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The electrode material has played an essential role in the performance of supercapacitors. In this paper, we report a mesoporous polymorphic CoSe 2 @N-doped carbon (CoSe 2 @N–C) material synthesized by a facile and efficient in-situ microwave process derived from cobalt organic framework (Co-MOF). The as-synthesized CoSe 2 @N–C electrode shows polymorphism with a stable mesoporous morphology and exhibits enhanced electrochemical performance which is mainly attributed to the synergistic effects of N-doped carbon material, mesoporous structure and polymorphism resulting from selenization. Furthermore, the as-constructed asymmetric supercapacitor (ASC): CoSe 2 @N–C//graphene aerogel (GA) displays a maximum energy density of 42.2 Wh kg−1 at the power density of 791.6 W kg−1 and long-term cycling life with capacitance retention of 94.4% after 5000 charge-discharge cycles. The results have shown a great potential for the CoSe 2 @N–C electrode in SC applications. • The mesoporous polymorphic CoSe 2 @N–C was synthesized by an in-situ microwave process derived from Co-MOF. • The CoSe 2 @N–C shows polymorphism with a stable morphology and exhibits enhanced electrochemical performance. • The as-constructed ASC: CoSe 2 @N–C//GA displays both high energy density and high power density. [ABSTRACT FROM AUTHOR]

A graphene and carbon nanotube wrapped Cobalt derivatives (Gr-CNT@Co) electrode material has been prepared by annealing the complex of ZIF-67 and graphene oxide. The as-prepared Gr-CNT@Co shows an interconnected porous network, a high specific surface (253.9 m2g−1), and a high specific capacitance of 1108F g−1 with high cycling stability. Furthermore, the constructed all-solid-state asymmetric supercapacitor based on Gr-CNT@Co positive electrode and N-doped graphene negative electrode exhibit both a high energy density of 36.55 Wh kg−1 and a power density of 685.3 W kg−1 showing very promising potential for portable power and flexible energy storage devices applications. [Display omitted] • A graphene and carbon nanotube wrapped cobalt electrode (Gr-CNT@Co) was prepared. • The interconnected Gr-CNT@Co material shows excellent electrochemical performance. • Gr-CNT@Co//N-doped rGO all-solid-state asymmetric supercapacitor was fabricated. • The ASSC delivers a high energy density of 36.55 Wh kg−1 at 685.3 W kg−1. Metal-Organic Framework (MOF) materials attract increasing interest for their energy storage application by converting MOF into MOF derivatives. Herein, a graphene and carbon nanotube wrapped Cobalt derivatives (Gr-CNT@Co) electrode material is prepared by annealing the complex of ZIF-67 and graphene oxide. The as-prepared Gr-CNT@ Co shows an interconnected porous structure, a high specific surface (253.9 m2g−1), and a high specific capacitance of 1108F g−1 with high cycling stability. Furthermore, the constructed all-solid-state asymmetric Gr-CNT@Co// N-doped rGO device exhibits a high energy density of 36.55 Wh kg−1 at 685.3 W kg−1, as well as an excellent cycle capacitance retention (78%) after 6000 cycles at 1.5Ag−1, which shows that Gr-CNT@Co is very promising electrode material for portable energy storage devices applications. [ABSTRACT FROM AUTHOR]

In this manuscript, we construct a hierarchical Ni 3 S 2 /CoFe LDH/Ni foam (Ni 3 S 2 /CoFe LDH/NF) hybrid by a facile hydrothermal synthesis followed by an electrodeposition without using any chemical binder. The as-constructed Ni 3 S 2 /CoFe LDH/NF exhibits an ultrahigh areal capacitance of 5.08 F cm−2 and an excellent rate capability with a capacitance retention of 73.8% at the high current density of 20 mA cm−2. Furthermore, the constructed asymmetric supercapacitor (ASC) based on the Ni 3 S 2 /CoFe LDH/NF anode and the activated carbon (AC) cathode shows both a high power density of 986 W kg−1 and a high energy density of 47.31 Wh kg−1 with high cycling stability of 93.4% initial capacitance after 5000 cycles, demonstrating an enormous potential for the practical application in energy storage devices. [Display omitted] • A hierarchical Ni3S2/CoFe LDH/NF hybrid was constructed by a facile hydrothermal synthesis followed by an electrodeposition without using any chemical binder. • Ultrahigh areal capacitance and excellent rate capability are achieved for the Ni 3 S 2 /CoFe LDH/NF electrode. • The constructed ASC exhibits the outstanding energy storage performance. • This fabrication strategy could be extended to other LDH-based electrode materials. Transition metal layered double hydroxides (TM LDHs) nanosheets have stimulated tremendous research enthusiasm, which is gifted with their tunable chemical compositions, large layer distances and superior electrochemical performance. However, the small number of electroactive sites and the low electrical conductivity have restricted their applications in electrode materials. Herein, we construct a hierarchical Ni 3 S 2 /CoFe LDH/Ni foam (Ni 3 S 2 /CoFe LDH/NF) hybrid by a facile hydrothermal synthesis followed by an electrodeposition without using any chemical binder. The as-constructed Ni 3 S 2 /CoFe LDH/NF exhibits an ultrahigh areal capacitance of 5.08 F cm−2 and an excellent rate capability with a capacitance retention of 73.8% at the high current density of 20 mA cm−2. Furthermore, the constructed asymmetric supercapacitor (ASC) based on the Ni 3 S 2 /CoFe LDH/NF anode and the activated carbon (AC) cathode shows both a high power density of 986 W kg−1 and a high energy density of 47.31 Wh kg−1 with high cycling stability of 93.4% initial capacitance after 5000 cycles, demonstrating an enormous potential for the practical application in energy storage devices. [ABSTRACT FROM AUTHOR]

Bi 2 O 2 CO 3 and reduced graphene (rGO) are considered as promising electrode materials for the applications of supercapacitor due to their high specific capacitance and high cycle property, respectively. However, the poor conductivity of Bi 2 O 2 CO 3 and low specific capacitance of rGO have restricted their practical application. In this research, we have prepared a novel Bi 2 O 2 CO 3 /rGO composite electrode with a unique flower-like microstructure by a facile hydrothermal synthesis. The as-prepared Bi 2 O 2 CO 3 /rGO composite electrode exhibits a high capacitance of 667 Fg-1 at 1 Ag-1, which is attributed to the short pathways for rapid ionic diffusion provided by the flower-like microstructure and the addition of high-conductive rGO. Furthermore, the asymmetric solid supercapacitor (ASSC) was assembled by using the Bi 2 O 2 CO 3 /rGO and the N/S co-doped rGO electrode, which shows excellent capacitive performance with the capacitance of 68 Fg-1 at 1 Ag-1 and high energy density of 19.85 Wh kg−1 at power density of 1051 W kg−1. In addition, the device exhibits remarkable cycle stability of about 92.6% after 4000 cycles at a current density of 3 Ag-1. The results have provided an effective way for significant improving the capacitance of Bi 2 O 2 CO 3 electrode and realizing its practical application in ASSC. • A flower-like Bi 2 O 2 CO 3 /rGO electrode was prepared by a facile hydrothermal process with significantly enhanced capacitance. • The Bi 2 O 2 CO 3 /rGO electrode exhibits high capacitance due to the flower-like microstructure and the addition of rGO. • An asymmetric solid-state supercapacitor (ASSC) was constructed by using Bi 2 O 2 CO 3 /rGO and N/S co-doped rGO as electrodes. • The ASSC exhibits excellent capacitance, high energy density at high-power density and remarkable cycling stability. [ABSTRACT FROM AUTHOR]

In this manuscript, we report a one-step microwave-hydrothermal preparation of NiS/rGO hybrid electrode material. Compared to the conventional multi-step preparation process, the new method is green without using any chemical surfactant and the preparation time is significantly reduced from several days to only 6 h. The as-prepared NiS/rGO hybrid exhibits a low resistance of ~0.48 Ω, ultrahigh specific capacitance of 1745.67 F g−1 at 1 A g−1 and a high capacity retention of 451.21 F g−1 at 10 A g−1 after 3000 consecutive cycles with high reproducibility. The assembled symmetric solid-state supercapacitor (SCC) based on NiS/rGO hybrid electrode material shows a specific capacitance of 14.20 F g−1, a high energy density of 7.1 Wh kg−1 and a high power density of 1836 W kg−1, demonstrating a great potential for the application in the field of energy storage devices. • A novel and high-efficiency one-step microwave-hydrothermal method was developed to prepare NiS/rGO hybrid electrode material. • The as-prepared NiS/rGO hybrid electrode exhibits an ultrahigh specific capacitance of 1745.67 F g−1 at 1 A g−1. • The assembled symmetric solid-state supercapacitor based on NiS/rGO hybrid electrode exhibits both a high energy density of 7.1 Wh kg−1 and a high power density of 1836 W kg−1. • The rGO film has played an important role for improving the aggregation and conductivity of NiS nanoparticles in NiS/rGO hybrid. The NiS/reduced graphene (rGO) hybrid has recently attracted increasing interest due to its synthetic effect to improve the conductivity and volume expansion of NiS during charge-discharge cycles as well as the capacitive performance of graphene. However, the preparation of high-performance NiS/rGO hybrid electrode material is still a challenging issue due to its complex multi-step preparation process, which causes low reproducibility, long-time and large-energy consuming. Herein, we report a one-step microwave-hydrothermal preparation of NiS/rGO hybrid electrode material. Compared to the conventional multi-step preparation process, the new method is green without using any chemical surfactant and the preparation time is significantly reduced from several days to only 6 h. The as-prepared NiS/rGO hybrid exhibits a low resistance of ~0.48 Ω, ultrahigh specific capacitance of 1745.67 F g−1 at 1 A g−1 and a high capacity retention of 451.21 F g−1 at 10 A g−1 after 3000 consecutive cycles with high reproducibility. The assembled symmetric solid-state supercapacitor (SCC) based on NiS/rGO hybrid electrode material shows a specific capacitance of 14.20 F g−1, a high energy density of 7.1 Wh kg−1 and a high power density of 1836 W kg−1, demonstrating a great potential for the application in the field of energy storage devices. [ABSTRACT FROM AUTHOR]