Wu Tzu-Ho, Liang Wei-Yuan
Department of Chemical and Materials Engineering, National Yunlin University of Science and Technology, 123 University Road, Section 3, Douliou, Yunlin 64002, Taiwan.
ACS Appl Mater Interfaces. 2021 May 26;13(20):23822-23832. doi: 10.1021/acsami.1c05150. Epub 2021 May 11.
Aqueous zinc-ion batteries are considered promising next-generation systems for large-scale energy storage due to low cost, environmental friendliness, and high reversibility of the Zn anode. However, the interfacial charge-transfer resistance for the insertion of divalent Zn into cathode materials is normally high, which limits the kinetics of Zn transfer at the cathode/electrolyte interface. This study reveals the presence of rich structural water in spinel ZnMnO (ZnMnO·0.94HO, denoted as ZMO), synthesized by a scalable and low-temperature process, significantly overcoming the great interfacial charge-transfer resistance. ZMO exhibits excellent electrochemical performance toward Zn storage, that is, high capacity (230 and 101 mA h g at 0.5 and 8 A g), high specific energy/specific power (329 W h kg/706 W kg and 134 W h kg/11,160 W kg), and stable cycle retention (75% after 2000 cycles at 4 A g) can be achieved. On the contrary, the controlled sample ZMO-450 with deficient structural water, prepared by post-heat treatment of ZMO at 450 °C, demonstrates limited discharge capacity (45 and 15 mA h g at 0.5 and 8 A g). As examined by electrochemical impedance spectroscopy, rich structural water in ZMO effectively reduces the activation energy barrier upon Zn insertion, rendering fast interfacial kinetics for Zn storage. Benefiting from rich structural water in ZMO, the involvement of Zn during the charge/discharge process exhibits good reversibility, as characterized by X-ray diffraction and X-ray photoelectron spectroscopy.
水系锌离子电池由于成本低、环境友好以及锌负极的高可逆性，被认为是大规模储能领域有前景的下一代系统。然而，二价锌插入阴极材料时的界面电荷转移电阻通常较高，这限制了锌在阴极/电解质界面的转移动力学。本研究揭示了通过可扩展的低温工艺合成的尖晶石型ZnMnO（ZnMnO·0.94H₂O，记为ZMO）中存在丰富的结构水，显著克服了巨大的界面电荷转移电阻。ZMO在锌存储方面表现出优异的电化学性能，即高容量（在0.5和8 A g时分别为230和101 mA h g⁻¹）、高比能量/比功率（329 W h kg⁻¹/706 W kg⁻¹和134 W h kg⁻¹/11,160 W kg⁻¹），并且在4 A g下循环2000次后仍能保持75%的稳定循环保持率。相反，通过在450℃对ZMO进行后热处理制备的结构水不足的对照样品ZMO-450，其放电容量有限（在0.5和8 A g时分别为45和15 mA h g⁻¹）。通过电化学阻抗谱检测发现，ZMO中丰富的结构水有效降低了锌插入时的活化能垒，实现了锌存储的快速界面动力学。受益于ZMO中丰富的结构水，通过X射线衍射和X射线光电子能谱表征，锌在充放电过程中的参与表现出良好的可逆性。
