(Invited) Developing in Situ Optical Imaging Techniques to Understand Battery Solid Electrolyte Interface Formation

Abstract

Developing in situ Optical Imaging Techniques to Understand Battery Solid Electrolyte Interface FormationXiaonan Shan. Xu Yang, Guangxia Feng, Yaping Shi, ECE, University of Houston Increasingly complex and heterogeneous chemical reactions on the battery and catalytic electrode surfaces require the characterization methods to provide a complete picture of molecular interactions across the interface in situ. For example, the biggest challenge in accelerating the Li metal batteries towards higher energy density is the lack of fundamental understanding of interfacial chemical reaction on the electrode surface. During the initial lithiation cycles, a solid electrolyte interphase (SEI) forms on the electrode surface due to the electrochemical instability of the electrolyte. Inhomogeneity in reaction activity/deposition rate, chemical compositions, and ionic and electrical conductivity on the battery electrode will cause the non-uniform Li-ion diffusion, and lead to inhomogeneous nucleation and dendrite formation. The traditional imaging and measurement techniques have experienced challenges to characterize these complicated interfacial chemical reactions. For example, most of the methods only provide rich information at a certain time point in the dynamic process, or measure an average result over a large area during the reaction. On the other hand, these interfacial reactions are highly dynamic and spatially varied, and the signals at different time points or different locations could be totally different. We have developed a multimodal optical imaging platforms to image the battery electrode reaction dynamics across the interfaces throughout the entire reaction process. The platform includes surface plasmon microscope, optical reflection microscope, and Raman spectrometry. The platform provides us important interfacial chemical information including SEI formation and chemical compositions: 1) The plasmonic imaging technique provide us information of localized SEI thickness and localized charging status during the reactions; 2) optical reflection microscope allow us to study the SEI and Li nucleation dynamics; and 3) Raman spectrometry provide us chemical composition information. The integration of all the information obtained from this multimodal imaging platform will allow us fundamentally understand SEI formation and electrochemical reaction on the anode electrode.