Disordered-carbon anode

P. Papanek, W.A. Kamitakahara, P. Zhou J.E. Fischer (2001). J. Phys. Condens. Mat., 13, 8287-8301. Neutron scattering studies of disordered carbon anode materials. 

The processes taking place in the first intercalation of lithium into an alloy anode in a lithium-ion battery assembled in the discharged state are expected to be similar to those in a disordered carbon anode. 

The use of non-graphitic (disordered) carbons as anode materials in lithium ion cell is highly attractive for two reasons ... 

Xing and Dahn recently reported [70] that <2 R for disordered carbon and MCMB 2800 can be markedly reduced from about 180 and 30mAhg l to less than 50 and lOmAhg-1 respectively, when the carbon anode and cell assembly are made in an inert atmosphere and never come in contact with air. This indicates that these carbons contain nanopores that... 

In this paper, we presented new information, which should help in optimising disordered carbon materials for anodes of lithium-ion batteries. We clearly proved that the irreversible capacity is essentially due to the presence of active sites at the surface of carbon, which cause the electrolyte decomposition. A perfect linear relationship was shown between the irreversible capacity and the active surface area, i.e. the area corresponding to the sites located at the edge planes. It definitely proves that the BET specific surface area, which represents the surface area of the basal planes, is not a relevant parameter to explain the irreversible capacity, even if some papers showed some correlation with this parameter for rather low BET surface area carbons. The electrolyte may be decomposed by surface functional groups or by dangling bonds. Coating by a thin layer of pyrolytic carbon allows these sites to be efficiently blocked, without reducing the value of reversible capacity. 

Concerning binder-filler compatibility, the ideal anode carbon should be a pure, homogeneous, moderately-disordered carbon structure. To this end, coal-tar pitch with 10-25% QI produces the most... 

Carbon and graphite are used in batteries as electrodes or as additives in order to enhance the electronic conductivity of the electrodes. As electrodes, graphites and disordered carbons reversibly insert lithium, and hence they may serve as the anode material in -> lithium batteries. Graphitic carbons intercalate lithium in a reversible multi-stage process up to LiC6 (a theoretical capacity of 372 mAh g-1) and are used as the main anode material in commercial rechargeable Li ion batteries. As additives, carbon and graphite can be found in most of... 

To date, all commercial Li-ion batteries use carbonaceous materials as the anode-active material. Fig. 3A shows the structural schematics of typical carbonaceous materials in the field. Among various carbonaceous materials, graphite and disordered carbons have been employed dominantly in Li-ion batteries. Graphite has a typical layered structure that consists of stacked graphene sheets with an ABAB. .. sequence... 

Disordered carbons have received much attention for their use as anodes in lithium batteries, where they present high lithium storage capacities [6, 7]. However they still have an important iiTeversible capacity and hysteresis between charge and discharge, that limits their market competitiveness versus graphite electrodes. 

Wang, H., Abe, T, Maruyama, S., Iriyama, Y, Ogumi, Z., and Yoshikawa, K. [2005]. A disordered carbon as a novel anode material in lithium-ion cells. Ordered two- and three-dimensional arrays self-assembled from water-soluble nanociystal-micelles, Adv. Mater., 17, pp. 2857-2590. 

The insertion mechanism of the lithium ion into various kinds of carbons, when used as an anode in Li ion batteries has been extensively studied both experimentally and theoretically. However, the electrochemical insertion process is not yet fully understood. Polyparaphenylene (PPP)-based disordered carbon has a superior lithium storage capacity when used as an anode in the Li ion battery, and thus attracts much attention. In order to investigate the insertion mechanism of lithium into this material, the uptake and release processes of lithium were monitored by in situ Raman spectroscopy [90]. It was found that the band intensities of the characteristic peaks of disordered carbon decrease upon the discharging process and increase with the charging process, with quite good reversibility. Moreover, the frequency of the band related to the intraring C-C stretching mode of PPP at 1605 cm also... 

Fig. 8.7 In situ static Li NMR of a disordered carbon-Li metal battery cell taken over three charge and discharge cycles. Peaks at 0 ppm and 260 ppm correspond to lithium in the electrolyte/SEI and Li metal anode respectively. Resonances in the range of 0-140 ppm are assigned to Li environments inserted into the disordered carbon (Erom [31])...

Electrolyte decomposition is a major concern when intercalating Li ions on a carbonaceous matrix. When graphite is used as the anode, exfoliation of the electrode structure occurs when LiC10.,/PC is used as the electrolyte, but the same electrolyte system can be used for disordered carbons such as those derived from petroleum coke. The most common nonaqueous electrolyte is LiPF6 in EC/DEC. A number of products from electrolyte decomposition have been identified by Aurbach et Also, inorganic compounds such as LiCO, LijO, CO, and Hj have been reported as being produced by reactions with the organic products or trace water. ... 

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