Study On Electrochemical Properties Of Mesocarbon Microbeads And TiO₂ For Sodium-ion Batteries

Mesocarbon microbead?MCMB?has been extensively studied in the field of lithium-ion batteries due to its internal microcrystalline structure and its unique spherical layered structure.It has also attracted widespread attention in the field of anode materials for sodium-ion batteries.This paper explored its energy storage mechanism.The anatase TiO₂ has been considered as a promising anode material for sodium-ion batteries because of its high specific capacity,good stability and rate performance.The competitiveness of anatase TiO₂ mainly lies in the high specific surface area and three-dimensional open structure of TiO₂,which provides an effective site for sodium localization and sodium ion diffusion.In order to improve its conductivity and reduce the change of volume before and after charging and discharging,the TiO₂ was modified by MCMB by simple calcination method.MCMB carbonized at 800 ^oC,and used as the anode material for sodium-ion batteries.They have wider interlayer spacing?d=347 pm?than natural graphite?d=335 pm?.The MCMB anodes for SIBs exhibit a capacity of 180 mAh g^-1 at a current density of 25 mA g^-1 after 100 cycles and show high coulombic efficiency?⁹9%?with nice cycle stability.It is detected that sodium successfully intercalate into the graphite layers of MCMB during cycling.We suggest that MCMB anodes mainly store energy by a sodium intercalation mechanism.In addition,this study is helpful to understand the lithium storage mechanism of MCMB as anodes for lithium-ion batteries.The anatase TiO₂/MCMB composites were synthesized by a simple calcination method and calcined at different temperatures of 500,600,and 800°C.The study found that the composites carbonized at 600 ^oC as the anode materials for sodium ion batteries delivered a high capacity of 163.1 mAh g^-1 and a high coulombic efficiency of 99.75%even after 100 cycles.The MCMB improved the conductivity of the anode materials.The method of calcination enlarges the interplanar distance of TiO₂ which facilitates the free insertion/extraction of Na⁺as well as decreases the volume change.For the superior electrochemical performances,TiO₂/MCMB composites will become a promising anode material for sodium-ion batteries.