A P2‐Type Layered Superionic Conductor Ga‐Doped Na2Zn2TeO6 for All‐Solid‐State Sodium‐Ion Batteries

• Published in: Chemistry : a European journal Vol. 24; no. 5; pp. 1057 - 1061
• Main Authors: Li, Yuyu, Deng, Zhi, Peng, Jian, Chen, Enyi, Yu, Yao, Li, Xiang, Luo, Jiahuan, Huang, Yangyang, Zhu, Jinlong, Fang, Chun, Li, Qing, Han, Jiantao, Huang, Yunhui
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 24.01.2018
• Subjects: all-solid-state batteries; Batteries; Chemistry; Conductivity; Conductors; Einstein equations; Electrochemistry; Grain; Interlayers; NMR; Nuclear magnetic resonance; P2-type; Powder; Rechargeable batteries; Sodium; Sodium-ion batteries; Solid state; Substitutes; superionic conductor; Zinc; P2-type; All-solid-state batteries; sodium-ion batteries; Superionic conductor
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201705466

Here, a P2‐type layered Na2Zn2TeO6 (NZTO) is reported with a high Na+ ion conductivity ≈0.6×10−3 S cm−1 at room temperature (RT), which is comparable to the currently best Na1+nZr2SinP3−nO12 NASICON structure. As small amounts of Ga3+ substitutes for Zn2+, more Na+ vacancies are introduced in the interlayer gaps, which greatly reduces strong Na+–Na+ coulomb interactions. Ga‐substituted NZTO exhibits a superionic conductivity of ≈1.1×10−3 S cm−1 at RT, and excellent phase and electrochemical stability. All solid‐state batteries have been successfully assembled with a capacity of ≈70 mAh g−1 over 10 cycles with a rate of 0.2 C at 80 °C. 23Na nuclear magnetic resonance (NMR) studies on powder samples show intra‐grain (bulk) diffusion coefficients DNMR on the order of 12.35×10−12 m2 s−1 at 65 °C that corresponds to a conductivity σNMR of 8.16×10−3 S cm−1, assuming the Nernst–Einstein equation, which thus suggests a new perspective of fast Na+ ion conductor for advanced sodium ion batteries. Higher conductivity: A Gallium‐doped P2‐type layered material Na1.9Zn1.9Ga0.1TeO6 (NZTO‐G0.1) showed an amazing ionic conductivity of 1.1×10−3 S cm−1 at RT as a solid electrolyte material for all‐solid‐state sodium‐ion batteries; higher than NASICON and Na‐β“‐Al2O3. Combining the result of 23Na‐NMR, EIS, and BVS analyses, NZTO‐G0.1 exhibits high stability under ambient conditions and excellent electrochemical performance.