Zhang Wenhai, Song Ruizhen, Meng Hong, Tang Yakun, Zhang Yue, Liu Lang, Han Ping, Deng Limin, Cao Yuliang
State Key Laboratory of Chemistry and Utilization of Carbon Based Energy Resources, College of Chemistry, Xinjiang University, Urumqi, Xinjiang, 830017, P. R. China.
Engineering Research Center of Organosilicon Compounds & Materials of Ministry of Education, College of Chemistry and Molecular Sciences, Wuhan University, Wuhan, 430072, P. R. China.
Adv Sci (Weinh). 2025 Sep 23:e13835. doi: 10.1002/advs.202513835.
The aromatic nature of coal results in highly graphitized hard carbon (HC), which significantly impacts its sodium storage performance. Constructing oxygen-containing functional groups (OFGs) can effectively enhance sodium storage performance, but the mechanistic role of OFGs in governing the surface chemical evolution of coal-based HC remains poorly understood. Herein, OFGs are introduced into coal molecules through various pre-oxidation methods. Comprehensive in situ/ex situ testing elucidated that different OFGs have different effects on the intramolecular rearrangement of coal. Compared with C═O, -OH, and C─O─C groups, the carboxyl can inhibit decarboxylation during pyrolysis, raising the upper limit of the temperature window for intramolecular carbon rearrangement from 500 to 600 °C. This effect reduces intermolecular condensation efficiency during carbonization, thereby suppressing soft carbon formation. The strategy concurrently enlarges graphite-like interlayer spacing and creates closed pores, ultimately enhancing the sodium storage capacity of coal-based HC. The optimized HC shows enhanced capacity (308 mAh g) with a 1.4 times increase in low-voltage plateau capacity compared to the unmodified HC. This work elucidates the structure-function relationship between specific OFGs and carbonization behavior, develops a practical strategy to modulate coal's molecular rearrangement via targeted surface chemistry, and contributes to achieving low-cost, high-performance HC in advanced SIBs.
煤的芳香性导致了高度石墨化的硬碳（HC），这对其储钠性能有显著影响。构建含氧官能团（OFGs）可以有效提高储钠性能，但OFGs在控制煤基HC表面化学演化中的作用机制仍知之甚少。在此，通过各种预氧化方法将OFGs引入煤分子中。全面的原位/非原位测试表明，不同的OFGs对煤的分子内重排有不同的影响。与C═O、-OH和C─O─C基团相比，羧基可以抑制热解过程中的脱羧反应，将分子内碳重排的温度窗口上限从500℃提高到600℃。这种效应降低了碳化过程中的分子间缩合效率，从而抑制了软碳的形成。该策略同时扩大了类石墨层间距并形成了封闭孔隙，最终提高了煤基HC的储钠能力。优化后的HC表现出增强的容量（308 mAh g），与未改性的HC相比，低电压平台容量增加了1.4倍。这项工作阐明了特定OFGs与碳化行为之间的结构-功能关系，开发了一种通过靶向表面化学调节煤分子重排的实用策略，并有助于在先进的钠离子电池中实现低成本、高性能的HC。
