Shen Chao, Wang Chuan, Jin Ting, Zhang Xianggong, Jiao Lifang, Xie Keyu
State Key Laboratory of Solidification Processing, Center for Nano Energy Materials, School of Materials Science and Engineering, Northwestern Polytechnical University and Shaanxi Joint Laboratory of Graphene (NPU) Xi'an 710072, P. R. China.
Wuhan Institute of Marine Electric Propulsion, China Shipbuilding Industry Corporation, Wuhan 430064, China.
Nanoscale. 2022 Jun 30;14(25):8959-8966. doi: 10.1039/d2nr00172a.
Hard carbon (HC) is most likely to be a commercialized anode material for sodium-ion batteries (SIBs). However, its low initial coulombic efficiency (ICE) impedes its further large-scale industrialization. Since the ICE is greatly related to the side reactions of the electrolyte on the HC surface, herein, we focus on tailoring the surface chemistry of HC a facile low-temperature oxygen plasma (LTOP) treatment technique. The modified HC after a suitable treatment time possesses a highly ordered and low defect surface without a negligible change in layer spacing, thus facilitating Na deinsertion/insertion and reducing the HC/electrolyte side reactions. Moreover, LTOP treatment also brings oxygen functional groups (CO) to the HC surface to enrich Na storage active sites. Consequently, the modified HC reveals a higher ICE of 80.9% compared to 60.6% in the bare HC. Also, the modified HC delivers an ultrahigh specific capacity of 331.0 mA h g at 0.1 A g and exhibits superior rate performance with a high specific capacity of 211.0 mA h g at 5 A g. This work provides a feasible strategy to tailor the surface chemistry of HC for high-efficiency Na-storage and provides a novel avenue to construct high-efficiency SIBs.
硬碳（HC）极有可能成为商业化的钠离子电池（SIB）负极材料。然而，其较低的首次库仑效率（ICE）阻碍了它进一步大规模工业化应用。由于首次库仑效率与电解质在硬碳表面的副反应密切相关，在此，我们聚焦于通过一种简便的低温氧等离子体（LTOP）处理技术来调整硬碳的表面化学性质。经过适当处理时间后的改性硬碳具有高度有序且缺陷少的表面，层间距变化可忽略不计，从而有利于钠离子的脱嵌/嵌入，并减少硬碳/电解质之间的副反应。此外，低温氧等离子体处理还使硬碳表面带有氧官能团（CO），以富集储钠活性位点。因此，改性硬碳的首次库仑效率达到了80.9%，相比之下，未处理的硬碳仅为60.6%。而且，改性硬碳在0.1 A g电流密度下具有331.0 mA h g的超高比容量，在5 A g电流密度下仍具有211.0 mA h g的高比容量，展现出优异的倍率性能。这项工作为通过调整硬碳表面化学性质实现高效储钠提供了一种可行策略，并为构建高效钠离子电池开辟了一条新途径。
