Adv. Funct. Mater.: 纳米级氧化锌涂层提高锌负极的长久稳定性

一、 【导读】 

水系锌电池因成本低、绿色环保等优点，具有较大的应用前景；然而其锌金属负极的枝晶生长问题影响了电池的寿命，甚至还带来电池短路风险，这对水系锌电池的商业化进程是一大阻碍。涂层改性是应对锌枝晶的重要方法之一，低成本的涂层改性锌负极材料极具吸引力。

二、【成果掠影】

近日，温州大学袁一斐、何坤教授和浙江大学陆俊教授等人开发了一种氧化锌纳米涂层改性锌负极材料。材料是通过简单的水热处理和低温烧结制备的，通过氟化铵刻蚀剂去除了商业锌片表面的缺陷，利用尿素络合剂原位构建了纳米级涂层。本工作的改性锌负极材料与其合成方法是首次报道。相关研究成果以题“Long-cycling zinc metal anodes enabled by an in situ constructed ZnO coating layer”发表在国际顶尖材料类期刊 Advanced Functional Materials上。

 三、【核心创新点】

1) 所开发的改性锌负极材料及其合成方法是首次报道；2) 氧化锌纳米涂层改性锌负极材料具有成本低、稳定性高的优点；3) 联合有限元模拟、FIB/HADDF-STEM表征、原位光学实验分析了锌枝晶抑制机理。

 四、【数据概览】

图1  a) The schematic fabrication process of the ZnO-Zn sample; SEM images of b) Zn foil and c, d) ZnO-Zn samples; e) TEM-EDS mapping of the sample cut from c; f) XRD patterns of the samples, where "sample 1" represents the Zn foil after hydrothermal treatment, "sample 2" represents the powder detached from Zn foil after 4 h of hydrothermal processing, and "sample 3" corresponds to the product obtained after heating sample 2 in air; g) the high-magnification TEM image of sample 3 in f; h) the digital images describing the contact angle of the electrolyte on Zn and ZnO-Zn samples.

本工作的材料合成方法是水热法、低温烧结，扫描电镜图表明涂层呈凹状形貌，应用FIB、TEM技术获得涂层厚度约500 nm，改性材料的电解液润湿性增强。

图2  a, b) XPS spectra (survey spectrum, Zn 2p); c) the optical image of Zn foil; SEM images of d) Zn and g) ZnO-Zn samples; finite element simulation analysis, the simulative electrical field models based on e) Zn and h) ZnO-Zn electrodes; the simulative zinc ion concentration field models based on f) Zn and i) ZnO-Zn electrodes.

XPS表征揭示涂层与锌片之间属化学结合，改性材料具有良好的结构稳定性。有限元模拟数据表明涂层均匀了电极表面的电场和浓度场，这利于实现均匀的锌沉积。

图3 The galvanostatic cycling test of symmetric coin-type cells based on Zn and ZnO-Zn electrodes at a) 5 mA cm^-2 and c) 10 mA cm^-2 with 1 mAh cm^-2; b) rate performance of symmetric coin-type cells based on ZnO-Zn electrodes at various current densities from 1 to 8 mA cm^-2 with 1 mAh cm^-2 (10 cycles per step); d) the side-view SEM image of the plated ZnO-Zn electrode at 10 mA cm^-2 with 10 mAh cm^-2 in symmetric coin-type cells; e) overpotential of Zn and ZnO-Zn anodes at 1 mA cm^-2; f) the linear sweep voltammetry of Zn and ZnO-Zn samples; g) voltage profiles of Zn//Ti and ZnO-Zn//Ti asymmetric cells at 5 mA cm^-2.

改性样品在5 mA cm^-2/1 mAh cm^-2条件下稳定循环1765 h；在50 mA cm^-2大电流下，稳定充放电达3800次，展现了优异的稳定性。

图4 a) 3D images of the Zn electrode after being plated at 5 mA cm^-2 with 1.25 mAh cm^-2 in the optical cell; b) performance comparison of the various Zn anodes; in situ optical observations of c) Zn and f) ZnO-Zn samples being plated at 5 mA cm^-2; SEM images of d, e) Zn and g, h) ZnO-Zn anodes at the plated state after 50 cycles at 5 mA cm^-2 with 1 mAh cm^-2 in symmetric coin-type cells; i) the preparation of the cross-sectional sample of the plated ZnO-Zn anode; j) HAADF-STEM and k) TEM images of the cross-sectional sample; l) HRTEM images of Zn electrodepositions near the interface (marked with a blue frame in k).

原位光学观察发现氧化锌纳米涂层有效抑制了锌枝晶的不可控生长，HADDF-STEM表征揭示了锌沉积发生在改性涂层的上方。

五、【成果启示】

综上所述，本工作开发了一种低成本、高性能的氧化锌纳米涂层改性锌负极材料，结合有限元模拟、原位光学观察、HADDF-STEM等方法技术分析了锌枝晶抑制机理，在水系锌电池的实际应用和电极反应理论方面均具有一定的价值。

原文详情：Qingqing Ren^†, Xinyue Tang^†, Kun He*, Congmin Zhang, Wei Wang, Yaqing Guo, Zixuan Zhu, Xiaofen Xiao, Shun Wang, Jun Lu*, Yifei Yuan*，Advanced Functional Materials，2