Synthesis, Modification And Electrochemical Performance Of Petroleum Pitch Based Hollow Carbon Spheres

Owing to the global energy crisis and environmental pollution issue are pressing, it is urgent to developing the clean, sustainable energy to replace the fossil fuel resource. How to use clean energy effectively, however, is the development of electrical energy storage(EES) systems. Carbon materials have been playing a significant role in the development of alternative clean and sustainable energy technologies. Among these materials, hollow carbon sphere(HCS) have been widely used in energy storage, because of their unique structure, low density, large cavity volume, excellent electrical conductivity, good thermostability. Typically, the fabrication of hollow carbon spheres by hard template method, and carbon source mainly include gaseous carbon source and solid carbon source. Petroleum pitch has been frequently-used to preparation of various carbon materials, such as carbon spheres, carbon tube, carbon fiber. However, there are few reports about to prepare HCS form petroleum pitch. The mesoporous HCS were synthesized by CVD method using silica nanospheres as template and petroleum pitch as carbon source, further modifications of surface and are applied in lithium ion battery and lithium-sulfur battery.(1) First, we successfully synthesis SiO2 spheres with about 200 nm diameter which its uniform size and monodispersed, then the surface modified with CTAB and TEOS. Finally, the mesoporous SiO2@m-SiO2/CTAB spheres with diameter 360 nm were obtained. Petroleum pitch as carbon source, it would pyrolysis to hydrocarbon molecules at high temperature to deposit into the structure of template. Meanwhile, we examined the different thickness of hollow carbon spheres obtained from the different proportion of CTAB and TEOS.(2) We introduced acetonitrile as nitrogen source in the growth of carbon spheres, then pitch and acetonitrile together deposited into the structure of template, the hollow carbon spheres obtained with cladding graphitic carbon layers. We also study the modified of surface under HNO3 vapor. The sample show excellent electrochemical performance, The NHCS-O electrode still maintained a specific reversible capacity 616 mAh g-1 after 250 cycles at a high current rate of 500 mA g-1.(3) The unique properties of HCS are beneficial to limit polysulfide ions due to their excellent conductivity, large cavity volume and porous structure. We choose the thin wall hollow carbon spheres which prepared in second chapter, then strengthen the capacity of control sulfur by change the hydrophobic under treatment of HNO3 vapor. We also investigated the electrochemical behavior of different sulfur content. The HCSO/S-67 electrode still maintained a specific reversible capacity 531 mAh g-1 after 100 cycles at a high current rate of 0.1C.