Research On The Design, Construction And Performance Of Porous Carbon Fiber-based Anode Materials For Lithium-ion Batteries

With the development of smart wearable electronic devices and new energy vehicles, lithium ion batteries?LIBs?with the merits of lightweight,portable and high energy density have once again attracted great attention of researchers.The common anode materials of LIBs are traditional carbon materials,however,the low energy density of carbon materials seriously influences the operation life of the equipment.In recent years,transition metal compounds have been considered as promising anode materials due to their high energy density.Nevertheless,the rapid capacity attenuation during cycling caused by the inevitable volume expansion seriously restricts its further development.Herein,based on the electro-blown spinning technique,porous carbon nanofiber anode materials of LIBs were successfully prepared through the construction of porous structure and the mixing of functional nano transition metal compounds,which solved the problems of low specific capacity of carbon materials and volume expansion of transition metal compounds.The main research contents were as follows:?1?Axial multi-channel Mn S@CNF nanofiber composites were prepared by the electro-blown spinning and subsequent high temperature carbonization.The effects of different Mn SO₄ loading amount and different calcination temperature on the morphology and structure of fibers were systematically studied,and the formation mechanism of axial multi-channel structure was analyzed.The characterized results showed that the Mn S@CNF_5.8/900 had an obvious axial multi-channel structure,largest specific surface area and uniform distribution of Mn S nanoparticles.As anodes material of LIBs,Mn S@CNF_5.8/900 presented a high specific capacity,good rate capability and excellent cycling stability.?2?Fe₇S₈@MPCNF composite nanofibers were successfully prepared by electro- blown spinning and subsequent high temperature carbonization.The effects of pore forming agent loading content on the thickness of the protective skin,the internal pore structure of fibers and the storage performance of Li⁺were systematically studied.The results showed that the obtained Fe₇S₈@MPCNF_-2 had the largest surface area,suitable thickness of protective skin and optimal hierarchical porous structure.As anode material of LIBs,the discharge specific capacity was maintained as high as 546 m Ah g^-1 after 500 cycles at a current density of 1 A g^-1,and the capacity retention rate was kept as high as 86%.?3?Based on the electro-blown spinning technique,Mo S₂,Mo O₂ and Mo Nnanoparticles embedded in carbon nanofibers with protective skin and interconnected porous structure were successfully prepared by the controlling of calcination environments.The protective skin acting as a barrier could prevent the shedding of active nanoparticles and provide long electron transport pathways.The interconnected porous structure could effectively shorten the Li⁺transport pathway and supply enough space for the volume expansion of active materials.As anode materials of LIBs,the three nanofibers anode materials demonstrated a high cycling stability and good rate capability.?4?Metal sulfide nano-framework particles embedded in porous carbon nanofibers were successfully prepared by electro-blown spinning technique.The effects of Ni/Co ratios on the morphology and size of the metal sulfide nano-framework particles were studied,and the storage performance of Li⁺were systematically investigated.The results showed that the metal sulfide nano-framework possessed abundant micropores.As the Co²⁺loading content increasing,the size of metal sulfide nano-framework particles was decreased,but the specific surface area and electroconductivity were gradually increased.As LIBs anodes,Ni/Co_1:2NFs@PCNF demonstrated the highest specific capacity and satisfactory cycling performance.