OPTIMIZING IONIC CONDUCTIVITY OF POLYMER ELECTROLYTES THROUGH SALT COMPOSITION AND THERMAL CONDITIONS
DOI:
https://doi.org/10.67772/bjp7m205Keywords:
Polymer electrolytes, Ionic conductivity, Lithium salts, Salt concentration, Thermal conditions, Electrolyte optimizationAbstract
For electrochemical application, polymer electrolytes need to be optimized in both composition and operating temperature, so as to obtain high ionic conductivity. The impact of lithium-salt chemistry, salt concentration, and thermal condition on the ionic conductivity of poly(ε-caprolactone)-based polymer electrolytes has been assessed based on 711 experimental observations, which correspond to 17 salt chemistries and 51 salt–molality formulations. Median conductivity was used to summarize replicate measurements and log₁₀ conductivity was used for distributional comparisons at the four key thermal conditions (30, 50, 70 and 90 °C). The median conductivity increased from 3.03 × 10⁻⁷ S cm⁻¹ at 30 °C to 4.39 × 10⁻⁵ S cm⁻¹ at 90 °C, with a significant and highly consistent thermal effect across complete formulations. The conductivity and salt concentration had a non-linear relationship, with intermediate salt loadings often proving superior. LiFSI at 1.0 mol kg⁻¹ showed the best overall performance throughout the entire thermal range, while LiBOB at 0.6 mol kg⁻¹ and LiDFOB at 2.2 mol kg⁻¹ showed the highest performance at about 70 and 90 °C, respectively. Arrhenius-type analysis further demonstrated formulation-specific temperature sensitivity. In general, optimization of ionic conductivity was best achieved by considering the salt, its concentration and thermal condition together. The results provide a set of optimum conductivities for the compositions and as a function of temperature, and they support the selection of polymer-electrolyte formulations for transport performance under multiple conditions.
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