Effect of the Nature of a Heterogeneous Dopant on the Transport and Thermodynamic Properties of Composites Based on n-Methyl-n-Butylpiperidinium Tetrafluoroborate

Composite solid electrolytes based on n-methyl-n-butylpiperidinium tetrafluoroborate [(CH₃)(C₄H₉)C₅H₁₀N]BF₄–A (where A is γ-Al₂O₃, SiO₂) were synthesized, and their thermal and electrically conductive properties were studied. The conductivity of the (1 – x)[C₁₀H₂₂N]BF₄–xAl₂O₃ composites passes through a maximum at x ~ 0.9, reaching 4.6 × 10^–4 S/cm at 130°C for 0.1[C₁₀H₂₂N]BF₄–0.9Al₂O₃. The absence of a thermal effect at the melting temperature of the ionic salt, showing high ionic conductivity, indicates that at x ≥ 0.9 n-methyl-n-butylpiperidinium tetrafluoroborate is in the amorphous state, and ion transport occurs along the ionic salt/oxide interface. In the case of the [C₁₀H₂₂N]BF₄–SiO₂ composites, the effect of a heterogeneous dopant on the ion transport is less significant, and the conductivity is due to the ionic salt of the additive present in the pores.