Preparation And Properties Of Lithium-rich Manganese-based Cathode Material Li 1.2 Ni 0.15 Co 0.1 Mn 0.55 O 2

The energy storage elements used on most portable 3 C electronic products in recent years are lithium-ion secondary batteries.With the development of the electric automobile industry,the demands on the energy density of energy storage materials have become higher.However,the energy densities of cathode materials are generally low.Thus it is badly in need of developing a kind of cathode material with high capacity.The Li rich cathode material has drawn attentions from more and more people due to its characteristic of high working voltage,high specific capacity,low cost,environment friendly,etc.Synthesizing Li1.2Ni0.15Co0.1Mn0.55O2 cathode material by sol-gel method,this paper studies respectively the influences of factors such as the amount of complexing agent citric acid,the pH value of the solution before forming the sol,sintering temperature as well as sintering time on the properties of materials in the synthesizing process.Through the tests of representations on shape and structure as well as the electrochemical property,it is determined that the electrochemical properties of Li1.2Ni0.15Co0.1Mn0.55O2 obtained with the quantity relative ratio of the citric acid to transition metal materials being 1.6:1,pH value being 7.5,pre-sintering for 5 hours at 500? and high temperature sintering for 15 hours at 850? are best.The material synthetized under those conditions is characterized by complete stratified structure,small and evenly distributed particles.The retention rate of the capacity is up to 82%after first discharging capacity up to 244.6 mAh g-1 in 2-4.8 V voltage range and 0.2 C multiplying power and 30 times of circulation.In order to further enhance the electrochemical properties of the materials,this paper introduces final heat treatment modification to the material,explores the influences of dry cold air quenching and water quenching on the properties of the material,and obtains the influences of different methods of final heat treatment modification on the properties of the material.Through comparison,it shows that the cathode material obtained by dry cold air quenching under ambient temperature is high with specific capacity.Charge-discharge tests are carried out to the material in 2-4.8 V voltage range with 40 mAh g-1 current density,the first discharging capacity is as high as 268.4 mAh g-1,but with relatively poor cycle performance.After the optimization of quenching temperature,it is found that the material obtained after high temperature sintering is cooled down to 650 0 C along with the furnace first and then be treated with dry cold air quenching is featured by high specific discharge capacity and good cycling property,and the discharging capacity under 0.2 C multiplying power reaches to 180 mAh g-1.In addition,the specific discharge capacity,cycling property and rate capability of the synthesized material by water quenching method are improved after 24 hours of heating at 80?.