| Energy shortage and environmental pollution have become two serious issues in the international community, which is primarily due to the excessive exploitation and utilization of fossil energy. Therefore, it is urgent to develop renewable clean energy. However, most of the renewable energy such as wind energy and solar energy are uncontrollable and intermittent, unable to provide reliable energy supply. On the other hand, the rapid development of electronic information technique and clean electric vehicles promoted the energy demand for high power and long service life. With the advantages of high energy density, high working voltage, good charge retention, and wide range of working temperature etc., lithium-ion batteries (LIBs) has been widely used as the power sources of the portable electronic devices since it was developed, and will extend to large-scale energy storage and high power electric vehicles in future. In order to promote and achieve this big vision, it is important to improve energy density, power density, cycling performance, and service security of LIBs. It is crucial to realize the large scale and controllable preparation of metal oxide anode material with high capacity and/or high security, which is proposed as the primary anode materials for advanced LIBs. On the other hand, it can be anticipated in the future, with the large-scale applications of LIBs in electric vehicle and energy storage systems, the limited lithium resources will be hardly fulfill the growing demands, which will seriously influence the sustainable development of LIBs. As the alternative of LIBs, sodium-ion batteries (SIBs) share similar electrochemical behavior as LIBs; Besides, compared to lithium, sodium possesses more earth reserves and lower usage cost. Therefore, developing high performance SIBs will exert profound effects on large-scale energy storage power station in the future. At present, the development of SIBs is still on the re-starting stage, while the electrode material keeps as the bottleneck which restricts the advance of SIBs. Correspondingly, the exloration for high performance electrode material of SIBs is vital for the practical applications of SIBs.The present research work mainly include two aspects of LIBs and SIBs. On one hand, the combustion method, with the nature of large scale production and simple synthesis process, is adopted for the preparation of oxide anode materials of LIBs, including lithium titanate based composites and iron oxide based composites. The overall electrochemical properties of active material are improved by tailoring the way of compositing and the composition of the composites. On the other hand, series of transitional metal oxides and Sb2O3 film are explored as high performance SIBs anode material for the first time. The electrochemical reaction process and mechanism of sodium storage are discussed in detail. The present work on high performance oxide anodes for SIBs might shed a light on the development of SIBs.In chapter 1, a general introduction is given as the following:the development history of LIBs, the working principle and the feature of LIBs, the research status of three types of anode material (insertion, conversion and alloying). The research significance of SIBs and the research status of anode materials for SIBs are also provided.In chapter 2, the experimental reagents, equipment and processes used in the this dissertation are briefly introduced, followed by a detailed description on the electrode preparation process for LIBs and SIBs.In chapter 3, lithium titanate was prepared by simple and large scale combustion method, then composited with different materials after optimization of experiment parameter. Firstly, different amount of transition metal oxides including Fe2O3 and CuO were composited with Li4Ti5O12, resulting in obvious capacity improvement compared to pure Li4Ti5O12. High capacity and stable cycling performance can be obtained when the adding amount of Fe2O3 and CuO was 5 wt%, the reversible capacity of Li4Ti5O12/Fe2O3 and Li4Ti5O12/CuO composites can be kept as 172 mAh g-1 after 100 cycles. Even under a high rate of 20 C, the reversible capacity of Li4Ti5O12/CuO composite can reach as high as 106 mAh g-1. The improvement of the electrochemical property can be ascribed to the contribution of high theoretical capacity of transition metal oxides, and electric conductivity enhancement by pure metal generated during the conversion reaction, leading to improved rate performance of the active material.In chapter 4, on the basis of the chapter 3, a facile and scalable process for synthesizing Fe3O4/C composites via a solution combustion technique followed by carbon-coating annealing treatment is developed. The as-prepared Fe3O4/C sample containing about 13.9 wt% carbon displays an attractive cycling performance up to 100 times (～470 mAh g-1 retained at 100 mAg-1). In addition, the Fe3O4/C electrode shows good rate capability, a capacity of 530 mA h g-1 at 92.4 mA g-1 is still recoverable and sustainable up to 60 cycles after charge/discharge process at high rates. The enhanced electrochemical performance can be attributed to the improved electron transport from the consecutive carbon layer and Li+diffusion due to the nanoscale nature of the Fe3O4 active materials.In chapter 5, to explore high performance anode materials for SIBs, series of simple transition metal oxides (TMOs) is successfully demonstrated as anodes for SIBs for the first time. Fe2O3、NiO、Co3O4 and Mn3O4 films were deposited by ESD technique, all these anodes showed comparable electrochemical activity with Na. For Fe2O3 anode, a reversible capacity of 386 mAh g-1 at 100 mA g-1 is achieved over 200 cycles; as high as 233 mAh g-1 is sustained even cycling at a large current-density of 5 A g-1. Then the sodium uptake/extract is confirmed by the ex situ characterization, in the way of reversible conversion reaction. The pseudocapacitance-type behavior is also observed in the contribution of sodium capacity.In chapter 6, Sb2O3 film was firstly prepared by ESD as high performance of SIBs anode material. The reaction mechanism between Sb2O3 and Na was confirmed by ex-situ characterization, namely conversion-alloying reaction, which is effictive in stabilizing the structure of the active material, accelerating the kinetics of the reaction and lowing down the reaction potential, thus obtaining high capacity and energy density. Based on this unique mechanism, the Sb2O3 anode exhibits a high capacity of 550 mAh g-1 at 0.05 A g-1 and 265 mAh g’1 at a 5 A g-1. A reversible capacity of 414 mAh g-1 at 0.5 A g-1 is achieved after 200 stable cycles.Finally, in chapter 7, an overview and the deficiency of the dissertation are summerized. Some prospects and suggestions on the possible future research are presented. |
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