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The aminated beta-cyclodextrin (β-CD-N) molecules were first used to modify graphene for fabricating the hybrid film electrode (G/β-CD-N) using a method combining mild water bath heat-treatment and vacuum filtration. As compared with pure graphene film (G) and beta-cyclodextrin (β-CD) modified graphene film (G/β-CD), the prepared G/β-CD-N hybrid film exhibits better hydrophilic property, thermal stability and higher mechanical flexibility. Particularly, the G/β-CD-N hybrid film has a remarkably high areal specific capacitance (614 mF cm-2 at 0.5 mA cm-2), good mechanical flexibility (maintaining 98.2% for 1000 bending/unbending cycles) and long-term cycle stability (maintaining 96.8% for 10000 charge/discharge cycles). Moreover, the assembled G/β-CD-N based flexible and symmetric all-solid-state supercapacitor shows an excellent volumetric specific capacitance of 22.53 F cm-3 at 0.5 mA cm-2 and a high energy density of 3.13 mWh cm-3 at a power density of 0.014 W cm-3. The high comprehensive performances of the developed hybrid film electrodes can be ascribed to the combined effects of β-CD molecules and the amination process. This work provides a new approach for the fabrication of flexible supercapacitor with high performance. [ABSTRACT FROM AUTHOR]

Waste fiberboards were used to produce N, O co-doped carbon dots (CDs) by acid etchingmethod. The graphene hydrogels decorated with N, O co-doped CDs (GCD) were synthesized via hydrothermalmethod and optimized through differentmass ratios. The optimal composite electrode exhibited a high specific capacitance of 335.1 F g-1 at 1 A g-1, and a good mechanical flexibility with about 90.6% capacitance retention after 500 bending/unbending cycles. Furthermore, the assembled flexible supercapacitor owned an ideal cycling stability of 83.4% after 10000 charge/discharge cycles at 5 A g-1. Such results demonstrated that N, O co-doped CDs played an essential and unique role in composite graphene hydrogel for improving the electrochemical performance of the flexible supercapacitor. [ABSTRACT FROM AUTHOR]

In this paper, litchi-like microspheres structures of NiCo2Se4 @carbon microspheres (NCSC) hybrids were successfully synthesized via a simple two-step hydrothermal method. The effects of the content of NiCo2Se44 on the structure of NCSC composites are investigated. The morphology and nanostructure of the as-obtained NCSC hybrids were examined by XRD, XPS, FESEM and TEM. The results indicate that the carbon microspheres (CM) were uniformly covered with NiCo2Se44 and with the increase of NiCo2Se44 content, the superficies of NCSC also exhibits homogeneous rough nanoparticles and regular spheres connect with each other. Meanwhile, the electrochemical tests indicate a suitable mass ratio of NiCo2Se44 and carbon microspheres (2:3) showed the highest specific capacitance value (1394 F g-1 at the current density of 0.5 A g-1, 766 F g-1 even at the current density of 50 A g-1), excellent rate property and outstanding cycling stability (80.093% of the initial value after 10000 cycles at the current density of 5 A g-1). Benefiting from the above integrated advantages, asymmetric supercapacitors (ASC) fabricated with NCSC composites as the positive electrode and porous activated carbon as negative electrode operating at the voltage window of 0-2 V deliver a high energy density of 101 Wh kg-1 at a power density of 0.749 kW kg-1, with the specific capacitance retention of 81.095% after 10000 cycles at the current density of 10 A g-1, superior to most of reported supercapacitors. [ABSTRACT FROM AUTHOR]

A simple and template-free method for fabrication of a modified porous graphene hydrogel electrode was developed. The method involved adding natural organic phytate in the pure graphene hydrogels. Benefiting from the introduced phosphate groups and positively charged metal ions, the flexible magnesium phytate/graphene (Mg-P/G) hydrogel electrode showed large specific capacitance of 281 F/g with a small charge transfer resistance of 0.3 Ω. Furthermore, the flexible supercapacitor showed prominent cycling stability (about 100% retention in capacitance over 10000 cycles) and excellent mechanical flexibility (about 97.5% of its original capacitance after 500 bending cycles). [ABSTRACT FROM AUTHOR]