(Invited) Multi-Modal Operando Analysis of Lithium-Solid Electrolyte Interfaces

Abstract

Solid-state batteries (SSBs) have the potential to revolutionize energy storage by increasing energy density and improving safety compared to state-of-the-art Li-ion batteries with liquid electrolytes. However, the formation of solid-solid interfaces poses unique challenges compared to solid-liquid interfaces. This requires new methods to study the fundamental behavior of solid-solid interfaces, and understand their dynamic evolution during cycling1.In this talk, I will present a suite of multi-modal in situ/operando characterization approaches that we have used to study Li metal-solid electrolyte interfaces during cycling. First, to gain an improved understanding of the electrochemical stability, I will discuss operando X-ray photoelectron spectroscopy (XPS) analysis of lithium metal-solid electrolyte interfaces2. This approach allows us to directly observe interphase formation and evolution as the electrochemical potential of the solid-electrolyte surface is biased to potentials below the thermodynamic potential for Li plating. A range of sulfide and oxide ceramic electrolytes were explored, since they exhibit a range of (in)stability levels during Li metal plating.To compliment these spectroscopic measurements, a range of in situ/operando microscopy techniques will also be presented. First, operando optical microscopy results will be presented, which allow for direct observation of the nucleation and growth of Li filaments both into, and out of, solid electrolyte surfaces2-3. By time synchronizing the optical video analysis with the electrochemical signatures of plating and stripping, new insights into the dynamic evolution of morphology and associated electrochemical analysis can be obtained. This micro-scale imaging will also be complimented by in situ analysis at the nanoscale, through a combination of scanning electron microscopy (SEM) and transmission electron microscopy (TEM). By integrating the observations across this multi-modal characterization approach, the implications for SSB performance and stability will be discussed, and critical needs for future research will be described.1) K. B. Hatzell, X. C. Chen, C. L. Cobb, N. P. Dasgupta, M. B. Dixit, L. E. Marbella, M. T. McDowell, P. P. Mukherjee, A. Verma, V. Viswanathan, A. S. Westover, W. G. Zeier “Challenges in Lithium Metal Anodes for Solid State Batteries” ACS Energy Lett. 5, 922 (2020).2) A. L. Davis, R. Garcia-Mendez, K. N. Wood, E. Kazyak, K.-H. Chen, G. Teeter, J. Sakamoto, N. P. Dasgupta “Electro-Chemo-Mechanical Evolution of Sulfide Solid Electrolyte/Li Metal Interfaces: Operando Analysis and ALD Interlayer Effects” J. Mater. Chem. A 8, 6291 (2020).3) E. Kazyak, R. Garcia-Mendez, W. S LePage, A. Sharafi, A. L. Davis, A. J. Sanchez, K.-H. Chen, C. Haslam, J. Sakamoto, N. P. Dasgupta “Li Penetration in Ceramic Solid Electrolytes: Operando Microscopy Analysis of Morphology, Propagation, and Reversibility” Matter 2, 1 (2020).