Sb and O co-doping in Li10SiP2S12 to reduce orthorhombic phase content and improve electrochemical performance

Li₁₀SiP₂S₁₂ (LSiPS) electrolyte is chosen for the study considering that the solid-state electrolyte has high ionic conductivity along with good electrochemical performance. However, LSiPS electrolyte has two phases during the synthesis process, and the orthorhombic phase content is reduced by doping and modification of it thereby improving the electrochemical properties of the substance. In this work, a series of modified sulfide solid electrolytes are synthesized using Sb₂O₅ as dopant. The ionic conductivity of Li₁₀SiP_1.7Sb_0.3S_11.25O_0.75 (LSiPSbSO) electrolyte can reach 1.18 mS cm^-1 when the doping amount of Sb₂O₅ is x =0.3. X-ray diffraction (XRD) test proves that the doping of Sb₂O₅ can reduce the orthorhombic phase content of β-Li₃PS₄. Density functional theory (DFT) calculations show that the doping of Sb and O lowers the Li⁺ migration barrier, promotes the diffusion of Li⁺, and improves the conductivity of lithium ions. LSiPSbSO electrolyte has superior electrochemical performance as well as better air stability. The assembled lithium symmetric battery has a stable cycling process of 622 h at 0.1 mA cm^-2 current density. Charge-discharge experiments of all-solid-state batteries assembled with LSiPSbSO electrolyte confirm higher specific capacity and cycling stability. This work combines systematic experimental characterization and sufficient theoretical calculations to demonstrate that the modified electrolyte has superior ionic conductivity and high air stability and can be applied to all-solid-state lithium batteries.