Enhancing ionic conductivity in solid electrolyte by relocating diffusion ions to under-coordination sites.

Solid electrolytes are highly important materials for improving safety, energy density, and reversibility of electrochemical energy storage batteries. However, it is a challenge to modulate the coordination structure of conducting ions, which limits the improvement of ionic conductivity and hampers further development of practical solid electrolytes. Here, we present a skeleton-retained cationic exchange approach to produce a high-performance solid electrolyte of LiZrSiPO stemming from the NASICON-type superionic conductor of NaZrSiPO. The introduced lithium ions stabilized in under-coordination structures are facilitated to pass through relatively large conduction bottlenecks inherited from the NaZrSiPO precursor. The synthesized LiZrSiPO achieves a low activation energy of 0.21 eV and a high ionic conductivity of 3.59 mS cm at room temperature. LiZrSiPO not only inherits the satisfactory air survivability from NaZrSiPO but also exhibits excellent cyclic stability and rate capability when applied to solid-state batteries. The present study opens an innovative avenue to regulate cationic occupancy and make new materials.