Carbon films from polyacrylonitrile

Renschler, Clifford L.; Sylwester, Alan P.; Salgado, Leonardo

doi:10.1557/jmr.1989.0452

Cited by 57 publications

(38 citation statements)

References 11 publications

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“…These must, however, be carefully chosen. Polyaromatic compounds or polymers with low H/C ratios are sometimes used to produce conductive carbons at temperatures above 1000°C [14,15,16] but may not decompose completely at the low synthesis temperatures (<750°C) at which LiFePO 4 is produced. The carbon content in these samples is increased over materials processed without the additives, but electrochemical performance is poor, presumably because of the rather low electronic conductivities of the incompletely decomposed coatings [9].…”

Section: Resultsmentioning

confidence: 99%

Impact of carbon structure and morphology on the electrochemical performance of LiFePO4/C composites

Doeff

Wilcox

et al. 2007

J Solid State Electrochem

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The electrochemical performance of LiFePO 4 /C composites in lithium cells is closely correlated to pressed pellet conductivities measured by AC impedance methods. These composite conductivities are a strong function not only of the amount of carbon, but of its structure and distribution. Ideally, the amount of carbon in composites should be minimal (less than about 2 wt. %) so as not to decrease the energy density unduly. This is particularly important for plug-in hybrid electric vehicle applications (PHEVs) where both high power and moderate energy density are required. Optimization of the carbon structure, particularly the sp 2 /sp 3 and D/G (disordered/graphene) ratios, improves the electronic conductivity while minimizing the carbon amount.Manipulation of the carbon structure can be achieved via the use of synthetic additives including iron-containing graphitization catalysts. Additionally, combustion synthesis techniques allow co-synthesis of LiFePO 4 and carbon fibers or nanotubes, which can act as "nanowires" for the conduction of current during cell operation.

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Section: Resultsmentioning

confidence: 99%

Impact of carbon structure and morphology on the electrochemical performance of LiFePO4/C composites

Doeff

Wilcox

et al. 2007

J Solid State Electrochem

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“…15,19 This presents a dilemma since undesirable particle growth of LiFePO 4 is rapid at 700ºC or above. Still, the differing D/G ratios obtained on the materials in this study suggest that the carbon structure can be manipulated to some extent by proper choice of organic precursors and processing conditions, even at 600ºC.…”

Section: Resultsmentioning

confidence: 99%

Electrochemical Performance of Sol-Gel Synthesized LiFePO[sub 4] in Lithium Batteries

Doeff

Kostecki

et al. 2004

J. Electrochem. Soc.

265

176

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LiFePO 4 , Li 0.98 Mg 0.01 FePO 4 , and Li 0.96 Ti 0.01 FePO 4 were synthesized via a sol-gel method, using a variety of processing conditions. For comparison, LiFePO 4 was also synthesized from iron acetate by a solid state method. The electrochemical performance of these materials in lithium cells was evaluated and correlated to mean primary particle size and residual carbon structure in the LiFePO 4 samples, as determined by Raman microprobe spectroscopy. For materials with mean agglomerate sizes below 20 µm, an association between structure and crystallinity of the residual carbon and improved utilization was observed. Addition of small amounts of organic compounds or polymers during processing results in carbon coatings with higher graphitization ratios and better electronic properties on the LiFePO 4 samples and improves cell performance in some cases, even though total carbon contents remain very low (<2%). In contrast, no performance enhancement was seen for samples doped with Mg or Ti. These results suggest that it should be possible to design high power LiFePO 4 electrodes without unduly compromising energy density by optimizing the carbon coating on the particles.

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“…Reflections from the GP zones appear as continuous streaks because of the very thin disk morphology of the zones (one unit cell in thickness). The continuous nature of the streaks shows that the zones are monoatomic layers of Cu atoms known as GPI zones: streaks from GPII zones, or 0', would show intensity maxima halfway between the fcc Bragg reflections (13). The streaks are very pronounced in regions with dense GP zones ( Fig.…”

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Conducting Carbon Wires in Ordered, Nanometer-Sized Channels

Bein

1994

Science

379

187

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The encapsulation of graphite-type carbon wires in the regular, 3-nanometer-wide hexagonal channels of the mesoporous host MCM-41 is reported. Acrylonitrile monomers are introduced through vapor or solution transfer and polymerized in the channels with external radical initiators. Pyrolysis of the intrachannel polyacrylonitrile results in filaments whose microwave conductivity is about 10 times that of bulk carbonized polyacrylonitrile. The MCM host plays a key role in ordering the carbon structure, most likely through the parallel alignment of the precursor polymer chains in the channels. The fabrication of stable carbon filaments in ordered, nanometer-sized channels represents an important step toward the development of nanometer electronics.Intensive efforts under way to increase computing speed and storage density in information processing could culminate in the design of nanometer-sized, moleculebased electronic devices (1). One major challenge in this context is to achieve communication with individual nanometersized structures or molecules. Encapsulation of conducting structures in ordered, insulating host systems is a promising approach toward controlled electronic access to individual nanometer-sized objects.We have used the well-defined subnanometer-sized channels of zeolites as hosts for several different conjugated polymers such as polypyrrole, but the small diameter of these channels appears to inhibit significant conductivity (2, 3). Con (Fig. 1). This loading corresponds well with the saturation expected from the pore volume (0.64 ml/g), obtained from nitrogen absorption isotherms.For polymerization, sample AC-MCM was mixed with distilled water under nitrogen (typically 1.00 g with 20 ml of water).The temperature was raised to 40°C, and then 20 mg of K2S208 and 10 mg of NaHSO3 were added as radical initiators. The mixture was stirred for 20 hours at 40°C, and the resulting white solid (PAN-MCM) was washed with water and then evacuated.

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Carbon films from polyacrylonitrile

Cited by 57 publications

References 11 publications

Impact of carbon structure and morphology on the electrochemical performance of LiFePO4/C composites

Impact of carbon structure and morphology on the electrochemical performance of LiFePO4/C composites

Electrochemical Performance of Sol-Gel Synthesized LiFePO[sub 4] in Lithium Batteries

Conducting Carbon Wires in Ordered, Nanometer-Sized Channels

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