Manganese oxide nanoflower/carbon nanotube array (CNTA) composite electrodes with hierarchical porous structure, large surface area, and superior conductivity was controllable prepared by combining electrodeposition technique and a vertically aligned CNTA framework. This binder-free manganese oxide/CNTA electrode presents excellent rate capability (50.8% capacity retention at 77 A/g), high capacitance (199 F/g and 305 F/cm 3 ), and long cycle life (3% capacity loss after 20 000 charge/discharge cycles), with strong promise for high-rate electrochemical capacitive energy storage applications.In development of energy storage devices, nanostructured electrode materials have attracted great interest, as they show not only higher capacities but also better rates than traditional materials. 1-6 Nanostructured electrode materials are key components in the advancement of future energy technologies; thus, strategies for preparing high-performance nanomaterials are required. 5 However, direct synthesis of complex nanostructures still remains a challenge in areas of materials science. 7,8 Nowadays, much research on electrochemical capacitors (ECs) is aimed at increasing power and energy densities as well as lowering fabrication costs while using environmentally friendly materials. Specifically, it was found that RuO 2 exhibits prominent capacitive properties as ECs electrode materials; 9 however, its high cost excludes it from wide application. Relatively low cost materials such as MnO x and NiO x can also be used as electrode materials, but their poor rate capability need to be enhanced. 10,11 Manganese oxides (MO) have been thoroughly investigated because of their importance in industrial applications, such as catalysis and energy storage. [12][13][14][15][16] Over the years various nanostructured manganese oxides, including dendritic clusters, nanocrystals with different shapes, nanowires, nanotubes, nanobelts, and nanoflowers, have been synthesized. [17][18][19][20][21][22][23][24] In order to greatly increase electrochemical performance of manganese oxides, a hierarchical porous structure 25 with high electronic conductivity 26 must be considered. Nevertheless, up to now, no method has been reported to fabricate hierarchical porous and binder-free manganese oxide composite electrodes with superior electronic conductive paths. In this paper, we realized this goal by a combination of a carbon nanotube array (CNTA) framework and an electrodeposition technique to fabricate a composite structure, that is, well-dispersed manganese oxide nanoflowers on a vertically aligned CNTA. CNTA is excellent for electrodepositing transition metal oxides because of its regular pore structure, high surface area, homogeneous property (binderfree), and excellent conductivity. [27][28][29][30] The experimental results show that the manganese oxide/CNTA composite electrode exhibits superior rate performance (50.8% capacitance retention at 77 A/g) in an EC, thus, making it very promising for high-rate electrochemical capacitive energy ...

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The long-standing issue of lithium dendrite growth during repeated deposition or dissolution processes hinders the practical use of lithium-metal anodes for high-energy density batteries. Here, we demonstrate a promising lithiophilic–lithiophobic gradient interfacial layer strategy in which the bottom lithiophilic zinc oxide/carbon nanotube sublayer tightly anchors the whole layer onto the lithium foil, facilitating the formation of a stable solid electrolyte interphase, and prevents the formation of an intermediate mossy lithium corrosion layer. Together with the top lithiophobic carbon nanotube sublayer, this gradient interfacial layer can effectively suppress dendrite growth and ensure ultralong-term stable lithium stripping/plating. This strategy is further demonstrated to provide substantially improved cycle performance in copper current collector, 10 cm2 pouch cell and lithium–sulfur batteries, which, coupled with a simple fabrication process and wide applicability in various materials for lithium-metal protection, makes the lithiophilic–lithiophobic gradient interfacial layer a favored strategy for next-generation lithium-metal batteries.

Gelatin, a renewable animal derivative composed of various proteins, was used as a precursor for nitrogen-doped porous carbon with high surface areas for supercapacitors for the first time. The preparation procedure is very simple, including the carbonization of gelatin under inert atmosphere, followed by NaOH activation of the carbonized char at 600 C for 1 h. The porosity and surface chemistry of the carbon depend strongly on the weight ratio of NaOH/char, with the specific surface area and nitrogen content varying between 323 and 3012 m 2 g À1 and between 0.88 and 9.26 at%, respectively. The unique microstructure and nitrogen functionalities enable the carbon to exhibit a high capacitance of up to 385 F g À1 in 6 mol L À1 KOH aqueous electrolytes, attributed to the cocontribution of double layer capacitance and pseudo-capacitance. It also shows excellent rate capability (235 F g À1 remained at 50 A g À1 ) and cycle durability, making it a promising electrode material for supercapacitors.

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Hierarchical porous carbon for high volumetric energy density supercapacitors is prepared using biomass derivatives through a facile and green process.

Carbon nanotubes ͑CNTs͒ are promising electrochemical double-layer capacitor electrode materials because they have excellent conductivity and mesopores ͑2-50 nm͒ dominated pore structures. Electrochemical properties of an ultralong ͑1.0 mm͒ aligned carbon nanotube array ͑ACNTA͒ electrode and an entangled CNT ͑ECNT͒ electrode in ionic liquid electrolyte were studied by cyclic voltammetry, galvanostatic charge/discharge, and ac impedance. The ACNTA electrode obtains higher specific capacitance, lower equivalent series resistance, and better rate capability than the ECNT electrode. The reason is that ACNTA electrode possesses larger pore size and more regular pore structure and conductive paths, which are revealed by N 2 adsorption and scanning electron microscopy results, than ECNT electrode.