| Summary: | 碩士 === 元智大學 === 化學工程與材料科學學系 === 100 === In this study, ZnO is used to modify the surface of the Li(Ni1/3Co1/3Mn1/3)O2 by sol-gel method and improve the capacity of cycle stability. The Li(Ni1/3Co1/3Mn1/3)O2 powder is coated with ZnO films, to avoid direct contact reaction between the electrode and electrolyte. It also product a stable solid electrolyte interphase (SEI) layer which can helps to prevent corrosion by the electrolyte. The advantages of sol-gel method are small particle size, high purity and uniformity, etc. The electrochemical performance of Li(Ni1/3Co1/3Mn1/3)O2 can be improved by ZnO coating. The structure, morphology and electrochemical properties of Li(Ni1/3Co1/3Mn1/3)O2 were characterized by XRD, FE-SEM and charge-discharge analysis system and the Li+-ion diffusion coefficient was measured by EIS, CV and GITT method.
The XRD patterns show the structure of Li(Ni1/3Co1/3Mn1/3)O2 didn’t change with ZnO coating and it also shows two peaks at (110) and (002) for ZnO. The SEM images show surface roughness if Li(Ni1/3Co1/3Mn1/3)O2 decreased with ZnO coating amount increased. The particle size analyzer shows that the particle size have two distribution range, one was 0.2~2.7 μm and the other one was 4.3~36.5 μm. The TEM images show the Li(Ni1/3Co1/3Mn1/3)O2 particle was coated with a film and the EDX analysis confirmed that the film was ZnO. The charge-discharge curves show that the coating with 0.5wt% ZnO had highest capacity in the charge-discharge rate of 0.1C~5.0C. The cycle stable also shows the sample coating with 0.5wt% ZnO was the best, the capacity preserve 89% after 50cycle. The Li+-ion diffusion coefficient was calculated by EIS, CV and GITT methods, shows the Li+-ion diffusion coefficient was strongly depend on different model and the concentration of Li+-ion inserted the Li(Ni1/3Co1/3Mn1/3)O2 structure.
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