Study On Synthesis And Properties Of Coal Tar Pitch Based Sodium Ion Battery Anode Material

Sodium ion battery has many advantages such as abundant sodium and low cost,which is a major strategic demand for achieving"carbon peak and carbon neutralization"by using clean renewable energy such as solar energy and wind energy.The preparation of anode materials with high quality and low cost is significant to the advancement of sodium ion batteries.Coal tar pitch is a kind of low cost coal chemical resource,which possesses advantages of high abundance and high carbon yield,serving as a superior raw material for carbon anode preparation.Preparing coal-based functional carbon materials with unique structure,adjustable components and large-scale production demonstrates great potentials in the carbon anode field of high performance and low cost sodium ion batteries.This can be realized through improving the conductivity,optimizing surface/interface chemical properties,and increasing the number of active sites based on the typical feature of polycyclic aromatic hydrocarbons of coal tar pitch,representing the frontier direction of high value-added utilization of chemical resources and serving as the research background of this work.The specific research contents are shown as below:Using coal tar pitch as carbon source,urea and sulfur powder as nitrogen source and sulfur source respectively,nitrogen and sulfur co-doped porous carbon materials derived from coal tar pitch（NSPC122-600）were successfully prepared by template assistance and high temperature carbonization.NSPC122-600 can be cycled 300 times at a high current density of 1 A g^-1 with a specific capacity up to 354.2 m Ah g^-1,demonstrating excellent long cycle stability and high sodium storage capacity.Structure-activity relationship studies shows that NSPC122-600 has a channel structure with suitable size（40～80 nm）,which facilitates the effective infiltration of electrolyte and rapid diffusion of sodium ions.Nitrogen and sulfur co-doping can provide a large number of active sites for sodium ion adsorption,enhance the superiority of sodium storage by pseudocapacitance,and accelerate the insertion/release of Na⁺by expanding the distance between carbon layers,revealing the important role of surface chemistry in improving the performance of sodium storage.Using coal tar pitch as soft carbon precursor,polystyrene microspheres as template and hard carbon precursor,pitch derived hard/soft carbon composite（NS-HSPC144-600）was successfully constructed by annealing treatment.NS-HSPC144-600 delivers high sodium storage capacity.The specific capacity of501 m Ah g^-1 at 0.05 A g^-1 is obtained,and even at 5 A g^-1,it could still reach172.7 m Ah g^-1.It is worth mentioning that NS-HSPC144-600 also achieves excellent long cycle stability,maintaining a specific capacity of about 340 m Ah g^-1 after 300 cycles at 1 A g^-1.These excellent properties are attributed to the high electrical conductivity and fast ion diffusion of NS-HSPC144-60,which is rich in amorphous carbon structure and a small amount of graphite microcrystalline region.This work reveals the key role of the unique microstructure of carbon materials with amorphous carbon as the main component and graphitized carbon as the auxiliary component in high performance sodium storage.