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In this paper, we investigated the quantum capacitance and the integrated charge of graphene-based materials based on first-principles density functional theory calculations. Transition metals doped in a graphene plane will not move out of the graphene plane and will finally form an accurate symmetrical structure. Meanwhile, for transition metals doped out of plane, regardless of the positions that the metals were placed, they will conform to the same stable M-MV complexes eventually. Meanwhile, the introduction of N atoms makes the Al atom hybridization state tend to be consistent. Al3-NNN (the Al-embedded, nitrogen doped monovacancy graphene-based complexes, and the number of N atoms represents the number of N atoms surrounding the Al) and Al4-NNNN (Al-embedded, nitrogen doped divacancy graphene-based complexes) have the same Al atom hybridization, but it is different in the Al doped monovacancy graphene complexes (Al-MV) and the Al doped divacancy graphene complexes (Al-DV). In addition, we also found that both the Sc doped monovacancy graphene and the Al4-N (Al-embedded, nitrogen doped divacancy graphene-based complexes) can be used as candidates for the negative electrode materials of asymmetric supercapacitors. The results can provide valuable insights into the design and preparation of electrodes for high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

This study focuses on a supercapacitor with displaying variations in color schemes depending on the level of energy storage. In this paper, hydrogen-bonded graphene/polyaniline (HbG/PANI) was successfully synthesized by electrochemical polymerization method. The results showed that the high capacitance (598 F g at 1.0 A g) and more excellent capacity retention were achieved for HbG/PANI as supercapacitor electrode than that of PANI (217 F g at 1.0 A g). In addition, the HbG/PANI also was exhibited fast (72 s) and reversible with the change of color at different potential (0-1 V) as electrochromic device. Excellent electrochemical properties were attributed mainly to the stable chemical bonding of HbG between PANI and ITO, which was conducive to the ion transport and electron conduction. Significantly, we proposed a smart supercapacitor and simultaneously monitored the level stored energy by visual change. The findings showed that the proposed supercapacitor with electrochromic function opens a new path for the future development of smart devices with visualized energy levels. [ABSTRACT FROM AUTHOR]

Graphene-based nanocomposites have been one of the most attractive electrode materials of supercapacitors. But in most cases, graphene-based nanocomposites always use single nanoparticle as active material, which cannot meet the increasing demand for next generation of energy storage devices. In the present paper, we prepared FeO-Ni(OH)/graphene nanocomposite by simple one-step hydrothermal method. The dual-particle system reveals a synergistic effect between FeO and Ni(OH), i.e., Ni(OH) can enhance the electrical conductivity of FeO, and then FeO can act as electrical conductivity bridges between Ni(OH) nanoparticles and RG. As a result, the FeO-Ni(OH)/graphene nanocomposite presents impressing electrochemical performance, including high specific capacitance (~857 F/g), good rate capability, and outstanding cycling stability (after 5000 cycles, 100 % retention). [ABSTRACT FROM AUTHOR]