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Synthesis of LiNi0.8Co0.2O2 Nano Particles Coated with LiCoO2 Using Sol-Gel Method

Hamedi Jouybari, Yaser | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40327 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Asgari, Sirous
  7. Abstract:
  8. Nitrates of lithium, cobalt and nickel were used to synthesize LiNi0.8Co0.2O2 cathode material through sol-gel technique. Various synthesis parameters such as calcination time, temperature, chelating agent and the solvent were studied to determine the optimized condition for processing the cathode nono materials. TG/DTA tests were used to identify the optimized calcination temperature. Different techniques such as ICP, XRD and TEM were employed to characterize the chemical composition, crystal structure, size and morphology of the powders. Micron and nano-sized powders were produced using citric / oxalic and TEA as chelating agent, respectively. Results show that the best condition for synthesizing of LiNi0.8Co0.2O2 is at 700 °C for 8 hours by using TEA as chelating agent. TG/DTA tests, On the other hand, they show a higher calcination temperature about 800 °C for citric acid and oxalic acid. While TEA produces nanosize-particles, citric and oxalic acids produce particles in micron size range. After determination of best parameters among temperature, time and chelating agent, the influence of solvent on results was investigated. With respect to the XRD data, of distilled water and etanol alcohol as solvent, distilled water shows better results such as less R parameter and higher I003 / I104 ratio, i.e. better hexagonal ordering and electrochemical properties. Finally, synthesized cathode powder of LiNi0.8Co0.2O2 was coated with 8 wt% LiCoO2. Crystal structure and the thickness of coat were characterized by using TEM and XRD tests. Then optimized powders were used as cathode material to assemble Lithium batteries. To ensure that the batteries are humidity free, NMR and DSC tests were taken from its ingredients. Batteries were packed and Charge-discharge tested. Results show the highest discharge capacity equal to 173 mAh/g at a constant current of 0.1 mAcm-2, between 3.0 and 4.2 V for cathode powder of uncoated LiNi0.8Co0.2O2 using TEA as chelating agent. LiCoO2 coated LiNi0.8Co0.2O2 had a higher life cycle and lower capacity loss rather compared to that of uncoated LiNi0.8Co0.2O2. Results of this investigation may be used to produce powders of optimized properties for Li-ion battery applications
  9. Keywords:
  10. Sol-Gel Method ; Nanopowder ; Lithium Batteries ; Cathode Materials

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