Role of Oxygen Functional Groups in Carbon Nanotube/Graphene Freestanding Electrodes for High Performance Lithium Batteries

Authors

  • Hye Ryung Byon,

    1. RIKEN Advanced Science Institute, 2- 1 Hirosawa, Wako, Saitama 351-0198, Japan
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  • Betar M. Gallant,

    1. Electrochemical Energy Lab, Department of Mechanical Engineering and Materials, Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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  • Seung Woo Lee,

    1. Electrochemical Energy Lab, Department of Mechanical Engineering and Materials, Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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  • Yang Shao-Horn

    Corresponding author
    1. Electrochemical Energy Lab, Department of Mechanical Engineering and Materials, Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
    • Electrochemical Energy Lab, Department of Mechanical Engineering and Materials, Science and Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
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Abstract

Hierarchical functionalized multiwalled carbon nanotube (MWNT)/graphene structures with thicknesses up to tens of micrometers and relatively high density (>1 g cm−3) are synthesized using vacuum filtration for the positive electrode of lithium batteries. These electrodes, which are self-standing and free of binder and current collectors, utilize oxygen functional groups for Faradaic reactions in addition to double-layer charging, which can impart high gravimetric (230 Wh kg−1 at 2.6 kW kg−1) and volumetric (450 Wh L−1 at 5 kW L−1) performance. It is demonstrated that the gravimetric and volumetric capacity, capacitance, and energy density can be tuned by selective removal of oxygen species from as-prepared functionalized MWNT/graphene structures with heat treatments in H2/Ar, potentially opening new pathways for the design of electrodes with controlled surface chemistry.

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