In Situ Dendrite Suppression Study of Nanolayer Encapsulated Li Metal Enabled by Zirconia Atomic Layer Deposition

Progressing toward the emerging era of highenergy-density batteries, stable and safe employment of lithium (Li) metal anodes is highly desired. The primary concern with Li metal anodes is their uncontrollable dendrites growth and extreme sensitivity to parasitic degradation reactions, raising the alarms for battery safety and shelf life. Nanolayer protection encapsulation, which is conformal and ionically conductive with a high-kappa dielectric property, can suppress the degradation and empower stabilization of Li metal. In this work, engineering of a zirconia (ZrO2) encapsulation layer on Li metal enabled by atomic layer deposition (ALD) was employed and investigated for surface-enhanced dendrite suppression properties using in situ optical observations and electrochemical cycling. The ALD process involved a combination of plasma subcycle activation and thermal subcycle activation in increasing the surface functionalization and chemisorption sites for precursors to obtain highly dense and conformal deposition. The encapsulation of Li with ZrO2 ALD nanolayer further demonstrated excellent tolerance to atmospheric exposure for at least 1-5 h because of a conformal physical barrier, and excellent heat tolerance up-to 170-180 degrees C (close to Li melting point) and high rate capability due to thermal resistive property and high ionic transport property, respectively, of the ZrO2 ceramic. The results establish a technology transferable to other metal anode chemistries and offer a potential insight into carrying out solid-state electrolyte multilayer coatings with high processing temperature flexibility and thereby providing a leap in the advancing of a range of high energy density all-solid-state batteries.