煤显微组分对成炭过程及储钠行为的影响

Influence of coal macerals on carbonization process and sodium storage behavior

  • 摘要: 煤成本低廉、芳香结构丰富,是制备钠离子电池硬炭负极材料的优质前驱体。目前煤基硬炭材料的结构调控及储钠性能优化已有较为深入的研究,然而煤的组成复杂,煤自身组成对成炭过程及储钠行为的作用机制尚未明晰。基于此,以新疆烟煤为前驱体,采取密度梯度离心法富集煤中有机显微组分,并在酸洗脱灰后通过高温炭化制备不同显微组分基硬炭材料。探究各显微组分在热解过程的差异及其对硬炭材料中石墨微晶生长过程、孔隙结构和表面元素组成的影响,并结合恒电流充放电、恒电流间歇滴定、电化学交流阻抗和循环伏安测试等方法探究各显微组分基硬炭材料储钠行为的差异。结果表明,镜质组与惰质组热解过程存在差异,惰质组的热稳定性更好,镜质组更易生成片层尺寸更大的石墨微晶,在相同炭化处理温度下镜质组基硬炭的石墨化程度更高,且镜质组基硬炭材料表面含氧官能团的总量高于惰质组基硬炭材料。在储钠行为方面,镜质组基硬炭与惰质组基硬炭的电化学性能随着炭化处理温度展现出不同的变化规律,其中镜质组经1 200 ℃炭化制得的硬炭材料因其较多的层间储钠位点与含氧官能团总量表现出最优的储钠性能,其在0.02 A·g−1电流密度下可逆容量达到305.8 mA·h·g−1,首周库伦效率为82.2%,并且其在0.2 A·g−1电流密度下仍能保持235.7 mA·h·g−1的可逆容量,倍率性能优异。

     

    Abstract: Coal has the advantages of low cost and rich aromatic structure, which makes it a high-quality precursor for the preparation of hard carbon anode materials for sodium-ion batteries. Currently, there has been extensive research on the structural regulation and sodium storage performance optimization of coal-based hard carbon materials. However, the composition of coal is complex, and the mechanism of coal composition on carbon formation and sodium storage behavior is not clear. Based on this, the density gradient centrifuge method is used to enrich the organic maceral in coal with Xinjiang bituminous coal as precursor and different maceral-based hard carbon materials are prepared by acid elution of ash and high temperature carbonization treatment. The study investigated the variations in the pyrolysis process of each maceral and their impacts on the growth of graphite microcrystals, pore structure, and surface elemental composition in hard carbon materials. Furthermore, the discrepancies in sodium storage behavior among hard carbon materials derived from different macerals are explored through galvanostatic charge-discharge, galvanostatic intermittent titration technique, electrochemical impedance spectroscopy, and cyclic voltammetry. The findings indicate disparities in the pyrolysis processes of vitrinite and inertinite. Specifically, inertinite exhibits superior thermal stability compared to vitrinite. Moreover, vitrinite tends to yield graphite microcrystals with larger layer sizes, the graphitization degree of vitrinite-based hard carbon is higher at the same carbonization temperature. Additionally, vitrinite-based hard carbon demonstrates elevated concentrations of oxygen-containing functional groups on its surface in contrast to inertinite-based hard carbon. In terms of sodium storage behavior, the electrochemical properties of vitrinite-based hard carbon and inertinite-based hard carbon showed different changes with the carbonization temperature. Notably, the hard carbon material synthesized through vitrinite carbonized at 1200 ℃ demonstrated the most favorable sodium storage performance, it boasts a high capacity of 305.8 mA·h·g−1 at a current density of 0.02 A·g−1, and a high initial Coulombic efficiency of 82.2% is displayed. It is pointed out that under the current density of 0.2 A·g−1, the capacity still kept 235.7 mA·h·g−1. The excellent electrochemical properties attributed to its increased interlayer sodium storage sites and concentration of oxygen-containing functional groups.

     

/

返回文章
返回