Performance And Modification Of Lithium Nickel Colbat Aluminium Oxides Cathodic Materials Prepared From A New Aluminum Source

As a promising cathodic material,lithium nickel cobalt aluminum oxide has many advantages,such as high capacity,high density,high energy density,moderate price.However,till now above cathodic material possesses the disadvantages of normal cycling life,bad rate performance,low initial columbic efficiency and low safety to limit its application field.In this dissertation,the synthesis and modification of series of lithium nickel cobalt aluminum oxides with a layer α-NaFeO2 structure by a method of"coprecipitation-sintering" using a polyaluminium chloride as the start reactant.Many advanced technique,such as x-ray powder diffraction,charge-discharge test,cyclic voltammetry,electrochemical impedance spectroscopy,x-ray photoelectron spectrum,scanning electron microscope,were employed to investigate which is the key factor to determine the electrochemical performance of as-prepared samples.The main conclusions are as followsing.1.Series of the samples with a theoretical composition of LiNi0.8Co0.15Al0.05O2 prepared by using a Li2CO3,NiCl2·6H2O,CoCl2·7H2O and polyaluminium chloride as start reactants in various sintering temperatures.The experimental result shows that the sample sintered at 810℃ has the best electrochemical performance.The sample exhibits the 1st cycle capacity of 164mAh/g,40th cycle capacity of 155mAh/g，respectively,and the capacity retention of 94.5%in 40 cycles while discharged at the 1C rate,and it also exhibits the capacity of 170mAh/g(0.2C rate),150mAh/g(2C rate),120mAh/g(10C rate),respectively.2.Series of the samples with various theoretical compositions prepared by using a Li2CO3,NiCl2·6H2O,CoCl2·7H2O and polyaluminium chloride as start reactants at 810℃.The experimental result shows that the sample with theoretical composition of LiNi0.85Co0.17Al0.03O2 possesses the best electrochemical performance in all as-prepared samples.It exhibits the 1st cycle capacity of 164mAh/g,40th cycle capacity of 157mAh/g,respectively,and the capacity retention of 95.7%in 40 cycles.3.Series of the coated samples composed of various quality ratios of LiNi0.5Co0.2Mn0.3O2 and LiNi0.8Co0.15Al0.05O2 by using a method of "wet grinding-sintering" at 780℃.The experimental result shows that the sample with 1 wt.%LiNio.5Coo.2Mno.3O2 coated LiNi0.8Co0.15Al0.05O2 possesses the best electrochemical performance in all as-prepared samples.It exhibits the 1st cycle capacity of 170mAh/g,40fh cycle capacity of 166mAh/g,respectively,and the capacity retention of 97.6%in 40 cycles.And it also exhibits the capacity of 170mAh/g(0.2C rate),159mAh/g(2C rate),140mAh/g(10C rate),respectively.The coating obviousl improves the discharge capacity,cycling life and rate performance of the as-prepared samples.