Ultrasonic Spraying of Flow Battery Materials
Ultrasonic Spraying of Flow Battery Materials – Cheersonic
In the energy field, flow batteries, as a highly promising energy storage technology, are receiving more and more attention. The quality of their performance is closely related to multiple key materials, and in the preparation and application of these materials, ultrasonic spraying technology is emerging and showing unique advantages. The key materials that determine the power of flow batteries mainly include bipolar plates, electrodes, diaphragms and electrolytes. Below we will explore these materials and the application of ultrasonic spraying in them.
Bipolar plates: performance and challenges coexist
Bipolar plates play a vital role in flow batteries. They have two main functions. First, they are responsible for conducting electrons, ensuring the connectivity of the internal circuit of the battery and ensuring the smooth transmission of current. Second, they can effectively isolate the current collector from the electrolyte inside the electrode to prevent the current collector from being damaged by corrosion. At present, the most commonly used bipolar plate materials are graphite plates and conductive plastics.
Graphite plates are usually processed and manufactured with graphite powder as raw material. Its significant advantage is good conductivity, which makes the polarization and power increase of liquid flow batteries not limited by the bipolar plate part. The graphite plates used in liquid flow batteries can be divided into ordinary graphite plates and engraved flow channel graphite plates. Engraved flow channel graphite plates can increase the mass transfer rate of the battery stack, but it is accompanied by a substantial increase in the cost of bipolar plates. In addition, under the condition of high-power operation of the liquid flow battery stack, the graphite plate may undergo electrochemical corrosion, and even perforation after long-term operation, which will cause the electrolyte to flow out and corrode the current collector.
Conductive plastics have the characteristics of low density and better processing performance than graphite plates. However, its disadvantage is that the conductivity is low, which to some extent limits the power increase of liquid flow batteries.
In this context, ultrasonic spraying technology has brought new opportunities for the preparation of bipolar plates. Ultrasonic spraying can accurately and evenly spray functional coating materials on the surface of bipolar plates. In this way, the corrosion resistance of bipolar plates can be improved without significantly increasing costs. For example, spraying a special corrosion-resistant coating on the surface of the graphite plate can effectively reduce the risk of electrochemical corrosion during high-power operation and extend the service life of the bipolar plate. At the same time, for conductive plastic bipolar plates, ultrasonic spraying can evenly disperse highly conductive nanomaterials on their surface, thereby improving the conductivity of the conductive plastic bipolar plate and alleviating its limitation on the power increase of the flow battery.
Electrode: A key component that provides a reaction site
In a flow battery, the electrode does not directly participate in the reaction like other secondary batteries, but is responsible for providing or accepting the electrons required for the electrochemical reaction and serves as the place where the battery reaction occurs. Therefore, the electrodes used in flow batteries are generally porous materials with good conductivity, acid and alkali resistance, and corrosion resistance, such as carbon felt, graphite felt, etc. In some flow batteries, such as zinc-based and iron-based flow batteries, metal materials with high specific surface area can also be used as electrodes to improve the reversibility of the battery reaction.
Due to the different problems that need to be solved for different flow batteries, scholars often make different types of modifications to the electrodes. Common modification methods include using metal or metal oxide as a load, organic loading, and modification of carbon material electrode functional groups.
Ultrasonic spraying has significant advantages in electrode preparation and modification. When preparing electrodes, ultrasonic spraying can accurately control the amount and distribution of spraying materials, making the porous structure of the electrode more uniform. This helps to increase the specific surface area of the electrode, thereby increasing the contact area between the electrode and the electrolyte and improving the efficiency of the battery reaction. During the electrode modification process, ultrasonic spraying can accurately spray the modified material to a specific position on the electrode surface to achieve a more efficient modification effect. For example, when loading metal oxides onto the surface of carbon felt electrodes, ultrasonic spraying can evenly disperse the metal oxides on the fiber surface of the carbon felt, improve the stability and effectiveness of the load, and thus improve the performance of the electrode.
Diaphragm: a barrier to ensure the normal operation of the battery
In a flow battery, the role of the diaphragm is not just to simply separate the positive and negative half-cells, it also needs to conduct ions between the positive and negative electrodes to form a path to balance the charge. In view of the fact that all-vanadium, iron-chromium, zinc-based and other systems require strong acid or strong base as supporting electrolyte, the diaphragm must have good acid and alkali resistance. At the same time, since the flow battery needs to be tightened and compressed, the diaphragm should also have excellent mechanical properties.
The diaphragms for flow batteries can be divided into cationic membranes, anionic membranes, amphoteric membranes and microporous membranes according to the type of conductive ions. Among the cationic membranes, commonly used ones include perfluorosulfonic acid resin membranes (Nafion membranes), sulfonated polyetheretherketone membranes (SPEEK membranes) and other cation-conducting diaphragms. Nafion membranes have the advantages of good conductivity and excellent mechanical properties, but there is a relatively serious problem of cross-contamination, which has a certain negative impact on coulomb efficiency, and its cost is expensive. However, on the whole, it is still the most commonly used diaphragm in industrialized flow batteries. SPEEK membranes have the advantages of relatively low cost, no fluorine element, belonging to environmentally friendly materials, and less cross-contamination in flow batteries, but their conductivity and mechanical strength are slightly worse than Nafion membranes.
Anion membranes conduct anions such as Cl- or HSO4-, and polybenzimidazole membranes (PBI membranes) are commonly used. Compared with cationic membranes, cross-contamination of flow batteries using anion membranes can be significantly suppressed, thereby ensuring higher efficiency. The emergence of amphoteric exchange membranes is because a single cationic membrane or anionic membrane is difficult to take into account both ion selectivity and ion conductivity at the same time, while amphoteric membranes containing both cationic and anionic functional groups have broad application prospects. Microporous membranes are generally difficult to be used directly in flow battery systems and need to be used in combination with other materials, such as Diramic membranes, which have an average pore size of 95 nm. Due to the low cost of microporous membranes, they also have certain development potential in flow batteries.
Ultrasonic spraying also has unique value in the preparation of diaphragms. Ultrasonic spraying technology can spray a layer of nano-coating with special functions on the surface of the diaphragm. This coating can improve the ion conductivity of the diaphragm and enhance the mechanical strength and acid and alkali resistance of the diaphragm. For example, by spraying nano-titanium dioxide coating, the acid resistance of the diaphragm can be improved, the erosion of the diaphragm by the acidic electrolyte can be reduced, and the service life of the diaphragm can be extended. Moreover, the nano-coating can also optimize the ion selectivity of the diaphragm, further reduce cross-contamination, and improve the overall performance of the flow battery.
Electrolyte: The core influencing factor of battery performance
The electrolyte is a vital component of the flow battery. The solubility of the active substance in the electrolyte and the number of electrons gained and lost directly determine the capacity of the flow battery, and its ionic conductivity greatly affects the power and efficiency performance of the battery. In addition, the power and energy density of the flow battery will also vary depending on the different positive and negative active substances. At present, there are many types of active substances available for flow batteries, which is also one of the important features and advantages of flow batteries.
Although ultrasonic spraying technology is relatively less used in the preparation of the electrolyte itself, its application in other key materials in contact with the electrolyte (such as bipolar plates, electrodes, and diaphragms) indirectly has a positive impact on the performance of the electrolyte. By improving the compatibility of these materials with the electrolyte, the role of active substances in the electrolyte can be better exerted, the ionic conductivity can be improved, and the overall performance of the flow battery can be improved.
In summary, bipolar plates, electrodes, diaphragms and electrolytes, as key materials that determine the power of flow batteries, each face different challenges and opportunities. Ultrasonic spraying technology has shown many advantages in the preparation and performance optimization of these key materials, providing strong support for improving the performance of flow batteries and promoting their industrial development. With the continuous advancement and innovation of technology, ultrasonic spraying is expected to play a more important role in the field of flow batteries and help energy storage technology reach new heights.
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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