Characterization Of Heattreated Polyparaphenylene-Based Carbons

Abstract

ABSTRACTRaman spectroscopy and TEM measurements were recently performed on a series of polyparaphenylene (PPP)-based carbon samples which were heat-treated to temperatures between 600°C and 3000°C. Particular attention is focused on the development of carbonaceous structures at low heat-treatment temperatures (THT) in the range 600°C ≤ THT ≥ 800°C. PPP-based carbons heat treated in this temperature range have been found to have a very high affinity for the electrochemical introduction of lithium, which is of particular interest in ‘rocking-chair’ rechargeable Li batteries. Specific (Faradaic) capacities of up to 1120 mAh/g have been obtained for PPPbased carbon anodes with a THT of 700°C, which is about three times the capacity of GIC-based anode materials. At a heat-treatment temperature of 700° C, the PPPbased carbon has a disordered-granular appearance, as observed from TEM, while a ribbon-like graphitic structure is seen for heat treatment near 3000°C. Furthermore, Raman spectra show that, near a THT of 700° C, these PPP-based materials undergo a carbonization transformation from a mostly polymer-type extended lattice to a disordered carbon matrix, which undergoes partial graphitization at higher THT. Upon the introduction of small amounts of substitutionally-doped Boron (1% - 3% atomic), various properties are substantially modified. In this work we briefly discuss the effect of B-doping on the PPP-based carbon structure.