Study On Preparation Process Of Nanofiber And Its Application Based On Blowing Spinning

The commercial lithium-ion batteries currently generally use graphite as the anode material,while the theoretic capacity of graphite is only 372 mAh/g,and it has been increasingly unable to meet the requirement for large high energy density.Therefore,developing anode materials of lithium-ion batteries with good cycle performance and discharge capacity is a research focus in present.The transition metal oxides are inexpensive and their theoretical specific capacities are about three times higher than those of commercial carbon material,but it is prone to the large volume expansion-contraction in the process of charging and discharging,resulting in the deterioration of cycle performance.To overcome these limitations,an effective way to electrochemical performance is to combine transition metal oxides with carbon and preparing nano-materials.Nanoscale materials can shorten diffusion paths of lithium-ions.And the recombination of materials can buffer the damage of electrode structure caused by volume deformation during the cycle process.In the thesis,their electrochemical performance of SnO₂ and Co₃O₄ are improved by using blowing spinning technology to fabricate nano-sized transition metal oxides and combine transition metal oxides with carbon nanofibers.The research contents of this thesis are as follows:?1?SnO₂ and Co₃O₄ nanofibers were prepared by blowing spinning process and their microstructures were examined by SEM to study the effects of process parameters on the diameter distribution of blowing spinning nanofibers.And they are used as anode to assemble lithium ion batteries and the electrochemical performance of lithium ion batteries based on different anodes was tested.The experimental results show that the increase of the injection rate and the concentration of binder have a tendency to increase the nanofiber diameter;the increase of the air flow pressure has a tendency to decrease the nanofiber diameter;the effect of the working distance is not obvious.The initial discharge specific capacities of blow-spinning SnO₂ and Co₃O₄ nanofiber as the anode material of lithium-ion batteries were respectively 1011mAh/g and 1120mAh/g at the current density of 0.5C,which were higher than the theoretical discharge capacity.?2?The F-doped tin oxide?FTO?nanofibers were prepared by blowing spinning process and the composite Co₃O₄-FTO nanofibers were prepared by soaking the blow-spinning Co₃O₄ nanofibers in an unbonded FTO precursor spinning solution.And they are used as anode to assemble lithium ion batteries and the electrochemical performance of lithium ion batteries based on different anodes was tested.The experimental results show that compared with Co₃O₄ nanowires and FTO nanowires,the composite Co₃O₄-FTO nanofibers as the anode material of lithium-ion batteries exhibited higher lithium ion storage capacity,more excellent cycle performance and rate performance.Its initial discharge capacity is 1321 mAh/g,and its discharge capacity still maintain 400 mAh/g at the current density of 0.5C after 50 cycles.The performance is better than bare FTO nanowire anode.?3?Composite carbon fibers?CF?with SnO₂ and Co₃O₄ were prepared by blowing spinning process and the composite carbon fibers were used as anode to assemble lithium ion batteries and the electrochemical performance of lithium ion batteries based on different anodes was tested.The first discharge specific capacity was as high as 1490mA·h/g and the specific capacity was at 559 mAh/g after 50 charge/discharge cycles.