Preparation And Application Of Two-Dimensional Nanosheet LiNi_0.8Co_0.15Al_0.05O₂ Cathode Material

With the depletion of resources,lithium-ion batteries get strong support and development as green clean energy.The cathode material is the main factor affecting the lithium-ion battery.Ternary materials have draw attention of domestic and foreign people due to its high specific capacity.Japan Toyota use NCA(LiNi_0.8Co_0.15Al_0.05O₂)cathode materials in its PHEVs,Tesla also use the Japanese production of NCA ternary battery 18650 in its electric car.In domestic,there has not yet achieved industrial production.There are some problems in the preparation of nickel-rich ternary materials,such as harsh preparation conditions,storage difficulties and cationic mixing.The synthesis conditions affect the properties of the material greatly,therefore it should be optimized from some key factors in the synthesis process,which is of great significance to the NCA material to achieve industrialization as soon as possibale.In this paper,the preparation of the precursor is discussed.Microwave synthesis is used,which is different from the commonly used co-precipitation method or sol-gel method.The method has some unique advantages such as simpleness,rapidness,the reaction efficiency,the quality and repetition rate and so on.Mainly prepared precusor with nano-sheet morphology.Ni_0.84Co_0.16?OH?₂?NC?nanosheet precursors,the morphology is uniform,the dimension is large,and the average thickness is about 5nm.After the preparation of pure phase nickel hydroxide cobalt nanosheets,the synthesis conditions of NCA materials are explored.The NCA cathode material is prepared by high temperature sintering,NCA cathode material with nanosheet morphology ia synthesized for the first time in this paper.First samples are calcined at 500°C for 5 hours,and then conducted the final calcination.At present,a large number of researches and literatures had reported the high temperature sintering time in the range of 10-15 hours,which made the battery product time period long.Firstly,this paper explore the impact of the holding time,and calcined at 750?for 5 h,10 h and 15 h,respectively.The results shows that as the time prolonged,the grain grow up and the nanosheets become thicker.However,the crystallinity of the materials became better,and the optimum temperature is 10 h.The effect of sintering temperature on the morphology and properties of NCA is investigated at the optimum holding time of 10 h.And being sintered at 650?,700?,750?and 800?,the experimental results show that the sintering temperature rose,the material morphology become worse.However,when sample is sinteredat 700?,the nanostructures remain well,and the mesoporous and macropores are distributed on the nanosheets,which increased the specific surface area.I_?003?/I_?104?is maximum,electrochemical performance is also best.At 1C,first specific capacity yielded 181mAh/g;At 0.1C,after 50 times cycles,90%of capacity retention rate is retained,which shows good cycle performance.