Preparation Of TiO₂/carbon Nanofiber Composite Material And Its Electrochemical Performance Based On The Decomposition And Regulation Of Blowing Agent

At present,inactive components such as collectors,conductive materials and binders account for more than 40% of the total electrode mass in the electrodes of traditional lithiumion batteries.However,the contribution of these materials to the electrochemical energy storage performance of the electrodes is negligible,and the mass specific capacity of the electrodes is greatly reduced.Therefore,in order to improve the energy density of batteries,researchers try to prepare freestanding lithiumion battery electrodes.A simple and effective method for preparing nanofibers by electrospinning has shown great potential in the preparation of supporting-free lithiumion battery anode materials.Moreover,the electrochemical performance of electrodes prepared by electrospinning has much room for improvement,including the improvement of conductivity and specific surface area,control of nanostructures and other modification methods.However,there are few studies on the effects of synchronous enhancement of conductivity and specific surface area on the electrochemical properties of electrode materials,and the process used for microcontrol of nanostructures is more complex than that of electrospinning,which is not conducive to large-scale application.Therefore,the purpose of this project is to prepare titanium dioxide@carbon nanofibers composite without supporting electrodes by electrospinning and modify it by foaming agent,so as to enhance the conductivity of the composite,improve the specific surface area and control the nanostructure,and ultimately achieve further improvement of its electrochemical properties.This paper mainly includes the following contents:?1?By introducing different proportions of diisopropyl azodicarbonate into electrospinning solution,the nitrogen doping and specific surface area of nano-fibre composite of titanium dioxide@carbon were increased synchronously,the conductivity of the composite was improved,and the number of active site for lithium ion reaction increased.So the electrochemical properties of the composite were improved.On the condition of optimum blowing agent ratio,the nitrogen content of the composite fiber increased from 7.18%to 10.21%,and the specific surface area increased from 72.66 m² g^-1 to 111.15 m² g^-1.The synergistic effect of the two factors endowed the composite the best electrochemical performance.At current density of 100mA g^-1,the specific capacity reaches 336 mAh g^-1.In order to further study the change of electrochemical kinetics of samples,the storage mechanism of lithium ion in samples before and after adding the optimum foaming agent was further analyzed by power law.The results showed that the capacity contribution of the pseudocapacitor in the electrode decreases from 60.8%to 47.4%.It also proved that the addition of foaming agent increases the proportion of diffusion capacity in the material.?2?Titanium dioxide nanoparticles were modified by betaine,and titanium dioxide@carbon nanofibers with uniform"seed"morphology were prepared by electrospinning method accompanied with carbonization at high temperature.Under the effect of high temperature,betaine can not only drive titanium dioxide nanoparticles to migrate onto the surface of nanofibers by decomposition gas,but also doped nitrogen in the composites as a precursor of nitrogen element.At the same time,carbon nanofibers become porous due to the decomposition of betaine.The composite material made excellent electrochemical performance as anodic electrode of lithium ion batteries After 100 cycles at 100mA g^-1 current density,the discharge capacity was stable at 322 mAh^-1.