Elsevier

Electrochimica Acta

Volume 53, Issue 7, 25 February 2008, Pages 3084-3093
Electrochimica Acta

Doping effects on structure and electrode performance of K-birnessite-type manganese dioxides for rechargeable lithium battery

https://doi.org/10.1016/j.electacta.2007.11.038Get rights and content

Abstract

The potassium birnessites doped with Al, Ni, and Co were prepared by calcination and aqueous treatment, which showed that single phase products were obtained with Ni and Al up to 5 at.% and Co up to 25 at.% addition to strating KMnO4. The discharge–recharge capacities and capacity retentions in an aprotic Li cell were not improved by the Ni and Al dopings, but those of the cobalt doped birnessite were improved. The initial discharge capacities of the undoped and cobalt doped birnessites were 170 and 200 mAh g−1 with capacity retentions of 56 and 80% during the initial 20 cycles, respectively. The reasons for the improvement of the battery performance by Co doping were considered as follows: (i) a change in the stacking structure, (ii) a decrease in the charge transfer resistance, and (iii) improved structural stability of the oxide. Their micro structures were evaluated by X-ray diffraction, photoelectron and Raman spectroscopies, and electron microscopy. Also, potassium birnessite synthesized by adding about 3 times excess potassium indicated that the stacking structure was similar to the 30 at.% cobalt doping sample, furthermore, the better capacity retention was achieved as cathode in a Li cell.

Introduction

Manganese oxides have been studied for electrochemical energy storage due to being a low toxic and inexpensive material which form lamellar, spinel and tunnel frameworks [1], [2], [3]. The electrochemically active materials, which have a working potential for Li insertion/deinsertion around 3–4 V vs. Li, are strong candidates for lithium (ion) batteries. As one of the manganese oxides, the birnessite-type manganese oxide is a hydration-layered manganese oxide, which forms MnO2 sheets of MnO6 octahedra assembled in layers and has cations of pillar (mainly alkaline ion) and lattice water in the interlayer space. Up to now, the syntheses of the birnessite are achieved by various methods such as a calcination reaction [4], [5], [6], [7], [8], [9], [10], [11], [12], sol–gel synthesis [12], [13], [14], [15], hydrothermal synthesis [16], [17], etc. The structural details of potassium-containing birnessite were investigated as previously reported [4], [5], [6], [7], [8]. These materials show a working potential around 3 V vs. Li and high discharge capacities during initial cycling, though there is the problem of structural collapse resulting in discharge capacity fading [5], [15]. In order to improve the battery performance, Franger et al. [15] and Tsuda et al. [13] reported the enhancement of the cycle performance by Co doping in birnessite.

Previously, we reported the synthesis of a birnessite by utilizing the thermal decomposition of KMnO4 and its electrochemical performance in Li cells [9], [10]. In the present paper, we report that potassium birnessites made by thermal decomposition reaction of KMnO4 mixed with Co, Ni, Al, Mn, and K nitrates, and we investigated the relation between the synthetic conditions and electrochemical performance.

Section snippets

Experimental

The layered manganese dioxides doped with Al, Ni, or Co were obtained by the calcinations of mixtures (about 0.5 g) of KMnO4 and Al, Ni, or Co nitrate, respectively, which were dissolved in several ml of distilled water, at 600 °C (50 °C h−1) for 5 h in air. The calcined sample was ultrasonically treated for 5 min in a sufficient amount of water. The precipitate in the ultrasonically treated solution was then separated by filtration, washed with water until neutral, and dried at 80 °C for 24 h in air.

Results and discussion

Fig. 1 shows the TG curve of the KMnO4 powder. Below 230 °C, the weight of KMnO4 is constant. At temperatures higher than 230 °C, the weight quickly decreased to 85.5%, and then the weight did not change up to 600 °C. The weight loss around 250 °C is due to the thermal decomposition of KMnO4 as previously reported [11]. The weight loss is expressed by the following equation.5KMnO4  3MnO2 + K2MnO4 + K3MnO4 + 3O2Based on this thermal decomposition, the weight loss due to the O2 evolution is estimated to be

Conclusion

The potassium birnessites doped with Co, Ni, or Al were successfully obtained from KMnO4 mixed with these nitrates by a calcination synthesis. Among the doped compounds, Co-25 birnessite has the highest discharge capacity of 200 mAh g−1 and capacity retention of about 80% for 20 cycles. It was found that the electrochemical performance of birnessite doped with appropriate amount of cobalt was improved due to the change in the stacking structure and the decrease in the charge transfer resistance.

Acknowledgements

The authors thank Dr. T. Sasaki and Mr. K. Saka for their helpful assistance in the experimental work. This study was partially supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan, Yazaki Memorial Foundation for Science and Technology, and Iwatani Naoji Foundation's Research Grant.

References (22)

  • S.-T. Myung et al.

    Solid State Ionics

    (2006)
  • H.Y. Lee et al.

    C. R. Acad. Sci., Ser. IIc: Chim.

    (1999)
  • M. Tsuda et al.

    J. Power Sources

    (2002)
  • C. Julien et al.

    Solid State Ionics

    (2003)
  • S. Franger et al.

    J. Power Sources

    (2002)
  • S. Komaba et al.

    Electrochem. Acta

    (2005)
  • T. Ohzuku et al.

    J. Electrochem. Soc.

    (1990)
  • M.M. Doeff et al.

    J. Electrochem. Soc.

    (2001)
  • S.H. Kim et al.

    Chem. Mater.

    (1999)
  • S.H. Kim et al.

    J. Electrochem. Soc.

    (2000)
  • A.-C. Gaillot et al.

    Chem. Mater.

    (2003)
  • Cited by (0)

    View full text