Unveiling the controversial mechanism of reversible Na storage in TiO2 nanotube arrays: Amorphous versus anatase TiO2 |
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Authors: | Bella Federico Muñoz-García Ana B. Meligrana Giuseppina Lamberti Andrea Destro Matteo Pavone Michele Gerbaldi Claudio |
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Affiliation: | 1. GAME Lab, CHENERGY Group, Department of Applied Science and Technology-DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy;2. Department of Chemical Sciences, University of Naples Federico Ⅱ, Via Cintia 21, University Campus of Monte Sant'Angelo, 80126 Napoli, Italy;3. MPMNT Group, Department of Applied Science and Technology-DISAT, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino, Italy;4. LITHOPS S.r.l., Strado del Portone 61, 10137 Torino, Italy |
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Abstract: | Due to their inherent safety,low cost,and structural stability,TiO2 nanostructures represent a suitable choice as anode materials in sodium-ion batteries.In the recent years,various hypotheses have been proposed regarding the actual mechanism of the reversible insertion of sodium ions in the TiO2 structure,and previous reports are often controversial in this respect.Interestingly,when tested as binder-and conducting additive-free electrodes in laboratory-scale sodium cells,amorphous and crystalline (anatase) TiO2 nanotubular arrays obtained by simple anodic oxidation exhibit peculiar and intrinsically different electrochemical responses.In particular,after the initial electrochemical activation,anatase TiO2 shows excellent rate capability and very stable long-term cycling performance with larger specific capacities,and thus a clearly superior response compared with the amorphous counterpart.To obtain deeper insight,the present materials are thoroughly characterized by scanning electron microscopy and ex situ X-ray diffraction,and the insertion of sodium ions in the TiO2 bulk phases is systematically modeled by density functional theory calculations.The present results may contribute to the development of more systematic screening approaches to identify suitable active materials for highly efficient sodium-based energy storage systems. |
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Keywords: | sodium battery TiO2 nanotube array anode modeling insertion mechanism |
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