Na⁺ transport and structural evolution in NaTFSI-Doped PMMA gel polymer electrolytes

In this work, poly(methyl methacrylate) (PMMA) was incorporated with sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) and processed under vacuum to form GPE membranes. Structural interactions between Na⁺ ions and the PMMA host were confirmed by Fourier transform infrared (FTIR) analysis, while differential scanning calorimetry (DSC) showed a noticeable reduction in both the glass transition and crystallization temperatures, indicating enhanced chain flexibility and reduced crystallinity. Electrochemical impedance spectroscopy revealed that the sample with 20 wt% NaTFSI exhibited the highest ionic conductivity, reaching 3.65 × 10⁻⁴ S cm⁻¹ at room temperature. Additionally, a sodium-ion transference number of 0.50 was recorded, indicating selective and efficient Na⁺ transport through the polymer matrix. These results highlight the suitability of NaTFSI-doped PMMA GPEs for advanced sodium-ion devices where ionic mobility and polymer dynamics are crucial for performance.