Probing Evolution of the Li/β-Li3PS4 Solid-State Electrolyte Interface

Abstract

With electric vehicle (EV) U.S. market share estimated at 2.1% in 2018, the transition to less carbon-emissive transportation is well underway.1 Solid state Li ion conductors are a next-generation battery technology that are particularly promising for EVs, offering the capacitive benefits of Li metal anodes while mechanically resisting evolution of the Li interface and thus prolonging lifetime. Additionally, solid electrolytes are not flammable, providing greater safety than liquid counterparts. Despite theoretical mechanical resistance, interface evolution and Li protrusions are empirically observed in solid state batteries and there is debate as to whether these protrusions nucleate at the Li anode or within the ceramic electrolyte.2,3 Variables that affect these protrusions include interfacial contact, imperfect electronic insulation within the electrolyte, electrolyte density, and pre-existing defects.3 Operando X-ray imaging is key to accessing the buried interface between the Li anode and solid electrolyte non-destructively and is a flexible technique that allows for control of factors that may influence the sites of Li microstructure growth as well as Li microstructure morphology.4,5 In this work, to understand the influence of these factors under realistic operating conditions, operando X-ray tomography is combined with in situ heating and pressure control. Cells of Li, β-Li3PS4 electrolyte, and a blocking contact are constructed and studied during cycling at elevated temperature and pressure. Electrolyte density and defects depend on the composition and synthesis of the ceramic conductor, therefore, two syntheses of electrolyte with different particle sizes are compared. Controlling pressure and temperature addresses the remaining factors of interest as pressure is a key parameter in the stability of interfacial contact while temperature affects the electronic, as well as the ionic, conductivity. Deconvoluting the influence of these variables on Li evolution and morphology is vital to understanding fundamental behaviors of all-solid batteries under realistic conditions. R. Irle, EV-volumes.com (2019) http://www.ev-volumes.com/country/usa/.E. J. Cheng, A. Sharafi, and J. Sakamoto, Electrochim. Acta, 223, 85–91 (2017).F. Han, A. S. Westover, J. Yue, X. Fan, F. Wang, M. Chi, D. N. Leonard, N. J. Dudney, H. Wang, and C. Wang, Nat. Energy (2019).N. Seitzman, H. Guthrey, D. B. Sulas, H. A. S. Platt, M. Al-Jassim, and S. Pylypenko, J. Electrochem. Soc., 165, 3732–3737 (2018).E. Kazyak, S. William, C. Haslam, J. Sakamoto, N. P. Dasgupta, E. Kazyak, R. Garcia-mendez, W. S. Lepage, A. Sharafi, A. L. Davis, A. J. Sanchez, K. Chen, C. Haslam, J. Sakamoto, and N. P. Dasgupta, Matter, 2, 1025–1048 (2020).