Phosphorus, nitrogen and oxygen co-doped polymer-based core-shell carbon sphere for high-performance hybrid supercapacitors

Co-doping heteroatoms of the carbon lattice has been proven as an efficient strategy that can improve the capacitive performance, due to the synergetic effect of several dopants. Herein, a series of phosphorus, nitrogen and oxygen, co-doped polymer-based carbon spheres were prepared by the suspension polymerization method and chemical activation with phosphoric acid at different temperatures. The presence of heteroatoms was confirmed by X-ray photoelectron spectroscopy and elemental analysis. The structure of the carbons was characterized by scanning electron microscopy, Raman spectroscopy and nitrogen adsorption. Carbon obtained at 800 degrees C with a P, N and O doping level of 11.17 at%, 2.79 at% and 11.77 at% respectively, shows a capacitance of 157 F g(-1) at the current density of 0.05 A g(-1). Moreover, the electrode can survive at a wide potential window of 1.5 V with only 15% decrease in capacity after 10000 cycles at a current density of 5 A g(-1), providing a high energy density of 10 Wh kg(-1) and a high power density of 750 W kg(-1). For the outstanding features, it is expected that the phosphorus, nitrogen and oxygen co-doped carbons will be a very suitable material not only for supercapacitors, but also for lithium batteries and oxygen reduction reaction. In addition, the co-doping method described here might be extended to the preparation of other kinds of porous carbon materials. (c) 2018 Elsevier Ltd. All rights reserved

Poly(vinylidene fluoride) as a porogen to prepare nitrogen-enriched porous carbon electrode materials from pyrolysis of melamine resin

Nitrogen-enriched carbons with hierarchical pore structures were prepared by the direct pyrolysis of melamine resin and poly(vinylidene fluoride) (PVDF) in an inert atmosphere. Our preparation method produced carbons that feature high micropore surface areas of up to 966 m(2) g(-1), with the peak micropore width around 0.5-0.6 nm, and 3-4 nm mesopore channels without the need for a template or activation post-carbonization. The carbons were characterized using N-2 and CO2 sorption analyses, X-ray photoelectron spectroscopy and elemental analysis. The concentrations of nitrogen at the carbon surface were in the range 3.1-4.5 at.%. The electrochemical performance of carbon electrodes was evaluated using cyclic voltammetry, galvanostatic charge-discharge techniques and impedance spectroscopy in 1 MH2 SO4 and 1 M TEABF(4)/acetonitrile. Electrochemical tests in aqueous electrolyte showed excellent rate performance with capacitive behaviour up to 500 mV s(-1) and a specific capacitance of 125 F g(-1) at the current density of 0.05 A g(-1) in a two-electrode cell. In both aqueous and organic electrolytes, good cycling performance are obtain with 96% and 77% of the initial capacitance after 10,000 and 5000 cycles, respectively. (C) 2015 Elsevier Ltd. All rights reserved

Nanorods of vanadium compounds: synthesis, characterisation, and application in electrochemical energy storage

The synthesis and characterisation of nanorods of vanadium pentoxide, V(2)O(5), vanadium trioxide, V(2)O(3), vanadium dioxide, VO(2)(B), and vanadium nitride, VN, are presented, and their application in electrochemical supercapacitors and lithium-ion batteries is outlined. Specifically, a novel method for the preparation of V(2)O(5) nanorods is discussed. It involves ball milling as a first step and controlled annealing as a second step. Nanorods of V(2)O(5) can be converted into those of other vanadium-related phases by simple chemical reduction treatments. Such chemical transformations are pseudomorphic and often topotactic, that is, the resulting nanorods belong to a different chemical phase but tend to retain the original morphology and preferential crystal orientation dictated by parent V(2)O(5) crystals. The corresponding properties of nanorods for their prospective application in electrochemical energy storage (lithium-ion batteries and electrochemical supercapacitors) are discussed. The synthesised V(2)O(5) nanorods possess a stable cyclic behaviour when they are used in a cathode of a lithium-ion battery and are suitable for use in an anode. VN nanorods synthesised by NH(3) reduction of V(2)O(5) were found to possess pseudocapacitive properties in aqueous electrolytes. <br /

Heteroatom-doped graphene for electrochemical energy storage

The increasing energy consumption and environmental concerns due to burning fossil fuel are key drivers for the development of effective energy storage systems based on innovative materials. Among these materials, graphene has emerged as one of the most promising due to its chemical, electrical, and mechanical properties. Heteroatom doping has been proven as an effective way to tailor the properties of graphene and render its potential use for energy storage devices. In this view, we review the recent developments in the synthesis and applications of heteroatom-doped graphene in supercapacitors and lithium ion batteries

Nitrogen and phosphorous co-doped graphene monolith for supercapacitors

The co-doping of heteroatoms has been regarded as a promising approach to improve the energy-storage performance of graphene-based materials because of the synergetic effect of the heteroatom dopants. In this work, a single precursor melamine phosphate was used for the first time to synthesise nitrogen/phosphorus co-doped graphene (N/P-G) monoliths by a facile hydrothermal method. The nitrogen contents of 4.27-6.58at% and phosphorus levels of 1.03-3.00at% could be controlled by tuning the mass ratio of melamine phosphate to graphene oxide in the precursors. The N/P-G monoliths exhibited excellent electrochemical performances as electrodes for supercapacitors with a high specific capacitance of 183Fg(-1) at a current density of 0.05Ag(-1), good rate performance and excellent cycling performance. Additionally, the N/P-G electrode was stable at 1.6V in 1m H2SO4 aqueous electrolyte and delivered a high energy density of 11.33Whkg(-1) at 1.6V

Carbon materials and their energy conversion and storage applications

Carbon, one of the oldest elements recognized and utilized by human civilizations, is also one of the most abundant and versatile materials. It has been used since the pre-historic era as a charcoal for writing and has been intensively studied for hundreds of years. Nevertheless, carbon is still under intensive study because of its unique properties and extensive applications

Enhanced performance of a pillared TiO2 nanohybrid as an anode material for fast and reversible lithium storage

TiO nanohybrid material with pillared nanostructure is prepared via an exfoliation/reassembly process of exfoliated TiO nanosheets and TiO nanoparticles, followed by a calcination treatment. The as-prepared material consists of TiO nanoparticles (≈5–8 nm) randomly distributed in the interlayers of reassembled TiO nanosheets, resulting in a high specific surface area of 207 m g, which can effectively facilitate lithium diffusion and accommodation. The formed disordered TiO pillared material can deliver a specific discharge capacity of 349 mA h g at 0.2 C with sufficient lithium intercalation and exceptional cycling stability for up to 150 cycles, and survive more than 350 continuous cycles with almost no capacity fading at 1 C, 5 C and 10 C. The superior electrochemical properties of our TiO nanohybrids demonstrate sufficient and reversible lithium insertion/extraction, and ultrafast lithium diffusion and storage capabilities