As the most mature liquid flow battery, all vanadium flow battery has developed rapidly in the direction of energy storage. This is largely due to its large energy storage capacity, excellent charging and discharging properties, adjustable output power, high safety performance, long service life, free site selection, environmental friendliness, and low operation and maintenance costs. Compared with traditional lead-acid batteries and new lithium batteries, it has strong long-term energy storage advantages. The basic principle diagram is shown below.

Source: International Renewable Energy Agency, based on Linden and Reddy, 2002.

In China, according to incomplete statistics from titanium media in 2021, the current cost of all vanadium flow batteries is approximately 3-3.2 yuan/Wh, while the average cost of lithium batteries may only be 1.2-1.5 yuan/Wh, which is about 40% of the cost of all vanadium flow batteries. Although all vanadium flow batteries have technological and safety advantages, the high initial cost of all vanadium flow batteries has to some extent limited their industrial development, making their commercialization process still relatively slow. However, the cost reduction accompanying technological development and the lower maintenance costs in the later period still make them highly attractive. According to relevant institutions, with the gradual development of all vanadium flow battery technology and industrialization, its cost is expected to be reduced to 2 yuan/Wh by 2030, achieving a significant cost reduction.

Structural diagram of all vanadium flow battery

Taking an all vanadium flow battery with a basic energy storage capacity of 10 kW/120 kWh as an example [1], its cost mainly includes three almost equal parts: stack cost, electrolyte cost, and peripheral equipment cost. Its main components include proton exchange membrane, electrode material, bipolar plate material, current collector, active electrolyte and electrolyte tank, catalyst, etc. Public information shows that vanadium electrolyte is one of the core materials in all vanadium flow battery systems, accounting for over 40% of the system cost. Its performance will directly affect the working efficiency, operating conditions, and service life of the battery system; The cost of fuel cells accounts for more than 35% of the total cost of all vanadium flow batteries, with the main cost coming from the cost of ion exchange membranes and other component costs accounting for about 25%. The specific cost composition can be referred to in the following figure.

According to the International Renewable Energy Agency IRENA, the total installation cost of flow batteries can be reduced by two-thirds by 2030. According to its published data, the total installation cost of all vanadium flow batteries was $315 per kilowatt hour in 2016, and is expected to decrease to $108 per kilowatt hour by 2030, while the total cost of all vanadium flow batteries is expected to not exceed $360 per kilowatt hour. Liquid flow batteries have high initial costs, but their service life is long, and their batteries can usually cycle over 10000 cycles. Therefore, in the long run, liquid flow batteries still have significant cost advantages. Research has shown [2] that it is feasible to reduce costs to $120/kWh (excluding installation costs) for all vanadium flow batteries with an annual power generation of approximately 10 GWh.

Source: International Renewable Energy Agency, based on Noack et al., 2016.

Source: International Renewable Energy Agency, based on Darling et al., 2014.

     At present, the path to reduce the cost of all vanadium flow batteries is mainly considered from the following aspects:

(1) Improving the chemical cycling stability of materials: The chemical stability of electrolyte materials, electrode materials, and separator materials in the structure of flow batteries helps to extend the service life of the flow battery system and reduce the overall cost of the system;

(2) Reducing material costs: Reducing the costs of active redox substances, electrolytes, and battery stack materials mainly used in all vanadium flow battery systems is also an important means to achieve overall cost reduction of the system;

(3) Improving overall system performance: including improving film conductivity, promoting electrode catalytic reaction kinetics, enhancing reaction activity, thereby achieving a reduction in battery stack size with fixed energy output. According to relevant literature reports [3], by regulating the overall performance of liquid flow batteries, the energy density can be increased from 15Wh/L-70Wh/L to 117Wh/L.

In terms of ion exchange membrane materials, the Nafion proton exchange membrane produced by DuPont is currently mainly used in the commercial field for flow batteries. Nafion membrane uses sulfonic acid groups as exchange groups as the standard separator for all vanadium redox flow batteries. Its stability in the electrolyte is high, but due to the high permeability and non degradability of vanadium ions, especially its expensive price, it limits the further development of flow batteries. Therefore, the current strategy for cost reduction in ion exchange membranes mainly focuses on reducing film resistance, reducing vanadium ion penetration, improving the performance of proton exchange membranes for flow batteries, avoiding active substance pollution to extend the service life of ion exchange membranes, and improving overall system performance, in order to achieve cost reduction in flow batteries.

In terms of active substances, due to the fact that the active substances in all vanadium flow batteries are mainly vanadium ions with different valence states, and water is used as the electrolyte solvent. According to data from the United States Geological Survey (USGS), the world's proven vanadium ore reserves total 22 million tons, with China's reserves reaching 9.5 million tons, accounting for 43% of the total; Russia and South Africa are ranked second and third respectively, accounting for 23% and 16% of global vanadium ore reserves. Currently, China's vanadium ore production accounts for 62% of the world's total production, and vanadium ore production and reserves are relatively abundant. This is also why China and Western countries prefer the all vanadium flow battery system in the selection of flow battery routes. However, Western countries are more inclined to develop zinc bromide flow battery systems with average performance due to vanadium ore reserves. Therefore, trying to reduce costs in vanadium ore resources is also a means to reduce the overall cost of all vanadium flow batteries. In addition, there are other methods that can be adopted to reduce the cost of all vanadium flow batteries. For example, the liquid flow battery system can achieve cost reduction by integrating stacks; In addition, the use of saltwater electrolytes can effectively reduce costs while sacrificing certain performance, by constructing a saltwater electrolyte battery energy storage system to achieve cost reduction for flow batteries. Below, based on public information, we will conduct a certain analysis of the world's mainstream all vanadium flow battery manufacturers, and summarize and sort out their mentioned cost reduction and performance advantages.

The developer of the next-generation liquid flow battery energy storage system claims that WattJoule's 2020 product ElectriStor Gen1 has achieved a price of $200/kWh, only one-third of the market price. In its upcoming second and third generation products, with significant improvements in energy density and efficiency, the cost of vanadium electrolyte continues to decrease, and its product prices will drop to $150/kWh and $100/kWh, respectively. According to its public information, compared to vanadium electrolytes used in all vanadium flow batteries on the market, which have low energy density, limited temperature range, require active cooling equipment, and expensive high-purity vanadium, WattJoule vanadium electrolyte achieves an increase in electrolyte energy density without the need for expensive cooling equipment. Moreover, while ensuring the same energy output, it achieves a generational reduction in vanadium dosage and required purity, thereby achieving a significant reduction in overall cost.

ElectriStor parameter indicators and prices

WattJoule has achieved a reduction in system installation costs and footprint by increasing the energy density and output power density of electrolyte storage. The improvement and expansion of the working temperature range have reduced the use of air conditioning, cooling machines, and other equipment in all vanadium flow battery systems, thereby achieving an overall reduction in system costs and operating costs. WattJoule's vanadium electrolyte reduces its required purity through advanced utilization methods, and it can currently achieve direct use of industrial grade purity vanadium, simplifying and upgrading the electrolyte production process, significantly reducing the manufacturing cost of its electrolyte. This is also described as a confidential purification process in the industry. In addition, according to its official disclosure, the core competitiveness of its products mainly includes four aspects: liquid electrolytes, energy conversion stacks, core material kits, and system supporting software. It can be seen that the current theoretical analysis in academia and the promotional strategies of some companies show much lower costs than the actual installation cost of bidding (more than 3000 yuan/KWh), which also means that there is still huge cost reduction space for all vanadium flow batteries after achieving large-scale production. These low-cost values also indicate the possible cost limit in the future and the huge potential for application and promotion of all vanadium flow batteries.

Schematic diagram of WattJoule electrolyte production process

LE SYSTEM Co., Ltd., a Japanese company specializing in liquid flow batteries, also emphasized in its public information that its biggest advantage in producing all vanadium liquid flow batteries is to effectively recover and efficiently utilize vanadium from industrial waste through its original technology, thereby significantly reducing its costs. It mainly recovers and purifies ammonium metavanadate from electrostatic precipitator ash (EP soot) in petroleum coke power plants. The specific method is to use a reduction furnace calcination to remove impurities from ammonium metavanadate raw materials to obtain vanadium dioxide, which is then subjected to secondary reduction and purification in a reduction cylinder to obtain a 3.5 valent vanadium electrolyte.

VRB Energy stated in its public information that its product VRB-ESS possesses the world's most advanced vanadium redox battery technology. Its core technologies include proprietary low-cost ion exchange membranes and bipolar materials, long-life electrolyte formulations, and innovative flow cell designs. VRB Energy claims that its technological advancements have significantly reduced the cost of core battery pack components. Its fifth generation battery stack design features advanced flow field design, which can optimize the distribution of electrolyte in the battery stack, achieve overall efficiency improvement, and optimize material utilization. It claims that its proprietary electrolyte formula is designed for low-cost manufacturing, optimal performance, and long lifespan, thus achieving a significant reduction in system costs while ensuring performance. And its second-generation VRB-ESS has reduced costs by 35%, reduced footprint by 50%, and improved performance by 10% compared to previously installed systems.

China GEC Jinneng Technology claims in its public information that it has the world's leading global patented technology for ultra-high cost-effective energy storage vanadium batteries. It has huge technological advantages, product advantages, and cost advantages in the use of perfluorinated ion membranes, electrodes, stacks, electrolytes, and full system modularization of vanadium batteries. GEC achieves the production of perfluorinated ion exchange membranes through its independently developed solution casting method. The technology is simple, the production equipment is cheap, the regeneration and recycling of perfluorinated ion exchange membranes can be achieved, the membrane cost is low, the crystallinity is high, the tensile modulus is large, isotropic, and the lifespan is long. It can be well applied to all vanadium flow batteries and reduce costs. The high-performance all vanadium flow batteries produced by it have achieved low flow resistance, low resistance, high current density, high power density, wide operating temperature, no need for heat exchangers, high energy efficiency, high modularity, low production cost, long service life, and much lower total life cost than traditional batteries such as lead-acid and lithium batteries through technological innovation. The high-performance vanadium electrolyte produced by it adopts a unique production formula, which can produce advantages such as high conductivity, wide working temperature, no need for heat exchangers, high stability, low migration of vanadium ions during charging and discharging, and small liquid level changes, which can greatly reduce costs. These technologies have also applied for corresponding invention patents.

HydraRedox, a Spanish company, claims to have developed a novel vanadium redox method that overcomes the shortcomings and limitations of traditional redox flow technology, thereby significantly reducing its costs. Its all vanadium flow battery system technology adopts a highly customized mode, with an expected lifespan of up to three times that of other technologies, and has excellent performance characteristics that can significantly reduce costs.

Power Stac emphasizes in official materials that its all vanadium flow battery system can achieve continuous and stable power supply at lower costs and longer lifespan. On its product data, it can be found that its electrolyte working temperature is wider than the industry level, reaching -30-60 degrees Celsius. As we mentioned, this can lead to a reduction in the use of cooling equipment, which may also be the reason for its cost advantage.

StorEn Technology claims that its all vanadium flow battery can achieve the highest power density at the lowest cost or cycle. It claims that the power density of the battery packs it produces is far higher than the current technological level. The MULTIGRIDS innovative flow design system developed by its team can reduce the cost of battery power by more than 50%, while maintaining the reliability and sustainability of battery pack operation by operating under lower pressure. And it is mentioned in its public information that its battery technology and patents combined with its proprietary Battery Management System (BMS) can make the battery almost maintenance free in the later stage, thereby greatly reducing battery maintenance costs. And the Multigrid system developed by it can eliminate the main technical obstacle of overcharging in the expansion of the flow battery stack size in all vanadium flow battery systems, avoid the increase in system complexity and cost caused by the stacking of a large number of small battery packs, and achieve the construction of large TITANstack stacks with thousands of amperes of current. Therefore, its technological innovation greatly reduces the complexity of the system and significantly reduces costs.

Rongke Energy Storage, a Chinese manufacturer of all vanadium flow batteries, is one of the more important manufacturers of all vanadium flow batteries in China. According to its data, Rongke Energy Storage Company continues to focus on innovative research and development in high-performance battery material technology (electrolytes, bipolar plates, ion membranes, etc.), high-power density stack technology, high-efficiency battery system technology, etc. The unique advantages of its technological innovation points have not been publicly disclosed from its public information. But it claims that its subsidiary Dalian Rongke Energy Storage Equipment Company has built the world's largest and most modern production base for all vanadium flow battery energy storage equipment, and Rongke Energy Storage has become a leading service provider in the development of the entire vanadium flow battery industry chain, complete independent intellectual property rights, and high-end manufacturing capabilities. The TPower product of Rongke Energy Storage, a Chinese manufacturer of all vanadium flow batteries, has also improved in operating temperature. According to its public information, its operating temperature is -35-40 degrees Celsius, while the operating temperature of the other two products is relatively narrow. Compared with the operating temperature of -40-50 degrees Celsius and higher efficiency shown in Visblue data, there is still some room for development.

Largeo's public information shows that the core competitiveness of its all vanadium flow battery products lies in its proprietary VRFB electrolyte treatment technology patent, industry-leading flow battery stack technology, and supply of high-purity vanadium products. According to its public information, its unique patented purification process solves several technical barriers in typical VRFB systems, and Largo has one of the world's highest quality vanadium resource mines, the Marac á s Menchen mine, which is one of the world's lowest cost primary vanadium producers, bringing a true cost advantage. The VCHARGE system it produces contains high-performance flow batteries that can reduce core battery materials by five times, significantly saving costs and occupying the smallest space in any known flow battery. And its VCHARGE system allows for matching power and energy with project requirements through multiple configurations, and its vertical stacking design allows for twice the power or energy density within the same footprint, with significant cost advantages, far ahead of current tank levels. In addition, the steel container design of its system provides strong protection for the battery, preventing weather, UV degradation, and damage, to prevent the cost advantage of the battery stack from deteriorating during long-term application, thereby bringing significant cost advantages.

VANEVO's cost reduction strategy mainly focuses on innovation in stack technology. The VANEVO all vanadium flow battery stack avoids the use of large end plates for support by removing sealing components, resulting in significantly lighter stack weight. Moreover, the stack is produced economically and efficiently through bonding rather than pressing, which is also the main technical content of its multiple core patents. Due to the reduction of spare parts usage and the implementation of automated production, its cost is significantly reduced.

The Volteria powerRFB produced by Voteria is also focusing on stack research. According to public information, the Volterins stack has proprietary design and manufacturing processes, and its stack is different from traditional stacking using gaskets, but instead uses high-precision laser welding technology for stacking. Washers often solidify over time and may lead to leakage, but the Volterio battery pack has excellent sealing performance through new processes. Moreover, due to the fact that the sealing gasket does not require compression force, it can reduce the use of more expensive end plates in Volterio battery packs, achieving compactness, lightness, safety and reliability while also having very advantageous cost-effectiveness. In addition, each Volteria stack has a dedicated electronic stack monitoring system configured inside the stack to ensure optimal operating conditions and a longer lifespan.

In summary, the cost reduction path of all vanadium flow batteries is an important step in their rapid development in the energy storage field. The current overall strategy is mainly to control costs by improving material chemical cycling stability, reducing material costs, and improving overall system performance. While technology continues to improve, we hold a very positive attitude towards the future role of all vanadium flow battery technology in the energy storage field.





reference material:

[1] Darling, R. M., Gallagher, K. G., Kowalski, J. A., Ha, S. and Brushett, F. R. (2014) 'Pathways to low cost electrochemical energy storage: a comparison of aqueous and non aqueous flow batteries', Energy Environment. Sci., vol. 7, no. 11, pp. 3459-3477 [Online]

[2] Minke, C., Kunz, U. and Turek, T. (2017) 'Technical economic assessment of novel advanced redox flow batteries with large area cells', Journal of Power Sources, vol. 361, pp. 105-114 [Online]

[3] Fan, L., Jia, C., Zhu, Y. G. and Wang, Q. (2017) 'Redox Targeting of Prussian Blue: Towards Low Cost and High Energy Density Redox Flow Battery and Solar Rechargeable Battery', ACS Energy Letters, vol. 2, no. 3, pp. 615-621 [Online]

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