Preparation And Modification Of Nickel,Cobalt And Manganese Lithium-ion Battery Cathode Material

With the rapid development of science and technology, with a good performance, lithium-ion battery is currently regarded as one of the best energy storage methods, and has a wide range of applications. The development in automotive applications of lithium-ion battery is currently one of the most primary directions. It requires that the lithium-ion battery have a higher energy density, rate performance and good cycle stability, and also have a lower cost, higher safety performance and environmental-friendly advantages. While, little lithium-ion battery cathode anode material can meet these requirements. Recently, the layer-layer-spinal structure cathode material has received extensive attention because of its better energy density and cycle performance. In order to further improve its electrochemical performance, doping and coating are used to modify the cathode materials.In this article, layer-layer-spinel solid solution anode material δ[0.5Li2 Mn O3·0.5Li Mn1/3Ni1/3Co1/3O2]·(1-δ)Li0.5Mn4/6Ni1/6Co1/6O2( also known as Lix Mn4/6Ni1/6Co1/6Oy)was prepared by two-step temperature co-precipitation, then doping and coating this materials series were doped and coated in order to improve their electrochemical performance. The initial synthesis temperature is variable, while the next synthesis temperature is a constant value in the preparation of the precursor by two-step temperature co-precipitation. The experimental result showed that the material was prepared by two-step temperature co-precipitation successfully. When the initial synthesis temperature is low(40 ℃), the shape of cathode material particles is integrity and the size is uniform, the electrochemical performance is also more stable. So it can be sure that T1 = 40 ℃, T2 = 80 ℃ is a better technological parameter to prepare cathode material by using two-step temperature co-precipitation.In order to improve the performance of the materials, F was substituted to modified the Li1.1Mn4/6Ni1/6Co1/6O2.30 and Li1.2Mn4/6Ni1/6Co1/6O2.35, from the conclusion we know that doping amount of 0.05 is the best by comparing the physical properties and electrochemical properties between the un-doped materiasl and modified materials. After modification, the capacity retention after 50 cycles of the material increased by 8% at 0.5 C rates, and the discharge specific capacity at 5 C was improved 10 ~ 20 m A·h/g compared with the pristine.Coated the prepared materials Li1.1Mn4/6Ni1/6Co1/6O2.30, Li1.2Mn4/6Ni1/6Co1/6O2.35 and Li1.3Mn4/6Ni1/6Co1/6O2.30 with Al F3, coating amounts are 1 wt%, 2 wt% and 3 wt%, respectively. The electrochemical properties are all improved after Al F3-coating and 2 wt% coating amount is the best one. After 50 charge-discharge cycles at 0.5 C, there is obviously improvement of its capacity retention about 10%. Rate performance was also increased about 20 m A·h/g.