In Situ Multimodal Optical Imaging Platforms to Study Battery Reactions

Abstract

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 platform to image the battery electrode reaction dynamics across the interfaces throughout the entire reaction process. The platform includes a 3D optical microscope, surface plasmon microscope, optical reflection microscope, and Raman spectrometry. The 3D optical microscope allows us to image the morphology changes during the battery reaction dynamics. The Zn deposition process on 3D Zn-Mn alloy electrode has been studied, and the 3D morphology and the Zn nucleation have been imaged in situ. We have also used the surface plasmon microscope, optical reflection microscope, and Raman spectrometry to study the SEI formation on Li metal electrodes. The platform provides us important interfacial chemical information, including SEI formation and chemical compositions: 1) The plasmonic imaging technique provides us information on 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.