Tang Christopher R, Singh Gurpreet, Housel Lisa M, Kim Sung Joo, Quilty Calvin D, Zhu Yimei, Wang Lei, Takeuchi Kenneth J, Takeuchi Esther S, Marschilok Amy C
Institute for Electrochemically Stored Energy, State University of New York at Stony Brook, Stony Brook, New York 11794, USA.
Phys Chem Chem Phys. 2021 Apr 14;23(14):8607-8617. doi: 10.1039/d1cp00516b. Epub 2021 Mar 26.
The electrochemical charge storage of sodium vanadate (NaVO or NVO) cathodes in aqueous Zn-ion batteries has been hypothesized to be influenced by the inclusion of structural water for facilitating ion transfer in the material. Materials properties considered important (morphology, crystallite and particle size, surface area) are systematically studied herein through investigation of two NVO materials, NaVO·0.34HO [NVO(300)] and NaVO·0.05HO [NVO(500)], with different water content, acicular morphologies with different size and surface area achieved via post-synthesis heat treatment. The electrochemistry of the two materials was evaluated in aqueous Zn-ion cells with 2 M ZnSO electrolyte using cyclic voltammetry, galvanostatic cycling, and rate capability testing. The thinner NVO(300) nanobelts (0.13 μm) demonstrate greater specific capacities and higher effective diffusion coefficients relative to the thicker NVO(500) nanorods. Notably however, while cells containing NVO(500) deliver lower specific capacity, they demonstrate enhanced capacity retention with cycling. The structural changes accompanying oxidation and reduction are elucidated via ex situ X-ray diffraction, transmission electron microscopy, and operando V K-edge X-ray absorption spectroscopy (XAS), where NVO material properties are shown to influence the ion insertion. Operando XAS verified that electron transfer corresponds directly to change in vanadium oxidation state, affirming vanadium redox as the governing electrochemical process.
在水系锌离子电池中，钒酸钠（NaVO或NVO）阴极的电化学电荷存储被认为受结构水的影响，结构水有助于材料中的离子转移。本文通过研究两种含水量不同的NVO材料，即NaVO·0.34H₂O [NVO(300)] 和NaVO·0.05H₂O [NVO(500)]，系统地研究了被认为重要的材料特性（形态、微晶和粒径、表面积），通过合成后热处理获得了具有不同尺寸和表面积的针状形态。使用循环伏安法、恒电流循环和倍率性能测试，在含有2 M ZnSO₄电解质的水系锌离子电池中评估了这两种材料的电化学性能。与较厚的NVO(500)纳米棒相比，较薄的NVO(300)纳米带（0.13 μm）表现出更大的比容量和更高的有效扩散系数。然而，值得注意的是，虽然含有NVO(500)的电池提供较低的比容量，但它们在循环过程中表现出增强的容量保持率。通过非原位X射线衍射、透射电子显微镜和原位V K边X射线吸收光谱（XAS）阐明了氧化和还原过程中伴随的结构变化，其中NVO材料特性被证明会影响离子插入。原位XAS证实电子转移与钒氧化态的变化直接相关，证实钒氧化还原是主要的电化学过程。
