Nov 20, 2015 - CaCO3 template method, using polyaniline as carbon and nitrogen precursors. ... resources make LIBs difficult to satisfy the requirement of large- scale energy storage. .... pore size distribution of the NMC). ACS Applied Materials & ..... ACS Publications website at DOI: 10.1021/acsami.5b06898. SEM and ...
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Nitrogen-Rich Mesoporous Carbon as Anode Material for HighPerformance Sodium-Ion Batteries Huan Liu,† Mengqiu Jia,† Ning Sun,† Bin Cao,† Renjie Chen,‡ Qizhen Zhu,† Feng Wu,‡ Ning Qiao,† and Bin Xu*,† †
State Key Laboratory of Chemical Resource Engineering, Beijing Key Laboratory of Electrochemical Process and Technology for Materials, Beijing University of Chemical Technology, Beijing 100029, China ‡ School of Materials Science & Engineering, Beijing Key Laboratory of Environmental Science and Engineering, Beijing Institute of Technology, Beijing 100081, China S Supporting Information *
ABSTRACT: Nitrogen-rich carbon with interconnected mesoporous structure has been simply prepared via a nanoCaCO3 template method, using polyaniline as carbon and nitrogen precursors. The preparation process includes in situ polymerization of aniline in a nano-CaCO3 aqueous solution, carbonization of the composites and removal of the template with diluted hydrochloric acid. Nitrogen sorption shows the carbon-enriched mesopores with a specific surface area of 113 m2 g−1. The X-ray photoelectron spectroscopy (XPS) analysis indicates that the carbon has a high nitrogen content of 7.78 at. %, in the forms of pyridinic and pyrrolic, as well as graphitic nitrogen. The nitrogen-rich mesoporous carbon shows a high reversible capacity of 338 mAh g−1 at a current density of 30 mA g−1, and good rate performance as well as ultralong cycling durability (110.7 mAh g−1 at a current density of 500 mA g−1 over 800 cycles). The excellent sodium storage performance of the nitrogen-rich mesoporous carbon is attributed to its disordered structure with large interlayer distance, interconnected porosity, and the enriched nitrogen heteroatoms. KEYWORDS: sodium-ion battery, mesoporous carbon, nitrogen-rich, capacity, cycle performance
1. INTRODUCTION
carbon materials is still a challenge so far, because their capacity or/and cycling life could not satisfy the SIBs application demand. Compared to bulk carbon materials, porous carbon materials can offer significant improvements on power and energy density, which are attracting increasing interests for energy storage/ conversion devices. The developed pores of the porous carbon materials provide sufficient contact area at the electrode/ electrolyte interface, continuous electron conduction pathways, and easy strain relaxation during charge−discharge process.17,18 Furthermore, doping with heteroatoms, particularly N atoms, is an effective way to enhance the electrochemical performance of carbon materials as the anode for LIBs and SIBs.17,19−21 Various nitrogen-rich precursors, such as melamine resin,22 polyacrylonitrile,23 polypyrrole,21,24 polyaniline,25,26 gelatin,17 and nitrogencontaining organic salt,27 have been used to prepare nitrogenrich porous carbons. The application of nitrogen-rich porous carbon have been widely investigated as electrode materials for supercapacitors and LIBs, but only a few works have been reported for application in SIBs so far. Nitrogen-doped porous
During the past several decades, lithium-ion batteries (LIBs) have attracted considerable attention, because of their high energy density and good cycle performance. However, the limited storage and the nature of the high cost of lithium resources make LIBs difficult to satisfy the requirement of largescale energy storage. Because of the natural abundance of sodium resources, with chemical characteristics similar to that of lithium, sodium-ion batteries (SIBs) are being recognized as one of the most promising alternatives for LIBs. 1−4 However, the exploration of suitable anode materials for SIBs is more difficult than for LIBs, because the ionic radius of the Na+ ion is larger than that of the Li+ ion.5 The interstitial space of graphite, which is the most commonly used anode material for LIBs, is not large enough to accommodate Na+ ions and to allow reversible and rapid sodium ion insertion/extraction. Disordered carbon with a large interlayer distance are regarded as one of the most suitable anode materials for SIBs. Various carbon materials such as carbon black,6 carbon spheres,7,8 carbon fibers,9−11 hollow carbon nanowires,12 and porous carbon13−16 have been used as anode materials for SIBs. Although much progress has been realized, the electrochemical performance of the disordered © 2015 American Chemical Society
Received: July 29, 2015 Accepted: November 20, 2015 Published: November 20, 2015 27124
DOI: 10.1021/acsami.5b06898 ACS Appl. Mater. Interfaces 2015, 7, 27124−27130
Research Article
ACS Applied Materials & Interfaces Scheme 1. Schematic of the Synthesis Steps for Nitrogen-Rich Porous Carbon
deionized water and acetone, and dried at 80 °C under vacuum, the PANI/CaCO3 composites were obtained. The composites were placed into a tubular furnace and heated at 700 °C for 2 h with a ramp rate of 10 °C min−1 in a N2 atmosphere to accomplish carbonization. Finally, the pyrolyzed products were washed with 1 M HCl and deionized water to remove the template. After being dried at 120 °C under vacuum for 8 h, the NMC sample was obtained. For comparison, nitrogen-rich carbon (NC) was prepared using a procedure similar to that used for NMC, only without CaCO3 template. Characterization. The morphology of the samples was observed by scanning electron microscopy (SEM) (JEOL, Model JSM-6701F) and transmission electron microscopy (TEM) (JEOL, Model 2100). The composition and crystallitic structure of the samples were characterized by powder X-ray diffraction (XRD) (Bruker D8 system, with Cu Kα radiation) and X-ray photoelectron spectroscopy (XPS) (Fisher Scientific, Model ESCALAB 250). The Raman spectrum was tested on a Raman spectrometer (Renishaw, Model 1000), using a 50 mW He−Ne laser (514 nm) with a CCD detector. The porosity parameters of the carbons were analyzed by nitrogen (77 K) adsorption/desorption (Micromeritics, Model ASAP 2460). The specific surface area (SBET) was obtained according to the conventional Brunauer−Emmett−Teller (BET) method. The total pore volume (Vt) was calculated by determining the amount of the adsorbed N2 at a relative pressure of 0.99. Besides, the adsorption branch of the isotherm was used to calculate the pore size distribution through the Barrett−Joyner−Halenda (BJH) method. Electrochemical Measurements. A slurry of active materials (80 wt %), conductive agent (Super-p, 10 wt %), and binder (polyvinylidene difluoride (PVDF), 10 wt %) in the NMP solvent was coated onto copper foil. After being dried at 120 °C for 12 h under vacuum, the as-prepared electrode was cut into pellets 10 mm in diameter, in which the mass loading was ∼0.8 mg cm−2. The obtained pellet was used as the working electrode to assemble the coin cell (2025-type) in an argon-filled glovebox (Mikrouna, H2O, O2
