Abstract In this work, flexible graphene supercapacitor electrodes were prepared from biomass-derived carbon dots/graphene composite film (CDGF) and hydrogel (CDGH) with/without an electrodeposited NiCo2S4 layer. Results showed that the dispersive CDs with abundant heteroatoms effectively inhibited the aggregation of graphene sheets and increased the number of active sites. By combining CDs modification and NiCo2S4 electrodeposition, the electrochemical performance of the prepared ternary composite electrodes is significantly enhanced. In particular, the CDGF-NiCo2S4 electrode has a specific capacitance of up to 1348 F g−1 at a current density of 0.5 A g−1. The resultant CDGF-NiCo2S4 flexible symmetric supercapacitor using 1.0 M H2SO4 as aqueous electrolyte shows a large specific capacitance (313 F g−1 at 0.5 A g−1) and a high energy density of 85.1 Wh kg−1 at a power density of 353 W kg−1. By contrast, the CDGH-NiCo2S4 flexible solid-state supercapacitor using polyvinyl alcohol (PVA)/H2SO4 as gel electrolyte has improved cycling stability (83.1% capacitance retention after 10000 charging/discharging cycles) and a better mechanical flexibility (96.8% capacitance retention after 1000 bending cycles). This work demonstrates the importance of CDs and metal sulfides in modifying graphene-based composite electrodes for flexible supercapacitor.

中文翻译：

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通过碳点改性和NiCo2S4电沉积增强柔性石墨烯超级电容器电极的电化学性能

摘要 在这项工作中，柔性石墨烯超级电容器电极由生物质衍生的碳点/石墨烯复合膜 (CDGF) 和水凝胶 (CDGH) 制备，带有/不带有电沉积 NiCo2S4 层。结果表明，具有丰富杂原子的分散CDs有效地抑制了石墨烯片的聚集并增加了活性位点的数量。通过结合CDs改性和NiCo2S4电沉积，制备的三元复合电极的电化学性能显着增强。特别是，CDGF-NiCo2S4 电极在 0.5 A g-1 的电流密度下具有高达 1348 F g-1 的比电容。使用 1.0 M H2SO4 作为水性电解质的 CDGF-NiCo2S4 柔性对称超级电容器显示出较大的比电容（0.5 A g-1 时为 313 F g-1）和 85 的高能量密度。1 Wh kg-1，功率密度为 353 W kg-1。相比之下，使用聚乙烯醇 (PVA)/H2SO4 作为凝胶电解质的 CDGH-NiCo2S4 柔性固态超级电容器具有更高的循环稳定性（10000 次充电/放电循环后电容保持率为 83.1%）和更好的机械柔韧性（10000 次充放电循环后电容保持率为 96.8%）。 1000 次弯曲循环）。这项工作证明了 CD 和金属硫化物在改性石墨烯基复合电极用于柔性超级电容器中的重要性。