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Wei, Wei
Publications (10 of 13) Show all publications
Wei, W., Valvo, M., Edström, K. & Nyholm, L. (2018). Size-dependent Electrochemical Performance of Monolithic Anatase TiO2 Nanotube Anodes for Sodium-ion Batteries. ChemElectroChem, 5(4), 674-684
Open this publication in new window or tab >>Size-dependent Electrochemical Performance of Monolithic Anatase TiO2 Nanotube Anodes for Sodium-ion Batteries
2018 (English)In: ChemElectroChem, Vol. 5, no 4, p. 674-684Article in journal (Refereed) Published
Abstract [en]

Well-defined, monolithic TiO2 nanotube thin films havebeen used as model anode electrodes to study Na-ion storage in anatase TiO2. It is shown that anatase TiO2 nanotubes with wall thicknesses up to 50 nm can be transformed into amorphous sodium titanate (e.g. Na0.2TiO2) nanotubes via an electrochemical activation process at about 0.2 V vs. Na+/Na. Due to the Na+ insertion and extraction reactions at about 0.55 and 0.75 V vs. Na+/Na, respectively, the activated TiO2 nanotubes exhibit reversible capacities of 170 mAh g-1. For the first time, it is shown that the nanotube length and wall thickness play critical roles in determining the electrochemical performances of this type of electrodes in Na-ion cells. An excellent rate performance, yielding capacities of about 33mAh g-1 at 20C and 161 mAh g-1 at C/5 rates, as well as a capacity retention of more than 97% after more than 350 cycles, could be achieved with nanotubes with a wall thickness of up to 20 nm. Thecycling rate for the nanotubes with a tube length of 4.5 μm should,however, be limited to 1C to guarantee a cycle life of about 200 cycles.

Keyword
TiO2, nanotubes, sodium, batteries, electrodes, free-standing, wall thickness, length
National Category
Inorganic Chemistry
Research subject
Chemistry with specialization in Inorganic Chemistry
Identifiers
urn:nbn:se:uu:diva-337289 (URN)10.1002/celc.201701267 (DOI)000425380200015 ()
Funder
Swedish Research Council Formas, 245- 2014-668StandUp
Available from: 2017-12-21 Created: 2017-12-21 Last updated: 2018-05-07Bibliographically approved
Wei, W., Björefors, F. & Nyholm, L. (2015). Hybrid Energy Storage Devices Based on Monolithic Electrodes Containing Well-defined TiO2 Nanotube Size Gradients. Electrochimica Acta, 176, 1393-1402
Open this publication in new window or tab >>Hybrid Energy Storage Devices Based on Monolithic Electrodes Containing Well-defined TiO2 Nanotube Size Gradients
2015 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 176, p. 1393-1402Article in journal (Refereed) Published
Abstract [en]

Well-defined TiO2 nanotube size gradient thin films, manufactured using a bipolar electrochemistry approach, can be used as versatile monolithic hybrid electrodes for energy storage devices. The nanotube size distribution within the gradients can readily be controlled by altering the bipolar current and/or the length of the bipolar titanium sheet. As the electrochemical properties of the gradient electrodes can be carefully tailored by modifying the nanotube size gradient, this approach provides new possibilities for the manufacturing of hybrid electrodes with integrated energy and power density gradients. The freestanding anatase TiO2 nanotube size gradient electrodes provide unprecedented capacities at cycling rates from C/5 (i.e. 162 mAh cm(-2) or 169 mAh g(-1)) to 50C (i.e. 40 mAh cm(-2) or 42 mAh g(-1)). It is likewise shown that the size gradient electrodes facilitate fundamental studies of the charge/discharge process of TiO2 based electrodes. The results demonstrate that the different shapes of charge and discharge curves of TiO2 nanotube electrode can be explained by inherent differences between the lithiation and delithiation processes.

Keyword
TiO2 nanotubes, size gradients, bipolar electrochemistry, Li-ion batteries, hybrid electrodes
National Category
Chemical Sciences
Identifiers
urn:nbn:se:uu:diva-264049 (URN)10.1016/j.electacta.2015.07.092 (DOI)000360918000167 ()
Funder
Swedish Research Council
Available from: 2015-10-06 Created: 2015-10-05 Last updated: 2017-12-01Bibliographically approved
Wei, W., Oltean, G., Tai, C.-W., Edström, K., Björefors, F. & Nyholm, L. (2013). High energy and power density TiO2 nanotube electrodes for 3D Li-ion microbatteries. Journal of Materials Chemistry A, 1(28), 8160-8169
Open this publication in new window or tab >>High energy and power density TiO2 nanotube electrodes for 3D Li-ion microbatteries
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2013 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488, Vol. 1, no 28, p. 8160-8169Article in journal (Refereed) Published
Abstract [en]

Highly ordered anodic TiO2 nanotube arrays with a tube length of 9 [small mu ]m are shown to provide areal capacities of 0.24 mA h cm-2 (i.e. 96 mA h g-1) at a charge/discharge current density of 2.5 mA cm-2 (corresponding to a rate of 5 C) and 0.46 mA h cm-2 (i.e. 184 mA h g-1) at 0.05 mA cm-2, when used as 3D free-standing anodes in Li-ion microbatteries. The present nanotube electrodes, which could be cycled for 500 cycles with only 6% loss of capacity, exhibited significantly higher energy and power densities, as well as an excellent cycling stability compared to previously reported TiO2-based Li-ion microbattery electrodes. The influence of parameters such as ordering, geometry and crystallinity of the nanotubes on the microbattery performance was investigated. A two-step anodization process followed by annealing of the nanotubes was found to yield the best microbattery performance. It is also demonstrated that the rate capability of the electrode depends mainly on the rate of the structural rearrangements associated with the lithiation/delithiation reaction and that the areal capacity at various charge/discharge rates can be increased by increasing the tube wall thickness or the length of the nanotubes, up to 0.6 mA h cm-2 for 100 cycles.

National Category
Nano Technology
Research subject
Materials Science
Identifiers
urn:nbn:se:uu:diva-202840 (URN)10.1039/C3TA11273J (DOI)000320876000012 ()
Funder
Swedish Research CouncilStandUp
Available from: 2013-06-27 Created: 2013-06-27 Last updated: 2017-12-30
Wei, W., Lee, K., Shaw, S. & Schmuki, P. (2012). Anodic formation of high aspect ratio, self-ordered Nb2O5 nanotubes. Chemical Communications, 48(35), 4244-4246
Open this publication in new window or tab >>Anodic formation of high aspect ratio, self-ordered Nb2O5 nanotubes
2012 (English)In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 48, no 35, p. 4244-4246Article in journal (Refereed) Published
Place, publisher, year, edition, pages
RSC Publishing, 2012
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-198880 (URN)10.1039/C2CC31007D (DOI)
Available from: 2013-04-27 Created: 2013-04-27 Last updated: 2017-12-06Bibliographically approved
Wei, W., Shaw, S., Lee, K. & Schmuki, P. (2012). Rapid Anodic Formation of High Aspect Ratio WO3 Layers with Self-Ordered Nanochannel Geometry and Use in Photocatalysis. Chemistry - A European Journal, 18(46), 14622-14626
Open this publication in new window or tab >>Rapid Anodic Formation of High Aspect Ratio WO3 Layers with Self-Ordered Nanochannel Geometry and Use in Photocatalysis
2012 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, no 46, p. 14622-14626Article in journal (Refereed) Published
Place, publisher, year, edition, pages
John Wiley & Sons, 2012
National Category
Nano Technology Nano Technology
Identifiers
urn:nbn:se:uu:diva-198871 (URN)10.1002/chem.201202420 (DOI)
Available from: 2013-04-27 Created: 2013-04-27 Last updated: 2017-12-06Bibliographically approved
Kirchgeorg, R., Wei, W., Lee, K., So, S. & Schmuki, P. (2012). Through-Hole, Self-Ordered Nanoporous Oxide Layers on Titanium, Niobium and Titanium–Niobium Alloys in Aqueous and Organic Nitrate Electrolytes. ChemistryOpen, 1(1), 21-25
Open this publication in new window or tab >>Through-Hole, Self-Ordered Nanoporous Oxide Layers on Titanium, Niobium and Titanium–Niobium Alloys in Aqueous and Organic Nitrate Electrolytes
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2012 (English)In: ChemistryOpen, ISSN 2191-1363, Vol. 1, no 1, p. 21-25Article in journal (Refereed) Published
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-198876 (URN)10.1002/open.201100012 (DOI)
Available from: 2013-04-27 Created: 2013-04-27 Last updated: 2017-12-06Bibliographically approved
Wei, W., Kirchgeorg, R., Lee, K., So, S. & Schmuki, P. (2011). Nitrates: A new class of electrolytes for the rapid anodic growth of self-ordered oxide nanopore layers on Ti and Ta. Physica Status Solidi. Rapid Research Letters, 5(10-11), 394-396
Open this publication in new window or tab >>Nitrates: A new class of electrolytes for the rapid anodic growth of self-ordered oxide nanopore layers on Ti and Ta
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2011 (English)In: Physica Status Solidi. Rapid Research Letters, ISSN 1862-6254, E-ISSN 1862-6270, Vol. 5, no 10-11, p. 394-396Article in journal (Refereed) Published
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-198879 (URN)10.1002/pssr.201105377 (DOI)
Available from: 2013-04-27 Created: 2013-04-27 Last updated: 2017-12-06Bibliographically approved
Wei, W., Jha, H., Yang, G., Hahn, R., Paramasivam, I., Berger, S., . . . Schmuki, P. (2010). Formation of Self-Organized Superlattice Nanotube Arrays – Embedding Heterojunctions into Nanotube Walls. Advanced Materials, 22(42), 4770-4774
Open this publication in new window or tab >>Formation of Self-Organized Superlattice Nanotube Arrays – Embedding Heterojunctions into Nanotube Walls
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2010 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 22, no 42, p. 4770-4774Article in journal (Refereed) Published
Keyword
anodization, nanotubes, superlattice, TiO, TiO2, Ta2O5
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-198870 (URN)10.1002/adma.201002091 (DOI)
Available from: 2013-04-27 Created: 2013-04-27 Last updated: 2017-12-06
Wei, W., Berger, S., Shrestha, N. & Schmuki, P. (2010). Ideal Hexagonal Order: Formation of Self-Organized Anodic Oxide Nanotubes and Nanopores on a Ti–35Ta Alloy. Journal of The Electrochemical Society, 157(12)
Open this publication in new window or tab >>Ideal Hexagonal Order: Formation of Self-Organized Anodic Oxide Nanotubes and Nanopores on a Ti–35Ta Alloy
2010 (English)In: Journal of The Electrochemical Society, Vol. 157, no 12Article in journal (Refereed) Published
National Category
Materials Chemistry
Identifiers
urn:nbn:se:uu:diva-198875 (URN)
Available from: 2013-04-27 Created: 2013-04-27 Last updated: 2013-04-27
Wei, W., Berger, S., Hauser, C., Meyer, K., Yang, M. & Schmuki, P. (2010). Transition of TiO< sub> 2 nanotubes to nanopores for electrolytes with very low water contents. Electrochemistry Communications, 12(9), 1184-1186
Open this publication in new window or tab >>Transition of TiO< sub> 2 nanotubes to nanopores for electrolytes with very low water contents
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2010 (English)In: Electrochemistry Communications, Vol. 12, no 9, p. 1184-1186Article in journal (Refereed) Published
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-198877 (URN)
Available from: 2013-04-27 Created: 2013-04-27 Last updated: 2013-04-27
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