Pyrograf IIITM,/sup> fibers (PR-19-PS, Applied Sciences, Inc.) with 100-300 nm diameters and ~ 10-100 ìm lengths were used with a low viscosity aliphatic epoxy resin (Clearstream 9000, Clearstream Products, Inc.) to produce composites. The VGCFs were oxidized in 69-71 wt% nitric acid (115°C) for various times (10 min to 24 h) to modify the surface to enhance fiber/matrix adhesion. Remarkably, little fiber weight loss was detected even after 24 h of oxidation. Composites containing 19.2 volume percent (29.4 weight percent) VGCFs were prepared. Their flexural strengths and flexural moduli were obtained. The flexural strengths did not increase using oxidized VGCFs. Fiber surfaces were characterized using N2 BET, CO2 DR, XPS, SEM, TEM and base uptake measurements. Increasing the oxidation time produced only small initial increases in surface area up to a limit. Significant surface oxygen was present before oxidation and the amount increased initially, though not continuously, with nitric acid oxidation.

Electrochemical copolymerizations of thiophene (Th) and 3,4-ethylenedioxythiophene (EDOT) was performed in this study. Incorporation of Th with EDOT units have accelerated deposition rate in relative to the simple polymerization behavior of EDOT. The electrochemical properties of poly(thiophene-co-3,4-ethylenedioxythiophene) (PTh-EDOT) are different from the homopolymers of polythiophene (PTh) and poly(3,4-ethylenedioxythiophene) (PEDOT). PTh-EDOT were then served as cathode materials of lithium-ion (Li-ion) batteries to test their capability to transfer lithium ion in 1.0 M LiPF6/ethylene carbonate/dimethyl carbonate solution. PTh-EDOT copolymer prepared from the monomer ratio of 1/1 (Th/EDOT) shows better stability than PEDOT and PTh homopolymers, polymer property enhancement by copolymerization is thus demonstrated. A composite electrode material PEDOT/LiCoO2 was prepared from the electrochemical polymerization of EDOT on LiCoO2 electrode was primarily prepared to inspect the influence of PEDOT on the electrochemical features of LiCoO2. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) show the successful deposition of PEDOT over LiCoO2 particles. Compared to the simple LiCoO2 electrode, PEDOT/LiCoO2 composite cathode shows enhanced properties including rate capability and cycle stability for potential Li-ion battery application. Nevertheless, differential scanning calorimetry (DSC) scans on the fully charged cathodes imply that PEDOT may reduce the thermal stability of LiCoO2. Two carbon materials, vapor grown carbon fibers (VGCF) and nano-scaled Ketjen black EC (KB), were implemented into LiCoO2 electrode. The influence of different carbon additive and their content on the performance of LiCoO2 such as rate capability and cycle ability has been evaluated. KB shows more positive effects than VGCF even in the case of a low 1 wt% content. Furthermore, incorporation of PEDOT was made by electrochemical deposition of EDOT on the preformed LiCoO2-VGCF and LiCoO2-KB composite electrodes. The influence of the carbon additives and the conductive PEDOT polymer on LiCoO2 was then investigated. Compared to the electrodes without PEDOT coating, PEDOT-incorporated composite electrodes show larger capacity, better transfer rate of lithium ions in electrolytes, and enhanced cycle ability. The electrochemical deposition of PEDOT on the LiCoO2/nano-carbon cathodes provides a new approach to implement the conducting polymers in Li-ion batteries.