In terms of the current development of liquid flow batteries in China, all vanadium liquid flow batteries are the most prominent, with the highest degree of commercialization and the largest installed capacity. Domestic enterprises and industrial supporting facilities engaged in all vanadium liquid flow batteries are becoming more mature, gradually entering the early stage of commercialization and developing rapidly. Compared to lithium resources, vanadium ore resources in China are relatively abundant and there will be no shortage.
The iron chromium flow battery is mainly limited by the severe hydrogen evolution reaction at its cathode, and the poor activity of chromium ions, which requires the use of catalysts. Although its raw materials are cheap and easy to obtain, its battery efficiency and overall power density are difficult to stabilize, so it is mainly in the engineering demonstration stage, and its development is far behind that of all vanadium flow batteries. In addition, the overseas dependence on chromium supply is close to 100%, which is a potential risk.
The development progress of zinc bromine and zinc iron flow batteries in China is slightly slower than that in foreign countries. They have characteristics such as high energy density and low material cost. However, in the long cycle process of zinc based flow batteries, zinc ions in the electrolyte are prone to diffuse to the protrusions on the electrode surface, forming zinc dendrites. The continuous growth of zinc dendrites will puncture the separator, ultimately leading to battery short circuit failure. Therefore, zinc based flow batteries must address the issues of zinc dendrite formation and growth in order to achieve true applications. Its future commercialization prospects are broad, but currently the domestic technology route and industrial chain are not yet mature and in the early stage, and continuous innovation and development are needed to achieve large-scale application.

As of the end of 2020, the cumulative installed capacity of energy storage projects currently in operation worldwide reached 191.1 gigawatts, with pumped storage having the largest cumulative installed capacity, accounting for 90.3%. Meanwhile, the installed capacity of electrochemical energy storage closely follows, accounting for 7.5%, including lithium-ion batteries, lead-acid batteries, sodium sulfur batteries, and flow batteries. Not long ago, the National Development and Reform Commission and the National Energy Administration issued the Implementation Plan for the Development of New Energy Storage during the 14th Five Year Plan period, which clearly stated the need to vigorously carry out research on key core technologies, equipment, and integrated optimization design such as sodium ion batteries, new lithium-ion batteries, lead carbon batteries, and flow batteries. The National Energy Administration has also put forward specific requirements for the safety of emerging electrochemical energy storage technologies in the "25 Key Requirements for Preventing Electricity Production Accidents (2022 Edition) (Draft for Comments)", and has explicitly removed ternary lithium-ion batteries and sodium sulfur batteries from the options for medium to large electrochemical energy storage.
There are still certain challenges in the engineering and commercialization of liquid flow batteries. Currently, the number of demonstration projects for liquid flow batteries is relatively small, mainly at the MW level, with hybrid demonstration being the majority. Combined with the mixed application and investigation of lithium-ion batteries such as iron lithium and ternary, there are relatively few independent demonstration projects for full liquid flow batteries. As of the end of 2021, the cumulative installed capacity of liquid flow batteries in China is approximately 200MW, accounting for about 0.4% of the cumulative installed capacity of energy storage. However, their installed capacity is rapidly increasing. According to relevant institutions, based on the cumulative 30GW of electrochemical energy storage in 2025, with the acceleration of commercial promotion of vanadium batteries, it is expected that the new installed capacity of all vanadium flow batteries will reach 1.7GW by 2025, with a new penetration rate of 20%; By 2025, the cumulative installed capacity of vanadium batteries will reach 4.3GW, with a cumulative penetration rate of 14%. The cumulative installed capacity of vanadium flow batteries reached 112% from 2020 to 2025, indicating a broad market prospect for vanadium flow batteries.

At present, high cost is the biggest obstacle to the commercialization of vanadium flow battery energy storage. Although the initial installation cost of all vanadium flow batteries in China is lower than the international level, it is still at a relatively high level compared to lead and lithium-ion batteries. Due to the scale effect brought by rapid development, the cost of lead and lithium-ion batteries has decreased rapidly in recent years, resulting in their increment far exceeding that of flow batteries. At present, the EPC cost of all vanadium flow battery energy storage systems is about 3-4 yuan/Wh, which is about twice that of lithium battery systems. Although according to relevant calculations, it is expected to reduce costs by half by 2030, it will still be higher than other competitive battery systems on the market.

The cost of an all vanadium flow battery system is influenced by multiple factors such as key materials, stack structure, and operating conditions. In the vanadium battery energy storage system, the vanadium electrolyte accounts for the largest proportion of cost, accounting for about 40% of the total cost. The cost of the battery stack reaches over 35%, while others account for about 25%. We have analyzed the cost reduction path of all vanadium flow batteries in previous articles, mainly focusing on improving the chemical cycling stability of materials, enabling them to have a longer service life in flow batteries, thereby reducing the overall system cost; On the other hand, by reducing the cost of materials used, the production cost of the electrolyte and stack with the highest cost proportion in the flow battery can be reduced, thereby reducing the overall cost of vanadium batteries; In addition, it also includes improving the overall performance of the system, achieving a reduction in stack size while maintaining constant output power, thereby reducing material usage.
For liquid flow battery energy storage systems, there are still some practical application issues that need to be further optimized. For example, low electrolyte solubility can lead to low energy density, and the porosity of the electrode can affect the polarization and energy efficiency of the battery. In addition, the design of the flow field structure will increase mass transfer resistance, and membrane selectivity may lead to ion cross permeation and electrolyte imbalance. Then, modeling accuracy issues lead to inaccurate estimation of performance parameters, resulting in a decrease in battery performance; Stacking layout leads to transmission delay and concentration polarization. The above issues may constrain the rapid promotion of all vanadium liquid flow systems.
Problems that may affect battery performance in engineering include electrochemical degradation of components, electrolyte leakage, and mechanical failures of critical components. During the operation of all vanadium flow batteries, there are phenomena such as uneven electrolyte distribution, flow dead zones, vanadium ion diffusion, hydrogen and oxygen evolution side reactions, electrolyte imbalance, capacity decay, self discharge, mass transfer blockage, local polarization, etc., which lead to a decrease in battery efficiency and affect the overall performance of the battery. These issues need to be addressed through operational optimization strategies such as flow field design, flow optimization, stack optimization, and energy reduction to ensure that the all vanadium flow battery system operates at its optimal state. Therefore, optimizing battery operation to improve overall battery performance and reduce the cost of key components can further promote the widespread commercialization of vanadium batteries. In this context, the structural design and operational optimization of all vanadium flow battery systems are important methods to improve battery performance, and usually do not require significant improvement costs. Therefore, the optimization of operating parameters is of great significance in the industrial application of battery systems.
Although all vanadium flow batteries have problems such as low energy density and complex operation, their advantages are also very prominent: low non flammable safety risk, long service life, recyclable electrolyte, flexible expansion of battery capacity, suitable for increasing discharge duration in the future, and can achieve 100% discharge without damaging the battery. Therefore, all vanadium flow batteries are very suitable for medium to large-scale energy storage applications, especially in new energy fields such as photovoltaics and wind energy. The success or failure lies in whether the entire industry can mobilize its efforts to reduce initial installation costs through the following channels:
Developing alternative materials with lower production costs;
Division of labor and meticulous work, reducing the processing costs of each component through standardized and large-scale production;
Optimize component design, engineering construction, and system operating parameters to achieve higher system efficiency.

往期更多内容：

全钒液流电池的成本结构分析以及提效降本路线

液流电池用双极板的类型与改进方向

全钒液流电池材料行业深度报告

液流电池流道设计类型对系统性能的影响

国家能源局：三元锂电池、钠硫电池不得用于中大型储能