力曲线用于硅负极材料表面膜的研究

An Investigation on the Solid Electrolyte Interphase of Silicon Anode for Li-Ion Batteries through Force Curve Method

利用原子力显微镜(AFM)力曲线模式来研究锂离子电池硅负极材料在含碳酸亚乙烯酯添加剂(VC)电解质首周循环时固态电解质相表面膜(SEI膜)的三维结构.测试表明SEI膜具有多层结构,同时得到SEI膜厚度、杨氏模量以及覆盖度在首周循环过程中的变化,采用三维图呈现了硅材料表面膜的分布.

Non-aqueous electrolyte has been widely used in commercial Li-ion batteries. Optimized choices are proceeding among the various types of salts and solvents, in an effort to achieve higher performance of electrolyte. However, the electrolyte will be reduced in low potential and the reductive product will be deposited on the surface of anode to form a passivating layer, solid electrolyte interphase（SEI）. Herein an atomic force microscopy（AFM） based method was introduced to study the structure and mechanical property of SEI on silicon thin film anode during the first cycle. Silicon has been known as the most potential candidate anode for next generation of Li-ion batteries. However, large volume change and unstable SEI formation during cycling are needed to be solved before practical application. In this study, the electrolyte was 1 mol·L-1LiPF6（EC：DMC = 1：1） containing 2% vinylene carbonate. Layered-structure such as single layer, double layers and triple layers of SEI were detected, and the Young＇s Modulus of the SEI was extracted from the force curves. Coverage of SEI was also obtained. A 3-D plot was introduced to real space mapping the formation of SEI on silicon anode at different cycle states.