Research On Preparation And Electrochemical Performance Of Negative Nanocarbon Fiber Reinforced Composites For Lithium Ion Battery

Lithium-ion batteries have been widely used in portable electronic devices and electric vehiccles due to their high energy density,long cycle life and excellent safety.As a crucial part of LIBs,the selection of the anode materials is of great significance to the overall properties.currently commercial graphite anode material,with a relative low theoretical gravimetric capacity(372mAh/g),is insufficient to satisfy the future energy storage requirment.(1)Porous carbon nanofibers were fabricated by electrospinning in a precursor solution,containing,polyacrylonitnle(PAN),Polystyrene(PS),N,N-dimethylformamide,etrahydrofuran.During thermal treatment,PS decomposition caused nanofibers to transform from a solid to a porous structure.removal of PS also decreased the fiber diameter and increased the pore volume of the carbon nanofibers,resulting in a substantial increase in specific surface area.The electrochemical performance of these2:1 PAN/PS-derived carbon nanofibers exhibited a discharge capacity of 416mAh/g under a current density of 200mA/g,Which was approximately two times that of the neat PAN-derived carbon nanofibers,they exhibited a discharge capacity of 353mAh/g after 100 cycles at a current density of 200mA/g corresponding to 84%retention,demonstrating the favorable cycle stability.(2)Combination of metal oxides and carbon has been a favourable practice for their applications in high-rate energy storage mesocopic electrodes.We report quasi1D Fe₃O₄–carbon composite nanofibers obtained by the electrospinning method,and evaluate them as anodes for Li-ion batteries.In the half-cell configuration,the anode exhibits a reversible capacity of 700mAh/g at a current rate of 0.2 C up to 100 cycles.At a higher current density of 5 C,the cells still exhibit a specific capacity of 180mA h/g Compared to pure electrospun Fe₂O₃ nanotubes,thecapacityretention of Fe₃O₄–C composite nanofiber electrodes is drastically improved.The good electrochemical performance is associated with the homogenous dispersed Fe3O4nanocrystals on the carbon nanofiber support.Such a structure prevents the aggregation of active materials,maintains the structure integrity and thus enhances the electronic conductivity during lithium insertion and extraction.(3)A general,scalable,eco-friendly and cost-effective approach for the fabrication of nano Fe₂O₃ anchored three-dimensional(3D)carbon nanofiber(CNFs)aerogels(Fe₂O₃/BC-CNFs).The preparation processes include carbonization at different temperatures and subsequent anchoring of Fe₂O₃ nano-particles on carbon nanofiber(CNFs)aerogels nanofibers with intrinsic 3D network structure three-dimensional porous electrode structures which are composed of interwelded ultrathin carbon nanofibrils,as a mechanically robust three-dimensional conductive porous network,as well as in situ assembly of nanostructured active anode materials into such a unique network.The significant improved cycling performance of the BC–CNFs/Fe₂O₃ when compared to the bare Fe₂O₃ clearly indicates that the introduced PBC plays a critical role in mechanically and electrically binding Fe₂O₃ nanoparticles together at the whole electrodescale,and also offering numerous interconnected voids in the porous BC-CNFs/Fe₂O₃ hybrid which is favorable for the fast diffusion and transport of lithium ions.In addition to its excellent flexibility,a stable capacity of 500 mAh/g for up to 100 cycles is also higher than most of carbon-Fe₂O₃ hybrids.The high reversible capacity and excellent rate capability are attributed to its 3D porous network structure with well-dispersed Fe₂O₃ nanoparticles on the surfaces of CNFs.