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標題: 電化學製備Co3O4/CoO薄膜鋰離子電池之負極特性研究
Preparation and Characterization of Electrochemical Co3O4/CoO coating on stainless steel as Negative Electrodes for Thin-Film Lithium Ion Batteries
作者: 謝孟峰
關鍵字: electrolytic deposition;電解沉積;Co3O4;CoO;lithium ion;negative electrode thin film batteries;四氧化三鈷;氧化鈷;薄膜鋰離子電池;負極
出版社: 材料工程學研究所
摘 要
本研究的目的在Co(NO3)2水溶液中利用電化學方法,以定電壓方式陰極沉積及燒結Co3O4/CoO薄膜於不銹鋼基材上,並利用XRD、TGA/DTA、SEM/EDS、AFM 和 RAMAN Spectroscopy及充放電測試,分析薄膜的特性和電化學的性質。
1. O2 + 4H+ + 4e- → 2H2O (0 V ~ 0. 06V vs. Ag/AgCl )
2. O2 + 2H2O+2e- → 4 OH- (0.06 V ~ -0.7 V vs. Ag/AgCl )
3. 2H2O + 2e- → H2 + 2OH- (-0.7 V ~ -2.5 V vs. Ag/AgCl )
Co3O4/CoO薄膜電極經由400℃ 5小時燒結後,在不同電解質LiPF6和LiClO4下進行CV及充放電測試,以鋰金屬當參考電極及輔助電極。於第一次放電時發生兩個反應:
1. Co3O4+2Li++2e- → 3Co+Li2O (0.0825V vs. Li+/Li)
2. CoO+2Li++2e- → Co+ Li2O (0.0254V vs. Li+/Li)
但在充電過程中僅:Co+ Li2O → CoO+2Li++2e- 發生,以CoO為主要活性物,在電解質比較中LiPF6的可逆性比LiClO4差。Co3O4/CoO薄膜電極於LiClO4電解質中,在50次充放電後電容量還有500mAh/g。

The electrolytic deposition of Co3O4 /CoO thin film on stainless steel was conducted in Co(NO3)2 aqueous solution to be used as a negative electrode in lithium ion thin film batteries. The cathode polarization curves includes 3 major electrochemical reactors:
1. O2 + 4H+ + 4e- → 2H2O (0 V ~ 0. 06V vs. Ag/AgCl )
2. O2 + 2H2O+2e- → 4 OH- (0.06 V ~ -0.7 V vs. Ag/AgCl )
3. 2H2O + 2e- → H2 + 2OH- (-0.7 V ~ -2.5 V vs. Ag/AgCl )
The coated specimen or the coating film carried out at 3rd step was subjected to annealing treatments and further characterized by XRD, TGA/DTA, SEM/EDS, AFM and RAMAN Spectroscopy. The as-coating film was Co(OH)2, condensed into CoO partially oxidized into Co3O4 at 200℃-400℃ with the particle size from 10 nm to 20nm, and obviously crystallized at 600℃-1000℃on the coated specimen.
The Co3O4/CoO coated specimen annealed at 400℃ for 5hrs was further characterized by CV analysis and charged-discharged tests in LiPF6 and LiClO4 electrolytes respectively using Li metal as the reference and auxiliary electrode. During the first discharging, two electrochemical reactions occurred : The 1st , Co3O4+2Li++2e-→ 3Co+Li2O and the 2nd ,CoO+2Li++2e- → Co+ Li2O. However, only the reverse of the 2nd was found for the 1st charging. Also, the reversibility in LiPF6 was worse than that in LiClO4, since LiF was formed. The capacity of Co3O4/CoO coated specimen was still found 500 mAh/g after 50 charged-discharged cycles test in LiClO4 electrolyte
Appears in Collections:材料科學與工程學系

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