Preparation of mesocarbon microbeads by thermal polymerization of the blended coal tar and biomass tar pitch as anode material for sodium-ion batteries

Abstract

Sodium ion batteries (SIBs) are capable of low redox potential, low cost and stable electrochemical performance and thus have attracted increasing attentions, while the defects of smaller theoretical specific capacity and the difficulty in ion insertion or ion extraction restrict their further improvements. To solve this problem, soft carbon anode materials such as mesocarbon microbeads (MCMBs) severed as anode were developed. In this work, Mesocarbon microbeads (MCMBs) were prepared from coal tar pitch (CTP) in the presence of biomass tar pitch (BTP) by heating-treatment from ambient temperature to 410°C for 7 h. XRD analysis indicates that graphite-like crystallites the carbonized MCMBs with an interlayer distance of 0.345-0.351 nm. Interlayer distance of carbonized MCMBs prepared from CTP is 0.336 nm. Raman analysis indicates carbonized MCMBs prepared with BTP possess more defect sites than those from CTP. MCMB anode prepared by CTP and BTP exhibits higher charge and discharge capacity, keeping a charge capacity of 236.6 mA h g-1 with the capacity retention rate 94.7% after 70 cycles. Co-carbonization of BTP and CTP are capable of enlarging the degree of cross-linking of MCMBs and form a relatively stable cross-linked structure inside, the layer spacing and microcrystalline structure of MCMBs is beneficial to the insertion/extraction of sodium ion. Sodium intercalation into graphene layers is the dominant step regarding sodium storage mechanism in MCMBs