Abstract
Atomistic analysis of the ion transport in polymer electrolytes for all-solid-state Li-ion batteries was performed using molecular dynamics simulations to investigate the relationship between Li-ion transport and polymer morphology. Polyethylene oxide (PEO) and poly(diethylene oxide-alt-oxymethylene), P(2EO-MO), were used as the electrolyte materials, and the effects of salt concentrations and polymer types on the ion transport properties were explored. The size and number of LiTFSI clusters were found to increase with increasing salt concentrations, leading to a decrease in ion diffusivity at high salt concentrations. The Li-ion transport mechanisms were further analyzed by calculating the inter/intra-hopping rate and distance at various ion concentrations in PEO and P(2EO-MO) polymers. While the balance between the rate and distance of inter-hopping was comparable for both PEO and P(2EO-MO), the intra-hopping rate and distance were found to be higher in PEO than in P(2EO-MO), leading to a higher diffusivity in PEO. The results of this study provide insights into the correlation between the nanoscopic structures of ion solvation and the dynamics of Li-ion transport in polymer electrolytes.
Highlights
In recent years, with the increase in energy demand and the seriousness of environmental problems, the demand for a new energy production technology that does not use fossil fuels has been increasing
Volel et al [5] used pulsed-field-gradient NMR (PFG-NMR) measurements to show that LiTFSI salts in poly-ethylene oxide (PEO) exhibit superior ionic conductivity compared to LiBF4 and LiClO4 salts
Devaux et al [7] evaluated the effect of polymer molecular weight on ionic conductivity and transport number in the PEO-LiTFSI system and reported small changes in these parameters when the molecular weight was of the order of 10 kg/mol
Summary
With the increase in energy demand and the seriousness of environmental problems, the demand for a new energy production technology that does not use fossil fuels has been increasing. Numerous studies have investigated solid electrolytes that do not leak and have a relatively high degree of freedom in design [2]. Polymer electrolytes are drawing attention because of their resistance to mechanical shocks, such as vibration, and their excellent mechanical properties [3]. One such polymer electrolyte is poly-ethylene oxide (PEO) [4]. Devaux et al [7] evaluated the effect of polymer molecular weight on ionic conductivity and transport number in the PEO-LiTFSI system and reported small changes in these parameters when the molecular weight was of the order of 10 kg/mol. A study attempted to improve the performance of the system by inserting additives into it [8]
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