| Summary: | 碩士 === 國立清華大學 === 材料科學工程學系 === 88 === Abstract
The objectives of this work are to study the feasibility of fabrication of carbon electrode in lithium-ion battery by using epoxy novolac resin (ENR) as the precursor. Carbon powders with the particle size less than 32μm were obtained by pyrolyzing the epoxy precursor. Various amounts of carbon nano powders with the average size of 20nm were introduced to the synthesis carbon powders. The effects of carbon nano powder on the charge-discharge capacity and efficiency of the carbon electrode were investigated.
In this work, X-ray and Raman spectrum analysis were adopted to investigate the microstructure of ENR carbon powders treated under different temperatures. Specific surface area , density , and element analysis of the mixed carbon powders were also measured. Moreover, the slow-scan cyclic voltammetry(C-V) was applied to test the electrochemical properties of the mixed carbon powders.
Based upon the X-ray and Raman spectrum analysis , it reveals that ENR carbon powder has amorphous structure which consists of single-carbon layer with the lateral size(La) of about 20~40A. The results of C-V test show that there is a broad oxidation peak around 0.5V~1.0V, which indicates the working voltage of the cells is unstable. The density increases with carbonization temperature; however, the specific surface area(BET) and [H]/[C] atomic ratio decrease with the temperature. The capacity and the irreversible capacity during the first charge-discharge cycle are affected by BET and [H]/[C] atomic ratio. In the first cycle of charge-discharge process, it is observed that ENR carbon powder fabricated under 8000C shows the highest charge capacity and irreversible capacity(48%). On the other hand, most of the carbon powders treated under four other temperatures show over higher irreversible capacity.In this study, although no positive effect on the electrochemical properties was observed when nano carbon powders were introduced, better understandings on the mechanisms of electrochemical properties of carbon electrode in lithium-ion battery were obtained.
|
|---|
