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Hierarchically nanostructured transition metal oxides for supercapacitors

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  • ReceivedJul 7, 2017
  • AcceptedAug 10, 2017
  • PublishedOct 17, 2017

Abstract

Highly efficient, clean, and sustainable electrochemical energy storage technologies have been investigated extensively to counter the shortage of fossil fuels and increasingly prominent environmental problems. Supercapacitors (SCs) have received wide attention as critical devices for electrochemical energy storage because of their rapid charging–discharging capability and long life cycle. Various transition metal oxides (TMOs), such as MnO2, NiO, Co3O4, and CuO, have been extensively studied as electrode materials for SCs. Compared with carbon and conducting polymers, TMO materials can achieve higher specific capacitance. For further improvement of electrochemical performance, hierarchically nanostructured TMO materials have become a hot research area for electrode materials in SCs. The hierarchical nanostructure can not only offer abundant accessible electroactive sites for redox reactions but also shorten the ion diffusion pathway. In this review, we provide an overall summary and evaluation of the recent progress of hierarchically nanostructured TMOs for SCs, including synthesis methods, compositions, structures, and electrochemical performances. Both single-phase TMOs and the composites based on TMOs are summarized. Furthermore, we also prospect the developing foreground of this field. In this view, the important directions mainly include: the nanocomposites of TMOs materials with conductive materials; the cobalt-based materials and the nickel-based materials; the improvement of the volume energy density, the asymmetric SCs, and the flexible all-solid-state SCs.


Funded by

the National Natural Science Foundation of China(51202106,21671170,21673203)

New Century Excellent Talents of the University in China(NCET-13-0645)

the Innovation Scientists and Technicians Troop Construction Projects of Henan Province(164200510018)

the Plan for the Scientific Innovation Talent of Henan Province

the Program for Innovative Research Team(in,Science,Technology)

the Science & Technology Foundation of Henan Province(122102210253,13A150019)

the Science & Technology Foundation of Jiangsu Province(BK20150438)

the Six Talent Plan(2015-XCL-030)

and China Postdoctoral Science Foundation(2012M521115)


Acknowledgment

This work was supported by the National Natural Science Foundation of China (51202106, 21671170 and 21673203) and New Century Excellent Talents of the University in China (NCET-13-0645), the Innovation Scientists and Technicians Troop Construction Projects of Henan Province (164200510018), the Plan for Scientific Innovation Talent of Henan Province, the Program for Innovative Research Team (in Science and Technology) in the University of Henan Province (14IRTSTHN004 and 16IRTSTHN003), the Science & Technology Foundation of Henan Province (122102210253 and 13A150019), the Science & Technology Foundation of Jiangsu Province (BK20150438), the Six Talent Plan (2015-XCL-030), and China Postdoctoral Science Foundation (2012M521115). We also acknowledge the Priority Academic Program Development of Jiangsu Higher Education Institutions and the technical support we received at the Testing Center of Yangzhou University.


Interest statement

The authors declare that they have no conflict of interest.


Contributions statement

Zheng M, Xiao X and Li L organized the literatures and wrote the manuscript. Gu P participated in writing and revising the manuscript. Dai X, Tang H, Hu Q, and Xue H revised the manuscript. Pang H provided the overall concept and revised the manuscript. All authors participated in the general discussion.


Author information

Mingbo Zheng received his PhD in material processing engineering from Nanjing University of Aeronautics and Astronautics in 2009. He was a postdoctoral researcher at Nanjing University from 2009 to 2012. He was an associate researcher at Nanjing University from 2012 to 2015. He is currently an associate professor at Yanzhou University. His research interests are in the field of materials for electrochemical energy storge, including supercapacitor, lithium-ion battery, and lithium-sulfur battery.


Huan Pang received his PhD degree from Nanjing University in 2011. He then founded his research group in Anyang Normal University where he was appointed as a distinguished professor in 2013. He has now jointed Yangzhou University as a University Distinguished Professor. His research interests include the development of inorganic nanostructures and their applications in flexible electronics with a focus on energy devices.


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  • Figure 1

    Schematic of the two different mechanisms of SCs: (a) EDLCs and (b) pseudocapacitors.

  • Figure 2

    (a) SEM and (b), (c) TEM images of the LT-MnO2. Electrochemical properties of the three samples; (d) galvanostatic charge–discharge curves at 0.5 A g−1; (e) specific capacitances at various current densities; (f) Ragone plots. Reproduced with permission from Ref. [79]. Copyright 2012, the Royal Society of Chemistry.

  • Figure 3

    (a) Schematic of the preparation of Co(OH)2 and Co3O4. TEM images for (b) Cu2O template, (c) Co(OH)2, and (d) Co3O4. (e) Charge–discharge curves of the HFC-250 electrode. (f) Plots of the specific capacitance of Co(OH)2, HFC-250, HFC-300, HFC-400, and Co3O4-com. (g) Rate capability of the HFC-250 electrode when the current density was progressively varied. Reproduced with permission from Ref. [93]. Copyright 2015, the American Chemical Society.

  • Figure 4

    (a) Schematic of the preparation of hierarchical NiO nanotube arrays on Ni foam. (b) SEM image of NiO nanotube arrays on Ni foam. (c) TEM image of NiO nanotube. (d) Schematic of the preparation of NiO–HMNAs on Cu foam. (e) and (f) SEM images of NiO–HMNAs. (g) Discharge curves of NiO nanotube arrays on Ni foam. (h) Cycling performance of the hybrid SC device based on NiO–HMNAs. Reproduced with permission from Ref. [101]. Copyright 2014, Elsevier. (d–f, h) Reproduced with permission from Ref. [103]. Copyright 2016, Elsevier.

  • Figure 5

    (a) Schematic of the preparation of CNRNP electrode; SEM images of (b) CNRNP, (c) CNFNF, and (d) FLC; (e) CV curves of all samples at 10 mV s−1; (f) specific capacitance of all samples at different scan rates; (g) charge-discharge curves of CNRNP. Reproduced with permission from Ref.[106]. Copyright 2014, the Royal Society of Chemistry.

  • Figure 6

    (a) Schematic of the preparation of NiCo2O4 MHSs; (b and c) FESEM images of the NiCo2O4 MHSs (NCO2) on Ni foam; (d) specific capacitance obtained from the discharge curves; (e) SEM image and (f) TEM image of the hierarchical NiCoO2 nanosheets; (g) cycling performance of NiCoO2 at 10 A g−1. (a, d) Reproduced with permission from Ref. [125]. Copyright 2014, the American chemical Society. (e–g) Reproduced with permission from Ref. [126]. Copyright 2014, Elsevier.

  • Figure 7

    (a and b) SEM images of ZnV2O4 NHNs; (c) crystal structure of spinel ZnV2O4 with corresponding atoms; (d) capacitance as a function of current density. Reproduced with permission from Ref. [127]. Copyright 2014, the American Chemical Society.

  • Figure 8

    (a) Schematic of the preparation of 3D CoO@MnO2 nanohybrid; (b) TEM image of the 3D CoO@MnO2; (c) charge–discharge curves of the CoO@MnO2; (d) cycle stabilities of the 3D CoO@MnO2 core–shell nanohybrid and CoO NWs at 5 A g−1. Reproduced with permission from Ref. [136]. Copyright 2017, the Royal Society of Chemistry.

  • Figure 9

    (a) SEM and (b) TEM images of the Fe3O4–MnO2 sample; (c) capacitance retention at 5 A g−1 over 5,000 cycles; (d, e) SEM images of the Co3O4 NAs (the inset shows TEM image of the Co3O4 NAs); (f, g) SEM and TEM images of Co3O4@MnO2 NAs. (h) Charge–discharge curves of the Co3O4@MnO2 composite. (i) Current density dependence of the specific capacitance of the MnO2 nanosheets, Co3O4 NAs and Co3O4@MnO2 NAs. (j, k) SEM and TEM images of Cu0.27Co2.73O4/MnO2; (l) the specific capacitances of the three electrodes as a function of current density. (a–c) Reproduced with permission from Ref. [137]. Copyright 2014, the American Chemical Society. (d–i) Reproduced with permission from Ref. [138]. Copyright 2014, Wiley-VCH. (j–l) Reproduced with permission from Ref. [139]. Copyright 2015, the Royal Society of Chemistry.

  • Figure 10

    (a) Schematic illustration for the fabrication of hierarchical ZnO@Au@NiO nanocomposite; (b) SEM images of ZnO@Au@NiO; (c) CV curves of two samples; (d) discharge curves of two samples; (e and f) energy level diagrams at the interface of ZnO–Au–NiO during charge–discharge process. Reproduced with permission from Ref. [151]. Copyright 2015, the American Chemical Society.

  • Figure 11

    (a) SEM and (b) TEM images of ZnO NR@NiO/MoO2 CNSAs; (c) the areal specific capacitances of the two electrodes as a function of current density; (d) SEM image of MnMoO4/CoMoO4 heterostructured nanowires; (e) TEM image at the heterojunction of the hierarchical MnMoO4/CoMoO4 heterostructured nanowires; (f) cycling performance of MnMoO4/CoMoO4 (3D) electrodes tested at 3 and 20 A g−1 (the inset shows charge–discharge curves cycled at the first and last five cycles at 3 A g−1). (a–c) Reproduced with permission from Ref. [176]. Copyright 2014, the American Chemical Society. (d–f) Reproduced with permission from Ref. [177]. Copyright 2011, Nature Publishing Group.

  • Figure 12

    (a) Schematic image for the design of hierarchical core-shell Co3O4@Ni–Co–O nanoarray (the Co3O4 nanosheet is shown in pink and the Ni–Co–O nanorod is shown in green); (b, c) SEM and TEM images of the hierarchical Co3O4@Ni–Co–O arrays; (d) galvanostatic discharge curves of the hierarchical Co3O4@Ni–Co–O arrays at various current densities; (e) schematic image for the design of hierarchical core-shell Co3O4@NiO arrays (in this work, three samples were fabricated by adding 1, 2, and 3 mmol Ni(NO3)2·6H2O during the synthesis process. These three samples were denoted as NWRAs-1, NWRAs-2, and NWRAs-3, respectively. Co3O4 nanowire arrays sample was denoted as NWAs); (f, g) SEM images of NWRAs-3 at different magnifications; (h, i) TEM and EDS mapping images of NWRAs-3; (j) galvanostatic charge and discharge curves at 10 mA cm−2; (k) plots of areal specific capacitance versus current density. (a–d) Reproduced with permission from Ref. [180]. Copyright 2012, Springer. (e–k) Reproduced with permission from Ref. [181]. Copyright 2014, Elsevier.

  • Table 1   Comparison of typical hierarchically nanostructured TMOs as electrodes of SCs in three-electrode systems

    Materials

    SSAa

    (m2  g−1)

    Electrolyte

    Capacitance/

    current density

    Retention (%)/cycles/current density

    Ref.

    Flower-like α-MnO2

    216

    1 mol L−1 K2SO4

    298 F g−1 /0.117 A g−1

    90/2000/2 A g−1

    [76]

    α-MnO2 microspheres

    /

    1 mol L−1 Na2SO4

    365 F g−1 /2 A g−1

    100/2000/2 A g−1

    [77]

    β-MnO2 nanoflowers

    267

    1 mol L−1 Na2SO4

    296.3 F g−1 /2 mV s−1

    /

    [78]

    MnO2 NFsb

    269

    1 mol L−1 Na2SO4

    176 F g−1 /20 A g−1

    100/2000/2 A g−1

    [79]

    δ-MnO2 microspheres

    238

    1 mol L−1 Na2SO4

    364 F g−1 /1 A g−1

    100/6000/10 A g−1

    [80]

    Co3O4 film

    /

    2 mol L−1 KOH

    352 F g−1 /2 A g−1

    /

    [91]

    Enoki mushroom-like Co3O4

    /

    6 mol L−1 KOH

    787 F g−1 /1 A g−1

    94.5/1000/10 A g−1

    [92]

    HFC Co3O4c

    245.5

    2 mol L−1 KOH

    948.9 F g−1 /1 A g−1

    /

    [93]

    NiO NWsd

    /

    6 mol L−1 KOH

    1493 F g−1 /3 A g−1

    87/2000/50 mV s−1

    [100]

    NiO NTAse

    165

    1 mol L−1 Na2SO4

    675 F g−1 /2 A g−1

    93.2/10000/2 A g−1

    [101]

    D–NiOf

    92.99

    2 mol L−1 KOH

    612.5 F g−1 /0.5 A g−1

    90/1000/0.5 A g−1

    [102]

    NiO–HMNAsg

    312.6

    2 mol L−1 KOH

    3114 F g−1 /5 mA cm−2

    87.6/4000/30 mA cm−2

    [103]

    CNRNPh

    /

    3 mol L−1 KOH

    800 F g−1 /200 mV s−1

    /

    [106]

    Flower-like CuO

    /

    5 mol L−1NaOH

    1641 mF cm−2 /2 mA cm−2

    79/10000/4 mA cm−2

    [107]

    Flower-shaped CuO

    119.6

    1 mol L−1 KOH

    520 F g−1 /1 A g−1

    95.2/5000/1 A g−1

    [108]

    Bi2O3 NBsi

    196

    1 mol L−1 Na2SO4

    250 F g−1 /100 mV s−1

    100/1000/100 mV s−1

    [113]

    Rod-like Bi2O3

    /

    6 mol L−1 KOH

    1350 F g−1 /0.1 A g−1

    97.6/1000/0.1 A g−1

    [114]

    NiCo2O4 microspheres

    148.5

    6 mol L−1 KOH

    1006 F g−1 /1 A g−1

    93.2/1000/8 A g−1

    [124]

    NiCo2O4 MHSsj

    118.3

    3 mol L−1 KOH

    2623 F g−1 /1 A g−1

    99.2/3000/10 A g−1

    [125]

    NiCoO2 NTsk

    98.9

    2 mol L−1 KOH

    1468 F g−1 /2 A g−1

    99.2/3000/10 A g−1

    [126]

    ZnV2O4 NHNsl

    /

    2 mol L−1 KOH

    385 F g−1 /0.5 A g−1

    89/1000/1 A g−1

    [127]

    CoO@MnO2 core-shell

    154.95

    6 mol L−1 KOH

    1835 F g−1 /1 A g−1

    97.7/10000/1 A g−1

    [136]

    Fe3O4–MnO2 microspheres

    /

    1 mol L−1 Na2SO4

    367.4 F g−1 /100 mV s−1

    76/5000/5 A g−1

    [137]

    Co3O4@MnO2 NAsm

    /

    1 mol L−1 LiOH

    1905.4 F g−1 /0.5 A g−1

    89.8/5000/2 A g−1

    [138]

    Cu0.27Co2.73O4/MnO2 NRAsn

    /

    6 mol L−1 KOH

    3.1 F cm−2 /24.8 mA cm−2

    /

    [139]

    NiCo2O4@MnO2 core-shell

    75.06

    1 mol L−1 NaOH

    1595.1 F g−1 /3 mA cm−2

    92.6/2000/40 mA cm−2

    [140]

    NiCo2O4@MnO2 nanosheets

    /

    1 mol L−1 KOH

    913.6 F g−1 /0.5 A g−1

    87.1/3000/0.5 A g−1

    [141]

    Dumbbell-like Au-Fe3O4

    /

    1 mol L−1 KOH

    464 F g−1 /1 A g−1

    86.4/1000/10 A g−1

    [146]

    Co3O4@Au@MnO2(NSs)HHso

    /

    1 mol L−1 LiOH

    1532.4 F g−1 /1 A g−1

    115/5000/10 A g−1

    [147]

    ZnO@Au@NiO

    /

    1 mol L−1 KOH

    3.5 F cm−2 /2 mA cm−2

    80.3/4000/30 mA cm−2

    [151]

    MnO2/RGO/CFp

    /

    1 mol L−1 Na2SO4

    13.7 F cm−3 /0.5 mA cm−2

    /

    [170]

    3D Co3O4-nb@CGq

    /

    30 wt.% KOH

    600.19 F g−1 /0.7 A g−1

    95.4/5000/1.1 A g−1

    [172]

    NiFe2O4-CTr

    /

    6 mol L−1 LiCl

    697 F g−1/5 mV s−1

    /

    [174]

    NiCo2O4/NGN/CNTss

    /

    6 mol L−1 KOH

    2292.7 F g−1/5 A g−1

    125/10000/30 A g−1

    [175]

    ZnO NR@NiO/MoO2 CNSAst

    /

    2 mol L−1 KOH

    1.18 F cm−2/5  mA cm−2

    91.7/4000/10 mA cm−2

    [176]

    MnMoO4/CoMoO4 nanowires

    54.06

    2 mol L−1 NaOH

    187.1 F g−1 /1 A g−1

    98/1000/20 A g−1

    [177]

    Co3O4@CoMoO4 core–shell

    61.4

    2 mol L−1 KOH

    1902 F g−1 /1 A g−1

    99/5000/5 A g−1

    [179]

    Co3O4@Ni–Co–O NSRAsu

    31.1

    1 mol L−1 KOH

    2098 F g−1/5 mA cm−2

    96/1000/30 mA cm−2

    [180]

    Co3O4@NiO NWRAsv

    116

    1 mol L−1 KOH

    2033 F g−1/5 mA cm−2

    100/1000/30 mA cm−2

    [181]

    α-Fe2O3 nanotubes

    /

    1 mol L−1 Li2SO4

    300.1 F g−1/0.75 A g−1

    /

    [183]

    SSA: specific surface area. b) MnO2 NFs: MnO2 nanoflakes; c) HFC Co3O4: hollow fluffy cages Co3O4; d) NiO NWs: NiO nanowires; e) NiO NTAs: NiO nanotube arrays;

    D–NiO: double-shelled NiO; g) NiO–HMNAs: hierarchical mesoporous NiO nanoarrays; h) CNRNP: CuO nanoribbon-on-Ni-nanoporous/Ni foam; i) Bi2O3 NBs: Bi2O3 nanobelts; j) NiCo2O4 MHSs: NiCo2O4 multiple hierarchical structures; k) NiCoO2 NTs: NiCoO2 nanotube; l) ZnV2O4 NHNs: ZnV2O4 novel hierarchical nanospheres; m) Co3O4@MnO2 NAs: Co3O4@MnO2 nanoneedle arrays; n) Cu0.27Co2.73O4/MnO2 NRAs: Cu0.27Co2.73O4/MnO2 nanorod arrays; o) Co3O4@Au@MnO2 (NSs) HHs: Co3O4@Au@MnO2 nanosheet hierarchical heterostructures; p) MnO2/RGO/CF: MnO2/reduced graphene oxide/carbon nanofiber; q) Co3O4-nb@CG: Co3O4 nanobeads−CNTs (carbon nanotubes)–GNSs (graphene nanosheets). r) NiFe2O4–CT: NiFe2O4 nanocone forest on carbon textile; s) NiCo2O4/NGN/CNTs: NiCo2O4 nanosheets on nitrogen-doped graphene/carbon nanotubes; t) ZnO NR@NiO/MoO2 CNSAs: ZnO nanorod@NiO/MoO2 composite nanosheet arrays; u) Co3O4@Ni–Co–O NSRAs: Co3O4@Ni–Co–O nanosheet@nanorod arrays; v) Co3O4@NiO NWRAs: Co3O4@NiO nanowire@nanorod arrays.

  • Table 2   Typical hierarchically nanostructured TMOs as cathodes of asymmetric SCs

    Cathode materials

    Anode materials

    Working

    voltage

    Device performancea

    Ref.

    Energy density

    Power density

    δ-MnO2 microspheres

    Activated carbon

    0–2 V

    48.06 W h kg−1

    1.0 kW kg−1

    [80]

    Enoki mushroom-like Co3O4

    Carbon

    0–1.5 V

    23.9 W h kg−1

    0.375 kW kg−1

    [92]

    CoO@MnO2 core-shell

    Nitrogen-doped graphene

    0–1.8 V

    85.9 W h kg−1

    852.4 W kg−1

    [136]

    NiCo2O4@MnO2 nanosheets

    Activated carbon

    0–1.5 V

    37.5 W h kg−1

    187.5 W kg−1

    [141]

    MnO2/RGO/CFb

    GH/CWc

    0–1.6 V

    0.63 mW h cm−3

    0.2 W cm-3

    [170]

    NiCo2O4/NGN/CNTsd

    NGN/CNTse

    0–1.55 V

    42.7 W h kg−1

    775 W kg−1

    [175]

    Co3O4@CoMoO4 core–shell

    CNTsf

    0–1.6 V

    45.2 W h kg−1

    400 W kg−1

    [179]

    Device performance: the energy density of the asymmetric SCs device under a certain power density. b) MnO2/RGO/CF: MnO2/reduced graphene oxide/carbon nanofiber; c) GH/CW: graphene hydrogel-wrapped Cu wire; d) NiCo2O4/NGN/CNTs: NiCo2O4 nanosheets on nitrogen-doped graphene/carbon nanotubes; e) NGN/CNTs: nitrogen-doped graphene/carbon nanotubes; f) CNTs: carbon nanotubes.

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