wileyonlinelibrary.comvolumetric capacitances of carbon-based electrodes are relatively low (e.g., ≈60 F cm −3 for commercial devices [ 7 ] and 250 F cm −3 for low-density carbon [8][9][10][11][12] ). In order to further increase volumetric capacitance, highly pseudocapacitive materials such as low-cost transition metal oxide/hydroxides are commonly introduced. [13][14][15][16][17] However, the charge transfer effi ciency, rate capability, and long-term cycle life of pseudocapacitive layers are typically poor because of their relatively low electrical conductivity. [ 13,[18][19][20] Consequently, many studies have focused on designing 3D templates with high surface area and electrical conductivity for pseudocapacitive metal oxides/hydroxides. [ 2,18,[21][22][23][24][25][26][27] Among these templates, macroporous graphene foam has engendered substantial interest as a promising binder-free and lightweight template. [ 22,[24][25][26][27] For instance, Lou and co-workers fabricated asymmetric supercapacitors on graphene foam/carbon nanotube hybrid fi lms with energy densities reported in the range 2.7-8.7 mWh cm −3 . [ 28 ] He et al. developed graphene foam/MnO 2 composite electrodes with an areal capacitance of 1.42 F cm −2 at low scan rates in a three-electrode confi guration and reported an energy density of 0.046 mWh cm −3 for two-terminal symmetric supercapacitor devices based on such electrodes. [ 29 ] Liu et al. fabricated solid-state graphene foam-based supercapacitor devices with an areal capacitance of the order of 10 mF cm −2 . [ 30 ] However, the surface area, electrical conductivity, and mechanical robustness of the templates must improve further for prospective applications in functional devices with high energy, power densities, and high rate capabilities.Graphitic petals (GPs), [ 31,32 ] containing a few layers of graphene that generally grow vertically to a substrate by catalyst-free microwave plasma chemical vapor deposition (MPCVD), are promising candidates as electrode materials with high surface area and electrical conductivity. For instance, Bo et al. recently summarized the advances of GP-based electrodes for supercapacitors, [ 33 ] and a related atomic mechanism for ion transport within GP channels has also been proposed. [ 34 ] GPs synthesized on various substrates have exhibited outstanding electrochemical performance as binder-free double-layer capacitor electrodes [35][36][37] and as effi cient nanotemplates for pseudocapacitive materials in prior work. [ 2,31,35,38 ] In particular, GPs synthesized on 3D substrates such as Ni foam [38][39][40] and carbon cloth [ 2,17 ] as A hierarchical structure consisting of Ni-Co hydroxide nanopetals (NCHPs) grown on a thin free-standing graphene petal foam (GPF) has been designed and fabricated by a two-step process for pseudocapacitive electrode applications. The mechanical behavior of GPFs has been, for the fi rst time to our knowledge, quantitatively measured from in situ scanning electron microscope characterization of the petal foams during in-pla...

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characteristics such as quantum confinement and surface effect, indicating great promise as LIB electrodes. [3,4] As a typical TMDs, WS 2 has gained tremendous attention because it possesses a higher theoretical specific capacity (433 mA h g −1 ) and a larger interlayer spacing of 0.64 nm than graphite, which contributes to more space for lithium-ion transport, consequently leading to superior property. [5,6] However, large volume change during charge/discharge process and poor conductivity lead to the decay of capacity and inferior rate performance, limiting its application in energy storage system. [7,8] To address this issue, many efforts have been devoted to the structure design such as hybridization with carbon materials and nanoengineering (such as WS 2 nanoplates in nitrogen-doped CNFs, WS 2 nanowires, WS 2 @graphene composites), [6,9,10] which are effective to buffer interior stress resulted from volume expansion, reduce structural pulverization, shorten ions transfer path, and inhibit agglomeration of materials. Moreover, electrospinning is one of the most effective ways to fabricate flexible membrane structures combining active materials with carbonaceous materials without complicated preparation process and the addition of binder that is electrically insulated and obstructive to ion transportation. [11] For instance, Zhang has reported flexible NiS/CNF and WS 2 /GCNF hybrids via electrospinning as anodes for LIBs with enhanced lithium storage property. [5,12] However, the electrochemical performance of most WS 2 composites reported is still limited by the sluggish reaction kinetics and inferior long-term stability.Capacitive processes that are related to atoms on or near the surface possess faster reaction kinetics and more stable cyclability, when compared with diffusion-controlled storage processes (insertion, conversion, and alloying) in traditional Li-ion storage applications. [13,14] Thus far, in addition to some active materials such as MnO 2 , Nb 2 O 5 , and RuO 2 with intrinsic capacitive behavior, extrinsic capacitive behavior with fast kinetics is also favorable for insertion-(TiO 2 , LiCoO 2 , LiMn 2 O 4 , etc.), conversion-(MoO 2 , V 2 O 5 , etc.), and alloying-type active materials for LIBs via surface and nanostructure engineering to create more reaction sites. [13,15,16] Thus, the design of LIB anode materials with capacitive behavior to induce outstanding electrochemical properties is increasingly imperative. However, Flexible electrodes have recently elicited attention due to their potential to be woven into textiles as flexible power supplies for wearable electronic devices. However, contemporary flexible electrodes generally suffer from the limited reaction kinetics and inferior stability. Here, a flexible WS 2 @CNFs membrane electrode is facilely fabricated via hydrothermal method and subsequent electrospinning to embed WS 2 nanosheets into interconnected framework of carbon nanofibers (CNFs). Benefitting from 3D porous architecture and good conductivity of CNFs, WS 2 @CNFs composit...

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Helical carbon nanofibers (HCNFs) coated-carbon fibers (CFs) were fabricated by catalytic chemical vapor deposition method. TEM and Raman spectroscopy characterizations indicate that the graphitic layers of the HCNFs changed from disorder to order after high temperature annealing. The electromagnetic parameters and microwave absorption properties were measured at 2–18 GHz. The maximum reflection loss is 32 dB at 9 GHz and the widest bandwidth under −10 dB is 9.8 GHz from 8.2 to 18 GHz for the unannealed HCNFs coated-CFs composite with 2.5 mm in thickness, suggesting that HCNFs coated-CFs should have potential applications in high performance microwave absorption materials

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