Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
1646255 | Materials Letters | 2012 | 4 Pages |
Expanded mesocarbon microbeads (EMCMB) are prepared by oxidizing pristine mesocarbon microbeads (MCMB). The d002 value calculated from X-ray diffraction results shows that the average interlayer distance of MCMB increases after oxidizing modification. The increased interlayer distance facilitates Li+ insertion kinetics, which causes an extraordinarily improved capacity of EMCMB (100 mAh g−1) at −40 °C, compared with pristine MCMB (almost no capacity at −40 °C). The facilitated Li+ insertion kinetics is analyzed by electrochemical impedance spectroscopy (EIS). EIS results demonstrate that both charge-transfer resistance and Li+ diffusion resistance of the EMCMB decrease obviously. The diffusion coefficients of Li+ in MCMB and EMCMB at −40 °C calculated from EIS are 2.46×10−17 cm2 s−1 and 1×10−15 cm2 s−1, respectively.
► Modifying commercial mesocarbon microbeads (MCMB) by oxidization expanding. ► An excellent capacity of 100 mAh g−1 at −40 °C. ► Smaller charge-transfer resistance and better Li+ diffusion kinetics at low temperature.