| Summary: | 碩士 === 輔仁大學 === 化學系 === 95 === Nano-layer surface-modified cathode materials (LiNi0.8Co0.2O2, LiNi0.8Co0.15Mn0.05O2 and LiNi1/3Co1/3Mn1/3O2) were synthesized by co-precipitation coating method. We had discussed the influences and effects of the Mn substitution and the nano-layer via the electrochemical property test and thermal analysis of the cathode materials. We also had analyzed the roles and the functions of the nano-layer on the surface of the materials by Transmission Electron Microscopy (TEM) and Energy Dispersive Spectrometers (EDS).
In this research, Mn substitution causes an increase of the surface area, but a decrease of the initial capacity. However, the cyclibility and thermal stability of materials are enhanced with the substitution of Mn.
The thickness of the nano-layer by processing Al- and Mg-modification can be found between 15 ~ 20nm and 10 ~ 15nm respectively. Although, Al element is only found on the surface of the material, the Mg element lies not only on the surface but also in the near-core area. Therefore, the cathode materials by Mg-modification have demonstrated the lower initial capacity, while the other materials by Al-modification still demonstrated the similar initial capacity as compared to the pristine materials. In addition, after nano-layer surface-modification, all materials have better cyclibility than the pristine material. In conclusion, with the proper nano-layer surface modification, the materials have not only maintained the good electrochemical performances, but are also efficiently improved on the thermal stability.
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