Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
Phys Chem Chem Phys. 2013 Jun 14;15(22):8736-43. doi: 10.1039/c3cp50352f. Epub 2013 Apr 30.
Monolithic Li2FeSiO4-carbon composites with well-defined macropores have been prepared from the silica-based gels containing Li, Fe, and carbon sources. The macroporous precursor gels can be fabricated by the sol-gel method accompanied by phase separation. A fine control of the macropore size in the resultant composites has been achieved by controlling the macropore size of the precursor gels simply by adjusting the starting compositions. The effects of pore properties on Li insertion-extraction capabilities have been investigated by utilizing the resultant Li2FeSiO4-carbon composites as the cathode of lithium ion batteries. The electrodes prepared from the Li2FeSiO4-carbon composites with different macropore sizes exhibit significant differences in the charge-discharge properties. The results strongly suggest that the smaller macropore size (equal to the thinner macropore skeletons) and the presence of micro- and mesopores in the macropore skeletons (hierarchically porous structure) are desirable for a better electrode in the case of Li2FeSiO4, which has extremely low ionic and electrical conductivities.
具有明确大孔的整体 Li2FeSiO4-碳复合材料已通过含有 Li、Fe 和碳源的基于硅石的凝胶制备。大孔先驱体凝胶可以通过溶胶-凝胶法伴随相分离来制备。通过简单地通过调整起始组成来控制先驱体凝胶的大孔尺寸，可以精细地控制所得复合材料中的大孔尺寸。通过将所得 Li2FeSiO4-碳复合材料用作锂离子电池的阴极，研究了孔性质对 Li 插入-提取能力的影响。由具有不同大孔尺寸的 Li2FeSiO4-碳复合材料制备的电极在充放电性能方面表现出显著差异。结果强烈表明，在 Li2FeSiO4 的情况下，较小的大孔尺寸（等于较薄的大孔骨架）和大孔骨架中存在的微孔和介孔（分级多孔结构）是理想的，因为 Li2FeSiO4 的离子和电导率极低。
