Study On Preparation Of Nano-cathode Material LiNi_0.5Co_0.2Mn_0.3O₂ By High-gravity Reaction Technology

With the over use of non-renewable energy,such as coal,oil and natural gas,it causes a series of energy and environmental problems,and it affects social development and human production and life.The development of new energy sources is imminent.The development and utilization of new energy is inseparable from the development of energy storage technology.Lithium ion batteries is widely used as a new type of green energy storage batteries.At the same time,with the rapid development of technology,the requirements of lithium-ion batteries are also increasing.The nanosized cathode material has excellent performance.Due to its small particle size,it can reduce the migration path of Li⁺,improve the deintercalation rate and the deintercalation amount of Li⁺,and can be quickly removed and embedded,so as to improve the performance of lithium ion battery.In the existing preparation method,it is difficult to produce nanosized cathode materials in a large scale.Therefore,it is very meaningful to develop a simple method for preparing nanosized cathode materials.This paper proposes a new method to prepare the cathode material of nanosized lithium nickel cobalt manganese oxide,which is called Rotating Bed with Helical Channels high-gravity reaction technology.Preparation of nanosized cathode materials uses the relevant principles of this technology.And we improve the properties of the material by surface coating and doping elements.?1?The optimum technological conditions for the preparation of nanosized precursors are explored by using the high-gravity reaction technique.And we mainly discuss the influence factors,such as comparison with conventional reactors,temperature,concentration,high-gravity level,p H,molar ratio of ammonia to metal ions.Finally,we get the best condition to prepare the precursor Ni_0.5Co_0.2Mn_0.3?OH?₂which is at low temperature?0?10??,concentration is 0.2mol/L,high-gravity level is1200rmp,p H is 11,ammonia and metal ion moles is 0.8/1.And the particle size can be about 200nm.SEM characterization shows that the particles are uniform and good dispersion.?2?The calcination process of the precursor and lithium salt is explored,such as the influence of calcination temperature,time,lithium salt content and lithium sources.Finally,Li₂CO₃ is used as the lithium source with lithium excess of 10%,and calcined at 900?for 10h,which can get the ternary material Li Ni_0.5Co_0.2Mn_0.3O₂ with an average particle size of 400nm and a specific surface area of 39.94m²/g.The first charge/discharge capacity of the material is 187m Ah/g and 156m Ah/g at 0.1C,respectively,and the capacity retention rate is 83.4%.Cyclic voltammetry and impedance test show that the material has good cyclic performance and conductivity.?3?The effect of Ti O₂ coating on its properties is investigated.The coating amounts are 0.2wt%,0.7wt%,1.2wt%,respectively.XRD indicated that the structure of the material was not changed after coating.Meanwhile,SEM showed that the morphology size of the material after coating was not changed.The electrochemical performance test show better performance than the uncoated material.The best coating amount is 0.7wt%.Its first charge/discharge ratio capacity is 201m Ah/g and171m Ah/g at 0.1C,respectively,and the capacity retention rate is 85.1%.it has better cycle performance.?4?The effect of Al ion doping on the properties of the material is investigated.The doping amounts are 1%,3%and 5%,respectively.XRD showed the structure of the material was not changed after doping Al.Meanwhile,SEM showed that the morphology of the material was also good and the average particle size was 400nm.Since the materials with the doping amount of 3%Al has the best crystalline ranking,and it indicates that it has better electrochemical performance.The test shows that the first charge/discharge specific capacity of the materials is 206m Ah/g and 175m Ah/g at 0.1C,respectively,and the capacity retention is 85.0%.And cyclic voltammetry and impedance tests show that the material has good cycling performance.