Application And Synthesis Of Carbon Nanotube As Conductive Agent For Cathode Materials In Li-ion Battery

In the past ten years,people's demand for Li-ion batteries has been increasing and the development of high-energy/power Li-ion batteries has become a fundamental requirement for the realization of new energy vehicles in worldwide.For light-weight flexible CNTs with high electrical conductivity and thermal conductivity,only a small amount of addition is required to construct an idea three-dimensional conductive network in the electrode.However,although carbon nanotubes have been recognized as the best conductive additives to improve the high rate and long cycle performance of Li-ion batteries,there are still many problems that limit its popularity in the Li-ion battery market,such as:?1?high quality CNTs are often accompanied by expensive metal catalysts and high-cost synthesis technologies,which makes it hard to achieve industrial-scale production.?2?CNTs often build long-distance conductive paths in the electrode,which is not conducive to electron transfer between adjacent quantities of active material;?3?CNTs produced by traditional technology are basically agglomerated and entangled with each other and contain a large amount of metal impurities,which makes it difficult to uniformly disperse in the electrode active material and poses a safety hazard to the battery.Therefore,there is still numerous works to be done to further promote the CNTs conductive agent in the Li-ion battery market.In response to the above problems,the main research contents of this article are as follows:?1?Fe-Al catalysts with different molar ratios were designed and prepared,and then propane was used as the carbon source to synthesize carbon nanotubes at a high temperature of 680?;The results show that when the Fe/Al molar value in the Fe-Al catalyst is 8/2,the surface of the synthesized CNTs is the smoothest and has the highest crystallinity,and the CNTs are utilized as conductive additives together with Super P in LiNi_0.5Co_0.2Mn_0.3O₂ cathode has the best electrochemical performance.Specifically,the capacity retention of CNT2/SP was 89.5%after 100 cycles at 1C and show the high capacity of 127.9 mAh·g^-1 at 10 C when applied to button batteries.Moreover,After the pouch cell is fabrication,the retention of 1000 cycles at 3 C high rate is much better than that of the commercial Super P.?2?Two different carbon nanotubes?CNT-A,CNT-B?and carbon black?Li 435?were used as raw materials,and the two CNTs conductive pastes were prepared using ultrasonic and sand milling dispersion technologies.Investigate their effect on the electrochemical performance of LiNi_0.5Co_0.2Mn_0.3O₂/graphite pouch cell.The results show that CNT-A with a large specific surface area and high conductivity shows the best cycling and rate performance when applied to batteries.When configured as a composite conductive agent paste,the best performance is when the ratio of CNT-A and Li-435 is 7:3,and the best ratio of CNT-B and Li-435 is 5:5,all the performance of composite conductive agent are better than the single conductive agent.Indicated that the introduction of carbon black Li-435 in CNTs can help it establish a short-range conductive path in the electrode to further improve the capacity and cycle performance of the battery.?3?Fe/Al₂O₃ catalyst was prepared on the surface of single crystal silicon by using a magnetron sputtering coating device,and high-purity vertical CNTs arrays?VACNTs?were synthesized by CVD method.Low content and high dispersion CNTs suspension were configured by ultrasonic and ball milling dispersion methods that requires only1.5 wt%as a conductive agent is sufficient to build a perfect conductive network in a LiNi_0.8Co_0.15Al_0.05O₂ electrode and exhibit excellent electrochemical performance.In the test,after the electrode of LNCA-VACNTs was cycled 120th at 1 C,its capacity retention was 85.2%,which was much higher than that of traditional CNTs-configured suspensions?capacity retention was 50.3%?and even surpass the stable dispersion CNTs conductive paste?capacity retention was 78.5%?.In the pouch cell test,only 0.5wt%of VACNTs and 1 wt%of Super P are sufficient to show better performance than commercial 3 wt%Super P batteries.