Preparation Of Petroleum Pitch-based Lithium Anode Materials And Their Lithium Storage Properties

Petroleum pitch is processed from the residue of crude oil distillation,and it becomes the precursor of many high-quality carbon materials due to its high aromatic molecular compounds.In this paper,we used petroleum pitch as the carbon source to prepare three kinds of anode materials for lithium-ion batteries?LIBs?,petroleum pitch-based mesocarbon microbeads?MCMB?,silicon/carbon nanosheets?Si/CNS?,MCMB/Si/petroleum pitch-based amorphous carbon?MCMB/Si/C?,and their lithium storage characteristics were studied and analyzed.For petroleum pitch-based MCMB,MCMB with the 5.32%yield were obtained at 410?,1 MPa and the aggregation time of 4 h.The lithium storage properties of carbonized and graphitized MCMB were examined,and the results showed that the carbonized MCMB presented obvious characteristics of amorphous carbon material with I_D/I_G of 0.48.After graphitization,the MCMB carbon layers became orderly arranged with I_D/I_G of 0.21 and crystallinity of 85.0%.When used as lithium anode materials at the current density of 50 mA g^-1,the charge and discharge specific capacity of carbonized and graphitized MCMB were 455/347?coulomb efficiency76.3%?and 409/321 mAh g^-1?coulomb efficiency 78.5%?,respectively.Moreover,both of them have excellent cyclic stability.For Si/CNS,a kind of Si/CNS composite with two-dimensional lamellar structure was prepared by using NaCl as template agent,petroleum pitch as carbon source and nano-Si as silicon source.In this composite,nano-Si was firmly wrapped in the CNS.When the Si content of Si/CNS is 37%,the initial charge and discharge capacity of Si/CNS is 1256/901 mAh g^-1 at 100 mA g^-1.After 100 cycles under 0.3 A g^-1,corresponding reversible specific capacity is 655 mAh g^-1.Compared with no NaCl,the lithium storage characteristics of silicon carbon composites with two-dimensional structure have been significantly improved.For MCMB/Si/C,the MCMB as the core,a kind of MCMB/Si/C composite material with core shell structure was obtained by TEOs hydrolysis,carbon coating of petroleum pitch pyrolysis and Mg reduction.In this material,nano-Si is sandwiched between MCMB and petroleum pitch-based amorphous carbon,which can not only effectively buffer the volume expansion of Si during cycling,but also improves the lithium storage capacity of MCMB.The results showed that under the current density of 100 mA g^-1,the reversible capacity of MCMB/Si/C composite material remained at401 mAh g^-1 after 120 cycles,and the corresponding capacity retention rate was 88%?This is a significant improvement over the original MCMB of 302 mAh g^-1.