Electrochemically Induced Structural Transformation in a γ-MnO2 Cathode of a High Capacity Zinc-Ion Battery System
Electrochemically Induced Structural Transformation in a γ-MnO2 Cathode of a High Capacity Zinc-Ion Battery System
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DOI：
10.1021/cm504717p
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发表时间：
2015-05-26
影响因子：
8.6
通讯作者：
Kim, Jaekook
中科院分区：
文献类型：
--
作者：
Alfaruqi, Muhammad H.;Mathew, Vinod;Kim, Jaekook
本研究对介孔γ - mno2阴极在锌离子电池电化学反应过程中的结构转变进行了深入的研究。结合原位同步加速器XANES和XRD研究发现，隧道型母相γ - mno2结构转变为尖晶石型Mn（III）相（ZnMn2O4）和两个新的中间相Mn（II）相，即隧道型γ - znxmno2和层状型L-ZnyMnO2，并且在电化学完全插入zn后，这些具有多氧化态的相共存。在连续的zn脱插/萃取过程中，大多数具有多氧化态的相被观察到恢复到母体γ - mno2相。介孔γ - mno2阴极通过简单的环境温度策略，然后在200℃下进行低温退火制备，在0.05 mA cm（-2）下提供285 mAh g（-1）的初始放电容量，并在1.25 V vs Zn/Zn2+附近确定平台。放电电极的原位HR-TEM研究有助于确定Mn（III）和Mn（II）相对应的晶格条纹宽度，并且通过ICP分析估计的化学计量成分似乎与原位发现一致。非原位XRD研究也证实了在重复放电/充电循环中发生相同的电化学反应。此外，目前的合成策略为开发具有成本效益和环境安全的纳米结构多孔电极提供了解决方案，用于廉价和环保的电池。
In the present study, an in-depth investigation on the structural transformation in a mesoporous gamma-MnO2 cathode during electrochemical reaction in a zinc-ion battery (ZIB) has been undertaken. A combination of in situ Synchrotron XANES and XRD studies reveal that the tunnel-type parent gamma-MnO2 undergoes a structural transformation to spinel-type Mn(III) phase (ZnMn2O4) and two new intermediary Mn(II) phases, namely, tunnel-type gamma-ZnxMnO2 and layered-type L-ZnyMnO2, and that these phases with multioxidation states coexist after complete electrochemical Zn-insertion. On successive Zn-deinsertion/extraction, a majority of these phases with multioxidation states is observed to revert back to the parent gamma-MnO2 phase. The mesoporous gamma-MnO2 cathode, prepared by a simple ambient temperature strategy followed by low-temperature annealing at 200 degrees C, delivers an initial discharge capacity of 285 mAh g(-1) at 0.05 mA cm(-2) with a defined plateau at around 1.25 V vs Zn/Zn2+. Ex situ HR-TEM studies of the discharged electrode aided to identify the lattice fringe widths corresponding to the Mn(III) and Mn(II) phases, and the stoichiometric composition estimated by ICP analysis appears to be concordant with the in situ findings. Ex situ XRD studies also confirmed that the same electrochemical reaction occurred on repeated discharge/charge cycling. Moreover, the present synthetic strategy offers solutions for developing cost-effective and environmentally safe nanostructured porous electrodes for cheap and eco-friendly batteries.