Nb and O co-doping in Li10SiP2S12: A strategy to lower Li-ion migration barrier and boost electrochemical performance

All-solid-state lithium batteries have garnered considerable interest owing to their ability to fundamentally and efficiently tackle the safety drawbacks of current commercial lithium-based batteries. Among the existing solid-state electrolyte systems, sulfide electrolytes stand out due to their high ionic conductivity and excellent ductility. In this study, Nb₂O₅ doping is employed to enhance the air stability and lithium ion (Li⁺) transport properties of Li₁₀SiP₂S₁₂. X-ray diffraction (XRD) analysis shows that the modified Li₁₀SiP_1.8Nb_0.2S_11.5O_0.5 (LSiPNbSO) electrolyte reduces the orthorhombic phase content of β-Li₃PS₄, with XRD Rietveld refinement revealing a decrease from 64.17 % to 15.25 %. Density functional theory (DFT) calculations demonstrate that Nb and O doping lowers the Li⁺ migration energy barrier, facilitates Li⁺ diffusion, and enhances Li-ion conductivity. The LSiPNbSO electrolyte achieves an ionic conductivity of up to 1.98 mS cm⁻¹. Air stability tests confirm the improved moisture resistance of LSiPNbSO. The assembled lithium-symmetric battery exhibits stable cycling for 800 h at a current density of 0.1 mA cm⁻², indicating that Nb and O doping enhances the stability of the electrolyte and the lithium metal anode. Additionally, all-solid-state batteries assembled with the LSiPNbSO electrolyte exhibit higher specific capacity and superior rate cycling performance.