High plating currents without dendrites at the interface between a lithium anode and solid electrolyte

Avoiding lithium dendrites at the lithium/ceramic electrolyte interface

and, as a result, avoiding cell short circuit when plating at practical current

densities remains a significant challenge for all-solid-state batteries.

Typically, values are limited to around 1 mA cm−2, even, for example,

for garnets with a relative density of >99%. It is not obvious that simply

densifying ceramic electrolytes will deliver high plating currents. Here we

show that plating currents of 9 mA cm−2 can be achieved without dendrite

formation, by densifying argyrodite, Li6PS5Cl, to 99%. Changes in the

microstructure of Li6PS5Cl on densification from 83 to 99% were determined

by focused ion beam-scanning electron microscopy tomography and used

to calculate their effect on the critical current density (CCD). Modelling

shows that not all changes in microstructure with densification act to

increase CCD. Whereas smaller pores and shorter cracks increase CCD, lower

pore population and narrower cracks act to decrease CCD. Calculations

show that the former changes dominate over the latter, predicating an

overall increase in CCD, as observed experimentally