Enhanced Elastic Migration of Magnesium Cations in alpha-Manganese Dioxide Tunnels Locally Tuned by Aluminium Substitution |
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| Authors: | Yaxi Ding Siwen Zhang Jiazhuo Li Ying Sun Bosi Yin Hui Li Yue Ma Zhiqiao Wang Hao Ge Dawei Su Tianyi Ma |
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| Affiliation: | 1. Institute of Clean Energy Chemistry, Key Laboratory for Green Synthesis and Preparative Chemistry of Advanced Material, College of Chemistry, Liaoning University, Shenyang, 110036 P. R. China;2. School of Science, RMIT University, Melbourne, VIC, 3000 Australia;3. State Key Laboratory of Solidification Processing, Center for Nano Energy Materials, School of Materials Science and Engineering, Shaanxi Joint Laboratory of Graphene, Northwestern Polytechnical University, Xi'an, 710072 P. R. China;4. College of Energy and Environment, Shenyang Aerospace University, Shenyang, 110136 P. R. China;5. School of Mathematical and Physical Sciences, Faculty of Science, University of Technology Sydney, Sydney, NSW, 2007 Australia |
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| Abstract: | The harsh conditions of large hydrated ion radius of Mg2+ cations and the strong electrostatic interaction with the host material put forward higher requirements for high-performance aqueous magnesium ion (Mg2+) energy storage devices. Herein, substituted aluminium ions (Al3+) doped α-MnO2 materials are prepared. The introduction of Al3+ cations adjust the local chemical environment inside the tunnel structure of α-MnO2 and precisely regulates the diffusion behavior of inserted Mg2+ cations. The shortened oxygens’ distance and abundant oxygen defects result in a substantially enhanced elastic migration pattern of Mg2+ cations driven by strengthened electrostatic attraction, which brings the lower diffusion energy barrier, improved reaction kinetics, and adaptive volume expansion as evidenced by Climbing Image-Nudged Elastic Band density function theory calculations coupled with experimental confirmation in X-ray photoelectron spectroscopy, electron paramagnetic resonance, and galvanostatic intermittent titration technique. As a result, this rationally designed cathode exhibits a high reversible capacity of 197.02 mAh g-1 at 0.1 A g-1 and stable cycle performance of 2500 cycles with 82% retention. These parameters are among the best of Mg-ion capacitors reported to date. This study offers a detailed insight into the local tunnel structure tunning effect and opens up a new path of modification for tunnel-type structural materials. |
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| Keywords: | Al substitutions aqueous Mg-ion capacitors electrochemical energy storage locally tuned structures |
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