, cutting raw material costs by 30% and raising vanadium recovery by 10%, with product purity reaching China’s national first‑class standard. The Institute of Process Engineering, Chinese Academy of Sciences, proposed an innovative “pre‑purification – reduction – extraction – deoiling” route that eliminates the intermediate high‑purity V₂O₅ step, produces no ammonia‑nitrogen wastewater, and reduces production costs by nearly 30% compared with conventional processes.

02 Ion Exchange Membrane Breakthroughs: Balancing High Ion Selectivity & Conductivity

Ion exchange membranes must combine high ion selectivity and high conductivity to avoid cross‑contamination of active materials and reduce ohmic loss.

Current research focuses on low‑cost non‑fluorinated porous membranes, modified perfluorinated sulfonic acid membranes, non‑fluorinated polymers and composite membranes. New weldable porous composite membranes paired with high‑conductivity bipolar plates have increased single‑stack volumetric power density from 70 kW/m³ to 130 kW/m³, lifting power from 30 kW to 70 kW at the same volume and cutting costs by 40%.

Sulfonated branched polybenzimidazole (sb‑PBI) membranes show excellent vanadium ion resistance, proton conductivity and selectivity. Their coulombic efficiency, voltage efficiency and energy efficiency all exceed those of commercial Nafion 212 membranes, and they remain stable after 1,170 charge‑discharge cycles.

03 Electrode & Bipolar Plate Optimization: Higher Catalytic Activity & Better Conductivity & Corrosion Resistance

Electrode optimization improves reaction kinetics mainly by enhancing catalytic activity and specific surface area. Common approaches include surface treatment of carbon felt/graphite felt (heat treatment, acid treatment, catalyst loading) and development of new carbon materials such as carbon nanotubes and graphene. A MOF‑derived SnO₂/graphite felt composite electrode raises energy efficiency to 82%, and the introduction of SrZrO₃ perovskite catalysts further optimizes anode reaction kinetics.

Bipolar plates require high conductivity, strong corrosion resistance and low cost. Current research covers optimized graphite plates, polymer/carbon composites, and coated metal plates. Flow field design is also critical: good design ensures uniform electrolyte distribution, low flow resistance and low pumping loss, thus improving overall performance.

04 Stack Design & System Integration: Toward High Power & High Uniformity

Stack design is moving toward high power and high consistency, with further cost reduction via higher integration and fewer connecting components.

In April 2025, Flow Energy Storage Technology Co., Ltd. launched a 125 kW high‑power stack and an 800 kW standardized energy storage system, achieving core innovations through gradient composite membranes, porous flow fields and topology‑optimized structures.

Efficient thermal management is critical for stable, high‑performance battery operation over a wide temperature range. Intelligent control systems significantly improve efficiency, reliability and lifetime through optimized charge‑discharge strategies, state estimation and fault diagnosis.

Artificial intelligence is increasingly integrated into flow batteries. Machine learning algorithms achieve SOC prediction error <3% by analyzing massive operational data. LSTM networks reach 92% accuracy in membrane degradation early warning. Reinforcement learning‑based dynamic flow regulation cuts energy consumption by 15%. Digital twin technology greatly improves system response speed.