The Research Of The Layered Lithium-rich Manganese, Nickel, Cobalt Base Solid Solution Cathode Material Of Lithium-ion Batteries

In this paper, We started from the layered ABO2 type transition metal oxide cathode Li Co O2, dopping Ni, Co to the layered manganese-based material to form the solid solution in order to improve the overall electrochemical properties. Then coated with the a kind of liquid polyacrylonitrile polymer material(LANO) which was synthetized by laboratory-made to improve the performance of cathode material. Constant current charging and discharging test, TG, XRD, SEM, EIS, CV were used to test and anylize the performance of the products under different influence factors, then the layered lithium-rich manganese, nickel, cobalt base solid solution cathode materials with good performance were achieved. The raw materials used in experiments were cheap and easy to get, environmental protection, non-toxic, and even at industrial levels; the methods used in the process were simple, economical, safe, reproducible, and suitable for mass industrial production.After a series of studies which were carried out on several different materials, the results we got as follows:1. In this paper, the precursors of the Li Co O2 cathode material were synthesised in different solvents by solid-liquid phase method, after presintering and different final sintering methods, then got the products. The best performance original sample— LCO-350(6)-600(12)-700(20)-H2 O was found, its first cycle discharge capacity reached to 206.9m Ah/g, average 168.9 m Ah/g at 0.1C, it was 15.685% higher than Li Co O2 of about 146 m Ah/g in the market, its crystal form was relatively complete, particles were small and relatively uniform, polymorphism was small; but after modified by coated with LANO, neither the discharge capacity, nor the cycle stability were little worse than the original one.2. In this paper, the precursors of the Li1+xNi0.3Mn0.7O2+y were synthesised by different precipitants in different precipitated methods through coprecipitation method, then added lithium source, milled, after presintering and final sintering, then cooled down in different way to get the original products, in addition we could coat it with different rito of LANO by another ball milling method to get the carbon coating one. The best performance sample(x=0.22)—Na OH[1]-850(10)-I-8%LANO-850(6~10) was found, its first cycle discharge capacity reached to 219.1m Ah/g, average 197.5m Ah/g at 0.1C, cycle performance was not bad, crystal form was relatively complete, particles were small but slightly reunite; Besides when the lithium content reach to x=0.33, its first cycle discharge capacity reached to 236.8m Ah/g, average 202.2m Ah/g at 0.1C, it was 12.33% higher than Li Ni1/3Co1/3Mn1/3O2 of about 180 m Ah/g in the market, its crystal form was relatively complete, particles were small and relatively uniform.3. In this paper, the precursors of the Li1.22Cox(Ni0.3Mn0.7)1-xO2+y were synthesised by different Co content raw material through coprecipitation method, then added lithium source, milled, after presintering and final sintering at different temperature for different time, then got the original products, in addition we could coat it with different rito of LANO by ball milling method to get the carbon coating one. The best original sample—x=0.12-850(10) was found, its first cycle discharge capacity reached to 251.2m Ah/g, average 222 m Ah/g at 0.1C; its first cycle discharge capacity reached to 152 m Ah/g, average 148 m Ah/g at 1C, its crystal form was relatively complete, particles were small, polymorphism was small. But after modified by coated with 20% LANO, the discharge capacity was almost the same, the cycle stability were little better than the original one. The best performance product we achieved was 23.33% higher than Li Ni1/3Co1/3Mn1/3O2 of about 180 m Ah/g in the market.4. In this paper, the precursors of the Li1.2Ni0.2Mn0.6O2 were synthesised by the different Li source with different Li content(98%~104%) and different citric acid concentration through spray drying method, after presintering and final sintering at different temperature for different time, then got the products. The best original sample—n(C6H8O7):n(Li OH)(102%)-1-950(10) was found, its first cycle discharge capacity reached to 242.2m Ah/g, average 236.82 m Ah/g at 0.1C; its average 159.34 m Ah/g at 1C, and it had very good cycle performance, its crystal form was relatively complete, particles were small and relatively uniform. But after modified by coated with 20% LANO, its first cycle discharge capacity reached to 270.1m Ah/g, average 252.43 m Ah/g at 0.1C; its average discharge capacity was 149.25 m Ah/g at 1C, it was not as good as the original one, but its cycle performance was quite good, crystal form was relatively complete, particles were small and relatively uniform. The best performance product we achieved was 38.38% higher than Li Ni1/3Co1/3Mn1/3O2 of about 180 m Ah/g in the market.5. In this paper, it is the spray drying method which is better than co-precipitation method in the preparation methods we used, not only the performance of products is superior, but also the particle size of products is smaller, the whole process is simple, easy to control, low energy consumption and is suitable for the continuous mass production; it is the suspension evaporated method which is better than ball milling method in solid-liquid phase mixing methods we used, not only the performance of products is superior, but also the particle size of products is smaller and the products have good repeatability.