Preparation And Study On Performance Of The Anode Materials For Lithium Ion Batteries Based On Organic Gel And Porous Silicon

Lithium ion batteries have many excellent performances among the chemical power sources such as the highest work voltage and energy density, longer cycle life and better safty, etc., which make them show the wide prospects of application and latent enormous economic effectiveness in many respects, for example, portable electric devices, electromobile, space technology, national defence industries, and so on. The preparation and study on performance of the anode materials for lithium ion batteries with high capacities and good cycle performance is one of critical factors on the development and application of lithium ion batteries at present. In this thesis, based on organic aerogel and porous silicon(PS) that are two types of materials in frontier field of materials science, carbon aerogel, carbon xerogel and free-standing porous silicon films were prepared and used as the anode materials for lithium ion batteries, and their performance of lithium ion storage and behavior of charge and discharge were studied. Meanwhile, the effects of synthetic conditions on their performance as anode materials were also analysed.(1) Carbon aerogel and xerogel were made from resorcinol-formaldehyde organic gels and used as the anode materials for lithium ion batteries. By discussing the influences of pyrolysis temperature, the level of the catalyst and the concentration of reactant in the preparation of carbon materials on their behavior of lithium ion storage, their performance of storing lithium ions and process of charge and discharge were studied in details. Moreover, the relationship between the structure of carbon aerogel and xerogel and the performance of storing lithium ions was analysed, and the mechanism of the storage of lithium ions in this type of porous carbon materials based on organicgels was also dicussed simply.(2) Using the monomer containing the element of nitrogen or silicon, the organic gels doped uniformly by nitrogen or silicon were synthesized and carbonized into nitrogen or silicon-doped carbon xerogels. The carbon xerogels doped by metal elements of cadmium, cerium and zirconium were also prepared by uniformly introducing into cadmium, cerium and zirconium in the synthesis of organic gels precursor. The performance of lithium ion storage and behavior of charge and discharge of these doped carbon anode materials were studied, and the effects of the level of doped elements on the structure of carbon materials, furthermore on the act of storing lithium ions were accompanyingly analysed.(3) The free-standing porous silicon films with continuous porous structure were prepared on single crystal silicon wafer by the method of anodic oxidation and electrochemical etching-electropolishing, and firstly used as the anode materials for lithium ion secondary batteries. The capacities of lithium ions storage and the process of charge and discharge of this nano-silicon anode materials as well as the influence of the structure of PS on behavior of storing lithium ions were inspected at length. On the other hand, through the process of charge and discharge in cells, the lithium of light metal element could be electrochemically doped into PS at different doping levels. The effects of Li-ion doping on the structure of PS and its properties were observed and studied, and based on the electrochemical Li-ion inserting approach an efficient method was presented to continuously tune the photoluminescence of PS from near infrared to blue.