Interface Lithiophobicity Regulation for Lithium Metal Solid-State Batteries

Abstract

Solid-state lithium batteries (SSLBs) using garnet electrolytes potentially have a higher energy density and are safer than commercial liquid organic electrolyte Li-ion batteries. However, SSLBs still face challenges of lithium dendrite growth and high interface resistance. In this work, we addressed both challenges by doping strontium (Sr) into lithium anodes. Different from all previous reported metal/metal oxide coating on garnet or lithium alloy anodes that forms lithiophilic interlayer at Li | garnet, strontium/strontium oxide are enriched on the interface between Li and garnet forming a lithiophilic/lithiophobic bifunctional layer of Li-Sr/SrO-doped-Li2O. This interlayer simultaneously reduces the interfacial resistance and suppresses the growth of lithium dendrite, which is confirmed by comprehensive material characterizations, simulations and electrochemical evaluations using Ta-doped LLZTO (Li6.5La3Zr1.5Ta0.5O12) as a model solid-state electrolyte. The unique stability of the lithiophobic SrO doped Li2O layer against Li prevents reducing the garnet and suppresses lithium dendrite, which distinguishes it from all reported alloy electron-conductor interlayers. The optimized Li-Sr | LLZTO | Li-Sr symmetrical cells have a critical current density of 1.3 mA/cm2 and can be cycled for 1,000 cycles under 0.5 mA/cm2 at room temperature. The bifunctional lithiophilic/lithiophobic interlayer provides a new strategy for high-performance garnet solid-state lithium batteries. Figure 1