Electrochemical and thermal behavior of copper coated type MAG-20 natural graphite

Abstract

Natural graphite powders, type MAG-20, were modified by electroless deposition of copper onto the graphite surface. The scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) of the modified graphite showed that almost all the copper covered the edge plane of graphite particles and the copper content increased from 6 to 17 at.% depending upon the plating time. Thermal gravimetric analysis (TGA) confirmed the copper composition obtained using EDS. TGA carried out under oxygen atmosphere showed that the combustion temperature decreased by 200 °C for a copper content from 0 to 16 at.%. Cycling the modified graphite at a C/10 rate showed that the initial large irreversible capacity typically present in untreated natural graphite was significantly reduced when the modified graphite contained 6–17 at.% copper coatings. A differential scanning calorimetry (DSC) comparison between fully lithiated copper coated MAG-20 with fully lithiated MCMB showed that the major exothermic peak for the MAG-20 modified graphite is lower in magnitude and is shifted to higher temperatures. However, both MAG-20 and MCMB types of lithiated graphite gave the same amount of total heat generation up to 350 °C.