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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.

Compression and shear wave experiments using plate impact loading were conducted on polycrystalline silicon carbide ͑SiC͒. The material was subjected to combined compression-shear loading to peak compressive stresses ranging from 3 to 18 GPa. The compression ͑shock͒ wave profiles and the propagation velocities of shear and longitudinal release waves in the shocked SiC were measured using in situ, electromagnetic velocity gauges. The Hugoniot elastic limit ͑HEL͒ of the material was found to be 11.5Ϯ0.4 GPa. The measured wave velocities were used to determine the elastic moduli of the material as functions of density compression in the shocked state. The data were further analyzed to obtain the mean stress response of the SiC under uniaxial-strain compression. The longitudinal and mean stress results completely characterize the material stress state. Numerical simulations were also carried out to verify the peak-state data analysis. Our results show that the Poisson's ratio of the material increases with elastic shock compression from an ambient value of 0.161 to 0.192 at the HEL. Above the elastic limit, the maximum shear stress supported by the material increases from 4.5 to 6.4 GPa at a peak stress of 18 GPa. This finding verifies independently the results from lateral manganin gauge measurements in the same material ͓R. Feng et al., J. Appl. Phys. 83, 79 ͑1998͔͒.

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Rational design and facile synthesis of porous carbon materials with optimized porosity are necessary to boost electrochemical performance for energy storage and conversion devices. In this work, we report the fabrication of three-dimensional (3D) highly crumpled porous carbons (HCPCs) inspired by the crumpled structure and functionality of renewable Moringa oleifera leaves by a facile postactivation-free method. The as-resulted HCPCs deliver an interconnected framework, abundant active interfaces, rich heteroatom content, and notably multidirectional porosity for fast ion transport and efficient charge storage. Employed as electrode materials for supercapacitors, the HCPCs exhibit ultrahigh rate capability of capacitance retention over 90% when increasing the current density from 1.0 to 50 A g–1 as well as outstanding cycling stability over 20 000 charge/discharge cycles. Furthermore, the HCPC-based symmetric supercapacitor manifests a high specific energy of 21.6 Wh kg–1, along with excellent structural and electrochemical stability after 20 000 cycles in aqueous medium. This work provides an appealing model of carbon material engineering inspired by the unique structure of natural leaves for fast and high-rate supercapacitors, as well as guidance for rational structural design in extended energy storage and conversion systems.

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A universal KOH-free strategy is developed to prepare nitrogen-doped carbon nanosheets (N-SCNSs) derived from edible oil residues with high specific surface area and high nitrogen content for application in high-rate and high-energy supercapacitors.

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