作为新兴的储能设备,水性锌离子电池(AZIBs)具有高安全性的突出优点,高能量密度,和环境友好引起了很多研究兴趣。在这里,通过掺入碳底物(NMC)和聚多巴胺(PDA)表面修饰,合理地构建了有利的荆棘状MnO2微/纳米结构(PDA@MnO2@NMC)。非原位X射线衍射和拉曼特征表明,MnOOH和ZnMn2O4产物的形成,对应于两个放电平台中的H+和Zn2+插入。密度泛函理论(DFT)计算还表明,PDA可以牢固地锚定在MnO2表面上,并防止MnOOH的溶解。此外,具有更多亲水基团的PDA可以捕获更多的H+,同时表面电容增加和第一放电平台的延伸,虽然NMC碳衬底可以为杂草生长的MnO2纳米线提供丰富的活性位点,提高导电性,促进离子和电子的快速传输。Further,电化学阻抗谱(EIS)和GITT结果表明,PDA@MnO2@NMC的欧姆电阻几乎降低到一半,特别是,离子扩散系数比纯MnO2提高30倍以上。因此,与纯MnO2相比,AZIB阴极中的PDA@MnO2@NMC表现出优异的电化学性能,有望在储能装置中具有有利的竞争力。
As emerging energy storage devices, aqueous zinc ion batteries (AZIBs) with outstanding advantages of high safety, high energy density, and environmental friendliness have attracted much research interest. Herein, the favorable thornlike MnO2 micro-/nanostructures (PDA@MnO2@NMC) are rationally constructed by the incorporation of both carbon substrates (NMC) and polydopamine (PDA) surface modifications. Ex situ X-ray diffraction and Raman characteristics show the formation of MnOOH and ZnMn2O4 products, corresponding to H+ and Zn2+ insertions in two discharge platforms. Density functional theory (DFT) calculations also demonstrate that PDA can firmly anchor onto MnO2 surfaces and prevent the dissolution of MnOOH. In addition, PDA with more hydrophilic groups can capture more H+ together with the increased surface capacitance and the extension of the first discharge platform, while the NMC carbon substrate can provide abundant active sites for the overgrown MnO2 nanowires, improve the conductivity, and promote fast ion and electron transportations. Further, electrochemical impedance spectroscopy (EIS) and GITT results show that the ohmic resistance of PDA@MnO2@NMC decreases to almost half and, in particular, the ion diffusion coefficient increases more than 30 times of pure MnO2. As such, PDA@MnO2@NMC in the AZIB cathode exhibits excellent electrochemical performance compared to the pure MnO2, which is expected to have favorable competitiveness in energy storage devices.