真空固相法合成Li2FeSiO4掺碳增容的对比

Contrastive studies of the effect of carbon doping on Li2FeSiO4 based on the vacuum solid-state reaction

摘要:

为改善低电导率Li₂FeSiO₄材料的电化学性能,采用真空固相法制备了Li₂FeSiO₄/C复合正极材料．利用X-射线衍射(XRD)、扫描电子显微镜(SEM)、激光粒径分析技术(LS)对比分析了样品掺碳前后的物相和形貌特点．结果表明:除了轻微缩小的晶粒和增加的Li₂SiO₃杂质含量,掺碳后产物的晶构和形态无其他显著变化．恒流充放电和容量间歇滴定技术(CITT)结果表明:Li₂FeSiO₄材料晶构转变需经多次循环(至少大于5次)完成;随掺碳后锂离子传输性能的改善,材料电化学性能有所提高,但基于固相合成工艺的碳包覆效果并不理想．

Abstract:

To improve the electrochemical performance of Li₂FeSiO₄ with low electric conductivity, the Li₂FeSiO₄/C composite materials were synthesized by a vacuum solid-state method. Compared with Li₂FeSiO₄, the carbon-doping samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser scattering technology (LS) respectively. There were no significant changes in the structure and morphology of the products before and after carbon doping, except for slight decrease of particle size and increase of Li₂SiO_3impurity. The results of constant current charge-discharge and capacity intermittent titration technique (CITT) showed that the crystal structure of Li₂FeSiO_4had been rearranged after several charge-discharge cycles (at least 5 cycles). Moreover, the improved Li+ conductive capacity enhanced the electrochemical performance of Li₂FeSiO₄ cathode. However, the effect of carbon-doping based on solid-state reaction on the quality needs to be further improved.