Studies On The Preparation Of Li–fe Composite Oxide Anode And Its Industry Application

The rapid development of portable consumer electronics, electric vehicles and smart grid energy storage devices for solar cells and wind energy accelerates the demand of high-performance lithium ion batteries, especially for high power density, high capacity density, low cost and long cycle life. Many studies have been performed to identify alternative materials for anode. A variety of transition metal oxides have been employed for this purpose. Materials based on iron oxide have been considered as potential substitute anode materials due to their high storage capacities, their low cost, environmental friendliness and the abundance of their raw materials. It includes the synthesis of Li-Fe composite oxide anode materials using a so-called self-catalytic reverse atom transfer radical polymerization approach in this Master thesis. And the improvement and optimization of anode electrode to meet the comecial application which includes optimizating peformance and crafts. Finally, we apply a solid-liquid reaction method to prepared copper sulfide (CuS).In Chapter 1, we introduce the history and status of lithium-ion batteries, the working principle and manufacturing procedure, anode materials especially transition metal oxides, the methodology and objectives of this thesis.In Chapter 2, we list the experimental chemicals and equipments used in the thesis. And we present the process of making a 3023 type coin cell in detail. The electrochemical and structural analyses methods are also described.In Chapter 3, we explore a new gel synthesis method named"self-catalytic reverse atom transfer radical polymerization"method to prepare Li-Fe composite oxide anode materials powders. This method is based on the "Radiated Polymer Gel"method and thermal acrylic acid polymerization process in our group and the reverse atom transfer radical polymerization (RATRP). In comparison with "Radiated Polymer Gel"method and thermal acrylic acid polymerization process, our method has some advantages including: no need of thermal or radioactive source; low energy consumption and easily controllable. While compared with the usual reverse atom transfer radical polymerization (RATRP), there is no need of poisonous initiator and catalyst in this method which is therefore a really green synthesis process. It has the potential to be used to synthesize nano-sized Li-Fe composite oxide in massive production.To address the issues of low initial coulombic efficiency and low energy efficiency of Li-Fe composite oxide, in Chapter 4, we mixed the Li-Fe composite oxide and graphite as a mixed anode to enhance the initial coulombic efficiency. In the same time, we also optimized the composition of the mixed anode laminate. The initial coulombic efficiency can be increased to 82.0% after optimization. Besides this, we developed the aqueous binder process of making the mixed Li-Fe composite oxide and graphite anode electrode laminate and optimized the composition. After optimization, the initial coulombic efficiency can reach 87.7%.In Chapter 5, we used a solid-liquid reaction method to prepare hexangular flower type copper sulfide (CuS). We also tested the electrochemical properties and conducted structural analyses of this copper sulfide.At last, in Chapter 6, the author listed the achievements and the deficiency in this thesis. And some prospects and suggestions in the future research directions are presented there.