层状LiCo_(1/3)Mn_(1/3)Ni_(1/3)O_2正极材料的Al掺杂改性

Modification of layered LiCo_(1/3)Mn_(1/3)Ni_(1/3)O_2 cathode materials with doping Al

通过共沉淀法制备了掺杂不同Al含量的LiMn1/3Ni1/3Co1/3-xAlxO2的锂离子电池掺杂性层状样品。对制得的样品进行充放电测试、循环性能测试、容量保持测试和循环伏安测试,对各样品的性能曲线进行分析后得到LiMn1/3Ni1/3-Co1/3-xAlxO2的最佳Al含量为1/24,有较良好的电化学可逆性和放电比容量。通过X射线衍射(XRD)和扫描电子显微镜(SEM)分析最佳掺杂比例LiMn1/3Ni1/3Co7/24Al1/24O2的样品与没有掺杂的空白样品LiCo1/3Mn1/3Ni1/3O2之间的结构差异,表面掺杂后LiMn1/3Ni1/3Co7/24Al1/24O2的颗粒更细、分布更均匀,还能有效抑制材料的阳离子混排,提高了晶体结构的有序化程度,并抑制了充放电过程中层状结构的坍塌,避免Li+通道被堵塞而影响材料的循环性能,使其具有更好的六方层状结构。进行0.5 C下的循环充放电测试,结果表明在450次循环后LiMn1/3Ni1/3Co7/24Al1/24O2的容量保持率相比未掺杂的LiCo1/3Mn1/3Ni1/3O2,从71.16%提高到了87.43%,从而证明LiMn1/3Ni1/3Co7/24Al1/24O2有更好的循环性能。

The Lithium-ion battery cathode materials Al-substituted LiMn1/3Ni1/3Co1/3O2 were synthesized by co-precipitation reactions. Effect of Al substitution for Co on LiMn1/3Ni1/3Co1/3-xAlxO2 was investigated. From X-ray diffraction（XRD） data and scanning electron microscopic（SEM） examinations, it was found that the as-synthesized LiMn1/3Ni1/3-Co1/3-xAlxO2 were crystallized in α-Na Fe O2 layered structure with Rm space group. The synthesized LiMn1/3Ni1/3Co7/24-Al1/24O2 exhibits smaller particle size and more ordered crystallinity, compared with the neat LiMn1/3Ni1/3Co1/3O2.Electrochemical investigation reveals that Al replacement for Co give rise to improved cycling performance. The capacity retention of LiMn1/3Ni1/3Co7/24Al1/24O2 electrode was 87.43% of the initial capacity after 450 cycles, in a voltage range of 2.8-4.3 V at 25 o C, whereas the undoped materials shows a capacity remaining of 71.16% under the same testing conditions.