Abstract:

Petroleum asphalt has the advantages of low price, high aromaticity and easy polycondensation, and is an ideal precursor for the preparation of high-additive hard carbon anode materials. However, the aromatic hydrocarbons and alkane in petroleum asphalt are prone to condensation and rearrangement during its direct carbonization, and resulting in high graphitization, small layer spacing coupled with few defect sites, which lead to a poor sodium-ion storage performance. Therefore, this work proposes to introduce NaCl pro-oxygenic agent into the asphalt pre-oxidation process for promoting oxidative cross-linking reaction, inhibiting the rearrangement of the asphalt molecular structure, which can reduce the graphitization degree of hard carbon, expand the layer spacing, and introduce abundant CO groups and closed-pore structures, thereby enhancing the sodium-ion storage performance of the pitch-based hard carbon anode. This asphalt-based hard carbon anode delivers high specific capacities of 285.0 and 145.0 mAh·g^-1 at 30 and 300 mA·g^-1, respectively, coupled with 96.3% initial coulombic efficiency. Meanwhile, it has a high plateau capacity of 173.2 mAh·g^-1 at 30 mA·g^-1, corresponding to 61.4% of the total specific capacity. In addition, the capacity retention rate of this anode is as high as 93.94% for 200 cycles at 0.1 A·g^-1, demonstrating an excellent cycling stability performance.

Key words: NaCl-assisted pre-oxidation, petroleum asphalt, hard carbon anode, sodium-ion battery, electrochemical performance

摘要：

石油沥青具有价格低廉、芳香性高、易缩聚等优点，是制备高附加性硬炭负极材料的理想前体。然而，直接碳化沥青的过程中芳香烃和烷烃易发生缩聚和重排，使其石墨化程度高、层间距小、缺陷位点少，导致储钠性能差。因此，提出在沥青预氧化过程中引入NaCl助氧剂，促进沥青的氧化交联反应，抑制沥青分子结构重排，降低硬炭的石墨化度，增大层间距，引入丰富的CO基团和闭孔结构，进而提升沥青基硬炭负极的储钠性能。在30 和300 mA·g^-1下沥青基硬炭负极的比容量高达285.0和145.0 mAh·g^-1，首次库仑效率为96.3%。同时，在30 mA·g^-1下的平台容量为173.2 mAh·g^-1，占总容量的61.4%。此外，该负极在0.1 A·g^-1下循环200圈的容量保持率高达93.94%，表现出优异的循环稳定性能。

关键词: NaCl辅助预氧化, 石油沥青, 硬炭负极, 钠离子电池, 电化学性能