Balancing stability and Li-ion conductivity of Li10SiP2O12 for solid-state electrolytes with the assistance of a body-centered cubic oxygen framework

Abstract

Li₁₀MP₂S₁₂ (LMPS, M = Ge, Sn, or Si) share an underlying body-centered cubic (bcc) anion framework enabling their high Li-ion conductivity. To take full use of the high conductivity of the bcc anion framework and boost the electrochemical stability, we have theoretically developed the chemistry of local structural motifs of LMPS to build the oxygen frameworks Li₁₀SiP₂O₁₂ (LSPO) and Li₁₉Si₂P₄O₂₃Cl (LSPOCl), which combine good electrochemical stability and high Li conductivity. They exhibit a wider electrochemical stability window compared to their sulfur analogue. At the anode side, they form ionic conductive but electronic insulating phases that prevent further reduction. The bcc oxygen framework allows Li cooperative migration with a low migration barrier (∼0.30 eV) in adjacent tetrahedral sites, which is most desirable for fast Li-ion conductors. The addition of halogen Cl contributes to the Li-ion migration because of the increased hybridization between the Si/P and Cl atoms. The LSPO and LSPOCl oxides with a bcc-type anion framework could be a viable way to overcome the trade-off between electrochemical stability and ionic conductivity.