Materials Chemistry and Physics 66 (2000) 83–89 Study of camphor-pyrolysed carbon electrode in a lithium rechargeable cell Mukul Kumar a,∗ , P.D. Kichambare a , Maheshwar Sharon a , Neil R. Avery b , Krista J. Black b a Department of Chemistry, Indian Institute of Technology, Bombay 400 076, India b CSIRO Division of Materials Science and Technology, Clayton South MDC, Vic. 3169, Australia Received 27 October 1999; received in revised form 14 February 2000; accepted 28 March 2000 Abstract Pure camphor pyrolysed at 900 ◦ C for 2 h in different gaseous environments yields graphite-like carbons which were used as a negative electrode in rechargeable carbon/Li cells. These cells were continuously cycled at a constant current of 300 A cm −2 for 10–20 days and reversible Li + intercalation capacities of 0.45–0.61 were observed. Kinetic analysis of such a cell was studied by complex impedance spectroscopy and current interruption. After initial irreversible passivation during the first discharge, fully reversible intercalation capacity was observed for subsequent charge–discharge cycles. This property makes the camphor-pyrolysed carbon (CPC) a promising electrode material for further investigation for making a rechargeable lithium battery. A CPC/Li cell model is proposed. The structural properties of the camphor-pyrolysed electrode material is discussed on the basis of SEM, TEM, XRD and FTIR analyses. © 2000 Elsevier Science S.A. All rights reserved. Keywords: Camphor; Carbon; Lithium battery; Li ion intercalation capacity; Kinetics 1. Introduction In the last one decade, there have been striking advances in the state-of-the-art of developing secondary lithium batteries and it has been established that it is possible to build rechargeable lithium battery [1]. The major hurdle in Li-electrode recyclability has been that Li can be plated with virtually 100% efficiency in a range of organic systems; however, the plated Li cannot be stripped off quantitatively, especially if the cell has been allowed to stand for a pe- riod beween plating and stripping. During charging, Li gets electrodeposited in granular form and the newly created sur- faces react rapidly with the electrolyte; and this continues once the charging current has been switched off. Some Li grains become partially undercut and others are completely isolated from the underlying Li metal by an insulating film. Discharge efficiency is therefore less than 100% and the isolated Li grains affect the morphology of any subsequent replating. After a few cycles, the capacity or ampere-hour efficiency of the cycle practically falls to zero. The first and foremost way out to this problem is to find an optimised electrolyte system which could result in a film practically impermeable to the solvent and stabilise the metal, but which would remain conductive to Li + ions. ∗ Corresponding author. An alternative way of attacking this problem is to mod- ify the lithium phase. Transition chalcogenides often form electronically conducting phases that are able to react either chemically or electrochemically with lithium in a reversible manner to form ‘intercalation’ compounds. This behaviour is, however, related to the structure of the host material. In many cases, the sructure has layers or channels which can incorporate guest atoms as if a ternary phase is formed with a minimum of structural deformation. Thus, a limitless num- ber of charge–discharge cycles is possible without signifi- cant degradation of the structural or electrical properties of the host lattice. The mobility of lithium in the host lattice is reasonably good so that the concentration polarisation is not objectionably high [2]. For preliminary screening of new electroactive materials for both negative and positive electrodes of lithium batteries [3,4], it is advisable to electrochemically cycle the material in half cells with a lithium metal counter electrode. Here, the counter electrode acts also as a reliable reference, elim- inating the need for a separate reference electrode when the positive and negative electrode materials are assem- bled to form a full lithium battery configuration. In the present study, we have tried to investigate the suitability of camphor-pyrolysed carbon (CPC) as a new electroactive material for the lithium battery. Our CPC samples prepared at 900 ◦ C have been found to facilitate Li ion intercalation as 0254-0584/00/$ – see front matter © 2000 Elsevier Science S.A. All rights reserved. PII:S0254-0584(00)00276-5