Synergistic H+/Zn2+ dual ion insertion mechanism in high-capacity and ultra-stable hydrated VO2 cathode for aqueous Zn-ion batteries
Synergistic H+/Zn2+ dual ion insertion mechanism in high-capacity and ultra-stable hydrated VO2 cathode for aqueous Zn-ion batteries
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DOI：
10.1016/j.ensm.2020.03.030
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发表时间：
2020-08
影响因子：
20.4
通讯作者：
Kaiyue Zhu;Tao Wu;Shichen Sun;Wessel van den Bergh;M. Stefik;Kevin Huang
中科院分区：
文献类型：
--
作者：
Kaiyue Zhu;Tao Wu;Shichen Sun;Wessel van den Bergh;M. Stefik;Kevin Huang
近中性电解质可充锌离子水溶液电池（ZIB）具有能量密度高、安全性好、成本低、环境友好等优点，是一种很有前途的固定式储能电池。然而，ZIB的发展目前受到缺乏高性能阴极材料和对阴极中真实离子存储机制的良好理解的阻碍。本文以一种很有前途的ZIB阴极--水合VO 2（H-VO 2）为模型材料，对离子存储机理进行了系统的实验和理论研究。我们显示出强有力的证据表明，H+和Zn 2+是协同参与在H-VO 2的离子存储。H+的插入/脱出导致电解液pH值的波动，可以看作是Zn（OH）2在H-VO 2阴极表面可逆沉淀/溶解的间接Zn 2+存储过程。第一性原理DFT计算进一步揭示了H+和Zn 2+各有其有利的插入位置和迁移路径，但在放电初期H+插入占主导地位，而在放电后期Zn 2+插入占主导地位。由于H+/Zn 2+的协同插入，H-VO 2基ZIB在低倍率和高倍率下均表现出较高的容量和稳定性，在0.1和5.0 A g-1下，200次（~1500 h）和3000次（~215 h）循环的留存率分别为410和200 mAh g-1，88%和70%。从这项研究中获得的新的基本见解加深了对水性锌离子电池化学的理解，以用于先进ZIB阴极的未来发展。
Rechargeable aqueous zinc ion batteries (ZIB) with near-neutral electrolytes are a promising candidate for stationary energy storage owing to their high-energy-density, high-safety, low-cost and environmental-friendliness. However, the development of ZIBs is currently hindered by the lack of high-performance cathode materials and a good understanding of the true ionic storage mechanism in cathodes. Herein, using a promising ZIB cathode, hydrated VO2(denoted as H-VO2), as a model material, we carried out a systematic experimental and theoretical work to elucidate the ionic storage mechanisms. We show strong evidence that H+and Zn2+are synergistically involved in the ionic storage in H-VO2. The H+-insertion/extraction, which leads to a pH swing of the electrolyte, can be viewed as an indirect Zn2+-storage through a reversible precipitation/dissolution of Zn(OH)2on the surface of H-VO2cathode. The first-principles DFT calculations further reveal that H+and Zn2+have their own favorable insertion sites and migration pathways, but H+-insertion predominates in the initial discharge stage whereas Zn2+-insertion controls in the late discharge stage. Because of the synergetic H+/Zn2+co-insertion, H-VO2-based ZIB exhibits a high capacity and stability at both low and high rates,e.g.410 and 200 mAh g-1, 88% and 70% retention rate for 200 (~1500 h) and 3000 cycles (~215 h) at 0.1 and 5.0 A g-1, respectively. The new fundamental insights gained from this study deepen the understanding of aqueous Zn-ion battery chemistry for future development of advanced ZIB cathodes.