STRUCTURAL-ANALYSIS OF POLYACENIC SEMICONDUCTOR (PAS) MATERIALS WITH (129)XENON NMR MEASUREMENTS

Structural analysis of the polyacenic semiconductor (PAS) material pre pared by the pyrolysis of phenol-formaldehyde resin at relatively low temperature (680 degrees C) has been performed by applying Xe-129 nucl ear magnetic resonance (NMR) measurements. One can obtain information on the microporous structure of the PAS material through adsorption of Xe atoms, since a Xe-129 nucleus is a very sensitive probe of its mic roscopic environment. All the introduced Xe atoms were adsorbed on the internal surface of the pure PAS sample, which indicated remarkably l arge surface area of the PAS material. The average pore size of the pu re PAS sample has been determined to be 7.7+/-1.6 Angstrom from the pr essure dependence of the Xe NMR chemical shift. In connection with the application of the PAS material to the electrode of the Li rechargeab le battery, changes in the Xe NMR spectrum brought about by extrinsic additives such as binder, electrolyte solvent, and the doped Li have b een investigated. In particular, it has been found that the Li-doping entirely prevents Xe atoms from entering into the micropores of the PA S material, probably due to adsorption of the solvent molecules on the internal surface of the micropores. (C) 1997 Elsevier Science Ltd.