New insight into the interaction between propylene carbonate-based electrolytes and graphite anode material for lithium ion batteries

Sufficient understanding of surface chemistry for electrode and electrolytes during an electrochemical process is a crucial issue to further improve the performance of lithium ion batteries (LIB). In this study, we systematically investigate the interaction between propylene carbonate (PC)-based electrolytes and graphite anode material, which has been under dispute for a long time in the electrochemical community, and a new physical model is proposed to explain the poor compatibility of PC with graphite. With the aid of scanning electron microscopy, focused ion beam workstation, Raman spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and thermogravimetry-differential scanning calorimetry, the cumbersome but intriguing questions on the poor compatibility are addressed: (i) Does PC truly have the ability to co-intercalate into graphite materials? Our answer is yes. (ii) Where is the intercalation site? It is around the crystal boundary. (iii) Why does the co-intercalation occur for PC not ethylene carbonateanother kind of useful electrolyte in LIB, since both of them have a similar molecular structure? The methyl group in the PC molecule is the main wire-puller, which makes decomposition products of PC puffed and thus incompetent in inhibiting the subsequent co-intercalation. Finally, three feasible strategies to overcome the poor compatibility are summarized.