Rational design of air-stable and intact anode-electrolyte interface for garnet-type solid-state batteries

Garnet-type solid-state electrolytes are a promising fast lithium-ion conductor due to their high room-temperature ion conductivity and inherent stability against lithium metal. However, interfacial lithiophobic Li 2 CO 3 makes garnet/Li interfacial ionic contact challenging. The general approach to physically or chemically eliminating Li 2 CO 3 inevitably leads to a Li-deficiency layer at the garnet surface, significantly retarding interfacial ion transport. Contrary to the aforementioned approach, herein we chemically upcycle the Li 2 CO 3 on the garnet surface via the double replacement reaction between Li 2 CO 3 and SiO 2 . This approach in-situ constructs an air-stable and lithiophilic Li x SiO y (LSO) on the garnet surface and averts the Li-deficiency layer formation. The LSO modified symmetric cell displays a low interfacial impedance of 3 Ω cm 2 and a high critical current density of 1.2 mA cm −2 at 30 0 C. This work provides a promising strategy to upcycle interfacial Li 2 CO 3 on the garnet electrolyte. We proposed an effective strategy to upcycle the Li 2 CO 3 impurities on the surface of the garnet electrolyte by transforming them into the desired LSO layer. Simultaneously, extra Li 2 CO 3 is added to prevent the formation of the Li-deficiency phase. • The detrimental Li 2 CO 3 on the garnet surface is chemically converted into air-stable lithiophilic Li x SiO y . • The extra supplied lithium prevents the formation of Li-deficiency defects at the garnet surface. • The air-stable Li x SiO y prevents the regeneration of surface Li 2 CO 3 upon exposure to air. • The assembled Li symmetric cell displays a high critical current density of 1.2 mA cm −2 and a low interfacial impedance (3 Ω cm 2 ) at 30 o C.