Lithium-ion battery separators based on sustainable collagen and chitosan hybrid membranes

This work focuses on the production of sustainable membranes based on collagen and chitosan as separators in lithium-ion batteries. Membranes were prepared by freeze-drying with varying collagen and chitosan contents. All membranes show interconnected pores with different pore sizes and porosity above 90 %, allowing high values of electrolyte uptake. As for thermal and mechanical characteristics, the addition of chitosan improves both thermal and mechanical stability. After 1 M LiPF₆ in EC:DMC electrolyte uptake, the ionic conductivity is above 0.49 mS·cm^-1 for all membranes and is most affected by the collagen content. Furthermore, the membranes present a lithium transfer number value of 0.2. In cathodic half-cells with LiFePO₄, the obtained room temperature discharge capacity is above 140 mAh·g^-1 at C/8 rate. For high C rates (C and 2C rates), the membranes with 80 wt % of collagen and 20 wt % of chitosan present 42 mAh·g^-1 after 100 cycles at C rate, demonstrating adequate reversibility. Considering the need for more environmentally friendly materials and methods compatible with a circular economy, the bio-based membranes developed in this work constitute an alternative for synthetic separators.