Elsevier

Electrochimica Acta

Volume 74, 15 July 2012, Pages 65-72
Electrochimica Acta

High specific capacity of TiO2-graphene nanocomposite as an anode material for lithium-ion batteries in an enlarged potential window

https://doi.org/10.1016/j.electacta.2012.03.170Get rights and content

Abstract

TiO2-graphene nanocomposite was first synthesized by a facile gas/liquid interface reaction. The structure and morphology were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and Brunauer–Emmett–Teller measurements. The results indicate that TiO2 nanoparticles (ca. 10 nm in mean grain size) were successfully deposited onto the graphene sheets during the gas/liquid interfacial reaction process. The electrochemical performance was evaluated by using coin-type cells versus metallic lithium in an enlarged potential window of 0.01–3.0 V. A high specific charge capacity of 499 mAh g−1 was obtained at a current density of 100 mA g−1. More strikingly, the TiO2-graphene nanocomposite exhibits excellent rate capability, even at a high current density of 3000 mA g−1, the specific charge capacity was still as high as 150 mAh g−1. The high specific charge capacities can be attributed to the facts that graphene possesses high electronic conductivity, and the lithium storage performance of graphene is delivered during discharge/charge processes of TiO2-graphene nanocomposite between 0.01 and 3.0 V.

Highlights

► TiO2-graphene composite was first synthesized by a gas/liquid interfacial method. ► The electrochemical performances were first evaluated between 0.01 and 3.0 V. ► The composite exhibits a high specific capacity and excellent rate performance.

Introduction

Lithium-ion batteries are the most attractive secondary batteries because of their high energy density, long cycling lifetime and excellent safety. The performance of lithium-ion batteries mainly depends on the physical and chemical properties of the cathode and anode materials. TiO2 has been regarded as a promising anode material for lithium-ion batteries due to its structural characteristics, low cost, safety and environmental benignity [1], [2], [3]. However, its practical capacity and high-rate capability are limited due to the low Li-ion diffusivity and electronic conductivity during reversible Li-ion insertion/extraction process [4], [5], [6]. In order to improve the electrochemical performance of TiO2 materials, nanotechnology has been explored to provide increased reaction active sites and short diffusion lengths for electron and Li-ion transport [7], [8], [9], [10], [11], [12], [13]. In addition, a variety of approaches have also been developed to increase the electronic conductivity of the TiO2, such as adding conductive agents (e.g. W [14], RuO2 [15]) and using conductive coating (e.g. carbon [16], [17], [18], [19], [20], [21], Sn [22], Ag [23]).

Graphene, a monolayer of carbon atoms with tight packing of the honeycomb lattice, possesses unique physicochemical properties including large surface area, good flexibility, superior electronic conductivity and high chemical stability [24], [25]. In the past two years, graphene sheets as an anode material for lithium-ion batteries have been investigated and exhibit a large reversible specific capacity (540–1264 mAh g−1) between 0.01 and 3.0 V [26], [27], [28], [29], [30]. In addition, graphene is also regarded as an ideal carbon nanostructure to improve the rate capability of TiO2 owing to its superior electronic conductivity and large surface area. Recently, several TiO2-graphene composites have been reported in lithium-ion batteries and other fields [31], [32], [33], [34], [35], [36], [37], [38]. For instance, Li et al. [31] synthesized mesoporous anatase TiO2 nanospheres/graphene composites and the composites were applied in lithium-ion batteries and photocatalysis. Yang et al. [32] fabricated sandwich-like, graphene-based titania nanosheets as an anode for lithium-ion batteries by a nanocasting method. However, all the reported TiO2-graphene nanocomposites were studied only in a narrow potential window of 1.0–3.0 V, which lead to low reversible capacity because graphene in these composites only acted as a conductive agent instead of a lithium storage material. In the past, in order to increase reversible capacity of TiO2-based nanomaterials, the electrochemical performance in an enlarged potential window was proposed. Marinaro et al. [39] investigated electrochemical behavior of rutile TiO2 using two different potential windows. They found that a high reversible capacity can be achieved by using an enlarged potential window. Yang et al. [19] prepared nanosized anatase TiO2 loaded porous carbon nanofibers (TiO2/PCNFs), and the TiO2/PCNFs presented a super high charge capacity of 687.2 mAh g−1 at a current density of 25 mA g−1 between 0.001 and 3.0 V. All the reported results showed that TiO2-based materials possess high reversible capacities in an enlarged potential window. Therefore, it can be expected that TiO2-graphene nanocomposite should possess a high capacity and excellent rate capability in the enlarged potential window of 0.01–3.0 V due to the graphene not only as a conductive agent but also as a lithium storage material.

In our previous work, Fe3O4/graphene and SnO2/graphene were successfully synthesized by a facile gas/liquid interface reaction, which is simple and low cost [40], [41]. Herein, the gas/liquid interface reaction method was first used to synthesize TiO2-graphene nanocomposite. The electrochemical performance of the obtained nanocomposite was investigated as an anode for lithium-ion batteries in two different potential windows (0.01–3.0 V and 1.0–3.0 V).

Section snippets

Materials preparation

Graphene sheets were prepared via a thermal exfoliation route involving graphite oxidation, followed by rapid thermal expansion in nitrogen atmosphere. Detailed preparation procedure can be found in our previous paper [26].

TiO2-graphene nanocomposite was synthesized by the gas/liquid interface reaction [40], [41], [42]. Briefly, in a 20 mL beaker, 0.7589 g of TiCl4 (Tianjin Kermel Chemical Reagent Co., Ltd., China) was dissolved in 20 mL of ethylene glycol (EG) (Beijing Chemical Reagent Co., Ltd.,

Microstructural characterization

Fig. 1 presents the schematic diagram for the preparation process of TiO2-graphene nanocomposite. TiCl4 and graphene sheets in EG solution was stored in the beaker, while aqueous ammonia solution (NH3·H2O) was placed in the autoclave liner outside the beaker. At the room temperature, the two solutions were separated by the beaker. At the elevated reaction temperature (180 °C), evaporated ammonia reacted with Ti4+ at the gas/liquid interface to produce Ti(OH)4, which in situ deposited onto the

Conclusions

TiO2-graphene nanocomposite was first synthesized by a facile gas/liquid interface reaction. The TiO2-graphene nanocomposite exhibits a high capacity and excellent rate performance in the enlarged potential window of 0.01–3.0 V. The excellent electrochemical performance can be attributed to the following reasons: (1) the lithium storage performance of graphene is delivered during discharge/charge processes of the TiO2-graphene nanocomposite between 0.01 and 3.0 V; (2) graphene sheets distributed

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (No. 20936001), the Cooperation Project in Industry, Education and Research of Guangdong Province and Ministry of Education of China (No. 2010B090400518) and the Fundamental Research Funds for the Central Universities, SCUT (2009220038).

References (47)

  • Z. Yang et al.

    Journal of Power Sources

    (2009)
  • J.S. Chen et al.

    Electrochemistry Communications

    (2009)
  • S. Bach et al.

    Electrochimica Acta

    (2010)
  • Y.H. Jin et al.

    Electrochimica Acta

    (2010)
  • H.E. Wang et al.

    Journal of Power Sources

    (2011)
  • F. Zhang et al.

    Journal of Power Sources

    (2011)
  • S.J. Park et al.

    Electrochimica Acta

    (2011)
  • S.K. Das et al.

    Materials Chemistry and Physics

    (2011)
  • X. Yang et al.

    Electrochemistry Communications

    (2011)
  • C. Lai et al.

    Electrochimica Acta

    (2010)
  • C. Lai et al.

    Journal of Power Sources

    (2011)
  • P. Lian et al.

    Electrochimica Acta

    (2010)
  • P. Guo et al.

    Electrochemistry Communications

    (2009)
  • G. Wang et al.

    Carbon

    (2009)
  • Y.H. Ding et al.

    Materials Research Bulletin

    (2011)
  • M. Marinaro et al.

    Journal of Power Sources

    (2011)
  • P. Lian et al.

    Electrochimica Acta

    (2010)
  • P. Lian et al.

    Electrochimica Acta

    (2011)
  • J. Yao et al.

    Electrochemistry Communications

    (2009)
  • P. Kubiak et al.

    Small

    (2011)
  • V. Luca et al.

    Chemistry of Materials

    (1999)
  • D.V. Bavykin et al.

    Advanced Materials

    (2006)
  • F. Wu et al.

    Journal of Materials Chemistry

    (2011)
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