增大层间距对天然石墨可逆储锂性能的影响研究

Influences of Increasing Interlayer Space on the Properties of Lithium Storage of Natural Graphite

利用石墨嵌入化合物(GIC)制备技术处理天然石墨,然后在其表面包覆一层软炭前驱体,并在惰性气氛下热处理.所得样品不但层间距保持了拉大的状态,而且还在天然石墨内部预留了膨胀空间.成功地找到了在保持天然石墨粒度和碳六角平面直径不显著改变情况下,提高石墨层间距,预留膨胀空间的石墨改性方法.分析表明,石墨嵌入化合物表面含有的大量含氧官能团,在软炭前驱体包覆石墨嵌入化合物的过程中,含氧官能团与沥青之间的反应和石墨嵌入化合物分解产生气体的溢出阻碍了层间距和预留空间的恢复.将这种材料用于锂离子电池负极材料,石墨的可逆储锂容量变化不大,但是倍率放电性能和循环性能得到明显改善.这主要是因为加大层间距和预留膨胀空间,拓宽了锂离子扩散通道,降低了石墨嵌锂膨胀引起的包覆层破裂.

The natural graphite was processed with technology of intercalation compounds （GIC）, coated with precursor of soft carbon, and heated under inert gas. The interlayer space of the sample was increased, and the room for expanding of the sample was reserved. The improving method of increasing the interlayer space and reserving room for expanding has been found successfully, on condition that the changes of the diameter of carbon hexagonal layer and the particle size were not obvious. The analysis showed that there were a lot of oxygen-containing functional groups on the surface of GIC. In the process of GIC being coated with soft carbon, the recovery of the interlayer space and room for expanding was blocked by the reaction between those functional groups and petroleum pitch, and by the gas emission resulted from GIC pyrogenation. Using this sample as anode material of lithium-ion batteries, the reversible capacity changed little, but the rate discharge performance and cycle performance were improved remarkably. This was because of the increasing of the interlayer space and reserving room for expanding resulted in the enlargement of Li-ion diffusion path and the decrease of the coating layer damage.