title: Removal of interstitial H2O in hexacyanometallates for a superior cathode of a sodium-ion battery.
abstract: Sodium is globally available, which makes a sodium-ion rechargeable battery preferable to a lithium-ion battery for large-scale storage of electrical energy, provided a host cathode for Na can be found that provides the necessary capacity, voltage, and cycle life at the prescribed charge/discharge rate. Low-cost hexacyanometallates are promising cathodes because of their ease of synthesis and rigid open framework that enables fast Na(+) insertion and extraction. Here we report an intriguing effect of interstitial H2O on the structure and electrochemical properties of sodium manganese(II) hexacyanoferrates(II) with the nominal composition Na2MnFe(CN)6·zH2O (Na2-δMnHFC). The newly discovered dehydrated Na2-δMnHFC phase exhibits superior electrochemical performance compared to other reported Na-ion cathode materials; it delivers at 3.5 V a reversible capacity of 150 mAh g(-1) in a sodium half cell and 140 mAh g(-1) in a full cell with a hard-carbon anode. At a charge/discharge rate of 20 C, the half-cell capacity is 120 mAh g(-1), and at 0.7 C, the cell exhibits 75% capacity retention after 500 cycles.
authors: Materials Science and Engineering Program and Texas Materials Institute and ‡Department of Chemistry and the Institute for Computational and Engineering Sciences, The University of Texas at Austin , Austin, Texas 78712, United States.
authors: Jie
authors: J
authors: Song
authors: Long
authors: L
authors: Wang
authors: Yuhao
authors: Y
authors: Lu
authors: Jue
authors: J
authors: Liu
authors: Bingkun
authors: B
authors: Guo
authors: Penghao
authors: P
authors: Xiao
authors: Jong-Jan
authors: JJ
authors: Lee
authors: Xiao-Qing
authors: XQ
authors: Yang
authors: Graeme
authors: G
authors: Henkelman
authors: John B
authors: JB
authors: Goodenough