Microstructure and electrochemical performance of LiNi0.6Co0.4−xMnxO2 cathode materials

LiNi0.6Co0.4−xMnxO2 (0.15 less-than over equal to x less-than over equal to 0.25) cathode materials for lithium-ion batteries are synthesized by calcining a mixture of Ni0.6Co0.4−xMnx(OH)2 and Li2CO3 at 890–950 °C for 15 h in a flowing oxygen atmosphere. The Ni0.6Co0.4−xMnx(OH)2 precursor is obtained by a chemical co-precipitation method at pH = 11. Thermal analysis of the precursor for LiNi0.6Co0.4−xMnxO2 (0.15 less-than over equal to x less-than over equal to 0.25) shows that the weight loss is about 30% until the temperature reaches 750 °C. The X-ray diffraction patterns indicate the pure, layered, hexagonal structure of LiNi0.6Co0.4−xMnxO2. Scanning electron micrographs reveal that the morphology of the samples is characterized by larger agglomerates (5–15 μm) of rather small layered particles (around 100 nm). The particle size tends to decrease with increasing Mn content. The electrochemical behaviour of LiNi0.6Co0.4−xMnxO2 powder is examined by using test cells cycled within the voltage range 3–4.3 V at the 0.1 C rate for the first cycle and then at the 0.2 C rate. LiNi0.6Co0.4−xMnxO2 (0.15 less-than over equal to x less-than over equal to 0.25) cathode materials exhibit good initial discharge capacity (165–180 mAh g−1) and a capacity retention of above 95% after 20 cycles. It is demonstrated that LiNixCoyMn1−x−yO2 electrodes are promising candidates for application as cathodes in lithium-ion batteries.