In Situ Measurements of Drastic Change of Electrical Conductivity and Structure upon Electrochemical Lithium Intercalation in Pyrolyzed Poly(hydrazocarbonyl-1-4-phenylenecarbonyl) Film

Autor: Takashi Banjyo, Katsumi Yoshino, Tsuyoshi Kawai, Nobuyuki Tokuda, Hisashi Araki, Kiyoshi Miyai, Young Bae Roh, Masaaki Takase
Rok vydání: 1994
Předmět:
Zdroj: Japanese Journal of Applied Physics. 33:5917
ISSN: 1347-4065
0021-4922
DOI: 10.1143/jjap.33.5917
Popis: Drastic changes of structure and electrical property of pyrolyzed polymers based on poly(hydrazocarbonyl-1,4-phenylenecarbonyl) (poly(terephthalohydrazide)) film have been investigated in an electrochemical cell with 1 M LiClO4 in a 70:30 mixture of propylene carbonate and 1,2-dimethoxyethane as the electrolyte, by means of in situ measurement techniques using the four-probe conductivity measurement method and X-ray diffraction method with a beryllium window. In the first redox cycle, the highly crystallized graphite prepared by pyrolysis at 2800°C exhibits large irreversible changes in both apparent conductivity and the layered structure, whereas the poorly crystallized carbon prepared by pyrolysis at 1300°C showed a good reversible change in structure but a large decrease in conductivity compared with that of the pristine sample. The two characteristic X-ray diffraction peaks of the distorted graphite layer observed only in the first discharge are attributed to the decomposition reaction of electrolyte and lithium ions in graphite layers. The passivation film formed on the surface by the first discharge also affects the characteristics. In the film prepared by pyrolysis at 1300°C, damage of disordered carbon layer structures occurred in the first charge process. The apparent diffusion coefficient of lithium in the disordered carbon was larger than that in graphite, and was activated with increasing number of cycles, while that of graphite was independent of the number of cycles.
Databáze: OpenAIRE
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