A Quantum Mechanics Investigation On The Structure And Performance Of Dopped Spinel Maganese Oxide

Lithium ion batteries are advantageous for their high energy density, high power density, long calendar life and better safety. It has been widely used in portable electronic devices and the prospect for future applications in electric vehicles, hybrid vehicles and stationary power generation, and thus was actively studied in recent years. The very first commercial application of LiCoO₂ cathode materials in rechargeable batteries was reported in 1990. Unfortunately, applications based on LiCoO₂ materials have been limited only to portable electronic devices due to lack of sufficient cobalt resources and the toxicity of these compounds. It is therefore highly desirable to develop lower cost, more environmentally friendly materials with richer natural resources. A large number of novel cathode materials alternative to LiCoO₂ have been proposed and actively pursued. Among them, the spinel type lithium manganese oxide LiMn₂O₄ presents a promising candidate for serving as a novel cathode material. With great manganese abundance in nature, lithium manganese oxide compounds can be made quite inexpensively. Unfortunately, lithium manganese oxide possesses the drawback of low discharge capacity and unstable structure upon applications in lithium-ion batteries, particularly at a higher temperature, as observed in many experiments. Thus, a large number of experiments have been undertaken to improve its electrochemical properties. Large amounts of manpower and material resources were taken away since there are too many experimental methods.In recent years, with the development of computer hardware and software, we can now predict almost all the chemistry properties semi-quantitatively or even quantitatively via computer simulation. Currently, theoretical calculations performed on spinel manganese cathode materials can not only interpret experimental results but also predict the performance of novel materials. The general principles formulated from them can then be used to guide the synthesis in experiments. In this paper, we calculate the spinel LiMn₂O₄ system using first principles studies based on density functional theory under general gradient approximation. We discussed the material properties and the status of lithium atom after the Lithium insertion by electronic structure analysis, as well as the effect of dopping to cyclic life and capacity of lithium ion battery. Furthermore, we present a criterion of Jahn-Teller effect, and explain the mechanism why dopping can restrain this distortion.We attempt to address several key issues concerning the structural variation, the energetics, the...