Real-Time Stress Measurement in SiO2 Thin Films during Electrochemical Lithiation/Delithiation Cycling
Real-Time Stress Measurement in SiO2 Thin Films during Electrochemical Lithiation/Delithiation Cycling
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DOI：
10.1007/s11340-017-0371-2
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发表时间：
2018-01
影响因子：
2.4
通讯作者：
Subhajit Rakshit;R. Tripuraneni;S. Nadimpalli
中科院分区：
文献类型：
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作者：
Subhajit Rakshit;R. Tripuraneni;S. Nadimpalli
氧化物涂层已被证明可以改善高密度电极材料（如Si）的循环性能。然而，目前还没有对这些氧化物涂层的力学特性进行研究。在这里，薄膜sio2电极在恒流条件下（以C/9的速率）在半电池结构中循环，锂金属箔作为反/参比电极，以1 M LiPF6in碳酸乙烯，碳酸二乙酯，碳酸二甲酯溶液（1:1:1,wt%）作为电解质。采用多光束光学传感方法，对电化学锂化/去电解过程中sio2薄膜电极的应力演化进行了现场测量。在锂化过程中，sio2发生了广泛的非弹性变形，峰值压应力为3.1 GPa；在脆化过程中，应力变为拉伸，峰值应力为0.7 GPa。建立了包覆二氧化硅纳米管的简单平面应变有限元模型，以了解电化学循环作用下核壳型微结构的力学响应；模型中使用实测应力响应来表示sio2的本构行为，而将Si作为一种弹塑性材料，其力学性能依赖于文献中获得的浓度。本文报告的结果提供了见解和定量理解，为什么高脆性的sio2涂层能够维持显著的硅芯体积膨胀（300%）而不破裂，并提高了硅的循环性能。此外，这里介绍的基本机械性能是未来设计和开发耐用的Si/ sio2核壳结构或sio2基电极的必要的第一步。
Oxide coatings have been shown to improve the cyclic performance of high-energy density electrode materials such as Si. However, no study exists on the mechanical characterization of these oxide coatings. Here, thin film SiO2electrodes are cycled under galvanostatic conditions (at C/9 rate) in a half-cell configuration with lithium metal foil as counter/reference electrode, with 1 M LiPF6in ethylene carbonate, diethyl carbonate, dimethyl carbonate solution (1:1:1, wt%) as electrolyte. Stress evolution in the SiO2thin film electrodes during electrochemical lithiation/delithiation is measuredin situby monitoring the substrate curvature using a multi-beam optical sensing method. Upon lithiation SiO2undergoes extensive inelastic deformation, with a peak compressive stress of 3.1 GPa, and upon delithiation the stress became tensile with a peak stress of 0.7 GPa. A simple plane strain finite element model of Si nanotube coated with SiO2shell was developed to understand the mechanical response of the core-shell type microstructures under electrochemical cycling; measured stress response was used in the model to represent SiO2constitutive behavior while Si was treated as an elastic-plastic material with concentration dependent mechanical properties obtained from the literature. The results reported here provide insights and quantitative understanding as to why the highly brittle SiO2coatings are able to sustain significant volume expansion (300%) of Si core without fracture and enhance cyclic performance of Si reported in the literature. Also, the basic mechanical properties presented here are necessary first step for future design and development of durable Si/SiO2core shell structures or SiO2-based electrodes.