A silicon anode for garnet-based all-solid-state batteries: Interfaces and nanomechanics

High-capacity electrode materials are indispensable for developing high energy density solid-state batteries. The lithium metal anode is attractive because of its high capacity and low electrochemical reduction potential, but its application is hampered by the dendrite issue. The silicon anode is a promising material having high capacity and invulnerability to undergoing dendrite formation, but is limited to the nanometer regime for the thickness of a Si anode. Herein, for the first time, we demonstrate a 1 μm thick solid-state silicon anode (10 times the typical thickness of Si anodes used in organic electrolyte) as an alternative to Li metal anode for solid-state batteries. This Si anode forms good contact with the garnet-type solid-state electrolyte and maintains structural integrity during the Li ion intercalation and extraction. The Si anode with the garnet electrolyte exhibits a high discharge capacity of 2685 mA h g−1 and an excellent initial Coulombic efficiency of 83.2%, higher than that of the Si anodes with an organic electrolyte (77.1%). Our mechanics modeling reveals that the strong nanomechanical constraints by the solid garnet electrolyte enables the substantial increase in the critical thickness of the Si anode from just nanometers to micrometers, toward high-capacity solid-state batteries.