| 초록 |
We use the technique of surface coating to improve the stability of NCM811 at higher voltages. The Al2O3 is coated in a uniform and conformal way on prefabricated electrodes using ALD that significantly prevented surface degradation over prolonged cycling. 1st cycle capacity of 190, 199, 188 and 166 mAh/g is obtained for pristine, 2, 5 and 10 cycles of ALD coated samples at 0.2C and maintains 145, 158, 151 and 130 mAh/g for high current rate of 2C in RT. The optimized Al2O3 modified cathode retained 75% of its capacity after 500 cycles at 5C with 0.05% capacity decay per cycle, compared with 46.5% retention for a pristine electrode, at an elevated temperature. Despite the insulating nature of Al2O3 coating, a nanometer layer is sufficient to improve the performance at elevated temperature. The protective nature of Al2O3 coating in preventing the detrimental surface reactions at high temperature is understood from the morphology changes between the pristine and cycled electrodes. |
