Ab Initio Calculations Of The Lithium Deintercalation In Anode Materials For Lithium-ion Batteries LiB_2.5BCuB_0.5BN

High voltages, high energy densities, low self-discharge rate, no memory effect, wide temperature range of operation, excellent cycle life and safety characteristics, so many outstanding features have made lithium ion secondary batteries widely used in cell phone, notebook PC, miniature vidicon etc. The lithium ion batteries also show good application prospect in electric vehicles, space flight, and spatial military. However, the present performances of lithium ion batteries still need to be improved. The key step is to seek for more suitable electrode materials, which should store enough lithium and have excellent reversibility of lithium intercalation/extraction in order to fulfill the cell performance of high voltage, high energy density and excellent cycle life. The commercial anodes are usually graphite and other carbonic materials. But due to the disadvantage of carbon based materials, better anode materials are eager to be found. A large number of alternative possibilities for anode materials have recently been studied and reported. Especially, the lithium ternary transition metal nitrides have attracted special attentions.In the present thesis, the first-principles calculations have been used to study the atomic structures, electronic properties and Li deintercalations in Li3N and in Li2.5Cu0.5N. Our study could provide some theoretical guides for the experimental studies on this anode material.The thesis consists of two parts. The first part consists of Chapter 1 and 2. In Chapter 1 the working principles of lithium ion batteries and the characteristics of primary electrode materials are introduced. In Chapter 2 the basic theories employed in this study and the first-principles methods used for the present calculations are described, including major ideas of density functional theory, the Hohenberg-Kohn theorem, the Kohn-Sham equation and the approximations for exchange and correlations (the local density approximation and the generalized gradient approximation). We also describe some details of the computational method, i.e. the ab initio pseudopotential method with the plane wave expansion. The major characters of the Vienna ab initio Simulation Package (VASP) which is used in our calculations are presented as well.In the second part (including Chapter 3 and 4) the atomic structures and electronic...