| Summary: | 碩士 === 逢甲大學 === 材料科學所 === 100 === Current collectors with low contact resistance for lithium ion batteries have been investigated in this thesis. Four types of current collectors, including AISI 304 stainless steel and three types of carbon coated stainless steels, were used for LiMn2O4/LiFePO4 electrodes to perform the capacity under C-rate charge-discharge. The carbon films were deposited on AISI 304 stainless steel by chemical vapor deposition (CVD). The types of carbon films were controlled by concentration of carbon source with C2H2/H2 ratio of 0.15, 0.45 and 1.4, respectively, and CVD reaction temperature of 810 oC. The three types of carbon coating are carbon filament (CF), carbon sphere (CS), and carbon transition (CT, a transition type in-between carbon filament and sphere), respectively, based on those surface morphologies. CT-typed current collector unequivocally demonstrate a remarkable improvement on capacity under all current rates particularly at high C-rate(10C). The CS and CT composed of continuous carbon layers are found to greatly reduce the contact resistance between the electrode layer and the current collector. We also found that the ohmic drop decreases at high rate resulting from carbon layer coating. The overall charge-transfer resistance can be reduced by carbon-coated current collector according the results of Nyquist plots. Therefore, the power performance of Li-ion batteries is enhanced by ~55%.
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