Elsevier

Electrochimica Acta

Volume 108, 1 October 2013, Pages 506-511
Electrochimica Acta

Porous CoO/C polyhedra as anode material for Li-ion batteries

https://doi.org/10.1016/j.electacta.2013.07.003Get rights and content

Highlights

  • Porous CoO/C polyhedra were synthesized by reducing Co3O4 polyhedra with sugar.

  • The CoO/C polyhedra exhibited an initial discharge capacity of 1025 mAh g−1.

  • Coulombic efficiency over 99% and improved rate capability were achieved for the CoO/C polyhedra.

  • Porous and hierarchical structure was responsible for the improved electrochemical performance.

Abstract

Uniform, hierarchical and porous CoO/C polyhedra were synthesized by impregnating hydrothermally fabricated Co3O4 polyhedra with sugar solution followed by calcination in inert atmosphere. Each CoO/C polyhedron was built up of numerous ordered nanoparticles (around 100 nm). As anode material for Li-ion batteries, the CoO/C polyhedra exhibited an initial discharge capacity of 1025 mAh g−1, and remained a reversible capacity of 510 mAh g−1 after 50 cycles at a current density of 100 mA g−1. High Coulombic efficiency over 99% and improved rate capability were achieved for the CoO/C polyhedra. Hierarchical structure and high porosity was benefit to the infiltration of electrolyte and tolerant volume expansion, and hence was responsible for the good electrochemical performance.

Introduction

Rechargeable lithium-ion batteries are promising power sources for a wide range of applications, such as portable electronic devices, electric vehicles and implantable medical devices because of their high energy capacity, long cycle life, low environment impact, etc. [1], [2], [3], [4]. The high capacity anode materials with smaller impedance and higher safety play important role in the development of high-performance lithium-ion batteries. Nano-metal oxides, especially nano-sized transition metal oxides are good substitutes for anode materials for LIBs due to their high capacity. In recent years, transition metal oxides such as CoO/Co3O4 [5], [6], [7], [8], [9], [10], MoO3 [11], SnO2 [12], NiO [13], [14], and ZnO [15] have shown promising applications in lithium ion battery due to their high theoretical capacity and high abundance. Nevertheless, these oxides generally suffer from rapid capacity fading upon cycling caused by large volume expansion during the repeated charge and discharge cycles [16], [17], [18]. Thus, it becomes important to overcome these drawbacks by new strategies. Many studies have considered doping, microstructure tailoring, synthesis of composites and surface modification to circumvent structural deterioration and aggregation of the active particles that occurs during discharge charge cycles. For examples, Co-doped NiO is demonstrated to have a better conductivity and hence improve electrochemical performance [19]. Various composites such as metal oxide/carbon nanotube [20], [21], [22], metal oxide/graphene [23], [24], and metal oxide/polyaniline [25] have been developed to improve the conductivity as well as to provide buffer matrix for volume variation of the metal oxide. Surface modified with metal nanoparticles with high conductivity and/or catalytic activity such as Ag [26], Ni [27] is also an effective way to improve the electrochemical performance of metal oxide. In addition, coating active electrode materials with conductive carbon which exhibits superior electrical conductivity and chemical stability has been widely adopted to prevent the exfoliation of active materials and improve the electrical conductivity of electrode materials. To some extent, thin carbon layers may also minimize the volume expansion/contraction and the aggregation of electrode nanoparticles effectively during charge/discharge processes. For instance, carbon coated α-Fe2O3 nanoparticles prepared using ferrocene as precursor exhibit high specific capacity of over 800 mAh g−1 at 0.13 A g−1, and excellent rate performance (over 400 mAh g−1 at 5 A g−1) [28].

Among the transition metal oxides, cobalt monoxide (CoO) is considered as an ideal anode material for LIBs owing to its high theoretical Li-ion storage capacity of 715 mAh g−1, whose completely reversible electrochemical reaction is as follows [29], [30]:CoO + 2Li+ + 2e  Co + Li2O

In previous reports, various morphologies have been synthesized through different methods. For examples, CoO hollow spheres and octahedral can be selectively synthesized via thermal decomposition of cobalt(II) acetylacetonate in 1-octadecene solution using oleic acid and oleylamine as capping ligands. The capacities of them, however, are relatively low (initial discharge capacities were ca. 300 and 500 mAh g−1, respectively for octahedral structures and hollow spheres). CoO octahedral nanocages synthesized via a coordination-mediated etching route exhibited enhanced lithium storage capacity of 807 mAh g−1 after 50 cycles [31]. CoO porous nanowire arrays can be prepared on titanium substrate throughout a two-step method by pyrolysis of cobalt–hydroxide–carbonate, and the CoO porous nanowire arrays delivered a reversible capacity of 670 mAh g−1 at 1 C rate after 20 cycles [32]. However, there are limited success in producing hierarchical CoO/C nanostructures with high reversible capacity combined with high Coulombic efficiency, good rate capability, and long cycle life.

In the present work, we develop a simple process to prepare porous CoO/C nanocomposites from the Co3O4 precursor through a soaking treatment in the presence of sugar, which acts as both the reducing agent and the carbon source. These porous CoO/C polyhedra have a hierarchical structure with high specific surface area and large pore volume. More attractively, a high reversible capacity with improved cycle life has been demonstrated for the as-prepared CoO/C polyhedra.

Section snippets

Materials synthesis

The Co3O4 polyhedra were prepared by combining a hydrothermal synthesis of uniform cobalt oxalate precursors with subsequent heat treatment [33]. Firstly, 20 ml of 1 M (NH4)2C2O4 solution were added to 20 ml of 1 M CoCl2 solution under stirring to form a suspension. The suspension was then transferred into a Teflon-lined stainless steel autoclave of 50 ml capacity, tightly sealed and heated at 200 °C in an electric oven for 24 h. Afterwards the autoclave was cooled to room temperature and the pink

Results and discussion

The structure of the crystalline phases was examined by X-ray diffraction (XRD). The XRD patterns of Co3O4 before and after reduction treatment are given in Fig. 1a. As one can see from Fig. 1a, all of the diffraction peaks of precursor can be indexed to the cubic phase of Co3O4 spinel with space group of Fd3¯m and the cell parameter of a = 8.084 Å (JCPDS No. 25-0250). The crystalline phase presented after high thermal treatment with sugar is identified by XRD as a pure cubic CoO (JCPDS Card No.

Conclusions

We have successfully fabricated the hierarchically porous CoO/C polyhedra from the Co3O4 precursor through a solution-annealing treatment using sugar as reducing agent and carbon source. The as-prepared CoO/C polyhedra are constructed by many interconnecting nanograins, exhibiting an interesting hierarchical porous structure. As a promising anode material, porous CoO/C exhibits high lithium storage and good cycling performance. It delivers an initial discharge capacity of 1025 mAh g−1 at a

Acknowledgments

This work was supported by the National Science Foundation of China (No. 21203168), the Program for New Century Excellent Talents in University of Ministry of Education of China (NCET-11-1081), and the Program for Zhejiang Leading Team of Science and Technology Innovation (2009R50020).

References (41)

  • X.H. Huang et al.

    Li0.68Ni1.32O2/Ag nanocomposite: a Li-intercalation anode material with higher Coulombic efficiency and better cycling performance

    Electrochemistry Communications

    (2008)
  • J.Y. Xiang et al.

    Electrochemical investigation on nanoflower-like CuO/Ni composite film as anode for lithium ion batteries

    Electrochimica Acta

    (2009)
  • A. Brandt et al.

    Ferrocene as precursor for carbon-coated alpha-Fe2O3 nano-particles for rechargeable lithium batteries

    Journal of Power Sources

    (2013)
  • M. Zhang et al.

    Synthesis and electrochemical performance of CoO/graphene nanocomposite as anode for lithium ion batteries

    Applied Surface Science

    (2012)
  • W.W. Yuan et al.

    Preparation of porous Co3O4 polyhedral architectures and its application as anode material in lithium-ion battery

    Materials Letters

    (2013)
  • H. Qiao et al.

    One-pot synthesis of CoO/C hybrid microspheres as anode materials for lithium-ion batteries

    Journal of Power Sources

    (2008)
  • A.S. Arico et al.

    Nanostructured materials for advanced energy conversion and storage devices

    Nature Materials

    (2005)
  • P.G. Bruce et al.

    Nanomaterials for rechargeable lithium batteries

    Angewandte Chemie-International Edition

    (2008)
  • M. Armand et al.

    Building better batteries

    Nature

    (2008)
  • B. Dunn et al.

    Electrical energy storage for the grid: a battery of choices

    Science

    (2011)
  • Cited by (53)

    • High capacity conversion anodes in Li-ion batteries: A review

      2019, International Journal of Hydrogen Energy
      Citation Excerpt :

      It is less expensive than CoO [98]. Therefore, NiO is one of the perspective anode materials in Li-ion batteries, which exhibits the advantages of high theoretical capacity (718 mAh/g), high natural abundance, low cost, nontoxicity, and environmental benignity [99–102]. Moreover, the density of NiO is 6.67 g/cm3, resulting in high volumetric energy owing to slow kinetics of the conversion reaction NiO +2 Li+ + 2e− ↔ Li2O + Ni and large volume change (∼95.69%) of NiO electrode.

    View all citing articles on Scopus
    View full text