Aligned nickel-cobalt hydroxide nanorod arrays for electrochemical pseudocapacitor applications

Salunkhe, Rahul R.; Jang, Kihun; Lee, Sung-Won; Ahn, Heejoon

doi:10.1039/c2ra01220k

Cited by 130 publications

(93 citation statements)

References 36 publications

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“…Energy storage has been revolutionized after the introduction of electrochemical capacitors or supercapacitors. Owing to their high power density, long cycle life, short charging time, good safety, and so forth [1][2][3][4][5]. They possess higher energy density compared to conventional capacitors and high power density than batteries.…”

Section: Introductionmentioning

confidence: 99%

Cobalt oxide (Co3O4)/graphene nanosheets (GNS) composite prepared by novel route for supercapacitor application

Naveen

Manimaran

Selvasekarapandian

2015

J Mater Sci: Mater Electron

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Cobalt oxide (Co 3 O 4 )-graphene nanosheets (GNS) composite was prepared using a novel route. Room temperature prepared graphite oxide was exfoliated at low temperature and subsequently reduced to GNS by chemical method. Successful compound formation was confirmed and structural details were obtained from XRD studies. Cobalt oxide was found to crystallize in spinel fcc structure with average crystallite size of 9 nm in the composite. FTIR and XPS study confirms the removal of oxygen containing functional group in reduced graphene and spinel formation of cobalt oxide in the composite. Raman spectra depict the reestablishment of sp 2 conjugated network of carbon atoms, on reduction to graphene. FESEM images reveal the nanosheet like morphology of the graphene being retained in the composite and promoting ion diffusion channels. Electrochemical characterization discloses the pseudocapacitive behaviour of the composite material. Higher specific capacitance of 650 F/g was exhibited by GNS-Co 3 O 4 at 5 mV/s scan rate. Symmetrical supercapacitor fabricated using GNS-Co 3 O 4 demonstrated superior power characteristics. Graphene in the composite has substantially increased the electron and ion transport in the electrode material leading to enhanced performance.

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Section: Introductionmentioning

confidence: 99%

Cobalt oxide (Co3O4)/graphene nanosheets (GNS) composite prepared by novel route for supercapacitor application

Naveen

Manimaran

Selvasekarapandian

2015

J Mater Sci: Mater Electron

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“…[15][16][17][18] Almost all efforts in this fi eld have been directed towards crystalline mixed-metal hydroxide materials because these compounds have superior electrochemical performance with high specifi c capacitance, excellent rate capability, high energy density, and high power density. [4][5][6][7][8][9][10]19,20 ] However, supercapacitors made from crystalline compounds usually exhibit a very poor or short cycle life, [4][5][6][7][8][9][10] which makes their practical use limited. Typically, the cycling stability of a Ni(OH) 2 -Co(OH) 2 -graphene asymmetric supercapacitor shows a 70% retention after 1000 cycles.…”

mentioning

confidence: 99%

A Simple Electrochemical Route to Access Amorphous Mixed‐Metal Hydroxides for Supercapacitor Electrode Materials

Gao

Wang

et al. 2014

Advanced Energy Materials

194

130

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mixed-metal hydroxide compounds such as Ni-Al, [ 3 ] Co-Ni, [4][5][6][7][8][9][10] Mn-Co, [ 11 ] Co-Ru, [ 12 ] Ni-Co-Cu, [ 13 ] and Ni-Co-Zn [ 14 ] have advantages over single-composition compounds as positive electrode materials for supercapacitors because mixed-metal compounds greatly promote the integrated electrochemical performance. [15][16][17][18] Almost all efforts in this fi eld have been directed towards crystalline mixed-metal hydroxide materials because these compounds have superior electrochemical performance with high specifi c capacitance, excellent rate capability, high energy density, and high power density. [4][5][6][7][8][9][10]19,20 ] However, supercapacitors made from crystalline compounds usually exhibit a very poor or short cycle life, [4][5][6][7][8][9][10] which makes their practical use limited. Typically, the cycling stability of a Ni(OH) 2 -Co(OH) 2 -graphene asymmetric supercapacitor shows a 70% retention after 1000 cycles. [ 8 ] Therefore, increasing the cycle life of mixed-metal hydroxide materials is a signifi cant challenge in supercapacitor applications.Although most positive electrode materials are based on crystalline mixed-metal hydroxides high activities can also be achieved with amorphous phases. It has been shown that the integrated electrochemical performance of amorphous metal hydroxides, such as Ni(OH) 2 and Co(OH) 2 , is commensurate with the crystallinity of the materials in the supercapacitor. [ 21,22 ] Considering the excellent electrochemical performance of crystalline mixed-metal hydroxide electrodes several benefi ts should be realizable by the development of amorphous mixed-metal hydroxide electrodes. However, commonly used methods for the production of amorphous oxide materials are not typically amenable to amorphous mixed-metal hydroxides. [ 18 ] We thus present a simple, facile, and chemically clean electrochemical method (experimental details in the Experimental Section and in Supporting Information S1) to prepare amorphous phases of mixed-metal hydroxides. They exhibited excellent performances as positive supercapacitor electrodes and a fabricated device showed a long-term cycling stability characterized by 94% retention after 20 000 cycles. This proof-of-principle investigation using amorphous mixed-metal hydroxides (amorphous Ni-Co-Fe hydroxide) demonstrates the broad applicability Supercapacitors or electrochemical capacitors, as energy storage devices, require very stable positive electrode materials for useful applications. Although most positive electrodes are based on crystalline mixed-metal hydroxides, their pseudocapacitors usually perform poorly or have a short cycle life. High activities can be achieved with amorphous phases. Methods to produce amorphous materials are also not typically amenable towards mixed-metal compositions. It is demonstrated that electrochemistry in an ambient environment can be used to produce a series of amorphous mixedmetal hydroxides with a homogeneous distribution of metals for use as positive electrode materials in a s...

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“…For example, either by precipitation and ''chimie douce'' method [9,22], at least 20% cobalt is needed for a stable Co-substituted Ni(OH) 2 [23]; the electrochemical cycling of Co-substituted Ni(OH) 2 allows up to 1.3 electrons per (Ni + Co) atom to be reversibly exchanged at the beginning, however, a slow evolution from the c/a-couple to the b (III)/b (II) couple occurs during long-range cycling, which is assigned to a partly reduction of Co 3+ into Co 2+ at the end of the discharge process [22]. As supercapacitor materials, Co 0.54 Ni 0.43 LDH has a specific capacitance of 2614 F g À1 by a polyvinyl pyrrolidone-assisted chemical co-precipitation method [24]; Co 0.72 Ni 0.28 LDH has a capacitance of 2104 F g À1 by electrochemical deposition [25]; aligned nickel-cobalt hydroxide nanorod arrays have a specific capacitance of 456 F g À1 with an energy density of 12.8 W h kg À1 [26].…”

Section: Introductionmentioning

confidence: 99%

The effect of cobalt on the electrochemical performances of Ni–Al layered double hydroxides used in Ni–M(H) battery

Hu¹,

Ji²,

Lei³

et al. 2013

Journal of Alloys and Compounds

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Aligned nickel-cobalt hydroxide nanorod arrays for electrochemical pseudocapacitor applications

Cited by 130 publications

References 36 publications

Cobalt oxide (Co3O4)/graphene nanosheets (GNS) composite prepared by novel route for supercapacitor application

Cobalt oxide (Co3O4)/graphene nanosheets (GNS) composite prepared by novel route for supercapacitor application

A Simple Electrochemical Route to Access Amorphous Mixed‐Metal Hydroxides for Supercapacitor Electrode Materials

The effect of cobalt on the electrochemical performances of Ni–Al layered double hydroxides used in Ni–M(H) battery

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