N-doped hollow porous carbon microspheres with high rate performance as anode for sodium-ion batteries

In this paper, using resorcinol/formaldehyde resin as a carbon source and ionic liquid [EMIM]DCA as a nitrogen source, N-doped hollow porous carbon microspheres (NHPCS) were simply prepared by a confined space pyrolysis process. The confined space of this strategy consists of a dense SiO2 shell. Benefiting from hollow porous structure and N doping, NHPCS has a larger electrode/electrolyte interface, a shorter Na+ transport length, increases the interlayer spacing, and provides more Na+ storage active sites, which are improved electrochemical performance. When used NHPCS as anode electrode for sodium-ion batteries, it shows high-rate performance for 232.8, 207.9, 190.6, 171.2, 147, 112.9, and 89.2 mAh g(-1) at 0.1, 0.2, 0.5, 1, 2, 5, and 10 A g(-1), respectively. After 900 cycles, it has a specific capacity of 112.7 mAh g(-1) at 5.0 A g(-1).