采用湿化学-后续热处理技术,合成了掺钴尖晶石锰酸锂材料。X 射线衍射(XRD)分析结果表明,钴的掺入没有改变材料的Fd3m结构。扫描电子显微镜(SEM)分析表明,所合成的材料颗粒均匀,形貌规整,粒径分布较窄。透射电子显微镜(TEM)结果表明, Li1.035Co0.035Mn1.930O4具有完好的结晶态。充放电测试结果表明,在室温下钴掺杂能够提高材料的电性能。当产物为Li1.035Co0.035Mn1.930O4时,其电性能达到最优：以0.5C充放电，首次放电容量为113 mAh/g,经过100次循环后容量保持率为93.8%,经过4C 放电后仍然能够保持0.5C 放电容量的76.1%；而未掺钴的Li1.035Mn1.965O4经过4C放电容量仅保持0.5C放电容量的64.8%。电化学阻抗测试结果表明,钴离子的掺杂能够提高锰酸锂材料的锂离子扩散速率。
Spinel powders of Li1.035CoxMn1.965-xO4 (x=0-0.100) systems were synthesized by a simple wet chemical process with post heat-treatment. X-ray diffraction (XRD) patterns reveal that the Co doping does not affect the Fd3m space group of the cathode materials. Scanning electron microscope (SEM) images show that the Li1.035CoxMn1.965-xO4 cathode materials have a uniform and nearly cubic morphology with a narrow size distribution. Transmission electron microscope (TEM) results demonstrate that the Li1.035Co0.035Mn1.930O4 powder has a good crystalline state. The electro-chemical testing results indicate that the prepared Co-doped Li1.035CoxMn1.965-xO4 samples show a better cycling ability and rate capability at room temperature than that of Co-free Li1.035Mn1.965O4. In particular, the Li1.035 Co0.035Mn1.930O4 sam-ple delivers a reversible specific capacity of 113 mAh/g in 1st cycle and retains 93.8%of its initial capacity after 100 cycles at 0.5C rate. When discharging at 4C rate, the Li1.035Co0.035Mn1.930O4 powder maintains 86 mAh/g, which is 76.1%of the reversible capacity at 0.5C. Comparatively, the Li1.035Mn1.965O4 powder maintains only 64.8%of its re-versible capacity at 0.5C discharge rate. The electrochemical impedance spectroscopy results show that Co ion doping can enhance the electrical conductivity and the Li-ion diffusion coefficient. These results indicate a superior cycling and rate performance compared with the pristine one.
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