Development of biomaterial-based membranes for sustainable redox flow batteries

As the key component in the redox flow battery (RFB) systems, the ion exchange membrane (IEM), which facilitates proton transport while preventing electrolyte crossover, plays an important role in determining the overall system performance. However, up till now, the common commercial Nafion membranes still face the challenges raised from high cost and environmental concerns. There is an urgent demand for the development of novel membranes with low cost, high performance, and environmental friendliness. Recently, there has been growing interest in bio-sourced materials such as lignin, cellulose, and chitosan for membrane fabrication. These renewable materials offer low-cost and sustainable alternatives, providing opportunities to improve the economic viability of RFB technology while meeting environmental regulations. This review focuses on the progress of biomaterial-based membranes developed for RFBs. The potentials and limitations of various bio-sourced materials as membrane matrices and additives are evaluated and discussed. Furthermore, future research directions are suggested to provide insights for the development of next-generation membranes that meet the stringent requirements of sustainable long-term energy storage solutions.