摘要:

Coke samples heat-treated between 1200 and 2800°C have been characterized by X-ray diffraction and their performance as electrodes for lithium batteries has been determined on coin cells with LiTFSI dissolved in EC/DMC as electrolyte. The data show that the electrochemical behaviour is strongly dependent on the structural characteristics of the carbon materials. It is shown that Mering's graphitization model can account for the values of reversible capacities measured for the different materials, as well as for the appearance of voltage plateaus for carbon heat-treated above 2000°C.

ISSN:1058-725X    

DOI:10.1080/10587259808045367

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We used a two-step fluorination of natural or synthetic graphites, the one at the ambient temperature in the presence of F2+ IF5+ HF and the second in the temperature range of 100 – 350°C in F2atmosphere. This led to graphite fluorides characterized by the planarity of the carbon hexagons (sp2hybridization), by the iono-covalent character of the C-F bondings and by the high F/C ratio, close to unity. These graphite fluorides were compared to conventional, highly covalent CFx(sp3hybridization) in their electrochemical performances in lithium batteries, especially regarding the high rate discharge capability. We found a large advantage with the iono-covalent CFxthat is they sustain a 5 C rate discharge where the covalent ones failed to discharge under 4 C. The difference is tentatively related to the internal structure and to the higher electrical conductivity of iono-covalent CFx.

ISSN:1058-725X    

DOI:10.1080/10587259808045368

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Carbon fluoride with a general formula (CFx)nrepresents an attractive cathode material for primary lithium cells operating in aprotic medium. (CFx)ncompound was obtained by the gaseous fluorination of carbon tissue at 450°C. The degree of fluorination, i.e. the value x for the final product, was equal to 0.95. During the electrochemical reduction of carbon fluoride, a ternary intercalated compound CLixF is formed which is chemically decomposed to carbon and lithium fluoride. Reduction process of (CFx)nis irreversible due to covalent C-F bonding with sp3hybridization. This discharge process was strictly controlled by diffusion of Li+into the layered host of carbon fluoride. X-ray method was applied for elucidation of reduction process.

ISSN:1058-725X    

DOI:10.1080/10587259808045369

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:1058-725X    

DOI:10.1080/10587259808045306

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor