Optimization of ionic conductivity of Li7La3Zr2O12 garnet-based solid electrolyte for lithium batteries by LiClO4 filler incorporation

Abstract

Garnet-based electrolytes with cubic structures have gained much interest as a promising solid-electrolyte for high-performance next-generation lithium metal batteries. Herein, Li₇La₃Zr₂O₁₂ is prepared by solid-state route and calcined at 950 °C for different intervals to ensure the cubic phase. X-ray diffraction analysis confirms the formation of cubic single-phase for calcination of 7 h. Instead of sintering at high temperatures, lithium perchlorate (LiClO₄) is added as filler in 0, 5, 10, and 15 wt% ratio through a solution-based method. Scanning electron microscopy reveals the pebbles-like morphology of Li₇La₃Zr₂O₁₂ and no significant change in shape and size is observed by adding LiClO₄. Elemental mapping and energy-dispersive X-ray spectroscopy confirm the presence of all elements and uniform distribution of LiClO₄. Electrochemical impedance analysis witnesses the reduction in grain boundary resistance and increase in ionic conductivity up to 0.231 mS cm⁻¹ by incorporating 10 wt% LiClO₄. Interface stability testing shows a very small overpotential of 0.014 V and stability for 250 h at 0.1 mA cm⁻². Linear sweep voltammetry shows the stability of Li₇La₃Zr₂O₁₂ with 10 wt% LiClO₄ up to 5.12 V. Stability analysis with LiFePO₄ cathode shows the specific discharge capacity of 116.92 mAh g⁻¹ for 1st cycle at 1C and a 87 % coulombic efficiency after 35th cycle. Ex-situ SEM analysis of solid-state electrolyte after first charge and discharge reveals the presence of no cracks while Ex-situ X-ray photoelectron spectroscopy shows the change in intensities of Li, O, Cl, and F due to the ionic movement of lithium. These findings reveal the promising role of LiClO₄ incorporation in increasing the ionic conductivity of Li₇La₃Zr₂O₁₂ and improving the battery performance by avoiding high-temperature sintering.