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Preparation and Modification of SnCo/C Composite Anode for Li-ion Battery

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Tutor: ChengXinQun
School: Harbin Institute of Technology
Course: Chemical Engineering and Technology
Keywords: Chemical reduction,Li-ion battery,anode material,SnCo/Ccomposite,Hydrothermal me
CLC: TM912
Type: Master's thesis
Year:  2012
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Abstract:
Developing new lithium ion secondary battery is the main way to solve theincreasingly serious energy problems in the present worldwide, while enhancingthe capacity and stability of the anode material is the main objective of the study.Tin is a promising new type of anode material for the high theoretical specificcapacity as990mAh/g and high-potential. But the big volume expansion of tin inthe charge and discharge cycle made it a large loop stability. Prepara tion alloysand compounds of tin and other elements is a good way to improve the material¡¯sperformance. This article prepared SnCo alloy by chemical reduction andSnCo/C composites by Hydrothermal Method.In the experiment, the affect of amount of carbon source to the materialproperties was learned. As the amount of carbon source increase, the firstspecific capacity and initial efficiency of the materials reduce, but the cycle ismore stable. When m(SnCo):m(Carbon source)=3:6£¬the capacity retention inthe50th cycles of the material is63.7%.In the experiment, the affect of amount of Co to the material properties waslearned. As the amount of Co increase, the first specific capacity and initialefficiency of the materials reduce, but the capacity retention increased. WhenSn:Co=1:1, the capacity retention in the50th cycles of the material is79.3%andthe capacity retention in the100th cycles of the material is72.1%.In the experiment, to develop the electrochemical performance of thematerial, the process was improved. And the prepared material was modified.Reaction under the conditions of ultrasound, the time and temperature ofreaction reduced. This reduced the probability of that tin was oxidized. Sochange the environment to ultrasound, the initial efficiency of the materialsincreased. In this condition, composites (Sn:Co=16:1) was prepared. The firstspecific capacity was808mAh/g, and the initial efficiency was58.5%whichhigher than that prepared in the condition of stiring for10%.Mixing the composites into hydrochloric acid solution. After it, the particlesize of composite has a small magnitude larger. The material became more neatly,and the surface became more smooth. Some dent appear in the surface. Theelectrochemical performance has a big development. The first specific capacitywas1085mAh/g. The nitial efficiency was51%. This was because the particlesize was smaller and the dent could accommodate electrolyte and the SEI waseasier to build. The capacity retention in the50th cycles of the material is69.3 higher than that of material which has not modified. This was because thesurface was smooth and the SEI was stable.A number of other improvements has been done in the experiment, suchchange the environment of reaction to environment on the gas protection, the tinoxide was proportionation restored in the750¡æhigh temperature treatment,the material modified with the alkali pretreatment and so on. Due to variousfactors the electrochemical properties of composite materials do not havechanges or became bad. So these method need further study.
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