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

Zhu, Lei; Wang, Youwei; Chen, Junchao; Li, Wenlei; Wang, Tiantian; Wu, Jie; Han, Songyi; Xia, Yuanhua et al. · Sci Adv · 2022

basic_science · Level V

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Abstract

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 Li<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> stemming from the NASICON-type superionic conductor of Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub>. The introduced lithium ions stabilized in under-coordination structures are facilitated to pass through relatively large conduction bottlenecks inherited from the Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> precursor. The synthesized Li<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> achieves a low activation energy of 0.21 eV and a high ionic conductivity of 3.59 mS cm<sup>-1</sup> at room temperature. Li<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> not only inherits the satisfactory air survivability from Na<sub>3</sub>Zr<sub>2</sub>Si<sub>2</sub>PO<sub>12</sub> 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.