Effects of ZnO Coating on the Electrochemical Performance & Thermal Stability of LiCoO2 as Cathode Materials for Lithium-Ion Batteries
- Effects of ZnO Coating on the Electrochemical Performance & Thermal Stability of LiCoO2 as Cathode Materials for Lithium-Ion Batteries
- 장원영; 최정우; 임종주; 이중기
- Issue Date
- 2009 MRS Spring Meeting
- VOL 1170E
- ZnO-coated LiCoO2 particles are prepared by plasma-enhanced chemical vapor deposition (PECVD) method in the coating range from 0.08 to 0.49wt.%, and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic absorption spectroscopy (AAS). From the charge-discharge cycling tests in the 3.0-4.5V range, it was shown that both bare and ZnO-coated LiCoO2 exhibit little differences in their discharge capacities during the initial 10 cycles. With subsequent cycles, the bare LiCoO2 abruptly degraded with cycling, while the ZnO-coated LiCoO2 faded relatively slowly. In addition, different coating amounts caused different capacity retention upon cycling.
To investigate the coating effect on the thermal stability of the charged cathode to 4.5V, the thermal decomposition behavior of both uncoated and coated LiCoO2 was examined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Both DSC and TGA data revealed that the ZnO-coated LiCoO2 electrodes have much smaller amount of exothermic reaction at higher onset temperature for thermal decomposition compared to uncoated electrode, and their thermal behavior with coating amount is almost consistent with the tendency of the results obtained from their cycling tests. These results indicate that the ZnO coating is effective in retarding the decomposition reaction of LiCoO2 with electrolyte as well as improving the capacity retention on cycling. The role of ZnO coating is further confirmed by impedance analysis.
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