High lithium-ion conductivity in all-solid-state lithium batteries by Sb doping LLZO

All-solid-state lithium batteries are considered to be the most promising electrochemical energy storage equipment due to their high safety, high energy density, and simple structure. However, the preparation of solid electrolytes with high lithium-ion conductivity and superior electrode–electrolyte interface contact is the development needs. In this study, the electronic structures of garnet-type Li7La3Zr2O12 (LLZO) and Sb-doped LLZO electrolytes were investigated using the first-principles method based on density functional theory (DFT). Theoretical calculations have confirmed that elemental doping facilitates the migration of lithium ions in solid-state electrolytes at the micro-atomic level. Based on the theoretical calculations and analysis results, Li6.7La3Zr1.7Sb0.3O12 (LLZSbO) with high ionic conductivity was synthesized by the conventional solid-state method. To reduce the interfacial impedance between electrolyte and electrode, the composite solid electrolytes (CSEs) containing LLZSbO active fillers were prepared by the solution casting method. The prepared CSEs exhibits a high ionic conductivity of 0.97 × 10–4 S cm−1 at 30 °C and a stable electrochemical window of 5.3 V as well as the lithium-ion transference number up to 0.37. The all-solid-state battery using the CSEs prepared with 20 wt% LLZSbO has excellent rate performance and cycle stability. The initial discharge specific capacity can reach 148.4 mAh g−1 when the rate is 0.1 C. The capacity can cover 138.8 mAh g−1 after 100 cycles at 0.2 C with a capacity retention rate of 97.5%.