In this study, we attempted a nanosized coating layer of commercial polypyrrole (PPy) on LiNi0.6Co0.1Mn0.3O2 (HNCM) cathode material to overcome the side reactions with electrolyte and a decrease in the capacity of the inert coating layer. The coating method using commercial PPy is very simple. The energy dispersive X-ray spectroscopy (EDS) analysis and transmission electron microscopy (TEM) images confirmed that PPy coating layer was well dispersed and nanosized. The alternating current (AC) impedance studies revealed that the coating of PPy significantly decreased the charge-transfer resistance of HNCM electrodes. Moreover, the 1 wt% PPy-HNCM electrode exhibited good electrochemical performance with a specific discharge capacity of 177.52 mA h g(-1) at a rate of 0.1 C in the voltage range 3.0-4.3 V, whereas the capacity of the HNCM electrode was only 167.13 mA h g(-1).

Iron-doped LiNi0.85Co0.1Al0.05O2 cathode materials with an α-NaFeO2 structure were synthesized by using co-precipitation and ball-mill methods. The structures of samples were confirmed by using X-ray diffraction, and the sizes and the morphologies of the particles were observed by using scanning electron microscopy. The initial discharge capacity value of the pristine cathode material was 206 mAh/g, but the Fe-doped LiNi0.85Co.1Al0.05O2 cathode material delivered an initial discharge capacity of 215 mAh/g. The capacity retentions of the Fe-doped LiNi0.85Co0.1Al0.05O2 cathode material were higher than those of the pristine cathode material at 55 • C. The lithium diffusion coefficients of the pristine material and the Fe-doped LiNi0.85Co0.1Al0.05O2 cathode material were calculated to be 4.5 × 10 −17 and 4.0 × 10 −17 cm 2 /s, respectively, after cycling at 55 • C. The Fe-doped LiNi0.85Co0.1Al0.05O2cathode material has the highest lithium diffusion coefficient and its electrochemical properties are better than those of the pristine material at high temperatures.