Na2FeP2O7 as a Promising Iron-Based Pyrophosphate Cathode for Sodium Rechargeable Batteries: A Combined Experimental and Theoretical Study

Authors

  • Heejin Kim,

    1. Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea
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  • R. A. Shakoor,

    1. Department of Chemical Engineering, College of Engineering, Qatar University, P.O.Box: 2713, Doha, Qatar
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  • Chansun Park,

    1. Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea
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  • Soo Yeon Lim,

    1. Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea
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  • Joo-Seong Kim,

    1. Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea
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  • Yong Nam Jo,

    1. Advanced Batteries Research Center, Korea Electonics Technology Institute (KETI), Bundang-gu, Seongnam-si, Gyeonggi-do, 463-816, Republic of Korea
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  • Woosuk Cho,

    1. Advanced Batteries Research Center, Korea Electonics Technology Institute (KETI), Bundang-gu, Seongnam-si, Gyeonggi-do, 463-816, Republic of Korea
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  • Keiichi Miyasaka,

    1. Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea
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  • Ramazan Kahraman,

    1. Department of Chemical Engineering, College of Engineering, Qatar University, P.O.Box: 2713, Doha, Qatar
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  • Yousung Jung,

    Corresponding author
    1. Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea
    • Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea.
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  • Jang Wook Choi

    Corresponding author
    1. Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea
    • Graduate School of EEWS (WCU), KAIST Institute NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Yuseong-gu, Daejeon, 305-701, Republic of Korea.
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Abstract

Considering the promising electrochemical performance of the recently reported pyrophosphate family in lithium ion batteries as well as the increasing importance of sodium ion batteries (SIBs) for emerging large-scale applications, here, the crystal structure, electrochemical properties, and thermal stability of Na2FeP2O7, the first example ever reported in the pyrophosphate family for SIBs, are investigated. Na2FeP2O7 maintains well-defined channel structures (triclinic framework under the P1 space group) and exhibits a reversible capacity of ≈90 mAh g−1 with good cycling performance. Both quasi-equilibrium measurements and first-principles calculations consistently indicate that Na2FeP2O7 undergoes two kinds of reactions over the entire voltage range of 2.0–4.5 V (vs Na/Na+): a single-phase reaction around 2.5 V and a series of two-phase reactions in the voltage range of 3.0–3.25 V. Na2FeP2O7 shows excellent thermal stability up to 500 °C, even in the partially desodiated state (NaFeP2O7), which suggests its safe character, a property that is very critical for large-scale battery applications.

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