Reversible Lithium Storage with High Mobility at Structural Defects in Amorphous Molybdenum Dioxide Electrode

Authors

  • Jun H. Ku,

    1. Seoul National University, Department of Chemical and Biological Engineering, Institute of Chemical Processes and WCU program of C2E2, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-744, Korea
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  • Ji Heon Ryu,

    1. Seoul National University, Department of Chemical and Biological Engineering, Institute of Chemical Processes and WCU program of C2E2, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-744, Korea
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  • Sun Ha Kim,

    1. Korea Basic Science Institute, Daegu Center, Daegu, 702-701, Korea
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  • Oc Hee Han,

    Corresponding author
    1. Korea Basic Science Institute, Daegu Center, Daegu, 702-701, Korea, Chungnam National University, Graduate School of Analytical Science & Technology, Daejeon, 305-764, Korea
    • Korea Basic Science Institute, Daegu Center, Daegu, 702-701, Korea, Chungnam National University, Graduate School of Analytical Science & Technology, Daejeon, 305-764, Korea
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  • Seung M. Oh

    Corresponding author
    1. Seoul National University, Department of Chemical and Biological Engineering, Institute of Chemical Processes and WCU program of C2E2, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-744, Korea
    • Seoul National University, Department of Chemical and Biological Engineering, Institute of Chemical Processes and WCU program of C2E2, 599 Gwanak-ro, Gwanak-gu, Seoul, 151-744, Korea.
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Abstract

This work demonstrates that structural defects in amorphous metal oxide electrodes can serve as a reversible Li+ storage site for lithium secondary batteries. For instance, molybdenum dioxide electrode in amorphous form (a-MoO2) exhibits an unexpectedly high Li+ storage capacity (up to four Li per MoO2 unit), which is larger by a factor of four than that for the crystalline counterpart. The conversion-type lithiation is discarded for this electrode from the absence of Mo metal and lithium oxide (Li2O) in the lithiated a-MoO2 electrode and the retention of local structural framework. The sloping voltage profile in a wide potential range suggests that Li+ ions are inserted into the structural defects that are electrochemically nonequivalent. This electrode also shows an excellent cycle stability and rate capability. The latter feature is seemingly due to a rather opened Li+ diffusion pathway provided by the structural defects. A high Li+ mobility is confirmed from nuclear magnetic resonance study.

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