Microstructure and electrochemical properties of some synthetic carbons

Abstract

Four kinds of synthetic carbons were prepared by vacuum pyrolysis of black polyacene-based polymers: poly[(Z)-1-methoxy-4-phenyl-1-buten-3-yne]-750 [poly(MPB EY)-750], poly(1,4-diphenyl-1-buten-3-yne)-750 [poly(DPBEY)-750], poly[5-(2-pyridyl)-2,4-pentadiyn-1-ol]-800 [poly(PyPDO)-800], and poly(2,4-hexadiyn-1,6-diol)-800 (PHDO-800). The carbonization yields and electrochemical properties of carbons were dependent on precursor polymers. The relationship between the structure of synthetic carbons and electrochemical behavior was investigated by transmission electron microscopy (TEM), discharge/charge tests and cyclic voltammetry studies. Precursor polymers from enynes yielded synthetic carbons with many defect sites. Poly(DPBEY)-750, poly(PyPDO)-800, and PHDO-800 show smaller charge capacities than graphite (372 mA h/g), while a large charge capacity of 496 mA h/g is observed from poly(MPBEY)-750 in the first cycle. Poly(PyPDO)-800 displays very large capacity on cyclic voltammetry tests compared to other carbon samples indicating that the kinetics of lithium insertion/deinsertion in poly(PyPDO)-800 is faster than those of other carbons. (C) 1999 Elsevier Science S,A. All rights reserved.