Chitosan-based polyelectrolyte complex membrane of carboxymethylchitosan and chitosan as alternative separator for zinc dendrite suppression in zinc-ion batteries

The use of zinc-ion batteries (ZIBs) as alternative energy storage devices is increasing owing to the high energy density, eco-friendliness, and ease of processing. However, the performance is limited by challenges such as zinc dendrite formation. Herein, polyelectrolyte complex membranes made from carboxymethylchitosan (CMCS) and chitosan (CS), denoted as chi-PEC, were developed as separators to suppress dendrite growth. CMCS and CS were mixed to form white precipitates, which were then centrifuged and compressed into membranes. Salt doping was applied during membrane formation to evaluate its effects. The membranes rely on dynamic ionic crosslinking—without chemical crosslinkers—between CMCS and CS functional groups, which promotes uniform zinc-ion distribution and minimizes ionic repulsion. The CMCS/CS membranes exhibited optimum conductivity of ion on approximately of 3.71 × 10⁻³ S cm⁻¹ and a transference number of zinc of around 0.52. After 200 charge–discharge cycles, zinc anodes with chi-PEC separators showed dense zinc deposition, indicating reduced dendrite formation and enhanced battery stability.