Preparation and sodium storage properties of coal tar pitch-based carbon anode materials
Sodium ion batteries have the advantages of high safety and low cost,holding sig-nificant promise for applications in low-speed electric vehicles and large-scale energy storage systems.The development of high performance and low-cost anode materials is crucial for the development of sodium ion batteries.Coal tar pitch with high carbon content and aromaticity is an excellent precursor material for carbon anode materials.However,direct high-temperature pyrolysis results in highly graphitized carbon with small interlayer spacing and few active sites,leading to relatively low sodium storage capacity.In this study,coal tar pitch was employed as raw material,leveraging the activation and catalytic effects of NaCl as template agent.The two were fully mixed at a certain mass ratio and carbonized at 800℃ to prepare pitch based hard carbon materials.X-ray diffraction(XRD),Raman spectroscopy,scanning electron microscopy(SEM),transmission electron microscopy(TEM),low-temperature nitrogen adsorption instrument,X-ray photoelectron spectroscopy(XPS),etc.were used to investigate the microstructure of carbon materials,and the sodium storage performance of coal tar pitch as an anode material for sodium ion batteries was explored using constant current charge dis-charge and cyclic voltammetry.The results show that the addition of NaCl significantly increase the specific surface area of the material,fostering the generation of more active sites,and facilitating the formation of localized graphite lamellae with an increase in the volume of closed pores.When the mass ratio of NaCl to coal tar pitch is 10:1,the prepared coal-based porous carbon PN2 has a highest specific surface area of 163 m2/g,showing both increase slope and plateau capacity.Therefore,the reversible specific capacity of PN2 at a current density of 50 mA/g is 229.6 mAh/g.When the cur-rent density is increased to 2 A/g,the reversible specific capacity of 99 mAh/g is still maintained,exhibiting good cycling stability with a specific capacity retention of 79.51%after 200 cycles.Mecha-nistic investigations reveal that the sodium storage behavior of coal tar pitch-based porous carbon can be ascribed to the integrated regulation of diffusion behavior and capacitance behavior.
coal tar pitchsodium ion batteryporous carbonanode materialelectrochemi-cal performance