Prawn Shell Derived Chitin Nanofiber Membranes as Advanced Sustainable Separators for Li/Na-Ion Batteries

Separators, necessary components to isolate cathodes and anodes in Li/Na-ion batteries, are consumed in large amounts per year; thus, their sustainability is a concerning issue for renewable energy storage systems. However, the eco-efficient and environmentally friendly fabrication of separators with a high mechanical strength, excellent thermal stability, and good electrolyte wettability is still challenging. Herein, we reported the fabrication of a new type of separators for Li/Na-ion batteries through the self-assembly of eco-friendly chitin nanofibers derived from prawn shells. We demonstrated that the pore size in the chitin nanofiber membrane (CNM) separator can be tuned by adjusting the amount of pore generation agent (sodium dihydrogen citrate) in the self-assembly process of chitin nanofibers. By optimizing the pore size in CNM separators, the electrochemical performance of the LiFePO₄/Li half-cell with a CNM separator is comparable to that with a commercialized polypropylene (PP) separator. More attractively, the CNM separator showed a much better performance in the LiFePO₄/Li cell at 120 °C and Na₃V₂(PO₄)₃/Na cell than the PP separator. The proposed fabrication of separators by using natural raw materials will play a significant contribution to the sustainable development of renewable energy storage systems.