(Invited) In-Operando Neutron Scattering Studies of Interfacial Electrolyte Chemistry

Abstract

The electrode-electrolyte interface plays a critical role in the performance of electrochemical energy storage systems. To understand the complex processes occurring at the interface of Li-ion or Na-ion batteries, and how these relate to processes occurring in the electrodes, multiple techniques are required. In addition to methods such as X-ray diffraction, Raman spectroscopy, and transmission electron microscopy that are available in the laboratory, specialized in-operando experiments at major facilities are being developed that provide unique information on the dynamic evolution in rechargeable batteries, electrochemical supercapacitors, and more. Here we discuss the use of small angle neutron scattering to investigate changes in solid electrolyte interphase (SEI) formation, pore filling, and electrode microstructure during cycling. This work relies upon the use of high surface area electrodes to provide sufficient signal for neutron scattering studies, which traditionally rely upon gram scale quantities of material. Additional ex-situ data may be collected using methods such as X-ray photoelectron spectroscopy (XPS) to help constrain the interpretation of the data. Up to now, several electrochemical systems have been investigated, in particular including carbonate electrolytes with LiPF6 or NaPF6 salts, and several ionic liquid-based electrolytes and salts. This talk will present work on various electrolyte systems, demonstrating the high level of detail provided, and illustrating the process of interpreting the scattering curves. Recent work on the electrolytes containing TFSI- and FSI- salts will be highlighted, along with improved understanding of concentrated electrolyte systems. Acknowledgement: Research was sponsored by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Materials Sciences and Engineering Division. Research at Spallation Neutron Source user facility was sponsored by the Division of Scientific User Facilities, Office of Basic Energy Sciences, US Department of Energy, under contract DE-AC05-00OR22725 with UT-Battelle, LLC.