Adv. Funct. Mater.: 納米級氧化鋅涂層提高鋅負極的長久穩定性

一、 【導讀】?

水系鋅電池因成本低、綠色環保等優點，具有較大的應用前景；然而其鋅金屬負極的枝晶生長問題影響了電池的壽命，甚至還帶來電池短路風險，這對水系鋅電池的商業化進程是一大阻礙。涂層改性是應對鋅枝晶的重要方法之一，低成本的涂層改性鋅負極材料極具吸引力。

二、【成果掠影】

近日，溫州大學袁一斐、何坤教授和浙江大學陸俊教授等人開發了一種氧化鋅納米涂層改性鋅負極材料。材料是通過簡單的水熱處理和低溫燒結制備的，通過氟化銨刻蝕劑去除了商業鋅片表面的缺陷，利用尿素絡合劑原位構建了納米級涂層。本工作的改性鋅負極材料與其合成方法是首次報道。相關研究成果以題“Long-cycling zinc metal anodes enabled by an in situ constructed ZnO coating layer”發表在國際頂尖材料類期刊 Advanced Functional Materials上。

?三、【核心創新點】

1) 所開發的改性鋅負極材料及其合成方法是首次報道；2) 氧化鋅納米涂層改性鋅負極材料具有成本低、穩定性高的優點；3) 聯合有限元模擬、FIB/HADDF-STEM表征、原位光學實驗分析了鋅枝晶抑制機理。

?四、【數據概覽】

圖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熱法、低溫燒結，掃描電鏡圖表明涂層呈凹狀形貌，應用FIB、TEM技術獲得涂層厚度約500 nm，改性材料的電解液潤濕性增強。

圖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表征揭示涂層與鋅片之間屬化學結合，改性材料具有良好的結構穩定性。有限元模擬數據表明涂層均勻了電極表面的電場和濃度場，這利于實現均勻的鋅沉積。

圖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.

改性樣品在5 mA cm^-2/1 mAh cm^-2條件下穩定循環1765 h；在50 mA cm^-2大電流下，穩定充放電達3800次，展現了優異的穩定性。

圖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).

原位光學觀察發現氧化鋅納米涂層有效抑制了鋅枝晶的不可控生長，HADDF-STEM表征揭示了鋅沉積發生在改性涂層的上方。

五、【成果啟示】

綜上所述，本工作開發了一種低成本、高性能的氧化鋅納米涂層改性鋅負極材料，結合有限元模擬、原位光學觀察、HADDF-STEM等方法技術分析了鋅枝晶抑制機理，在水系鋅電池的實際應用和電極反應理論方面均具有一定的價值。

原文詳情：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