Electrolytes for solid state lithium batteries in the [N13pip]ClO4-LiClO4-Al2O3 system for solid state lithium batteries

Abstract

The transport, electrochemical, structural, and thermal properties of electrolytes in the ternary system [N13pip]ClO4-LiClO4-γ-Al2O3 (N13pip is N-methyl-N-ethyl-piperidinium cation) were investigated at the molar ratio [N13pip]ClO4:LiClO4 = 0.82:0.18. The addition of alumina leads to a change in the thermodynamic properties of the [N13pip]ClO4-LiClO4 system that can be explained by a partial transfer of lithium perchlorate from the organic phase to the surface of γ-Al2O3. The highest ionic conductivity of 6.2∙10–4 S/cm at 110 °C was observed for the composition containing the volume fraction (f) of γ-Al2O3 equal to 0.5. The increase in conductivity compared to the binary system 0.82[N13pip]ClO4-0.18LiClO4 is achieved due to the amorphization of the organic salt near the salt/LiClO4/oxide interfaces. Galvanostatic cycling with Li electrodes shows that composites with f = 0.5 are stable at 110 °C for at least 68 charge/discharge cycles, and the electrolyte is shown to be electrochemically stable up to 5 V. This system can be used as a solid-state electrolyte in lithium-ion current sources.

Keywords

• solid state ionics
• organic ionic plastic crystals
• lithium-ion current sources
• solid composite electrolytes
• ionic conductivity