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Herein, we investigate the performance of an aqueous asymmetric supercapacitor (AAS) assembled by using novel nanostructured NiCo2O4 as the positive electrode and a polymer‐derived superactivated carbon (SAC) as the negative electrode. The combination of both the nanostructured NiCo2O4 and the carbon with hierarchical porosity and ultrahigh specific surface area (above 3000 m2 g−1) led to excellent rate performances and long stability of the system. The optimization of the AAS device is further achieved through the variation of mass ratio between positive and negative electrodes. The optimized AAS full cell exhibits reversibility within the 0.0–1.5 V operative voltage region, delivering a specific cell capacity of 24.6 mAh g−1 at a current density of 1 A g−1. This results in a remarkable energy density of 13 Wh kg−1 at a power density of 26.2 kW kg−1 and an excellent cycling durability above 87 % of the initial capacity after 10,000 charge–discharge cycles. [ABSTRACT FROM AUTHOR]

Ternary spinal NiCo2O4 nanostructure holds great promise as high-performance anode material for next generation Li-ion batteries because of its higher electrical conductivity and electrochemical activity. In this work, two-dimensional hexagonal NiCo2O4 nanoplates are synthesized by a simple and cost-effective template-free method through co-precipitation decomposition route using sodium hydroxide as the precipitant followed by annealing in air at 400 °C for 2 h. Various characterization methods prove that hexagonal NiCo2O4 nanoplates are successfully synthesized by this process and have high amount of mesopores on its surface. The electrochemical study of these hexagonal NiCo2O4 nanoplates as Li-ion battery anode shows that the highly mesoporous nanoplate morphology plays an important role in cycling stability and rate capability. As a result, the hexagonal NiCo2O4 exhibits a high reversible charge capacity of 918 mAh/g at a current density of 60 mA/g (0.06 C) with excellent capacity retention of 92% up to 50 charge-discharge cycles. [ABSTRACT FROM AUTHOR]

Nitrogen-doped turbostratic carbonnanoparticles (NPs) are preparedusing fast single-step flame synthesis by directly burning acetonitrilein air atmosphere and investigated as an anode material for lithium-ionbatteries. The as-prepared N-doped carbon NPs show excellent Li-ionstoarage properties with initial discharge capacity of 596 mA h g–1, which is 17% more than that shown by the correspondingundoped carbon NPs synthesized by identical process with acetone ascarbon precursor and also much higher than that of commercial graphiteanode. Further analysis shows that the charge–discharge processof N-doped carbon is highly stable and reversible not only at highcurrent density but also over 100 cycles, retaining 71% of initialdischarge capacity. Electrochemical impedance spectroscopy also showsthat N-doped carbon has better conductivity for charge and ions thanthat of undoped carbon. The high specific capacity and very stablecyclic performance are attributed to large number of turbostraticdefects and N and associated increased O content in the flame-synthesizedN-doped carbon. To the best of our knowledge, this is the first reportwhich demonstrates single-step, direct flame synthesis of N-dopedturbostratic carbon NPs and their application as a potential anodematerial with high capacity and superior battery performance. Themethod is extremely simple, low cost, energy efficient, very effective,and can be easily scaled up for large scale production. [ABSTRACT FROM AUTHOR]

Rod-shapedordered mesoporous carbons (OMCs) with different lengths,prepared by replication method using the corresponding size-tunableSBA-15 silicas with the same rodlike morphology as templates, areexplored as anode material for Li-ion battery. All of the as-synthesizedOMCs exhibit much higher Li storage capacity and better cyclabilityalong with comparable rate capability as compared with commercialgraphite. Particularly, the OMC-3 with the shortest length demonstratesthe highest reversible discharge capacity of 1012 mAh g–1at 100 mA g–1and better cyclability with 86.6%retention of initial capacity after 100 cycles. Although the Coulombicefficiencies of all the OMCs are relatively low at the beginning,they improve promptly and after 10 cycles reach the level comparableto commercial graphite. Based on their specific capacity, cycle efficiency,and rate capability, the OMC-3 outperforms considerably its carbonpeers, OMC-1 and OMC-2 with longer length. This behavior is mainlyattributed to higher specific surface area, which provides more activesites for Li adsorption and storage along with the larger mesoporevolume and shorter mesopore channels, which facilitate fast Li iondiffusion and electrolyte transport. The enhancement in reversibleLi storage performance with decrease in the channel length is alsosupported by low solid electrolyte interphase resistance, contactresistance, and Warburg impedance in electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

Phosphorus-doped ordered mesoporous carbons (POMCs) with different lengths were synthesized using a metal-free nanocasting method of SBA-15 mesoporous silica with different sizes as template and triphenylphosphine and phenol as phosphorus and carbon sources, respectively. The resultant POMC with a small amount of P doping is demonstrated as a metal-free electrode with excellent electrocatalytic activity for oxygen reduction reaction (ORR), coupled with much enhanced stability and alcohol tolerance compared to those of platinum via four-electron pathway in alkaline medium. Interestingly, the POMC with short channel length is found to have superior electrochemical performances compared to those with longer sizes. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI) in fractal dimension has been electrodepositedreproducibly on highly oriented pyrolytic graphite (HOPG) from 0.2M aniline in 1 M aqueous HCl solution by potentiodynamic sweepingin the range of −0.2 to 0.76 V vs Ag/AgCl at room temperature.Fractal growth of PANI dendrimers is affected by diffusion limitedpolymerization (DLP) at a sweep rate of 15 mV s–1for 43 min. This type of PANI dendrimer is prepared for the firsttime on such large area HOPG substrate by electrochemical techniqueusing rather simple cell setup. The fractal dimension has been determinedby chronoamperometry (CA) and box counting technique and is foundto vary from 1.4 to 1.9 with the duration of electropolymerization.The sweep rate, terminal oxidation potential, and the diverse surfaceanisotropy of the HOPG surface are found to be crucial factors incontrolling the growth of such PANI fractals. [ABSTRACT FROM AUTHOR]