Controlled synthesis of expanded mesocarbon microbeads (EMCMB) by H2SO4-HNO3-CrO3 oxidation for superior lithium-storage application

A controlled H2SO4-HNO3-CrO3 oxidation strategy has been demonstrated for the synthesis expanded mesocarbon microbeads (EMCMB) with good spherical morphology and high crystal structure. A series of EMCMB with different morphologies and structures were achieved by changing the oxidation time and temperature. The morphologies, structures and electrochemical properties of these samples have been systematically investigated by X-ray diffraction, scanning electron microscope and battery testing system. The results show that the optimal condition is: oxidation temperature is 80 °C and oxidation time is 17 h. Although the surface crack, the change of spherical degree and graphitization degree of the EMCMB sample is not obvious. When used as an anode in lithium ion batteries, the EMCMB is capable of reaching an extremely high first discharge capacity of 1039.0 mAh g−1, while maintaining a good electrochemical stability with a very high capacity of 593.4 mAh g−1 after 80 cycles. Relative to GMCMB, the specific capacity of EMCMB is much improved, and the stability is also excellent, indicating that the EMCMB should be a promising electrode material for lithium storage applications.