Lu Chunhong, Meng Jie, Zhang Juan, Chen Xinyi, Du Minzhi, Chen Yanping, Hou Chengyi, Wang Jilong, Ju Anqi, Wang Xinhou, Qiu Yiping, Wang Shiren, Zhang Kun
Department of Industrial and Systems Engineering , Texas A&M University , College Station , Texas 77843 , United States.
ACS Appl Mater Interfaces. 2019 Jul 17;11(28):25205-25217. doi: 10.1021/acsami.9b06406. Epub 2019 Jul 3.
Chemically converted graphene fiber-shaped supercapacitors (FSSCs) are highly promising flexible energy storage devices for wearable electronics. However, the ultralow specific capacitance and poor rate performance severely hamper their practical applications. They are caused by severe stacking of graphene nanosheets and tortuous ion diffusion path in graphene-based electrodes; thus, the ultralow utilization of graphene has been rarely carefully considered to date. Here, we address these issues by developing three-dimensional hierarchically porous graphene fiber with the incorporation of holey graphene for efficient utilization of graphene to achieve fast charge diffusion and good charge storage capability. Without deterioration in electrical but robust mechanical properties, the optimal graphene fiber shows ultrahigh specific capacitance of 220.1 F cm at current density of 0.1 A cm and boosted specific capacitance of 254.3 F cm at 0.1 A cm after nitrogen doping. Moreover, the nitrogen-doped 40% holey graphene hybrid fiber-assembled FSSC exhibits ultrahigh rate capability (96, 91, and 87% at current density of 0.5, 1.0, and 2.0 A cm, respectively, and 67% even at ultrahigh current density of 10.0 A cm) and excellent cycle stability (95.65% capacitance retention after 10 000 cycles). The contribution of three-dimensional interconnected hierarchically porous network to the enhanced electrochemical (EC) performance is semiquantitatively elucidated by Brunauer-Emmett-Teller and energy dispersive spectroscopy mapping. Our work gives insights into the importance of fully utilizing graphene and provides an efficient strategy for high EC performance in chemically converted graphene-based FSSCs.
化学转化的石墨烯纤维状超级电容器（FSSCs）是用于可穿戴电子产品的极具前景的柔性储能装置。然而，超低的比电容和较差的倍率性能严重阻碍了它们的实际应用。这些问题是由石墨烯纳米片的严重堆叠以及基于石墨烯的电极中曲折的离子扩散路径引起的；因此，迄今为止很少有人仔细考虑石墨烯的超低利用率。在这里，我们通过开发三维分级多孔石墨烯纤维并结合多孔石墨烯来解决这些问题，以有效利用石墨烯，实现快速电荷扩散和良好的电荷存储能力。在不降低电学性能但增强机械性能的情况下，最佳的石墨烯纤维在电流密度为0.1 A/cm时显示出220.1 F/cm的超高比电容，在氮掺杂后，在0.1 A/cm时比电容提高到254.3 F/cm。此外，氮掺杂的40%多孔石墨烯混合纤维组装的FSSC表现出超高的倍率性能（在电流密度为0.5、1.0和2.0 A/cm时分别为96%、91%和87%，即使在10.0 A/cm的超高电流密度下也为67%）和出色的循环稳定性（10000次循环后电容保持率为95.65%）。通过Brunauer-Emmett-Teller和能量色散光谱映射半定量地阐明了三维互连分级多孔网络对增强电化学（EC）性能的贡献。我们的工作深入了解了充分利用石墨烯的重要性，并为基于化学转化石墨烯的FSSCs中的高EC性能提供了一种有效策略。
