Ultrasonic Spraying of Vanadium Flow Battery Electrodes

At present, new energy industries such as wind power and photovoltaics are developing rapidly, but the inherent volatility and intermittency of new energy power generation have become a “stumbling block” in its process of high-proportion application. Under such a background, energy storage technology, as a key support for improving grid reliability and promoting new energy consumption, is receiving high attention from all walks of life. Liquid flow battery technology, especially all-vanadium liquid flow battery (VRFB), has become a “rising star” with great potential in the field of large-scale energy storage technology with its significant advantages such as high safety, high efficiency, long cycle life, and scalability and flexibility brought by modular design. However, the current situation of high cost of liquid flow batteries still exists, and improving battery power density and operating efficiency is one of the effective ways to reduce its cost.

As the core key material of liquid flow batteries, electrodes not only provide the necessary reaction site for redox reactions during the charging and discharging process, but also bear the heavy responsibility of building channels for the transmission of internal active substances. The performance of electrode materials directly affects the electrochemical reaction rate, battery internal resistance and electrolyte transmission conditions. Therefore, structural design optimization and surface property modification of electrode materials are of vital importance for improving battery power density, operating efficiency and service life, as well as reducing system costs.

At present, the electrode materials commonly used in all-vanadium liquid flow batteries are graphite felt (GF) or carbon felt materials. These materials have low cost, good conductivity, large specific surface area, and good chemical stability. However, they also have a series of problems such as solid-liquid interface incompatibility, limited number of active sites, and large mass transfer resistance. Past studies have mostly focused on modifying the chemical properties of electrode materials by means of heat treatment, electrochemical/chemical treatment, and functional material modification, so as to reduce battery polarization and improve battery performance. However, the impact of electrode structure design on electrolyte distribution and mass transfer and battery performance has received relatively little attention. This article will comprehensively review the electrode structure design at different scales from macro to micro, as well as its practical application in all-vanadium liquid flow batteries.

At the macro scale, structural parameters such as electrode compression ratio, electrode flow field structure, and electrode geometry have an important impact on battery performance. For example, a reasonable adjustment of the electrode compression ratio can change the pore structure inside the electrode, thereby affecting the transmission efficiency of the electrolyte in the electrode. When the electrode compression ratio is in an appropriate range, the electrolyte can flow more smoothly inside the electrode and fully contact the active material, thereby improving the charge and discharge performance of the battery. Optimizing the electrode flow field structure can guide the electrolyte to be evenly distributed on the electrode surface, avoid the situation where the local electrolyte concentration is too high or too low, and effectively improve the overall performance of the battery. As for the design of the electrode geometry, different shapes will affect the flow pattern of the electrolyte. Choosing a suitable geometry can enhance the interaction between the electrolyte and the electrode and improve the operating efficiency of the battery.

At the microscopic scale, the construction of a single-layer electrode with a multi-level pore distribution and a multi-layer electrode structure with a gradient distribution by physical and chemical methods can achieve a synergistic improvement in electrolyte transmission performance and electrochemical performance. The rich pore structure of the single-layer electrode with a multi-level pore distribution provides more channels for the transmission of the electrolyte, while also increasing the contact area between the active material and the electrolyte, and increasing the rate of the electrochemical reaction. The multilayer electrode structure with gradient distribution can adjust the electrode structure in a targeted manner according to the transmission requirements of the electrolyte in different areas. In the area close to the electrolyte inlet, larger pores can be designed to facilitate the rapid entry of the electrolyte into the electrode; in the part close to the reaction area, smaller pores are used to increase the active sites and improve the efficiency of the electrochemical reaction.

Here, we have to mention the innovative application of ultrasonic spraying technology in all-vanadium liquid flow battery electrodes. Ultrasonic spraying technology has many significant advantages. First, this technology can achieve high-precision coating preparation. In the process of making all-vanadium liquid flow battery electrodes, functionalized materials can be evenly and accurately coated on the electrode surface through ultrasonic spraying, effectively increasing the active sites of the electrode. Compared with traditional coating methods, ultrasonic spraying technology can control the error of coating thickness within a very small range to ensure the performance consistency of each electrode. This is undoubtedly extremely important for the large-scale production of all-vanadium liquid flow batteries, which can greatly improve the product yield.

Second, ultrasonic spraying technology can effectively improve the surface properties of electrodes. After coating the electrode surface with specific functional materials, the compatibility between the electrode and the electrolyte can be enhanced and the resistance of the solid-liquid interface can be reduced. This means that the electrolyte can diffuse more easily on the electrode surface and react with the active material, thereby improving the power density and operating efficiency of the battery. Moreover, the coating coated by this technology has good adhesion to the electrode substrate and is not easy to fall off, which can ensure the stability of the electrode during long-term use.

Third, ultrasonic spraying technology helps to optimize the microstructure of the electrode. When constructing a single-layer electrode or a multi-layer electrode structure with a multi-level pore distribution, the cavitation effect of ultrasound can be used to accurately control the size and distribution of the pores. By adjusting the parameters of ultrasound, an ideal pore structure can be formed inside the electrode, promoting the transmission and diffusion of the electrolyte, and further improving the performance of the battery. This ability to precisely control the microstructure is a major feature of ultrasonic spraying technology and an important advantage in the application of all-vanadium liquid flow battery electrodes.

In general, the reasonable design of the electrode structure from macro to micro can significantly improve the performance of all-vanadium liquid flow batteries. Ultrasonic spraying technology has shown great application potential in the field of all-vanadium liquid flow battery electrodes due to its unique advantages such as high-precision coating preparation, improvement of electrode surface properties and optimization of electrode microstructure. We believe that with the continuous development and improvement of technology, Cheersonic ultrasonic spraying technology will inject strong impetus into the industrialization process of all-vanadium liquid flow batteries and help them play a more important role in the field of large-scale energy storage.

About Cheersonic

Cheersonic is the leading developer and manufacturer of ultrasonic coating systems for applying precise, thin film coatings to protect, strengthen or smooth surfaces on parts and components for the microelectronics/electronics, alternative energy, medical and industrial markets, including specialized glass applications in construction and automotive.

Our coating solutions are environmentally-friendly, efficient and highly reliable, and enable dramatic reductions in overspray, savings in raw material, water and energy usage and provide improved process repeatability, transfer efficiency, high uniformity and reduced emissions.

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