Lithium ion conduction in sol-gel synthesized LiZr2(PO4)3 polymorphs

Abstract

Safety issue associated with the high flammability and volatility of organic electrolytes used in commercial rechargeable lithium ion batteries has led to significant attention to ceramic-based solid electrolytes. In the present study, lithium ion conduction in two polymorphs of LiZr2(PO4)3 synthesized via the sol-gel route has been investigated. Rietveld refinement of room temperature X-ray diffraction data of LiZr2(PO4)3 powders calcined at 900 °C and 1300 °C confirmed these to be the monoclinic phase with P21/n structure and rhombohedral phase with R3c structure, respectively. Increase in calcination temperature and resultant phase transformation improved the room temperature conductivity from 2.27×10−6 ohm-1m−1 for the monoclinic phase to 1.41×10−4 ohm−1m−1 for rhombohedral phase. Temperature dependence of conductivity was modeled using Arrhenius law and activation energy of ∼ 0.59 eV (for monoclinic phase) and ∼0.50 eV (for rhombohedral phase) were obtained.Safety issue associated with the high flammability and volatility of organic electrolytes used in commercial rechargeable lithium ion batteries has led to significant attention to ceramic-based solid electrolytes. In the present study, lithium ion conduction in two polymorphs of LiZr2(PO4)3 synthesized via the sol-gel route has been investigated. Rietveld refinement of room temperature X-ray diffraction data of LiZr2(PO4)3 powders calcined at 900 °C and 1300 °C confirmed these to be the monoclinic phase with P21/n structure and rhombohedral phase with R3c structure, respectively. Increase in calcination temperature and resultant phase transformation improved the room temperature conductivity from 2.27×10−6 ohm-1m−1 for the monoclinic phase to 1.41×10−4 ohm−1m−1 for rhombohedral phase. Temperature dependence of conductivity was modeled using Arrhenius law and activation energy of ∼ 0.59 eV (for monoclinic phase) and ∼0.50 eV (for rhombohedral phase) were obtained.