Dual Role of LiCl in High-Performance Hydrogel-Based Moist-Electric Generators: DFT, MD, and Regional Analysis...

The moist-electric generator (MEG), enabling sustainable flexible power for low-energy electronics─especially intelligent wearables─via ambient moisture harvesting, is emerging as a promising technology. Moisture adsorption and ionic mobility are decisive, yet their interplay in composite hydrogel MEGs remains unclear. This study has systematically investigated the synergistic moisture adsorption mechanism and ion migration behavior in polyacrylamide (PAM)/LiCl hydrogels. Density functional theory (DFT) calculations and molecular dynamics (MD) simulations demonstrate the dual role of LiCl in altering the dominant mechanism of water absorption and controlling the magnitude of ionic conductivity. DFT calculations demonstrated that the moisture adsorption process transitioned from being polymer-dominated to ion-dominated as LiCl loading increased. MD simulations revealed that excessive LiCl (>20 wt %) induced ion aggregation that hinders migration, with the energy barrier exceeding 13.63 kJ/mol (40 wt %) to overcome, whereas lower loadings (<20 wt %) limited the availability of charge-carrying ions. At 20 wt % LiCl loading, the ionic conductivity of the composite hydrogel reached a maximum of 3.297 S/m experimentally, and the corresponding open-circuit voltage (V_OC) also peaked at 0.45 V. A regional analysis tracked LiCl dissociation from PAM-bound states to hydrated diffusion, a transition difficult to characterize through experimental techniques, and showed that stable hydration shells hinder mobility. The simulation results show good consistency with the experimental data. The study clarifies how LiCl loading governs V_OC, defines optimal ion concentrations, and proposes hydration-shell-management strategies for high-performance moist-electric materials.