Structural and electrochemical studies of a hexaphenylbenzene pyrolysed soft carbon as anode material in lithium batteries

XRD, SEM micrographs, BET analyses and typical electrochemical experiments (cyclic voltammetry, step voltammetry and Li insertion/deinsertion at constant current) have been carried out to characterize a new type of soft carbons obtained by pyrolysis of hexaphenylbenzene (HPB). By means of XRD and cyclic voltammetry at least three different type of sites for lithium storage were found. The first is graphite like type with d(002) graphene layer distance greater than pure graphite; the second is associated to disordered volumes among crystallities and the third is represented by Li sites at the hydrogen-terminated edges of hexagonal carbon fragments, characterized by higher energy in comparison with simple insertion sites. These last two types of sites are able to store some extra lithium, compared to pure graphite. BET analyses and cyclic voltammetries demonstrate the key role of the milling time on the characteristics and properties of this HPB pyrolysed carbon. Specific capacities shown by this pyrolysed material in Li coin-type cell have been also reported. (c) 2005 Elsevier Ltd. All rights reserved.