Solution growth of NiO nanosheets supported on Ni foam as high-performance electrodes for supercapacitors
- Hailong Yan†1, 2,
- Deyang Zhang†1, 2,
- Jinyou Xu1, 2,
- Yang Lu1, 2,
- Yunxin Liu3,
- Kangwen Qiu†1, 2,
- Yihe Zhang4 and
- Yongsong Luo1, 2Email author
© Yan et al.; licensee Springer. 2014
Received: 20 June 2014
Accepted: 9 August 2014
Published: 22 August 2014
Well-aligned nickel oxide (NiO) nanosheets with the thickness of a few nanometers supported on a flexible substrate (Ni foam) have been fabricated by a hydrothermal approach together with a post-annealing treatment. The three-dimensional NiO nanosheets were further used as electrode materials to fabricate supercapacitors, with high specific capacitance of 943.5, 791.2, 613.5, 480, and 457.5 F g-1 at current densities of 5, 10, 15, 20, and 25 A g-1, respectively. The NiO nanosheets combined well with the substrate. When the electrode material was bended, it can still retain 91.1% of the initial capacitance after 1,200 charging/discharging cycles. Compared with Co3O4 and NiO nanostructures, the specific capacitance of NiO nanosheets is much better. These characteristics suggest that NiO nanosheet electrodes are promising for energy storage application with high power demands.
Supercapacitors, also called electrochemical capacitors, are the most promising energy storage and power output technologies for digital communication devices, hybrid electric vehicles, and other high-power energy sources, which are attributed to the advantages of high power density, short charging time, high cycle efficiency, and long cycle life [1–6]. However, due to the low energy density of current supercapacitor products, nowadays, developing novel electrode materials with enhanced energy density, while maintaining a high power density, good specific capacitance, and cycling stability for supercapacitors, has become a primary research focus. Unfortunately, the practical applications of supercapacitors are largely hindered due to the lack of high-performance electrode materials at a reasonable cost [7–9]. Carbon-based materials and many transition metal oxides have been widely investigated as electrode materials for supercapacitors with notable improvements achieved [10–13]. However, the relatively low specific and volumetric capacitances of carbon-based materials and extremely high cost of the state-of-art RuO2 materials have seriously limited their practical application in supercapacitors. The development of nanomaterials, especially metal oxides, will undoubtedly provide a promising solution to enhance the capacitive performance because of their high surface area, and ion transport pathways. Several promising materials, including nickel oxide, cobalt oxide, and manganese oxide, have been intensively studied as advanced electrode materials for supercapacitors [14–16]. Nickel oxide (NiO) has been intensively studied as supercapacitors for its high theoretical specific capacitance of 2,584 F g-1[17, 18]. In other words, lightweight and flexibility have become one of the most important development trends of portable electronics in these years [19, 20]. Whether flexible portable electronics become popular depends on the improvements of the technology, especially by developing the flexible high-performance energy storage devices.
A facile solution method is developed to grow NiO nanonsheets directly on Ni foam, which possess an enhanced electrochemical performance for supercapacitors. Our optimized supercapacitor shows a specific capacitance of 943.5 F g-1 at a current density of 5 A g-1. It is found that the specific capacitance of NiO nanonsheets is higher than those of Co3O4 and NiO nanostructures fabricated by the same method. It can be concluded that vertical NiO nanosheets would be particularly suited to the high-performance electrodes for supercapacitors.
Synthesis of NiO nanosheets on Ni foam
The morphology of the synthesized product was examined using field emission scanning electron microscopy (S4800, Hitachi, Chiyoda-ku, Japan). The chemical composition of the product was characterized by X-ray diffraction (XRD; D8 Advance X-ray Diffractometer, Cu Kα, λ = 1.5406 Å, Bruker, Saarbrucken Germany). Raman spectra were recorded on an INVIA Raman microprobe (Renishaw Instruments, Wotton-under-Edge, England) with a 532-nm laser excitation. The thermogravimetric analysis (TGA) curve was performed using a SDT Q600 TA with 100 ml min-1 of air flow from 20°C to 600°C at a heating rate of 10°C min-1.
The capacitive performance of the samples was tested on a CHI 660E electrochemical workstation (CH Instruments, Chenhua, Shanghai, YP, China) with cyclic voltammetry and chronopotentiometry functions using a three-electrode cell where Pt foil serves as the counter electrode and a saturated calomel electrode (SCE) as the reference electrode. The mass loading of unit area on the Ni foam can be calculated to be 1.78 mg cm-2. The electrolyte used was a 3 M KOH aqueous solution.
Results and discussion
where C m (F g-1) is the specific capacitance, I (A) is the discharge current, Δt (s) is the charging/discharging time, ΔV (V) is the voltage window for discharge, and m (g) is the mass of the active NiO material in the electrode. Thus, the specific capacitance can be calculated to be 943.5, 791.2, 613.5, 480, and 457.5 F g-1 at the scan rates of 5, 10, 15, 20, and 25 A g-1, respectively (Figure 6d). The specific capacitance of NiO nanosheets is much higher than that of NiO nanobelts, nanorods, and nanosheets reported previously [22–26]. To evaluate the important role of NiO nanosheets for high-performance electrodes, the specific capacitances of Co3O4 nanoneedles and NiO powders are also tested at the scan rates of 5, 10, 15, 20, and 25 A g-1, respectively. The specific capacitances of NiO nanosheets win out over those of Co3O4 nanoneedles and NiO powders (Additional file 1: Figure S2).
The improved electrochemical performance could be related to the following structural features. Firstly, the aligned NiO nanosheets with a high surface area facilitate ion diffusion from the electrolyte to each nanosheets, making full use of the active materials . Secondly, the vertical NiO nanosheets could ensure good mechanical adhesion, and more importantly, vertical nanosheets can build up a shortcut and high-speed bridge between the current collector and active materials (Additional file 1: Figure S3). Thirdly, Ni foam as the platform for sustaining nanosheets can withstand strain relaxation and mechanical deformation, preventing the electrode materials from seriously swelling and shrinking during the insertion-deinsertion process.
Well-aligned NiO nanosheets are fabricated by a hydrothermal approach, and it is used as binder-free electrodes for supercapacitors. The ultrathin NiO nanosheets supported on the nickel foam is able to deliver areal capacitances of 1.98 and 1.68 F cm-2 at current densities of 11.8 and 23.5 mA cm-2, respectively. The vertical NiO nanosheets on the substrate can withstand strain relaxation and mechanical deformation. When the electrode material is bent, it can still retain 91.1% of the initial capacitance after 1,200 charging/discharging cycles. The specific capacitance of NiO nanosheets is much higher than those of Co3O4 and NiO nanostructures. Such highly integrated binder- and additive-free electrodes made by electroactive NiO nanosheets might hold some potential for the fabrication of high-performance flexible energy storage devices.
This work was financially supported by the National Natural Science Foundation of China (Nos. U1304108, U1204501, and 11272274), the Science and Technology Key Projects of Education Department Henan Province (No. 13A430758), the Natural Scientific Foundation of Hunan Province (No. 13JJ4080), the Young Backbone Teacher of Xinyang Normal University (No. 2013GGJS-18), and the Innovative Research Team (in Science and Technology) in the University of Henan Province (No. 13IRTSTHN018).
- Wang H, Liang YY, Chen Z, Mirfakhrai T, Casalongue HS, Dai HJ: Advanced asymmetrical supercapacitors based on graphene hybrid materials. Nano Res 2011, 4: 729–736. 10.1007/s12274-011-0129-6View ArticleGoogle Scholar
- Fan ZJ, Yan J, Wei T, Zhi LJ, Ning GQ: Asymmetric supercapacitors based on graphene/MnO2 and activated carbon nanofiber electrodes with high power and energy density. Adv Funct Mater 2011, 21: 2366–2375. 10.1002/adfm.201100058View ArticleGoogle Scholar
- Yuan CZ, Yang L, Shen LF, Zhang XG, Lou XW: Single-crystalline NiCo2O4 nanoneedle arrays grown on conductive substrates as binder-free electrodes for high-performance supercapacitors. Energy Environ Sci 2012, 5: 7883–7886. 10.1039/c2ee21745gView ArticleGoogle Scholar
- Si WJ, Wu XZ, Zhou J, Guo FF, Zhuo SP, Cui HY, Xing W: Reduced graphene oxide aerogel with high-rate supercapacitive performance in aqueous electrolytes. Nanoscale Res Lett 2013, 8: 247–254. 10.1186/1556-276X-8-247View ArticleGoogle Scholar
- Hercule KM, Wei QL, Khan AM, Zhao YL, Tian XC, Mai LQ: Synergistic effect of hierarchical nanostructured MoO2/Co(OH)2 with largely enhanced pseudocapacitor cyclability. Nano Lett 2013, 13: 5685–5691. 10.1021/nl403372nView ArticleGoogle Scholar
- Mai LQ, Li H, Zhao YL, Xu L, Xu X, Luo YZ, Zhang ZF, Ke W, Niu CJ, Zhang QJ: Fast ionic diffusion-enabled nanoflake electrode by spontaneous electrochemical pre-intercalation for high-performance supercapacitor. Sci Rep 2013, 3: 1718/1–7.View ArticleGoogle Scholar
- Chmiola J, Largeot C, Taberna PL, Simon P, Gogotsi Y: Monolithic carbide-derived carbon films for micro-supercapacitors. Science 2010, 328: 480–483. 10.1126/science.1184126View ArticleGoogle Scholar
- Li ZJ, Zhou ZH, Yun GQ, Shi K, Lv XW, Yang BC: High-performance solid-state supercapacitors based on graphene-ZnO hybrid nanocomposites. Nanoscale Res Lett 2013, 8: 473–480. 10.1186/1556-276X-8-473View ArticleGoogle Scholar
- Wang DW, Li F, Liu M, Lu GQ, Cheng HM: Hierarchical porous graphitic carbon material for high-rate electrochemical capacitive energy storage. Angew Chem 2008, 47: 373–376. 10.1002/anie.200702721View ArticleGoogle Scholar
- Simon P, Gogotsi Y: Materials for electrochemical capacitors. Nat Mater 2008, 7: 845–854. 10.1038/nmat2297View ArticleGoogle Scholar
- Wen ZH, Ci SQ, Mao S, Cui SM, He Z, Chen J: CNT@TiO2 nanohybrids for high-performance anode of lithium-ion batteries. Nanoscale Res Lett 2013, 8: 499–506. 10.1186/1556-276X-8-499View ArticleGoogle Scholar
- Xu KB, Zou RJ, Li WY, Xue YF, Song GS, Liu Q, Liu XJ, Hu JQ: Self-assembling hybrid NiO/Co3O4 ultrathin and mesoporous nanosheets into flower-like architectures for pseudocapacitance. J Mater Chem A 2013, 1: 9107–9113. 10.1039/c3ta11099kView ArticleGoogle Scholar
- Najafabadi AI, Yasuda S, Kobashi K, Yamada T, Futaba DN, Hatori H, Yumura M, Iijima S, Hata K: Extracting the full potential of single-walled carbon nanotubes as durable supercapacitor electrodes operable at 4 V with high power and energy density. Adv Mater 2010, 22: E235-E241. 10.1002/adma.200904349View ArticleGoogle Scholar
- Lu XH, Zhai T, Yuan L, Hu B, Wang ZL: WO3-x@Au@MnO2 core–shell nanowires on carbon fabric for high-performance flexible supercapacitors. Adv Mater 2012, 24: 938–944. 10.1002/adma.201104113View ArticleGoogle Scholar
- Chen LY, Kang JL, Hou Y, Liu P, Hirata A, Chen MW: High-energy-density nonaqueous MnO2@nanoporous gold based supercapacitors. J Mater Chem A 2013, 1: 9202–9207. 10.1039/c3ta11480eView ArticleGoogle Scholar
- Zhong JH, Wang AL, Li GR, Wang JW, Ou YN, Tong YX: Co3O4/Ni(OH)2 composite mesoporous nanosheet networks as a promising electrode for supercapacitor applications. J Mater Chem 2012, 22: 5656–5665. 10.1039/c2jm15863aView ArticleGoogle Scholar
- Ding SJ, Zhu T, Chen JS, Wang ZY, Yuan CL, Lou XW: Controlled synthesis of hierarchical NiO nanosheet hollow spheres with enhanced supercapacitive performance. J Mater Chem 2011, 21: 6602–6606. 10.1039/c1jm00017aView ArticleGoogle Scholar
- Wang HL, Casalongue HS, Liang Y, Dai HJ: Ni(OH)2 nanoplates grown on graphene as advanced electrochemical pseudocapacitor materials. J Am Chem Soc 2010, 132: 7472–7477. 10.1021/ja102267jView ArticleGoogle Scholar
- Tang P, Han L, Zhang L: Facile synthesis of graphite/PEDOT/MnO2 composites on commercial supercapacitor separator membranes as flexible and high-performance pupercapacitor electrodes. ACS Appl Mater Interfaces 2014, 6: 10506–10515. 10.1021/am5021028View ArticleGoogle Scholar
- Luo YS, Luo JS, Jiang J, Zhou WW, Yang HP, Qi XY, Zhang H, Fan HJ, Yu YW, Li CM, Yu T: Seed-assisted synthesis of highly ordered TiO2@α-Fe2O3 core/shell arrays on carbon textiles for lithium-ion battery applications. Energy Environ Sci 2012, 5: 6559–6566. 10.1039/c2ee03396hView ArticleGoogle Scholar
- Yan J, Fan ZJ, Sun W, Ning GQ, Wei T, Zhang Q, Zhang RF, Zhi LJ, Wei F: Advanced asymmetric supercapacitors based on Ni(OH)2/graphene and porous graphene electrodes with high energy density. Adv Funct Mater 2012, 22: 2632–2641. 10.1002/adfm.201102839View ArticleGoogle Scholar
- Zhu JH, Jiang J, Liu JP, Ding RM, Ding H, Feng YM, Wei GM, Huang XT: Direct synthesis of porous NiO nanowall arrays on conductive substrates for supercapacitor application. J Solid State Chem 2011, 3: 571–578.Google Scholar
- Wang B, Chen JS, Wang ZY, Madhavi S, Lou XW: Green synthesis of NiO nanobelts with exceptional pseudo-capacitive properties. Adv Energy Mater 2012, 2: 1188–1192. 10.1002/aenm.201200008View ArticleGoogle Scholar
- Yan XY, Tong XL, Wang J, Gong CW, Zhang MG, Liang LP: Synthesis of mesoporous NiO nanoflake array and its enhanced electrochemical supercapacitor performance for application. J All Comp 2014, 593: 184–189.View ArticleGoogle Scholar
- Gao ZH, Zhang H, Cao GP, Han MF, Yang YS: Spherical porous VN and NiO as electrode materials for asymmetric supercapacitor. Electrochem Acta 2013, 87: 375–380.View ArticleGoogle Scholar
- Han DD, Jing XY, Wang J, Yang PP, Song DL, Liu JY: Porous lanthanum doped NiO microspheres for supercapacitor application. J Electroanal Chem 2012, 682: 37–44.View ArticleGoogle Scholar
- Yang J, Lian LF, Ruan HC, Xie FY, Wei MD: Nanostructured porous MnO2 on Ni foam substrate with a high mass loading via a CV electrodeposition route for supercapacitor application. Electrochim Acta 2014, 136: 189–194.View ArticleGoogle Scholar
- Gao ZH, Zhang H, Cao GP, Han MF, Yang YS: Spherical porous VN and NiO x as electrode materials for asymmetric. Electrochim Acta 2013, 87: 375–380.View ArticleGoogle Scholar
- Yang ZH, Xu FF, Zhang WX, Mei ZS, Pei B, Zhu X: Controllable preparation of multishelled NiO hollow nanospheres via layer-by-layer self-assembly for supercapacitor application. J Power Sources 2014, 246: 24–31.View ArticleGoogle Scholar
- Zhou C, Zhang YW, Li YY, Liu JP: Construction of high-capacitance 3D CoO@polypyrrole nanowire array electrode for aqueous asymmetric supercapacitor. Nano Lett 2013, 13: 2078–2085. 10.1021/nl400378jView ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited.