| Summary: | 碩士 === 國立臺南大學 === 材料科學系碩士班 === 95 === The anode material used in this research is natural graphite NG, which is cheaper and easier to obtain, and it has fewer procedure before powder using. However the disadvantages are: reversible capacity declines rapidly. Therefore this research uses thermal decomposition treatment to deposit different multiples of tin (Sn), which has good active material of Li storage, onto the surface of natural graphite. In order to understand the charge-discharge characteristics, cycle life, surface morphology, and thermal stability of such anode material, the samples were tested with cyclic voltammetry test, coin cell charge-discharge test, cycle life test, DSC measurement, SEM observation, EDS analysis, ESCA analysis, XRD analysis, etc.
The experiments show natural graphite which is modified with 75 multiples has best result in cycle life test. The capacity stayed on remarkable 260.07mAh/g after 50 cycles, which is 70% increase of unmodified NG carbon, 152.49 mAh/g. Under high discharge rate (1C-rate), the capacity still remains at 328.83 mAh/g(90.71％), which is better than NG carbon modified with different Sn multiples. DSC measurement also shows the onset temperature of exothermic peak appears later and not much higher, that is helpful for the safety of lithium-ion cells. Therefore the capacity and cycle life can be increased effectively by appropriate tin modification on the surface of natural graphite.
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