The Theoretical Studies Of The Organic Electrode Material For Li-ion Batteries By Dispersion-corrected Density Functional Method

With the rapid development of electric veicles and many new types of portable consumer electronics, Lithium-ion batteries(LIBs) have been obtained a extensive application which has the long cycle life, high operating voltage, no memory effect,and other advantages. The conventional electrode materials of LIBs are mostly based on expensive and depletable inorganic trasition matal compounds. The present project entitled advanced LIBs based on the use of renewable organic electrodes aims towards the design of greener electrochemical storage devices by introducing the concepts of sustainability and renewability at the electrode materials level by using organics. Up to now, many organic cathode materials have been reported. The organic conjugated compounds have been widely studied due to their beneficial properties including structural diversity, molecule level controllability, and high theroretical specific capacity.With the continuous development of the density functional theory(DFT) and its various functionals, DFT has become a promising calculation tool. However, the traditional DFT could not describle the long-range van der Waals(VDW) interaction between the molecules. So, one of the studied point in this dissertation, is study some of the main approaches suggested to include dispersion in DFT, in order to find out a functionals which can accurately calculate the performance of the materials.Based on this, we study the electrochemistry performance of various of organic conjugated carbonyl compounds. It can provide theoretical guidance for the experiment.The dissertation consists of five chapters and the content is as follows.In Chapter 1, a brief introdunction to the development history and working principle of LIBs is firstly given, and then intoduced several important inorganic cathode materials. Next, described the history and four categories of the organic cathode materials, especially for the conjugated carbonyl compounds. Evently, we introduced the main work and innovation point of this dissertation.In Chapter 2, we fistly summarized up the theoretical and computational chemistry, especially for the development of models of DFT. Next, we introduced some DFT functionals which could give a correction to the Dispersion interaction.We also illustrated the various studies of the electrode materials for LIBs based on the DFT. Finally, we introdunced the package in the dissertation.Chapter 3 repoted three kinds of DFT to calculated the organic lithium salts which including the conjugated carbonyl structure. Based on the experimental results,three functionals are compared with each other simply, and found out the most appropriate model of DFT. Finally, we researched the electrochemical performance of the lithium salt by the appropriate DFT model.Chapter 4 investigated the geometry and electronic structure of the organic cathode material which have a conjugated cyano structure. The research mainly start from the geometric structure and electronic structure and the structure density of states. Finally, we simulated the Li-ion diffusion pathways and analyzied the lithiation/delithiation mechanism.Chapter 5 focused on fourty kinds of organic materials which also have conjugated structure. We systematic studied therir theoretical capacity, theoretical potential and the lithiation/delithiation bad gap, so as to found out the conditions of the ideal organic candidate materials and give a theoretical guidance for the experiment. In addition, we studied the existence state of Li-ion in the organic crystal structure, and the analyzied the performance of the organic materials.The summary of theroretieal studies on the above organic electrode materials and the related outlook are presented in the last dissertation.