Preparation,characterization And Modification Of LiNi_0.8Co_0.15Al_0.05O₂ As Cathode For Lithium Ion Battery

The development of electric vehicle technology has expanded the space for secondary lithium ion battery,which also put forward higher requirements to the energy density,cycle stability and rate performance of the battery.Affected by this factors,the development of new lithium-ion battery cathode materials has been a hot research field of energy material.Nickel-based cathode material LiNi_0.8Co_0.15Al_0.05O₂?NCA?was chosen as the research object of this paper,because of its' high specific capacity,stable cycle performance and excellent rate capability.After systematicly studying the influence of co-precipitation process on the structure,particle diameter and electrochemical properties of products,NCA materials were successfully synthesized with good particles distribution,stable layered structure and excellent electrochemical properties.On this basis,NCA/LMO core-shell cathode material were prepared by a sol-gel method to further improve the rate capability and cycle stability of NCA cathode material.Ni0.8Co0.15Al0.05?OH?2.05 precursors were prepared by co-precipitation method with using nickel nitrate,cobalt nitrate and aluminum nitrate as raw materials.After being mixed with LiOH·H2O,preheated and heated at suitable temperatures,NCA products with high capacity,long cycle stability and high rate performance will be synthesized.Study shows: Precursors synthesized with the concentration ratio of ammonia and salt solution equals 2:1 and pH value of the solution equals 10 will get best appearance.NCA cathode synthesized by preheated the mixture of LiOH·H2O and precursor with the mol ratio equals 1.04 at 500oC for 6h,and then heated at 800 oC for 12 h in oxygen atmosphere shown best performance both layered structure and electrochemical performance.Rate performance test shown: when discharged at 0.1C,0.2C,5C and 10 C rate,The discharge specific capacity of NCA cathode materials prepared by the optimized condition equal 191.9?183.3?127.4 and 107.1mAh/g respectively.Cycle test shows the capacity retention ratio of materials was 82% after cycled for 50 cycles at the rate of 0.2C rate.Tests of NCA cathode materials prepared at optimization condition show that: layer structure deterioration caused by cation mixing and active substance reduction caused by the corrosion of HF are the two main reasons lead to cycle capacity fading.NCA/LMO core-shell cathode materials were prepared by sol-gel method to promote the cycle stability and rate capability of NCA material.Study shows: Gel precursors prepared with R:L eaual 12:1 was preheated at 360 oC for 10 h in air and heated at 800 oC for 10 h in oxygen will get the product.when the mass ratio of LMO and NCA equals 0.5%,coated products get best cycle performance.with the initial discharge specific capacity promoted from 167mAh/g to 174.4mAh/g,the capacity retention ratio is promoted from 74.7% to 80% after cycled at 1C rate for 100 times.When the mass ratio of LMO and NCA equals 3%,coated products get best high rate performance.The discharge specific capacity are promoted from 86.1mAh/g and 26.3mAh/g to 111.8 mAh/g and 97mAh/g at 10 C,15C rate respectively.