<p>The garnet-type Li₇La₃Zr₂O₁₂(LLZO) solid electrolyte has gained significant attention for next generation high-safety solid-state lithium batteries due to its high ionic conductivity and robust electrochemical stability. However, conventional solid-state reaction synthesis of LLZO requires high energy-intensive processing (&gt; 1200 ℃ for 6 + h) to achieve densification. To address this limitation, Ta-doped LLZO (LLZTO) can lower the synthesis temperature and enhance ionic conductivity. Herein, LLZTO ceramic powders are prepared by sol–gel method, with systematic investigation of the calcination temperature effects on the structure, morphology, and electrochemical properties. The ionic conductivity of LLZTO solid electrolyte prepared at a calcination temperature of 1100 ℃ can reach 2.6 × 10⁻⁴ S cm⁻¹. The initial discharge specific capacity of the battery is 126.55 mAh g⁻¹. After 75 cycles, the specific discharge capacity of the electrolyte is 126.11 mAh g⁻¹, and the capacity retention rate can reach 98.56%, demonstrating excellent electrochemical stability.</p>