Elucidating the characterisation of porous chitosan membrane soaked in ammonium acetate aqueous electrolyte: experimental, molecular dynamics analysis, and ionic behaviour

Porous membranes have received much attention for battery applications due to their ability to retain electrolytes within the membrane, unlike solid polymer electrolytes. Porous chitosan membranes were prepared via ultrasonic mix solution-cast and porogen-removal method using SiO 2 as the porogen-removal agent at different weight ratios from 0.4 to 4.0. The preparation of chitosan: SiO 2 with a weight ratio of 1:2.0 obtained the optimum pore size of 8.5 ± 0.4 μm based on morphology and average pore size calculation. Further soaking this membrane in 5.0 M NH 4 CH 3 COO aqueous electrolyte solution for 48 h (M5-5A48H) produced the highest ionic conductivity of (4.5 ± 1.7) × 10 − 3 S cm − 1 , highest electrolyte uptake (308.6 ± 15.4%), and lowest activation energy (0.04 ± 0.002 eV), with an amorphous structure. To validate the contribution of the H + charge carrier to the highest ionic conductivity, molecular dynamics analysis and an ionic systems approach were introduced to compare experimental data obtained from Fourier transform infrared (FTIR) spectroscopy with the computational approach. The study demonstrated that the porous chitosan membrane soaked in an NH 4 CH 3 COO electrolyte exhibits stable intermolecular interactions, primarily via hydrogen bonding. Optimisation and radial distribution function (RDF) analyses confirmed the structural integrity and consistency of these interactions across varying concentrations, with the highest peak indicating intermolecular binding between -NH 4 + and OH − . The ionic conductivity system also aligned with the experimental data (10 − 3 S cm − 1 ), confirming the role of H + from ammonium acetate (NH 4 CH 3 COO) as the primary charge carrier that contributes to the ionic conduction in porous chitosan membrane.