Lithium Nickel Cobalt Oxide Cathode Material Doped Study

With the development of science and technology, the electronic equipments are miniaturized increasingly, the performances of batteries are required to be enhanced. Lithium-ion battery is widely used in portable electronics due to its advantages of high specific capacity, low self-discharge, high voltage and non-pollution. Lithium-ion battery has the most development potential and a good prospect in applications.Exploiting new cathode materials is the key technology of lithium-ion batteries. Three rich lithium metal oxides, such as LiCoO₂, LiMn₂O₄ and LiNiO₂, were researched mainly at present. Layered LiNiO₂ has high specific capacity, low cost and non-pollution used as cathode material, which is regarded as one of the most promising to replace LiCoO₂ of commercial cathode material. LiNiO₂ doped with Co has better thermal stability and electrochemical properties, which was regarded as the most prospective cathode material.In order to enhance specific capacity and cycle stability of cathode material, LiNi_0.8Co_0.2O₂ was prepared by the chemical co-precipitation, mechanical activation and high temperature synthesis method. The precursor of Ni_0.8Co_0.2(OH)₂ powders were prepared by the chemical co-precipitation method, which was mixed with LiOH·H₂O in proportion by mechanical activation. LiNi_0.8Co_0.2O₂ was prepared by high temperature synthesis in the oxygen atmosphere. On the base of the preparation method, cathode material LiNi_0.8Co_0.2O₂ doped with Mg²⁺ and Al³⁺ was mainly studied in this dissertation.When the doping element is simplex, the initial charge/discharge specific capacities of LiNi_0.8Co_0.17Mg_0.03O₂ were 187.6mAh/g and 142.9mAh/g. The discharge specific capacity remained 128.6mAh/g after 20 cycles, the retention of discharge specific capacity was 90%. The initial charge/discharge specific capacities of LiNi_0.8Co_0.17Al_0.03O₂ were 190.3mAh/g and 157.2mAh/g. The discharge specific capacity remained 147.8mAh/g after 20 cycles, the retention of discharge specific capacity was 94%. When the doping elements are composite, the initial charge/discharge specific capacities of LiNi_0.8Co_0.17Mg_0.01Al_0.02O₂ were 200.2mAh/g and 164mAh/g. The discharge specific capacity remained 147.4mAh/g after 20 cycles, the retention of discharge specific capacity was 89.9%, the discharge specific capacity remained 150.4mAh/g after 50 cycles, the retention of discharge specific capacity was 91.7%, which has the best electrochemical property.