Computational Design and Experimental Synthesis of Air-Stable Solid-State Ionic Conductors with High Conductivity

All-solid-state Li-ion batteries are promising next- generation energy storage devices for enhanced safety and energy density compared to presently available lithium-ion batteries. The development of such batteries requires new materials with exceptional properties for use as solid-state ionic conductors. Here, we report the design and synthesis of Si-doped lithium tantalum phosphates as solid-state ionic conductors. First-principles computation based on density functional theory predicts high phase stability and ionic conductivity of Li1+xTa2P1-xSixO8. Experimental synthesis of the designed materials confirms these results with a remarkably high ionic conductivity of 1.18 mS cm(-1) (total conductivity) in Li1.4Ta2P0.6Si0.4O8 at room temperature, which rivals the best lithium oxide solid-state electrolytes such as Li-NASICONs, perovskites, and lithium garnets, with the advantage of being stable in ambient conditions. The improved performance is due to enhanced lithium diffusion by introducing Si into the phosphate groups and activating an isotropic diffusion pathway in the structure while simultaneously reducing the grain boundary resistance.

Automated summary

In this study, Si-doped lithium tantalum phosphates were designed and synthesized as solid-state ionic conductors, showing high ionic conductivity. The enhanced lithium diffusion and activation of an isotropic diffusion pathway in the structure, as well as the reduction of grain boundary resistance, contributed to the improved performance of the materials.