Correlated Migration Invokes Higher Na ⁺ ‐Ion Conductivity in NaSICON‐Type Solid Electrolytes

Journal Article · Tue Oct 01 00:00:00 EDT 2019 · Advanced Energy Materials

DOI:https://doi.org/10.1002/aenm.201902373· OSTI ID:1567906

Zhang, Zhizhen ^[1]; Zou, Zheyi ^[2]; Kaup, Kavish ^[3]; Xiao, Ruijuan ^[4]; Shi, Siqi ^[2]; Avdeev, Maxim ^[5]; Hu, Yong‐Sheng ^[6]; Wang, Da ^[2]; He, Bing ^[7]; Li, Hong ^[4]; Huang, Xuejie ^[4]; Nazar, Linda F. ^[3]; Chen, Liquan ^[4]

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1. Key Laboratory for Renewable Energy Beijing Key Laboratory for New Energy Materials and Devices Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China, Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 China, Department of Chemistry Waterloo Institute of Nanotechnology University of Waterloo 200 University Avenue West Waterloo Ontario N2L 3G1 Canada
2. School of Materials Science and Engineering Materials Genome Institute Shanghai University Shanghai 200444 China
3. Department of Chemistry Waterloo Institute of Nanotechnology University of Waterloo 200 University Avenue West Waterloo Ontario N2L 3G1 Canada
4. Key Laboratory for Renewable Energy Beijing Key Laboratory for New Energy Materials and Devices Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China
5. Australian Nuclear Science and Technology Organisation Locked Bag 2001 Kirrawee DC NSW 2232 Australia, School of Chemistry The University of Sydney Sydney 2006 Australia
6. Key Laboratory for Renewable Energy Beijing Key Laboratory for New Energy Materials and Devices Beijing National Laboratory for Condensed Matter Physics Institute of Physics Chinese Academy of Sciences Beijing 100190 China, Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Sciences Beijing 100049 China
7. School of Computer Engineering and Science Shanghai University Shanghai 200444 China

Abstract

Na super ion conductor (NaSICON), Na _{1+ n} Zr ₂ Si _n P _{3– n} O ₁₂ is considered one of the most promising solid electrolytes; however, the underlying mechanism governing ion transport is still not fully understood. Here, the existence of a previously unreported Na5 site in monoclinic Na ₃ Zr ₂ Si ₂ PO ₁₂ is unveiled. It is revealed that Na ⁺ ‐ions tend to migrate in a correlated mechanism, as suggested by a much lower energy barrier compared to the single‐ion migration barrier. Furthermore, computational work uncovers the origin of the improved conductivity in the NaSICON structure, that is, the enhanced correlated migration induced by increasing the Na ⁺ ‐ion concentration. Systematic impedance studies on doped NaSICON materials bolster this finding. Significant improvements in both the bulk and total ion conductivity (e.g., σ _bulk = 4.0 mS cm ⁻¹ , σ _total = 2.4 mS cm ⁻¹ at 25 °C) are achieved by increasing the Na content from 3.0 to 3.30–3.55 mol formula unit ⁻¹ . These improvements stem from the enhanced correlated migration invoked by the increased Coulombic repulsions when more Na ⁺ ‐ions populate the structure rather than solely from the increased mobile ion carrier concentration. The studies also verify a strategy to enhance ion conductivity, namely, pushing the cations into high energy sites to therefore lower the energy barrier for cation migration.

• Sponsoring Organization: USDOE
• OSTI ID: 1567906
• Journal Information: Advanced Energy Materials, Journal Name: Advanced Energy Materials Journal Issue: 42 Vol. 9; ISSN 1614-6832
• Publisher: Wiley Blackwell (John Wiley & Sons)
• Country of Publication: Germany
• Language: English