Significant Improvement of LiNi0.8Co0.15Al0.05O2 Cathodes at 60 degrees C by SiO2 Dry Coating for Li-Ion Batteries

Abstract

The cycling performance of a LiNi0.8Co0.15Al0.05O2 cathode at 60 degrees C was substantially improved by direct SiO2 dry coating. The SiO2-coated cathode was obtained from firing of the mixture consisting of SiO2 nanoparticles and the cathode powders with a weight ratio of 99:1 at 700 degrees C for 5 h. The first discharge capacity of the coated cathode was 172 mAh/g, whereas the uncoated one showed 182 mAh/g at 60 degrees C. However, the coulombic efficiency of the coated sample was 95%, which was 2% higher than that of the uncoated sample. Moreover, the discharge capacities of the coated cathode at 60 degrees C was about 2.5 times larger than those of the uncoated sample at rates of 0.5 and 1C, showing 146 and 109 mA/g, respectively. This capacity improvement at 60 degrees C is related to the fact that the highly distributed Si element near the surface, as a type of solid solution with LiNi0.8Co0.15Al0.05O2, diminishes the side reactions of the cathode and electrolyte at 60 degrees C.