Study On The Controllable Preparation And Lithium Storage Properties Of Metal Oxide(s) Nanostructures With Special Morphologies

Lithium ion battery(LIB)has become the competing research field that wearable electronic consumables and new energy automotive industry,because of its many advantages,such as higher energy density,lower self discharge,better cycling performance,memoryless effect and environmental protection.Therefore,the most important problem for researchers to be solved is to seek lithium battery electrode materials with large energy density and longer cycle life.In many electrode materials,the oxidation of transition metal atoms,due to the role of the applied voltage,fast redox reactions,and metal oxygen(sulfur)compounds with high theoretical lithium storage capacity,low cost,safe and reliable,therefore,the metal oxygen(sulfur)compounds nano materials have been widely studied as anode material for high-performance lithium ion battery.However,the volume expansion and contraction effect of metal oxygen(sulfur)compounds in the process of lithiation/lithiation,which seriously restricts its wide application.Therefore,aiming at these problems of metal oxygen(sulfur)compounds,several solutions are put forward in this paper,which greatly improve the rate performance and cycle life of lithium battery.The main research contents are as follows:(1)we use carbon template to adsorb Sn4+ as precursor and anneal in air to remove carbon template to get the porous SnO2 dumbbell shaped hollow sphere structure.SEM and TEM confirmed that the material shows a good porous and hollow spherical structure,the material distribution of uniform diameter is maintained at-2?m,and the outer shell is a porous structure with the size of nanoparticles stacked 16nm formed by BET analysis,the surface area of the material and void are 36.3m2/g and 1-3 nm respectively.Electrochemical performance tests show that lithium battery can maintain 511 mAh/g at the current density of 1600 mA/g;besides,the current density from 100 mA/g return to 695 mAh/g,showing a good performance of the reversible capacity.We circulate 100 cycles at 0.5 and 1.0 A/g and still remain at 583 and 602 mAh/g.Because the structure of materials,hollow and porous structure can shorten the transmission path for embedding and provide additional buffer space volume expansion and more active sites,which can greatly improve the performance of lithium ion battery.(2)By introducing carbon spheres as attachment support,C@MoS2 were prepared by L-cysteine assisted hydrothermal method,TEM and Mapping show that the sheet structure of MoS2 can coat tightly on the surface of carbon spheres,forming a regular and uniform core shell nanostructure.The electrochemical performance shows that the discharge capacity of the first cycle at the current density of 0.2 A/g is 1333 mAh/g,and it can remain at 753 mAh/g after 50 cycles.And under the large current density of 1 A/g,it can be maintained at 737 mAh/g more than 200 cycles.At the same time,the ratio performance shows that the capacity can rise to 850 mAh/g when the current density recover from 1600 to 100 mA/g.The excellent electrochemical performance is attributed to the unique layer design.Thin MoS2 slice can provide more active sites for lithium ion charging and discharging,and shorten the transmission path.And by introducing carbon spheres,the structure of MoS2 can be compactly wrapped on the surface of carbon spheres,which can not only improve the conductivity of composites,and effectively alleviate the MoS2 stable material structure due to the collapse of volume structure embedded with the capacity of lithium ion from extreme attenuation,and its electrochemical performance also has a substantial increase.(3)we prepared SnO2/MoS2 nanocomposites by hydrothermal synthesis on SnO2 nanosheets through two steps process.TEM showed that the laminated structure of the composites was obvious,the composite distribution was uniform,the lamellar thickness and size were all in the nanometer size range.For lithium ion battery anode material,the capacity is 1432.5 mAh/g,at the current density of 200 mA/g after 65 cycles.And after 200 cycles at 1.0 A/g,the capacity is still up to 920.1 mAh/g.The excellent electrochemical performance attribute to the good interlayer channel for lithium ion transport and buffering space for volume expansion.The large specific surface area can provide more lithium ion contact sites.Moreover,the partially bound Mo particles in interlayer structure during the incomplete redox process of MoS2,which can play a synergistic effect to provide additional conductive properties for composite materials.