Building a Better Li-Garnet Solid Electrolyte/Metallic Li Interface with Antimony

Abstract

The deployment of Li-garnet Li7La3Zr2O12 (LLZO) solid-state electrolytes in solid-state batteries is severely hampered by their poor wettability with metallic Li. In this work, Sb is presented as a compelling interfacial layer allowing superior wetting of Li onto a LLZO surface, resulting in a remarkably low Li/LLZO interfacial resistance of 4.1(1) Ω cm2. An atomistic insight into Sb-coated LLZO interface using soft and hard X-ray photoelectron spectroscopy and focused ion beam time-of-flight secondary ion mass spectrometry shows the formation of a Li-Sb alloy as an interlayer. It is determined that the Li/Sb-coated LLZO/Li symmetrical cells exhibit a high critical current density of up to 0.64 mA cm−2 and low overpotentials of 40–50 mV at a current density of 0.2 mA cm−2 without applying external pressure. The electrochemical performance of Sb coated-LLZO pellets is also assessed with an intercalation-type V2O5 cathode. Li/Sb-coated-LLZO/V2O5 full cells deliver stable capacities of around 0.45 mAh cm−2, with a peak current density of 0.3 mA cm−2.