摘要:

A photocatalyst for the production of hydrogen due to UV-illumination of water was prepared by the reduction of CrO3-graphite intercalation compound (CrO3-GIC) in K-naphtalenide/anhydrous THF solution. The creation of active sites on the catalyst surface was estimated during the activity measurements performed in dynamic conditions. The EDX analysis revealed an exact coincidence of the distribution lines for chromium and potassium in the whole of graphite flakes of the CrO3-GIC/K photocatalyst.

ISSN:1058-725X    

DOI:10.1080/10587259808045357

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Graphite samples with different crystalline characteristics were evaluated as negative materials for lithium ion batteries. Conversely to non crystalline coke materials, they were found to experience exfoliation problems to a variable extent during the first electrochemical reduction process. A clear correlation was found between their rhombohedral phase content and their resistance to exfoliation.

ISSN:1058-725X    

DOI:10.1080/10587259808045358

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

CxN compounds were coated on two kind of graphites, natural graphite treated with 94%HN03solution and the natural graphite without treatment, by chemical vapor deposition. XPS and Raman spectroscopy revealed that these materials were not mixtures of CxN and graphites, but CxN coated-graphites. As anodes of secondary lithium battery, the CxN-coated graphites demonstrated the higher capacity than that of natural graphite, good cycleability, and gradual increase in the potential at the last stage of lithium deintercalation reaction.

ISSN:1058-725X    

DOI:10.1080/10587259808045359

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Polyparaphenylene powders are electrochemically reduced in LiCIO4-ethylene carbonate electrolyte. Intercalation of Li+ions occurs and leads to the formation of Li0.5(C6H4) compounds. Side reactions due to the electrolyte decomposition are responsible for the important irreversible electrochemical capacity observed during the first charge-discharge cycles. The degradation products were analyzed by TEM and EELS between 2.85 and 0.75 V.

ISSN:1058-725X    

DOI:10.1080/10587259808045360

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

PPP-based carbons prepared by the Kovacic and the Yamamoto methods give rise to slightly different polymer structures. The low temperature forms of PPP-Kovacic-based carbon heat treated around 700°C shows a Li storage capacity (1000mAh/g) which is 3 times larger than that of Yamamoto (280mAh/g) in the 2nd charging process. It is suggested that the texture as well as the microstructure of these carbons, as characterized by SEM, TEM, and Raman observations, affect the anode performance strongly.

ISSN:1058-725X    

DOI:10.1080/10587259808045361

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Effects of microtexture were analyzed using mesocarbon microbeads (MCMB) and two reference cokes heat-treated at 1000°C, a mesoporous saccharose coke and a lamellar anthracene coke. The electrochemical performance of MCMB heat-treated at 900°C (340mAh/g for the reversible capacity) are attributed to the specific microtexture of the beads, which are both lamellar (inner part) and mesoporous (outer part). The disorganised phase present at the surface of MCMB favors lithium sorption and further intercalation in the bulk. The electrochemical characteristics of saccharose coke were drastically changed by a mild oxidation at 450°C. The presence of oxygen at the surface plays an important role by enhancing lithium adsorption on surface sites prior to diffusion into the grains.

ISSN:1058-725X    

DOI:10.1080/10587259808045362

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The degree of reversible and irreversible insertion of lithium in the fibrous carbonaceous materials was estimated by charge-discharge characteristics. The electrochemical storage of lithium ions, i.e. specific capacity, widely ranged from 100 to 700 mAh/g depending on the textural properties and chemical composition of carbons. The elucidation of irreversible loss of capacity was undertaken for carbons obtained from different precursors and prepared in a wide range of temperatures. Especially, the role of heteroatoms in the process of lithium insertion was considered for carbons prepared at temperatures from 600°C to 1000°C. The value of electrochemical potentials for lithiated carbons, more or less close to the potential of metallic lithium, is influenced by the stoichiometry of the compound and the way of Li-C bonding. Some carbons pointed out a large hysteresis, i.e. a high divergence between average discharge and charge potential. The reversibility of lithium insertion was also investigated by the potentiodynamic technique.

ISSN:1058-725X    

DOI:10.1080/10587259808045363

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The graphite surface was modified in order to obtain the reversible lithium intercalation upon cycling in electrolytes containing only PC as a solvent species. Such surface modifications were obtained (i) by wetting graphite in chloro ethylene carbonate, or (ii) by forming previously a passivating layer by reducting graphite in EC or Cl-EC based electrolytes or finally (iii) by cycling in mixed PC+Cl-EC electrolytes. In all cases, high reversibility and high electrochemical capacities were obtained.

ISSN:1058-725X    

DOI:10.1080/10587259808045364

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A positive electrode made from natural graphite flakes and 20 wt% PP as binder was combined with a negative electrode made from carbon black and 10 wt% PTFE to yield a metal free rechargeable battery. Aqueous electrolyte; with strong acids were employed to meet the requirements of the graphite intercalation compounds (GIC). Aqueous HBF4(c = 2–8 M) was studied in detail. The reversible formation of the GIC C48BF4(2nd stage) was proved by XRD in the range c = 6–8 M. For c = 2 (4) M stage 5 (3) was foundaslimit. To make use of the GIC in an accumulator die electrolyte has to be cycled between 6 and 8 M upon charge and discharge. The current efficiency (reversibility) is almost 100% under these conditions. But the electrochemical equivalent for the GIC and the required electrolyte is as low as 9.4 Ah/kg, mainly due to the coinsertion of HBF4in theGIC.

ISSN:1058-725X    

DOI:10.1080/10587259808045365

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The first galvanostatic reduction curve of the lithium intercalation into several treated graphite samples is discussed with respect to the effect of surface treatment on the intercalation process.

ISSN:1058-725X    

DOI:10.1080/10587259808045366

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor