Carbonization of Highly Oriented Poly(tetrafluoroethylene)

Abstract

Defluorination of a film of highly oriented poly(tetrafluoroethylene) (PTFE) was carried out by the action of lithium and sodium amalgams. The reaction yields a composite product containing carbon with the equivalent amount of alkali metal fluoride. This material was studied by X-ray photoelectron spectroscopy, Raman spectroscopy, and atomic force microscopy. The carbonized film is sensitive to surface oxidation upon contact to air. Part of the carbon in the product shows an unusual structure based on sp-bonded carbon chains. The amalgam-induced defluorination of PTFE influences markedly the surface morphology on the micron scale. Moreover, the molecular-level ordering of the precursor is reconstructed in the product of carbonization, presumably due to oxidative breakdown.

A study of perfluorocarboxylate ester solvents for lithium ion battery electrolytes

“…These properties may also apply to similar heavily fluorinated species proposed for next generation Li-ion electrolytes [1,2,5,30,31]. In particular the defluorination reaction, which may impart unwanted electronic conductivity in the SEI, has been shown in poly(tetrafluoroethylene) to be related to neighboring CeF bonds [13,14], an issue that can be ameliorated with careful synthetic design.…”

“…We observe via X-ray photoelectron spectroscopy (XPS) that the SEI formed by this perfluorocarboxylate electrolyte on a Si electrode is composed of chemical moieties, e.g., organic carbonates and LiF, similar to those formed by traditional carbonate-based electrolytes at remarkably similar concentrations. However, electrochemical defluorination, well-known in poly(tetrafluoroethylene) (PTFE) [13,14], in combination with the high reduction potential (1.0e1.5 V) of the fluorinated solvent prevents effective electrode passivation, limiting the use of such fluorine-rich species as neat electrolyte solvents in Liion battery cells that require extended cycling.…”

Nanostructured Carbonaceous Materials from Molecular Precursors

“…The resulting materials contained a high content of sp-hybridized carbon. [199,200] Carbonization of highly oriented PTFE films with liquid lithium and sodium amalgams yielded grained carbon films in which the "ribbed" structure of the PTFE precursor was conserved to some extent, as evidenced by AFM. Similarly, vapors of low-molecular-weight perfluorinated alkanes were carbonized with alkali amalgams to produce films.…”

Nanostrukturierte Kohlenstoffmaterialien aus molekularen Vorstufen

“…Das entstandene Material wies einen hohen Anteil an sp-hybridisierten Kohlenstoffatomen auf. [199,200] Die Carbonisierung hochorientierter PTFE-Filme mit Lithium-oder Natriumamalgam resultierte in der Bildung von körnigen Kohlenstoff-Filmen. AFM-Aufnahmen bestätigten, dass die Filme die gerippte Struktur der Vorstufenfilme teilweise beibehielten.…”