CeO2纳米晶的添加对锂硫电池电化学性能的影响

以Ce(OH)₄为原料, 采用热分解法制备得到粒径小于10 nm的CeO₂纳米晶。制备得到的CeO₂纳米晶表面存在丰富的羟基和硝基, 作为硫正极添加剂, 一方面可以有效吸附硫和多硫化锂, 抑制多硫化锂在电解液中的溶解和穿梭效应的发生, 进而提高电池的循环性能。同时, 可以改善电极和电解液之间的接触性, 提高活性物质利用率。其中, 含有5wt%的CeO₂纳米晶的锂硫电池在0.1C和0.5C(1C=1675 mA/g)的充放电倍率下, 100周之后放电比容量分别达750 mAh/g和598 mAh/g, 远高于不含有CeO₂纳米晶的523 mAh/g和395 mAh/g, 同时, 循环前后的电池阻抗也明显降低。

Effects of CeO2 Nano-crystal on Electrochemical Properties of Lithium/Sulfur Batteries

The CeO₂ nano-crystal less than 10 nm was fabricated by using thermal decomposition method with Ce(OH)₄ as the raw material. CeO₂ nano-crystal with abundant -OH and -NO₂ was used as the additive in the sulfur cathode. The additive can adsorb sulfur and lithium polysulfides during charge/discharge process, suppressing the dissloving and migrating of lithium polysulfides in the electrolyte. Thus the “shuttle effect” caused by dissloving of lithium polysulfides can be evidently inhibited, resulting in the enhanced cycle performance and the improved coulombic efficiency of Li-S battery. Furthermore, CeO₂ nano-crystal with abundant -OH and -NO₂ is beneficial to enhance the wettability between electrolyte and sulfur cathode, improving the utilization rate of active material. With 5wt% CeO₂ nano-crystal added in the sulfur cathode, the discharge capacities at 0.1C and 0.5C (1C=1675 mA/g) after 100 cycles are as high as 750 mAh/g and 598 mAh/g, respectively, both much higher than those of the sulfur cathode without CeO₂ nanocrystal. Simultaneously, the resistance of the cell is also reduced evidently before and after cycling owing to the addition of CeO₂ nano-crystal in the cathode.