Details

Autor(en) / Beteiligte

• Kim, Yoong Ahm
• Kojima, Masahito
• Muramatsu, Hiroyuki
• Umemoto, Souichiro
• Watanabe, Takaaki
• Yoshida, Kazuto
• Sato, Keigo
• Ikeda, Takuya
• Hayashi, Takuya
• Endo, Morinobu
• Terrones, Mauricio
• Dresselhaus, Mildred S.

Titel

In Situ Raman Study on Single- and Double-Walled Carbon Nanotubes as a Function of Lithium Insertion

Ist Teil von

• Small (Weinheim an der Bergstrasse, Germany), 2006-05, Vol.2 (5), p.667-676

Ort / Verlag

Weinheim: WILEY-VCH Verlag

Erscheinungsjahr

2006

Link zum Volltext

Quelle

Wiley Online Library Journals Frontfile Complete

Beschreibungen/Notizen

• We investigated the electrochemical lithium ion (Li+) insertion/desertion behavior on highly pure and bundled single‐ and double‐walled carbon nanotubes (SWNTs and DWNTs) using an in situ Raman technique. In general, two storage sites could host Li+ in SWNT and DWNT bundles when varying an external potential: a) the outer surface sites, and b) the interstitial spaces within the bundles. The most sensitive changes in the tangential mode (TM) of the Raman spectra upon doping with Li+ can be divided into two regions. The first region was found from 2.8 to 1.0 V (the coverage of Li+ on the outer surface of a bundled nanotube) and was characterized by the loss of resonant conditions via partial charge transfer, where the G+ line of the SWNT and the TM of the outer tube of DWNTs experienced a highly depressed intensity, but remained almost constant in frequency. The appearance of a Breit–Wigner–Fano (BWF) profile provided strong evidence of metallic inner tubes within DWNTs. The second region was observed when the applied potentials ranged from 0.9 to 0 V and was characterized by Li+ diffusion into the interstitial sites of the bundled nanotube material. This phenomenon invoked a large downshift of the G− band in SWNTs, and a small downshift of the TM of the inner tube of DWNTs caused by expansion of the CC bonds due to the charge transferred to the nanotubes, and the disappearance of the BWF profile through the screening effect of the interstitial Li+ layers. Li ion storage in carbon nanotubes: The interstitial spaces in highly pure single‐ and double‐walled carbon nanotube foils, consisting of entangled tube bundles, in which the nanotubes are packed into hexagonal arrays (see HRTEM image), serve as Li ion storage sites. Their linear voltage profile, when combined with their expected high rate capability, make these foils attractive for use as anode materials for hybrid‐electrical‐vehicle‐targeted Li ion batteries.