Studies On Lithium Manganese Oxide Cathodes For Lithium-ion Batteries

Lithium-ion batteries are used for energy storage in number of applications such ascell phones, camcorders, lap-top computers, electric vehicles and hybrid vehicles, etc.The cathode materials occupy a lot of costs in lithium-ion battery, with the merits ofabundant manganese resources, lithium manganese oxide cathodes attracts lots ofinterests due to its high voltage, as well as its low cost, safety, non-toxicity, andenvironment friendliness. However, the application of lithium manganese oxides arelimited by the main drawbacks of this material lie on its low capacity, capacity fading andpoor cycling performance. So it is particularly important to improve electrochemicalproperties by doping different cations into the lithium manganese oxide cubic.The crystal structure was determined from the X-ray diffraction pattern, and themorphology was observed on scanning electron microscopy. The electrochemicalproperties of the product were studied by galvanostatic charge-discharge measurement. Inthis paper, three cations were used to modify lithium manganese oxide by coprecitationmethods in order to prepare electrode materials with better and reproducibleelectrochemical performance.(1) Li-rich lithium manganese oxide electrodes exhibit both spinel and layeredcharacter with the different ratio of Li∶Mn. The results indicated that thedischarge-capacity gradually doped as the lithium composition within the materialsdecreased, as well as the plateaus became more clear. Li1.15Mn2O4can be represented intwo-component notation,0.09Li2MnO3·0.91LiMn2O4, which exhibit betterelectrochemical performance due to the exists of using the Li2MnO3component tostabilize an electrochemically active spinel component.(2) Ni-doped spinel lithium manganese oxide are synthesized via co-precipitationmethod. The cubic spinel was slightly changed, and the grains size of the materialbecame much smaller compare to the pure spinel lithium manganese oxide. The decreasein cell should increase the stability of the spinel structure during insertion and de-insertion of lithium ions and increase the diffusion of lithium ions. Ni-doped materialshowed higher voltages deliver and increased energy density.(3) The study on the impact of cobalt ions on spinel lithium manganese oxide can befound that the mixed cobalt ions can obviously change the structure of the cubic, and thecrystal growth in a certain direction. The results showed that Li1.15Mn1.9Co0.1O4displayedregular octahedron and better electrochemical property. The addition of cobalt ions costspinel lithium manganese oxide significant loss of capacity, however, the cyclingbehavior had certainly improved. The process of the discharge capacity of capacity ofLi1.15Mn1.9Co0.1O4can be divided into roughly three stages: rose, maintain and slightlydecreased, the addition of cobalt ions can improve the stability of the material structureand exhibit a stable electrochemical performance.