Recently, Li Xianfeng, a researcher at the Energy Storage Technology Research Department of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences, has made progress in the large-scale preparation and application of membrane materials for high-performance, low-cost alkaline system flow batteries. The technology realizes the large-area preparation of the non-fluorine cation conducting membrane and its application in the energy storage technology of the alkaline system flow battery.

Energy storage is the key and supporting technology for building a new power system with new energy as the main body. Flow battery energy storage technology has the advantages of safety, reliability, long life and high efficiency, and is the preferred technology for large-scale energy storage. Therefore, reducing the cost, especially reducing the cost of the ion-conducting membrane material, the key material of flow batteries, is particularly important for promoting the practical process of flow batteries.

At present, the research on ion-conducting membranes for alkaline system flow batteries is very limited. Due to its excellent stability, perfluorosulfonic acid ion exchange membrane (Nafion) has become the preferred membrane material for current flow batteries and even alkaline system flow batteries. . However, Nafion membranes have problems such as complex production process, by-products in the production process that are harmful to the environment and human health, expensive, and low ionic conductivity in alkaline systems, resulting in low battery efficiency. The development of non-fluorine anion exchange membranes with low cost, controllable structure and simple preparation process is expected to solve the above problems. However, in an alkaline system, the quaternary amine groups on the traditional non-fluorine anion-exchange membrane, the quaternary amine-type anion-conducting membrane, undergo Hoffman elimination and nucleophilic substitution reaction, which makes this type of membrane less stable.

In this work, the research team based on the structural design of ion-conducting membranes for alkaline systems (Nat. Commun., 2018; Angew. Chem. Int. Ed., 2020; J. Am. Chem. Soc., 2021; Adv. Funct. Mater., 2021), and a deep understanding of the mechanism of ion transport (Nat. Commun., 2021), through the electrophilic substitution reaction, a kilogram-scale sulfonated polyetheretherketone polymer resin was synthesized and then used continuous Roll-to-roll membrane production process, large-scale batch preparation of non-fluorine cation exchange membrane materials, and realization of its application in alkaline system flow batteries. The study found that the rigid skeleton structure and charge characteristics of the membrane material make it have excellent alkali resistance stability; the discrete -SO3H groups on the main chain can form a continuous hydrogen bond network in the membrane, so that OH- in the membrane The rapid transfer by the Grotthuss mechanism improves the conductivity of the membrane material. In addition, the research team used the membrane material developed by it to integrate a 4kW-class alkaline zinc-iron flow battery stack. Under the condition of a working current density of 80mA/cm2, the energy efficiency of the stack can reach more than 85%. This research is expected to improve the performance of the new-generation flow battery, accelerate its transition from the laboratory to the large-scale application, and play a role in reducing the cost of the new-generation flow battery energy storage technology and promoting the practical process of the flow battery energy storage technology.

The related research results, titled Low-cost Hydrocarbon Membrane Enables Commercial-scale Flow Batteries for Long-duration Energy Storage, were recently published in Joule. The above work was funded by the National Natural Science Foundation of China, the Electrochemical Energy Storage Technology Engineering Laboratory of the Chinese Academy of Sciences, and the Youth Innovation Promotion Association of the Chinese Academy of Sciences.

Dalian Institute of Chemical Physics has developed high-performance, low-cost membrane materials for alkaline system flow batteries

Source: Dalian Institute of Chemical Physics, Chinese Academy of Sciences