Synthesis Of Transition Metal Oxide/Carbon Nanotubes Composite Structure And Lithium Storage Performance

With the development of space technology and electric vehicle research,leading to the growing demand for high performance of the secondary battery,it becomes an urgent task to evolute a new kind of environmental-friendly battery which has high specific energy and specific power trait.The lithium ion secondary battery with the advantages of high operating voltage,high specific energy etc,has been one of the most promising high-energy batteries.The anode material is one of the key components of battery material.Carbon,as the commercial lithium ion battery?LIB?anode material,cannot have met the need of lithium ion battery applications in high-power devices due to its low specific capacities.Therefore,it needs urgently to develop high specific energy materials for LIB.Transition metal oxides have been promising anode materials for the LIBs owing to its high theoretical specific capacity,low cost and abundance.However,several hurdles such as poor conductivity and volumetric expansion need to be overcome for them to be commercially viable.In this paper,we constructed the secondary microstructure of CNTs embedded in transition metal oxides?NiO,Co₃O₄ and CuO?and explored the evolution rule of structure.With the help of high strength,tenacity and conductivity of CNTs and high theoretical specific capacity of TMO,as well as the secondary microstructure of CNTs embedded in TMO and the porous structure.We obtained the lithium ion battery cathode materials which have excellent comprehensive electrochemical properties,such as excellent rate performance,cyclic stability and so on.?1?Preparation of NiO/CNTs hollow microspheres and lithium storage performance:On the basis of surface functionalization of CNTs,NiC2O4/CNTs precursor were obtained through ultrasonic precipitation with ammonium oxalate as precipitant,then NiO/CNTs hollow microspheres was obtained after annealing.And we explored the effect of precipitant,the content of carbon nanotube,annealing temperature and atmosphere.Structure characterization showed that CNTs embedded in NiO hollow microsphere,and even bridged between the microspheres,and NiO hollow microsphere is made up of tiny nanoparticles.The electrochemical performance test results showed that NiO/CNTs obtained under the condition of ultrasonic reaction,8%CNTs and annealing 1h at 380? in air atmosphere has superior rate properties and cycle stability.It exhibited s showed a charge capacity as high as 455.1mAh/g when cycling at the rate 5 C and maintained 59.4%capacity of 0.1 C.After cycling for 100 times at 1 C,it maintained a capacity of 699.3mAh/g with retention 90.2%of the initial capacity and a high initial coulomb efficiency of 75.23%at 0.1C.The excellent electrochemical performance is mainly attributed to synergistic effect between excellent three dimensional conductive network,NiO hollow structure and abundant mesoporous structure.?2?Preparation of Co₃O₄/CNTs secondary Saqima-like microstructures and lithium storage performance:Co₃O₄/CNTs secondary microstructures compostite was obtained through the same method with cobalt chloride as the co'balt source and explored the evolution rule of this structure.Structure characterization showed that Co₃O₄/CNTs secondary Saqima-like microstructures are made up of nanoparticles with abundant pores,CNTs embedded in secondary microstructures and bridged between the secondary microstructures.The electrochemical performance test results showed that Co₃O₄/CNTs obtained under the condition of ultrasonic reaction,6%CNTs and annealing at 500? has the most excellent electrochemical performance.It exhibited an excellent rate capability of 618.7mAh/g at 5C and maintained 68.9%capacity of 0.1 C,and it delivers a high capacity of 627.3mAh/g at current density of 1C after 200 cycles with retention 79.4%of the initial capacity.In addition,it exhibited a high initial coulomb efficiency of 85.17%at 0.1C.It attribute to the closely linked nanoparticles avoided form the SEI film on its surface,and only formed a stable SEI film in the outer surface of the strip structure.?3?Preparation of CuO/CNTs mesoporous microspheres and lithium storage performance:CNTs embedded in CuO mesoporous microspheres were obtained through the same method with copper chloride as the copper source.Structure characterization showed that CNTs embedded CuO porous microspheres similar to NiO porous microsphere were secondary microstructures closely connected by nanoparticles.However,there is no any hollow structure and sufficient pore structure in CNTs/CuO.It exhibited an excellent cycle stability of 459.3mAh/g at 1C after 200 cycles,capacity retention rate is 111.2%compared with initial discharge specific capacity.The studies in this paper provide a feasible method for fabricating CNTs embedded in metal oxide secondary microstructures,and provide a kind of thought for improving comprehensive electrochemical properties of lithium ion battery anode materials,especially improving initial coulombic efficiency.What is more,we have laid a good foundation for the further development of transition metal oxides anode material for lithium ion battery.