Sodium Storage Mechanism Investigations through Structural Changes in Hard Carbons
Sodium Storage Mechanism Investigations through Structural Changes in Hard Carbons
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DOI：
10.1021/acsaem.0c01614
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发表时间：
2020-10-26
影响因子：
6.4
通讯作者：
Titirici, Maria-Magdalena
中科院分区：
文献类型：
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作者：
Alptekin, Hande;Au, Heather;Titirici, Maria-Magdalena
硬碳由于其相对低廉的成本和良好的电化学性能，被认为是最有前途的钠离子电池负极材料。尽管报道了许多硬碳的结构，但硬碳阳极的实际应用在很大程度上受到低初始库仑效率（ICE）的限制，并且钠的储存机制仍然是未知的。更好地了解钠离子在硬碳阳极中的行为对于开发更高效的钠离子电池至关重要。在1000 ~ 1900℃的温度下，通过水热炭化和热解，合成了一系列具有特定形貌和表面功能的硬碳材料，电化学结果揭示了恒流电位分布和不同ICE的不同钠化-脱钠趋势，并与理论研究进行了比较，以了解不同电压下不同硬碳结构对钠储存过程的影响。此外，通过原位扩张法研究了电极在循环过程中的膨胀；据我们所知，这是该技术首次应用于硬碳上，用于研究钠离子电池的离子储存机理。结合实验和理论结果，我们提出了一种钠离子在硬碳中的存储模型，该模型包括钠离子在缺陷位置的存储，在高压斜坡区通过嵌入，在低压高原区通过孔隙填充；这些发现对未来设计高容量、高效率的电极材料具有重要意义。
Hard carbons, due to their relatively low cost and good electrochemical performance, are considered the most promising anode materials for Na-ion batteries. Despite the many reported structures of hard carbon, the practical use of hard carbon anodes is largely limited by low initial Coulombic efficiency (ICE), and the sodium storage mechanism still remains elusive. A better understanding of the sodium-ion behavior in hard carbon anodes is crucial to develop more efficient sodium-ion batteries. Here, a series of hard carbon materials with tailored morphology and surface functionality was synthesized via hydrothermal carbonization and subsequent pyrolysis from 1000 to 1900 degrees C. Electrochemical results revealed different sodiation-desodiation trends in the galvanostatic potential profiles and varying ICE and were compared with theoretical studies to understand the effect of the varying hard carbon structure on the sodium storage process at different voltages. Furthermore, electrode expansion during cycling was investigated by in situ dilatometry; to the best of our knowledge, this is the first time that the technique has been applied to hard carbons for ion storage mechanism investigation in Na-ion batteries. Combining experimental and theoretical results, we propose a model for sodium storage in our hard carbons that consist of Na-ion storage at defect sites and by intercalation in the high voltage slope region and via pore filling in the low voltage plateau region; these findings are important for the design of future electrode materials with high capacity and efficiency.