Controllable Preparation And Functional Application Of Carbon Nanotube Arrays

Since the discovery of carbon nanotube(CNT),due to its unique hollow structure and large aspect ratio,it has excellent physical and chemical properties and has been widely concerned and applied by scholars at home and abroad.Especially for the aligned carbon nanotube array(CNTA),which has consistent orientation,uniform aspect ratio,independent of each other and easy dispersion,is a new type of carbon material with great potential.This paper takes the carbon nanotube array as the research goal,systematically studies its preparation process and growth mechanism;at the same time,explores the application prospects of carbon nanotube arrays in the field of anode materials and cathode conductive additives for lithium secondary batteries.The specific research content is as follows:1.Under the condition of not passing H₂and H₂O,using acetylene(C₂H₂)as a carbon source,a well-oriented carbon nanotube array was prepared directly on the surface of the sheet-shaped Fe-based alloy by the catalytic chemical vapor deposition(CCVD)method.And explored the suitable temperature and time for the growth of carbon nanotubes.The results showed that when the reaction temperature was around700°C and the reaction time was about 60 min,the pyrolysis rate of the carbon source,the activity of the catalyst and the precipitation rate of the carbon nanotubes were just in a equilibrium state,and the growing carbon nanotube array had the best graphitization degree and high purity.The preparation method has simple process,low cost and high yield,which is beneficial to the mass preparation of carbon nanotube arrays.2.The system is designed with a simple and controllable purification method,which effectively reduces the amorphous carbon and metal catalyst impurities in the carbon nanotube array,so that the purity of the carbon nanotube array reaches more than99%,and the morphology of the carbon nanotube array can be maintained.3.Preliminary researches on the application of carbon nanotube arrays and disordered carbon nanotubes in the anode materials of lithium secondary batteries are carried out respectively.It was found that the carbon nanotube array has a more developed mesoporous structure and electronic and ion conductive pathways,and it is easier to uniformly disperse on the surface of the current collector,making it possible for both small current density(0.1 A/g)or high current density(1 A/g),both showed better charging and discharging performance.It shows that the carbon nanotube array has a good application prospect in the application of lithium secondary battery anode materials.4.The application value of carbon nanotube array as a conductive agent in high energy density ternary cathode materials is explored.When the carbon nanotube array content is 5 wt%,a channel suitable for electron conduction and ion migration can be built on the surface of the ternary cathode material Li Ni_0.8Co_0.1Mn_0.1O₂(NCM 811),which is beneficial to improve the stability of the electrode material.In addition,under different rates(0.2C,0.5C,1C,2C,5C),its electrochemical performance has obvious advantages compared with commercial SP conductive agents,especially at high rate(5C)charge and discharge The improvement rate of discharge specific capacity is as high as 91%.