Carbonization of mesocarbon microbeads prepared from mesophase pitch with different anisotropic contents and their application in lithium-ion batteries

Abstract

To clarify the relationship between the chemical compositions of green mesocarbon microbeads (GMCMBs) and the electrochemical behavior of carbonized mesocarbon microbeads (CMCMBs) for lithium-ion batteries, GMCMBs were prepared by emulsifying mesophase pitch (MP) with various anisotropic contents derived from FCC decant oil. Subsequently, GMCMBs were carbonized at 1000 °C, and their electrochemical behaviors were investigated. It was found that the GMCMB prepared from MP with a high anisotropic content (98 vol%) exhibited highly ordered aromatic lamellae stacking (ID/IG = 0.68) and a high condensation degree (IOS = 0.268). Therefore, CMCMB-98 with a highly ordered structure (ID/IG = 1.01) and low porosity (SBET = 80 m2/g) was formed, resulting in a high initial coumbic efficiency (74.8%). In addition, the GMCMB prepared from MP with a low anisotropic content (12 vol%) had more alkyl side chains and light components (ICHS = 0.50 TS = 22.7 wt%). CMCMB-12 with high porosity (SBET = 390.65 m2/g) and disorder degree (ID/IG = 1.21) was produced after the carbonization process, leading to a high capacity and rapid solid-state diffusion speed of Li+. Hence, CMCMB-12 can deliver the highest reversible capacity (405 mAh g−1 at 500 mA g−1 over 200 cycles) and excellent rate performance.