Li6PS5Cl microstructure and influence on dendrite growth in solid-state batteries with lithium metal anode

Enabling lithium metal is key toward maximizing the energy density of solid-state batteries (SSBs) with a solid electrolyte (SE) as the separator. However, the formation of pores at the LiǀSE interface during stripping and short-circuiting during cathodic plating through dendrite growth hinder stable cycling at higher current density. The interface and bulk microstructure of SEs govern the dendrite growth mechanism and hence the maximum or critical current density (CCD) an SE can sustain before shorting. Herein, via the control of the grain size of Li6PS5Cl (LPSCl), we show that interface and bulk microstructure can be simultaneously tailored to significantly influence the CCD. Based on the microstructure-strength relationship, we discuss mechanical failure mechanisms in SSBs derived from correlations between focused ion beam (FIB)-SEM and electrochemical data analyses. We propose that the microstructural influence on local current density and dendrite growth is well connected to the concept of crack growth resistance, or "R curve behavior," observed in certain materials.