SHORT COMMUNICATION Expanded graphite as an intercalation anode material for lithium systems Jaromír Makovička & Marie Sedlaříková & Ana Arenillas & Jana Velická & Jiří Vondrák Received: 6 March 2008 / Revised: 17 August 2008 / Accepted: 24 August 2008 / Published online: 1 October 2008 # Springer-Verlag 2008 Abstract The expanded graphite (BOCHEMIE a.s., Czech Republic) was tested as the material for anodes of lithium secondary batteries. The irreversible charge was lowered and the cyclability improved if the material was annealed in CO 2 . The specific capacity approached theoretical value corresponding to the composition LiC 6 . Keywords Graphite . Anode . Mild oxidation CO 2 Introduction Intercalation compounds are created from materials which posses layer structure. Among them, the first to be described were the compounds based on graphite [1] or on layered dichalcogenides, and the process of their formation was called intercalation. The process consists in penetrating of sufficiently mobile particles—guest—into the interlattice space (van der Waals layers) in the host. The theoretical concentration limit for intercalation of lithium into graphite is given by bonding of one atom of Li on a hexagonal structural unit of graphite, which is described by the formula LiC 6 . Metallic lithium is commonly used as an anode material in lithium primary batteries. Among its main advantages are the high specific energy and specific charge related to the mass unit and the longest lifetime of all primary batteries due to negligible self-discharge. Moreover, a voltage of 3 V or more can be achieved, which is quite sufficient in most microelectronic devices. On the other hand, lithium metal as a negative anode for secondary cells—rechargeable accumulators, did not prove successful and was soon replaced by other materials, safer and with a longer lifetime expressed by a number of charging–discharging cycles. In these batteries, both electrodes are basically of the intercalation type. When they are operating, lithium ions move from one electrode to another, while no morphological changes in electrodes materials occur. The concentration of salt in the electrolyte remains constant, and only a small amount of electrolyte is enough to keep the cell working. Batteries of this type have been called “rocking chair” or “shuttle cock.” In the production of these batteries, a phenomenon well- known as the irreversible capacity [2] is encountered. Organic electrolyte is decomposed by catalysis on the surface of graphite particles and an ion-conducting film originates. Charging efficiency in initial charging is thus substantially decreased. In theory, the magnitude of the specific charge is usually considered by the limiting composition of a charged electrode corresponding to the intercalation compound given by the formula LiC 6 . In the Czech Republic, expanded (exfoliated) graphite is produced by the company BOCHEMIE a.s. Its particles are substantially enlarged through a chemical process, and a product called “expanded graphite” is manufactured and J Solid State Electrochem (2009) 13:1467–1471 DOI 10.1007/s10008-008-0662-8 J. Makovička : M. Sedlaříková : J. Vondrák Institute of Electrotechnology, Brno University of Technology, 602 00 Brno, Czech Republic M. Sedlaříková e-mail: sedlara@feec.vutbr.cz J. Velická : J. Vondrák (*) Institute of Inorganic Chemistry AV CR,v.v.i., 250 68 Husinec-Řež, Czech Republic e-mail: vondrakj@iic.cas.cz A. Arenillas Instituto Nacional del Carbón, CSIC, Apartado 73, 33080 Oviedo, Spain