| Summary: | This study investigates the dielectric relaxation and ionic conduction behavior of gel polymer electrolytes (GPEs) composed of poly(methyl methacrylate) (PMMA), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), and tetraethylene glycol dimethyl ether (TEGDME). GPE samples containing 5–30 wt.% NaTFSI were synthesized and analyzed using dielectric spectroscopy across 102 – 106 Hz and temperatures from 303 to 373 K. The 20 wt.% NaTFSI composition exhibited the highest ionic conductivity, attributed to optimal ion dissociation and enhanced motion of the polymer segments. Dielectric parameters, such as permittivity (εʹ, εʺ), electric modulus (Mʹ, Mʺ), and loss tangent (tan δ), demonstrated temperature- and frequency-dependent trends characteristic of ionic relaxation processes. The 20 wt.% NaTFSI composition (Na20) exhibited the highest ionic conductivity of 3.65 × 10−4 S cm−1 at 303 K, attributed to optimal salt dissociation and enhanced polymer chain mobility. Dielectric spectra revealed characteristic relaxation peaks, with Na20 showing the shortest relaxation time (τ = 2.65 s) compared to other compositions. The results confirm that a combination of hopping and segmental motion mechanisms governs ion conduction. These findings highlight the unique value of frequency-dependent dielectric analysis in elucidating coupled hopping and segmental motion mechanisms, offering a molecular-level understanding of polymer–ion interactions. This work provides a fresh perspective on tailoring PMMA-based GPEs for sodium-ion batteries, bridging critical knowledge gaps in sodium-conducting polymer electrolytes.
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