Lithiation Thermodynamics and Kinetics of the TiO 2 (B) Nanoparticles
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- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland; Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
- School of Applied Physics and Materials, Wuyi University, Jiangmen, Guangdong 529020, China; School of Chemistry, University of St. Andrews, North Haugh, St. Andrews, Fife, KY16 9ST, United Kingdom
- Adolphe Merkle Institute, University of Fribourg, Chemin des Verdiers 4, 1700 Fribourg, Switzerland
- X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, United States
- Departments of Materials and Chemistry, University of Oxford, Parks Road, Oxford, OX1 3PH, United Kingdom
- Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom
TiO2 (B) has attracted a lot of attention in recent years because it exhibits the largest capacity among all studied titania polymorphs with high rate performance for Li intercalation achieved when this material is nanostructured. However, due to the complex nature of its lithiation mechanism and practical challenges in probing Li local environments in nanostructured materials, a definitive understanding of the lithiation thermodynamics has yet to be established. A comprehensive mechanistic investigation of the TiO2 (B) nanoparticles is therefore presented using a combination of in situ / operando X-ray pair distribution function (PDF) and electrochemical techniques. The discharge begins with surface reactions involving surface hydroxyl groups. Such reactions contribute to the capacity loss and take place in parallel with Li insertion into the near-surface region of the nanoparticles. The Li bulk insertion starts with a single-phase reaction into the A2 site, a position adjacent to the b channel. A change of the Li diffusion pathway from that along this open channel to that along the c-direction is likely to occur at the composition of Li0.25TiO2 until Li0.5TiO2 is attained, leading to a two-step A2-site incorporation with one step kinetically distinct from the other. Subsequent Li insertion involves C’ site, a position situated inside the channel, and follows a rapid two-phase reaction to form Li0.75TiO2. Due to the high diffusion barrier associated with the further lithiation, Li insertion into the A1 site, another position adjacent to the channel neighboring the A2 sites, is kinetically restricted. It can be promoted by either nanostructuring or raising the operating temperature, the latter however triggering concurrent electrolyte decomposition giving rise to additional capacity loss. This study not only provides compelling experimental evidence for the unresolved reaction thermodynamics of nanoparticulate TiO2 (B), but also serves as a strong reference for future studies of the bulk phase, and for future calculations to study the kinetic properties of TiO2 (B).
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE Office of Science - Office of Basic Energy Sciences - Scientific User Facilities Division
- DOE Contract Number:
- AC02-06CH11357
- OSTI ID:
- 1415475
- Journal Information:
- Journal of the American Chemical Society, Vol. 139, Issue 38; ISSN 0002-7863
- Publisher:
- American Chemical Society (ACS)
- Country of Publication:
- United States
- Language:
- English
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