Introducing Jahn‐Teller Distortion in Inorganic Solid‐State Electrolytes to Improve Ionic Conductivity

ABSTRACT The Jahn‐Teller distortion, a geometric distortion in crystals to lower the energy in a specific electronic configuration, is avoided in electrode materials as it damages the battery under an electric field. In contrast to its conventional role in electrodes, we pioneer the reasonable application of Jahn‐Teller distortion to solve the sodium ion transmission issues caused by grain boundaries and voids of inorganic solid‐state electrolytes (ISEs) in solid‐state batteries. Based on high‐spin manganese ions (Mn 3+ ), it reveals that expanding interplanar spacing and forming the Mn 3+ doped Na 3 Zr 2 Si 2 PO 12 (NZSPM) glassy phases among NZSPM crystalline grains through introducing Jahn‐Teller distortion significantly enhances sodium ion transport by widening the sodium ion transport channel, weakening grain boundaries, and eliminating voids in ISEs. As‐formed NZSPM crystal‐NZSPM glass (C‐G) ISE provides an ionic conductivity of 0.498 mS cm −1 . Moreover, the Na||C‐G||NaNi 1/3 Fe 1/3 Mn 1/3 O 2 (NFM) cell delivers the performance comparable to traditional batteries (e.g.,>120 mAh g −1 at 0.1 C), but no dendrites are formed. Our findings advance the understanding of Jahn‐Teller distortion and provide guidelines for designing the nano‐microstructure of functional materials.