Elucidating the characterisation of porous chitosan membrane soaked in ammonium acetate aqueous electrolyte: experimental, molecular dynamics analysis, and ionic behaviour
摘要
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 SiO2 as the porogen-removal agent at different weight ratios from 0.4 to 4.0. The preparation of chitosan: SiO2 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 NH4CH3COO 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 NH4CH3COO 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 -NH4+ 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 (NH4CH3COO) as the primary charge carrier that contributes to the ionic conduction in porous chitosan membrane.