2015-Sustainable Industrial Processing Summit
SIPS 2015 Volume 9: Physics, Advanced Materials, Multifunctional Materials
| Editors: | Kongoli F, Dubois JM, Gaudry E, Fournee V, Marquis F |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2015 |
| Pages: | 275 pages |
| ISBN: | 978-1-987820-32-4 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Mechanism of Li Insertion into TiO2 Polymorphs
Marketa Zukalova1;1, Prague, Czech Republic;
Type of Paper: Regular
Id Paper: 376
Topic: 21
Abstract:
TiO2 (anatase) and TiO2(B)(monoclinic polymorph of TiO2) are attractive candidates for anodes in rechargeable Li-ion batteries, due to their cycling stability, reasonable capacity and operating potential. Li insertion into TiO2 polymorphs proceeds as a diffusion controlled process, where the peak current scales with square root of the scan rate. Excess Li can be accommodated either at the interfaces of the nanometer-sized particles or at the open channels in the structure of particular polymorphs by a pseudocapacitive faradaic process, which is not controlled by diffusion. In this case, currents in the peaks of cyclic voltammograms of Li scale with the first power of scan rate.
Li-insertion electrochemistry of TiO2(B) is basically different from that of anatase. Accommodation of Li in the TiO2(B) lattice manifests itself by two pairs of peaks in cyclic voltammogram with formal potentials of ca. 1.5 and 1.6 V. Zukalova et al found that Li-insertion into TiO2(B) is characterized by unusually large faradaic pseudocapacitance. This peculiar effect was ascribed to Li+ accommodation in open channels of TiO2(B) structure allowing fast Li-transport in TiO2(B) lattice along the b-axis (perpendicular to (010) face). Deeper insight into differences between charging mechanisms of TiO2(B) and anatase during Li+ insertion provides analysis of cyclic voltammograms of Li insertion. The ratio of capacitive contributions to overall charge of Li-storage was found to be over 30% higher in TiO2(B) compared to that in anatase nanocrystals. The predominant pseudocapacitive process in TiO2(B) was related to accommodation of Li inside the TiO2(B) open channels in monoclinic lattice.
This work was supported by the Grant Agency of the Czech Republic (contracts No. 13-07724S and 15-06511S).