Functionalized Graphene for High Performance Lithium Ion Capacitors

Authors

  • Ji Hoon Lee,

    1. Graduate School of EEWS (WCU), Korea Advanced Institute of Science and Technology, 373-1 Guseong Dong, Yuseong Gu, Daejon 305-701 (Korea)
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  • Weon Ho Shin,

    1. Graduate School of EEWS (WCU), Korea Advanced Institute of Science and Technology, 373-1 Guseong Dong, Yuseong Gu, Daejon 305-701 (Korea)
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  • Myung-Hyun Ryou,

    1. Graduate School of EEWS (WCU), Korea Advanced Institute of Science and Technology, 373-1 Guseong Dong, Yuseong Gu, Daejon 305-701 (Korea)
    2. Division of Materials Science, Korea Basic Science Institute, 169-148, Gwahak-ro,Yuseong Gu, Daejeon, 305-806 (Korea)
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  • Jae Kyu Jin,

    1. Materials R&D Center, SK innovation 325, Exporo, Yuseong-gu, Daejeon 305-712 (Korea)
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  • Junhyung Kim,

    1. Materials R&D Center, SK innovation 325, Exporo, Yuseong-gu, Daejeon 305-712 (Korea)
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  • Prof. Jang Wook Choi

    Corresponding author
    1. Graduate School of EEWS (WCU), Korea Advanced Institute of Science and Technology, 373-1 Guseong Dong, Yuseong Gu, Daejon 305-701 (Korea)
    2. KAIST Institute Nano Century, Korea Advanced Institute of Science and Technology, 373-1 Guseong Dong, Yuseong Gu, Daejon 305-701 (Korea)
    • Graduate School of EEWS (WCU), Korea Advanced Institute of Science and Technology, 373-1 Guseong Dong, Yuseong Gu, Daejon 305-701 (Korea)
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Abstract

Lithium ion capacitors (LICs) have recently drawn considerable attention because they utilize the advantages of supercapacitors (high power) and lithium ion batteries (high energy). However, the energy densities of conventional LICs, which consist of a pair of graphite and activated carbon electrodes, are limited by the small capacities of the activated carbon cathodes. To overcome this limitation, we have engaged urea-reduced graphene oxide. The amide functional groups generated during the urea reduction facilitate the enolization processes for reversible Li binding, which improves the specific capacity by 37 % compared to those of conventional systems such as activated carbon and hydrazine-reduced graphene oxide. Utilizing the increased Li binding capability, when evaluated based on the mass of the active materials on both sides, the LICs based on urea-reduced graphene oxide deliver a specific energy density of approximately 106 Wh kgtotal−1 and a specific power density of approximately 4200 W kgtotal−1 with perfect capacity retention up to 1000 cycles. These values are far superior to those of previously reported LICs and supercapacitors, which suggests that appropriately treated graphene can be a promising electrode material for LICs.

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