Na2FeP2O7: a safe cathode for rechargeable sodium-ion batteries

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American Chemical Society
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.
Lithium, Cathodes, Crystals, Chemistry, Iron, Sodium
Barpanda, P., Liu, G. D., Ling, C. D., Tamaru, M., Avdeev, M., Chung, S. C., Yamada, Y., & Yamada, A. (2013). Na2FeP2O7: a safe cathode for rechargeable sodium-ion batteries. Chemistry of Materials, 25(17), 3480-3487. doi:10.1021/cm401657c