A Cation and Anion Dual Doping Strategy for the Elevation of Titanium Redox Potential for High-Power Sodium-Ion Batteries |
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Authors: | Dr Mingzhe Chen Dr Jin Xiao Dr Weibo Hua Dr Zhe Hu Dr Wanlin Wang Dr Qinfen Gu Prof Yuxin Tang Prof Shu-Lei Chou Prof Hua-Kun Liu Prof Shi-Xue Dou |
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Institution: | 1. Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong, Innovation Campus, Squires Way, North Wollongong, NSW, 2522 Australia;2. School of Science, Hunan University of Technology, Zhuzhou, 412007 China;3. Institute for Applied Materials-Energy Storage Systems (IAM-ESS), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein-Leopoldshafen, Germany;4. Australian Synchrotron, 800 Blackburn Road, Clayton, VIC 3168 Australia;5. Institute of Applied Physics and Materials Engineering, University of Macau, Macau, China |
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Abstract: | Titanium-based polyanions have been intensively investigated for sodium-ion batteries owing to their superior structural stability and thermal safety. However, their low working potential hindered further applications. Now, a cation and anion dual doping strategy is used to boost the redox potential of Ti-based cathodes of Na3Ti0.5V0.5(PO3)3N as a new cathode material for sodium ion batteries. Both the Ti3+/Ti4+ and V3+/V4+ redox couples are reversibly accessed, leading to two distinctive voltage platforms at ca. 3.3 V and ca. 3.8 V, respectively. The remarkably improved cycling stability (86.3 %, 3000 cycles) can be ascribed to the near-zero volume strain in this unusual cubic symmetry, which has been demonstrated by in situ synchrotron-based X-ray diffraction. First-principles calculations reveal its well-interconnected 3D Na diffusion pathways with low energy barriers, and the two-sodium-extracted intermediate NaTi0.5V0.5(PO3)3N is also a stable phase according to formation energy calculations. |
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Keywords: | cation/anion doping elevation of potential sodium-ion batteries Ti-based polyanions zero strain |
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