Factors influencing charge capacity of vanadium pentoxide thin films during lithium ion intercalation/deintercalation cycles
- University of Surrey, Guildford GU2 7XH (United Kingdom)
The intercalation of vanadium pentoxide by lithium ions leads to a change in optical properties, a process that is of value in thin-film electrochromic devices. In this study, films of V{sub 2}O{sub 5}, deposited on indium tin oxide (ITO) glass coupons by a sol-gel process, were challenged by increasing numbers of charge-discharge cycles ranging from 72 to 589 full cycles. The samples were characterized by x-ray photoelectron spectroscopy (XPS) and then examined in the deintercalated state by time-of-flight secondary ion mass spectroscopy (SIMS). XPS enabled measurement of the thickness and composition of the solid-electrolyte interface and provided evidence of the residual V{sup 4+} concentration within the top few nanometers of the surface. The SIMS profile gave direct information on the thickness of the films and on the thickness loss caused by rinsing the samples after the electrochemical exposure. Determination, by SIMS, of the concentration of lithium ions has enabled a correction to be made for the amount of inactive material within the electrochemically active region of the film. The SIMS depth profiles for lithium in the four samples are similar, with a marked buildup of Li at the interface with the ITO. This interphase zone had a thickness of {approx}27 nm and was electrochemically inactive, enabling a further correction to be made. Thus, by means of the XPS and the SIMS results the chemistry and thickness of the films could be fully characterized. The remaining inconsistency between capacity (between 35% and 100% of the anticipated charge) and number of cycles is ascribed to edge effects arising from the method used for production of the coupons.
- OSTI ID:
- 21020888
- Journal Information:
- Journal of Vacuum Science and Technology. A, International Journal Devoted to Vacuum, Surfaces, and Films, Vol. 25, Issue 6; Other Information: DOI: 10.1116/1.2799961; (c) 2007 American Vacuum Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1553-1813
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
CAPACITY
ELECTROCHEMISTRY
ELECTROCHROMISM
INDIUM
ION MICROPROBE ANALYSIS
LITHIUM
LITHIUM IONS
MASS SPECTRA
MASS SPECTROSCOPY
OPTICAL PROPERTIES
SOL-GEL PROCESS
SOLID ELECTROLYTES
THICKNESS
THIN FILMS
TIME-OF-FLIGHT METHOD
TIN OXIDES
VANADATES
VANADIUM IONS
VANADIUM OXIDES
X-RAY PHOTOELECTRON SPECTROSCOPY