Graphite-graphene composite as an anode for lithium-ion batteries

Graphite-graphene composites (GGC) have been obtained as a result of mechanical treatment of thermoexpanded graphite (TEG). Raman spectroscopy proves the presence of ordered graphene in the GGC. The predominant formation of no more than 5 graphene sheets in the material is concluded from Raman data and SEM micrographs. Electrochemical tests of GGC samples show that in spite of quite low specific discharge capacity (290 mAhg⁻¹), a 20-fold increase in current density (from 50 to 1000 mA g⁻¹) does not lead to a change in the specific capacity upon deintercalation of lithium ions. This feature favorably differs the material studied from existing analogues. A decrease in the specific capacity during cycling of the GGC at a current density of 100 mA g⁻¹ after 95 cycles has not been noted. Exceptionally low decrease in the specific capacity upon the increase of the power load, perfect cycling stability and high Coulombic efficiency supported by electrochemical impedance analysis indicate good prospects of using GGC as a lithium-ion battery anode and for utilizing graphene additives to electrode materials of lithium-ion batteries operating at high discharge currents.