A new hybrid supercapacitor with excellent electrochemical performance is fabricated by using the flower-like Co(OH)2 and urchin-like VN.

How to exert the energy density advantage is a key link in the development of lithium–sulfur batteries. Therefore, the performance degradation of high-sulfur-loading cathodes becomes an urgent problem to be solved at present. In addition, the volumetric capacities of high-sulfur-loading cathodes are still at a low level compared with their areal capacities. Aiming at these issues, two-dimensional carbon yolk-shell nanosheet is developed herein to construct a novel self-supporting sulfur cathode. The cathode with high-sulfur loading of 5 mg cm−2 and sulfur content of 73 wt% not only delivers an excellent rate performance and cycling stability, but also provides a favorable balance between the areal (5.7 mAh cm–2) and volumetric (1330 mAh cm–3) capacities. Remarkably, an areal capacity of 11.4 mAh cm–2 can be further achieved by increasing the sulfur loading from 5 to 10 mg cm–2. This work provides a promising direction for high-energy-density lithium–sulfur batteries.

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Graphene nanoscroll (GNS) is a spirally wrapped two-dimensional (2D) graphene sheet (GS) with a 1D tubular structure resembling that of a multiwalled carbon nanotube (MWCNT). GNS provide open structure at both ends and interlayer galleries that can be easily intercalated and adjusted, which show great potential applications in energy storage. Here we demonstrate a novel and simple strategy for the large-scale preparation of GNSs wrapping Fe3O4 nanoparticles (denoted as Fe3O4@GNSs) from graphene oxide (GO) sheets by cold quenching in liquid nitrogen. When a heated aqueous mixed suspension of GO sheets and Fe3O4 nanoparticles is immersed in liquid nitrogen, the in-situ wrapping of Fe3O4 nanoparticles with GNSs is easily realized. The structural conversion is closely correlated with the initial temperature of mixed suspension, the zeta potential of Fe3O4 nanoparticles and the immersion way. Remarkably, such hybrid structure provides the right combination of electrode properties for high-performance lithium-ion batteries. Compared with other wrapping structure, such 1D wrapping structure (GNSs wrapping) effectively limits the volume expansion of Fe3O4 nanoparticles during the cycling process, consequently, a high reversible capacity, good rate capability, and excellent cyclic stability are achieved with the material as anode for lithium storage. The results presented here may pave a way for the large-scale preparation of GNS-based materials in electrochemical energy storage applications.

The utilization of porous carbon frameworks as hosts for sulfur loading is an important theme in current Li‐S battery research. Unfortunately, the high loading of insulating sulfur often leads to low specific capacities, poor rate properties, and rapid capacity loss. To address this challenge, a facile templating route to fabricate a novel host material, hierarchical porous carbon rods constructed by vertically oriented porous graphene‐like nanosheets (HPCR) is presented. With a high specific surface area, ultralarge pore volume, hierarchical porous structures, and ideal ion transfer pathways, HPCR is a promising candidate for high sulfur loading. When used as the active material for a sulfur cathode, the HPCR‐S composite with 78.9 wt% sulfur exhibits excellent rate performance (646 mAh g−1sulfur at 5 C) and cycling stability (700 mAh g−1sulfur after 300 cycles at 1 C). Even with a sulfur content of 88.8 wt%, the HPCR‐S composite, without any additional protective polymer coating, still delivers a good rate performance (545 mAh g−1sulfur at 3 C) and cycling stability (632 mAh g−1sulfur after 200 cycles at 1 C). More importantly, the high sulfur loading (88.8 wt%) ensures that the HPCR‐S composite has a high energy density (880 mAh cm−3cathode after 200 cycles at 1 C).

Thermally reduced graphene oxide (rGO)-wrapped ZnMn 2 O 4 nanorods have been successfully fabricated via a facile bottom-up approach. Characterization results show that porous ZnMn 2 O 4 nanorods are uniformly wrapped by ultrathin rGO sheets. The unique structure of this rGO-ZnMn 2 O 4 composite could facilitate both ion and electron diffusion, thus providing suitable characteristics of an anode material for high performance lithium-ion batteries. Specifically, the conductive rGO sheets could act as an efficient buffer to relax the volume changes from Li + insertion/extraction, and enable the structural and interfacial stabilization of ZnMn 2 O 4 crystals. As a consequence, a high and stable reversible capacity (707 mA h g À1 at 100 mA g À1 over 50 cycles) and an excellent rate capability (440 mA h g À1 at 2000 mA g À1 ) are achieved with this composite material.

†Electronic Supplementary Information (ESI) available: SEM image and XRD pattern of the MgO microrods; EDX spectrum of HPCM-900; SEM images of HPCM-800 and HPCM-700; the synthesis, SEM image, N2 sorption isotherms, and pore size distributions of HCS; the rate performances of HPCM-800 and HPCM-700 electrodes; the SEM image and rate performance of PUCN-900 electrode; Nyquist plots of the HPCM-900 and PUCN-900 electrodes; HPCM-900 and other graphene electrodes evaluated at high rate. SeePreventing the stacking of ultrathin 2D carbon nanostructures is a very important research theme in the field of energy storage. In this work, hierarchical porous carbon microrods composed of vertically aligned graphene-like nanosheets (HPCMs) are successfully fabricated via a facile Mg(OH)2-templating method. The unique structure of HPCMs is a desirable combination of 1D hierarchical structures, vertically aligned graphenes, and porous graphenes. With the hierarchical structure and pores, high specific surface area, large pore volume, and ideal charge transport and ion diffusion pathways, HPCMs are the potential candidates for high-performance electrode materials. When used as an anode for Li-ion batteries, the HPCMs electrode exhibits excellent capability (1150 mAhg -1 at 0.1 Ag -1 ), rate performance (246 mAhg -1 at 10 Ag -1 ), and cycling stability (833 mAhg -1 after 700 cycles at 1 Ag -1 ), which is superior to those of natural graphite and many graphenebased anodes.

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