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Understanding Failure Mechanisms of Solid Electrolyte Interphase on Silicon Anodes: An in-Situ AFM Approach

Monday, 20 June 2016
Riverside Center (Hyatt Regency)
R. Kumar, A. Tokranov, B. W. Sheldon (Brown University), Z. Huang, T. Mueller, C. Li (AFM Business Unit, Bruker Nano Surfaces), and X. Xiao (General Motors, R&D Center)
The formation and evolution of solid electrolyte interphase (SEI) directly governs the lifetime and performance of rechargeable Lithium-ion batteries. There are lots of studies dealing with chemistry of the SEI layer but very little information is available in terms of its mechanical behavior for example fracture behavior, strength etc. To enable utilization of high capacity anode materials such as Silicon which goes through large volume changes (~300%) during cycling, a mechanistic understanding of SEI layer is of critical importance. In this study we have used in-situ atomic force microscopy (AFM) to monitor the formation, evolution and failure of the SEI layer on patterned Si island electrodes. The unique PeakForce tapping mode was used to image the extremely fragile SEI layer, which is very challenging for conventional AFM modes in organic solvent. Our in situ studies show for the first time the in operando cracking of SEI layer and its evolution during cycling. Based on a succession of AFM images showing failure of SEI layer, we were able to calculate the critical strain at which this failure starts. A classical energy release rate approach was used to get a bound of fracture energy values of SEI layer for a range of elastic moduli of SEI layer. This study not only provides an in-depth understanding of failure modes of SEI layer but also offer guidance towards tailoring passivation layers for optimal battery performance.