Synthesis of functionalized 3D hierarchical porous carbon for high-performance supercapacitors

Electrochemical energy storage (EES) systems are attracting research attention as an alternative to fossil fuels. Advances in the design and composition of energy storage materials are particularly significant. Biomass waste-derived porous carbons are particularly suitable for use in EES systems as they are capable of tuning pore networks from hierarchical porous structures with high specific surface areas. These materials are also more sustainable and environmentally friendly and less toxic and corrosive than other energy storage materials. In this study, we report the creation of a three-dimensional hierarchical porous carbon material derived from betelnut shells. The synthesized three-dimensional (3D) hierarchical porous carbon electrode showed a specific capacitance of 290 F g−1 using 1 M KOH as an electrolyte at a current density of 1 A g−1 in three-electrode systems. Moreover, it offered a high charge/discharge stability of 94% over 5000 charge–discharge cycles at a current density of 5 A g−1. Two-electrode symmetric systems show a specific capacitance of 148 F g−1, good cyclic stability of 90. 8% for 5000 charge-discharge cycles, and high energy density of 41 Wh Kg−1 at the power density of 483 W Kg−1 in aqueous electrolyte.

Three-dimensional porous carbon decorated with FeS2 nanospheres as electrode material for electrochemical energy storage

In recent years, graphene-based materials have been in the forefront as electrode material for electrochemical energy generation and storage. Despite this prevalent interest, synthesis procedures have not attained three important efficiency requirements, that is, cost, energy, and eco-friendliness. In this regard, in the present work, graphene nanoplatelets with selectively functionalized edges (XGnPs) are prepared through a simple, eco-friendly and efficient method, which involves ball milling of graphite in the presence of hydrogen (H2), bromine (Br2), and iodine (I2). The resultant HGnP, BrGnP, and IGnP reveal significant exfoliation of graphite layers, as evidenced by high BET surface area of 414, 595, and 772 m(2) g(-1), respectively, in addition to incorporation of H, Br, and I along with other oxygen-containing functional groups at the graphitic edges. The BrGnP and IGnP are also found to contain 4.12 and 2.20 at % of Br and I, respectively in the graphene framework. When tested as supercapacitor electrode, all XGnPs show excellent electrochemical performance in terms of specific capacitance and durability at high current density and long-term operation. Among XGnPs, IGnP delivers superior performance of 172 F g(-1) at 1 A g(-1) compared with 150 F g(-1) for BrGnP and 75 F g(-1) for HGnP because the large surface area and high surface functionality in the IGnP give rise to the outstanding capacitive performance. Moreover, all XGnPs show excellent retention of capacitance at high current density of 10 A g(-1) and for long-term operation up to 1000 charge-discharge cycles.

Commercial-Level Energy Storage via Free-Standing Stacking Electrodes

Exploring the potential of natural pyrrhotite mineral for electrochemical energy storage

Three-dimensional beehive-like hierarchical porous polyacrylonitrile-based carbons as a high performance supercapacitor electrodes

Two-dimensional carbon-based nanomaterials have demonstrated great promise as electrode materials for electrochemical energy storage. However, there is a trade-off relationship between energy storage and rate capability for carbon-based energy storage devices because of the incrementing ion diffusion limitations, especially for thick electrodes with high mass loading. Herein, we report the cross-linked microporous carbon nanosheets enabling high-energy and high-rate supercapacitors. The as-fabricated microporous carbon nanosheets exhibit an extraordinary thickness-independent electrochemical performance. With the thickness of 15 μm, the as-fabricated carbon nanosheet electrode possesses areal/volumetric/gravimetric capacitance of 895 mF cm-2/596 F cm-3/358 F g-1. Even at a high electrode thickness of 125 μm, the as-fabricated thick electrode presents an ultrahigh areal/volumetric/gravimetric capacitance of 4102 mF cm-2/328 F cm-3/328 F g-1. Furthermore, the as-assembled symmetric supercapacitor delivers an outstanding energy density of 19.2 W h kg-1 at a power density of 135 W kg-1 and ultralong cycling stability (capacitance retention of 95% after 180 000 charge/discharge cycles) in an alkaline electrolyte. This work not only provides a facile method for low-cost preparation of carbon nanostructures and high-value utilization of biomass wastes but also offers new insights into rational design and fabrication of advanced electrode materials for high-performance electrochemical energy storage.

Three-dimensional hierarchical porous carbon derived from resorcinol formaldehyde-zinc tatrate/poly(styrene-maleic anhydride) for high performance supercapacitor electrode

Co-precipitation reaction: A facile strategy for designing hierarchical porous carbon nanosheets for EDLCs and zinc-ion hybrid supercapacitors

Ultrathin MoSe2 nanosheets decorated on carbon aerogel microspheres for high-capacity supercapacitor electrodes

Three-dimensional hierarchical porous tubular carbon as a host matrix for long-term lithium-selenium batteries

A facile self-doping and self-templating strategy to prepare three-dimensional nitrogen-doped hierarchical porous carbons via direct carbonization of mussel nacre (MN) is developed. Self-templating can be effective to retain the origin structure and the volatile organic components can serve as carbon precursors for porous carbon. The typical MN-derived carbon (MNC) carbonized at 800 °C is endowed with high surface area of unique hierarchical porosity (consisting of macropores, mesopores and micropores), and high content of heteroatom functionalities (1.30 at.% N). Consequently, the performance in the alkaline KOH electrolyte system was particularly promising with the MNC-6 electrodes showing a high capacitance of 243.7 F g−1 at a current density of 1.0 A g−1 and a promising cycling stability with 85.7% capacitance retention at 1.0 A g−1 after 10,000 cycles. The present work provides a new avenue for facile and high efficient construction of N-doped hierarchical porous carbons for potential supercapacitor.

Design and preparation of hierarchical porous carbon-based materials with bionic “ant nest” structure for high performance asymmetric supercapacitors

Silver decorated graphene nanocomposites toward electrochemical energy storage

Transition metal hydroxides and graphene composite holds great promise to be the next generation of high performance electrode material for energy storage applications. Here we fabricate the cypress leaf-like Cu(OH)2 nanostructure/graphene nanosheets composite through one-step in situ synthesis process, employed as a new type of electrode material for high efficiency electrochemical energy storage in supercapacitors. A solution-based two-electrode system is applied to synthesize Cu(OH)2/graphene hybrid nanostructure, where anodic graphene nanosheets firmly anchor cathodic Cu(OH)2 nanostructure due to the electrostatic interaction. The in situ self-assembly of Cu(OH)2/graphene ensures good structural robustness and the cypress leaf-like Cu(OH)2 nanostructure prompt to form the open and porous morphology. The hybrid structure would facilitate charge transport and effectively mitigate the volume changes during long-term charging/discharging cycles. As a consequence, the Cu(OH)2/graphene composite exhibits the highest capacitance of 317 mF/cm2 at the current density of 1 mA/cm2 and superior cyclic stability with no capacitance decay over 20,000 cycles and remarkable rate capability at increased current densities.