Browsing by Author "Chung, SC"

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    Na2FeP2O7: a safe cathode for rechargeable sodium-ion batteries
    (American Chemical Society, 2013-09-10) Barpanda, P; Liu, G; Ling, CD; Tamaru, M; Avdeev, M; Chung, SC; Yamada, Y; Yamada, A
    Vying for newer sodium-ion chemistry for rechargeable batteries, Na2FeP2O7 pyrophosphate has been recently unveiled as a 3 V high-rate cathode. In addition to its low cost and promising electrochemical performance, here we demonstrate Na2FeP2O7 as a safe cathode with high thermal stability. Chemical/electrochemical desodiation of this insertion compound has led to the discovery of a new polymorph of NaFeP2O7. High-temperature analyses of the desodiated state NaFeP2O7 show an irreversible phase transition from triclinic (P (1) over bar) to the ground state monoclinic (P2(1)/c) polymorph above 560 degrees C. It demonstrates high thermal stability, with no thermal decomposition and/or oxygen evolution until 600 degrees C, the upper limit of the present investigation. This high operational stability is rooted in the stable pyrophosphate (P2O7)(4-) anion, which offers better safety than other phosphate-based cathodes. It establishes Na2FeP2O7 as a safe cathode candidate for large-scale economic sodium-ion battery applications. © 2013, American Chemical Society.
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    A new polymorph of Na2MnP2O7 as a 3.6 V cathode material for sodium-ion batteries
    (Royal Society of Chemistry, 2013-01-01) Barpanda, P; Ye, T; Avdeev, M; Chung, SC; Yamada, A
    Exploring novel low-cost cathodes for sodium-ion batteries, here we unveil [small beta]-Na2MnP2O7, a new pyrophosphate cathode. Stabilizing into a triclinic structure, it was found to be electrochemically active, delivering a discharge capacity approaching 80 mA h g-1 along with the highest ever Mn3+/Mn2+ redox potential located at 3.6 V. © 2013, Royal Society of Chemistry