Core-shell Bi@ mesoporous carbon nanospheres as high rate and long life anodes for sodium ion batteries
(1. Institute of Energy Innovation, College of Materials Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, China;
2. Department of Microsystems, University of South-Eastern Norway, Horten 3184, Norway;
3. School of Metallurgy and Environment, Central South University, Changsha 410083, China;
4. National Engineering Research Centre of Advanced Energy Storage Materials, Changsha 410205, China)
2. Department of Microsystems, University of South-Eastern Norway, Horten 3184, Norway;
3. School of Metallurgy and Environment, Central South University, Changsha 410083, China;
4. National Engineering Research Centre of Advanced Energy Storage Materials, Changsha 410205, China)
Abstract: In order to restrain the huge volume expansion of bismuth (Bi) anodes in sodium ion batteries (SIBs), the core-shell structure Bi@mesoporous carbon nanospheres (Bi@mC) composite was designed and prepared by sol-gel method coupled heat treatment. Structural characterization displays that the average diameter of the as-prepared Bi@mC composites is about 200 nm and thickness of the N-doped mesoporous carbon shells is 20-30 nm. Electrochemical test and kinetic analysis results show that the mesoporous carbon shell can not only effectively relieve the stress caused by volume expansion of Bi and protect active material from pulverization caused by the stress during charging/discharging process, but also facilitate quick diffusion of sodium ions, thus improving rate and cycling performance. Bi@mC delivers a high specific capacity of 279 mA·h/g and a capacity retention of 97.6% after 3500 cycles at a current density of 5 A/g. Even at a high current density of 20 A/g, Bi@mC can still maintain a high specific capacity of 266 mA·h/g. Additionally, the Bi@mC//NVP full button sodium-ion batteries (SIBs) assembled using Bi@mC anode and Na3V2(PO4)3(NVP) cathode deliver an energy density of 182 W·h/kg.
Key words: sodium ion battery; bismuth; core-shell structure; sol-gel method; kinetic analysis