The thermal reaction of ternary electrolyte (1.0M LiPF6 in 1:1:1 ethylene carbonate/dimethyl carbonate/diethyl carbonate) with mesocarbon microbeads (MCMB) particles was investigated by the combined use of NMR, GC–MS, FTIR-ATR, TGA, XPS and SEM/EDS-element map. The thermal decomposition of ternary electrolyte is not inhibited by the presence of MCMB particles. The chemical composition and morphology of the surface of MCMB particles changes significantly upon storage in the presence of ternary electrolyte. Electrolyte decomposition products including oligocarbonates, oligoethylene oxides, polyethylene oxide (PEO), lithium fluorophosphates (Li x PO y F z ), and lithium fluoride are deposited on the surface of MCMB particles. The concentration of decomposition products on the surface of MCMB increases with increased storage time and temperature. The addition of dimethyl acetamide (DMAc) impedes the thermal decomposition of the electrolyte and deposition of electrolyte decomposition products on the surface of MCMB.