哈工大张乃庆AM：动态自适应界面涂层用于稳定锌金属负极

【研究背景】

水系锌（Zn）离子电池因其电极材料的广泛性、安全性、环保性和高能量密度而引起人们的广泛关注。锌离子电池采用金属锌作为负极，理论能量密度高达820 mAh/g，具有很好的发展潜力。然而，金属锌电池水系电解液中表面钝化和枝晶的生成问题导致了电池寿命的急剧衰减，严重制约了其实际应用。在充放电循环过程中，锌负极体积的剧烈变化导致了电极/电解质界面的不稳定。然而，现有的刚性界面涂层在循环过程中不能与锌保持共形接触，会发生不可逆的断裂。因此，这样的界面涂层不足以适应电极的这种变化，无法提供持续的保护。相反，高质量的动态界面将缓冲表面变化，始终与电极保持接触，并抑制枝晶的生长。因此，合理的界面设计至关重要。有必要构建一个动态的、自适应的保护层来持续保护锌负极。

【工作介绍】

近日，哈尔滨工业大学的张乃庆教授团队开发了一种高度自适应的PDMS（聚二甲基硅氧烷）/TiO_2-x涂层，它可以动态适应体积变化并均匀锌离子沉积，抑制树枝晶生长，以稳定Zn金属表面。合成的聚合物PDMS由于B-O键的微交联，具有粘弹性的力学特征，赋予其高动态适应性。而富氧空位TiO_2-x和PDMS的结合诱导了Zn²⁺的快速和均匀转移。优异的力学性能和快速传导为金属锌负极的稳定运行提供了有效保障。基于上述两种协同作用，金属锌负极获得了优异的循环性能。本文所构建的自适应界面层为锌负极的稳定运行提供了充分的保证。相关工作以“Dynamic and Self-adapting Interface Coating for Stable Zn Metal Anode”为标题发表在Advanced Materials期刊上。

【文章图表】

图1 界面涂层保护作用的原理示意图，以及材料的物理表征。(a) Schematic diagram of interface coating and protective mechanism. (b) Infrared spectra of different coatings. (c) Raman spectra of partial wave numbers. (d) X-ray diffraction patterns. (e) SEM image of the coating surface (the scale in the picture is 10 μm). (f) TiO_2-x high resolution transmission. (g) EPR to measure oxygen vacancy

图2 涂层材料的力学分析。(a) B-O bond dynamic change process. (b) Rheological test of coating Loss modulus and storage modulus of PDMS. (c) Rheological phase Angle of PDMS and PDMS/TiO_2-x. Optical photos of (d) Slow stretching at 0.5 cm s^-1 (e) Fast stretching at 30 cm s^-1

图3 保护涂层抑制枝晶生长的形貌。Effect of protective layer on inhibition of dendrite growth. SEM images of Zn metal deposited on PDMS/TiO_2-x coated Zn after 50 cycles under the capacity of a)0.5 mAh cm⁻², b)1 mAh cm⁻², c)3 mAh cm⁻² and current density of 1 mA cm⁻². Zn metal deposited on PDMS/TiO_2-x coated Zn after 100 cycles under the capacity of d)0.5 mAh cm⁻², e)1 mAh cm⁻², f)3 mAh cm⁻² and current density of 1 mA cm⁻² (g) optical photographs of bare Zn deposition cross section (h) optical photographs of deposition cross section with protective coating added

图4 锌在TiO_2-x氧空位的吸附能计算以及枝晶抑制的理论模拟。(a) Theoretical simulation models and surface adsorption energy of zinc with (a) TiO_2-x and (b) TiO₂. Bare zinc surface: (c) distribution of ion concentration and (d) current density. The electrode surface after adding PDMS/TiO_2-x coating: (e) Zn-ion concentration and (f) current density distribution

图5对称电池以及Zn||MnO₂电池的电化学性能。Battery cycle performance test: (a) Coulomb efficiency of different Zn electrodes at 0.5 mA cm⁻² and 0.5 mAh cm⁻². (b) The plating and stripping voltage profiles at 1 mA cm⁻² and 1 mAh cm⁻² (c) Coulomb efficiency of different Zn electrodes at 10 mA cm⁻² and 1 mAh cm⁻². (d) platting/stripping voltage curve of different Zn metal anodes at 10 mA cm⁻²,10 mAh cm⁻². (e) Long cycle performance of the Zn||MnO₂ battery at 1C. (f) 400th cycle charge-discharge curve. (g) Rate performance

Z. Guo, L. Fan, C. Zhao, et al. Dynamic and Self-adapting Interface Coating for Stable Zn Metal Anode, Advanced Materials, DOI:10.1002/adma.202105133