Negating the Interfacial Resistance between Solid and Liquid Electrolytes for Next-Generation Lithium Batteries

The combination of solid and liquid electrolytes Li SE SLEI enables the development of safe and high-energy batteries where the solid electrolyte acts as a protective barrier for a high-energy lithium metal anode, while the liquid electrolyte maintains facile electrochemical reactions with the cathode. However, the contact region between the solid and liquid electrolytes is associated with a very high resistance, which severely limits the specific energy that can be practically delivered. In this work, we demonstrate a suitable approach to virtually suppress such interfacial resistance. Using a NASICON-type solid electrolyte in a variety of liquid electrolytes (ethers, DMSO, acetonitrile, ionic liquids, etc.), we show that the addition of water as electrolyte additive decreases the interfacial resistance from >100 Omega cm(2) to a negligible value (<5 Omega cm(2)). XPS measurements reveal that the composition of the solid-liquid electrolyte interphase is very similar in wet and dry liquid electrolytes, and thus the suppression of the associated resistance is tentatively ascribed to a plasticizer or preferential ion solvation effect of water, or to a change in the interphase morphology or porosity caused by water. Our simple estimates show that the improvement in the solid-liquid electrolyte interphase resistance observed here could translate to an enhancement of 15-22% in the practical energy density of a Li-S or Li-O-2 ( )battery and improvements in the roundtrip efficiency of 21-28 percentage points.

Automated summary

The addition of water as an electrolyte additive in NASICON-type solid electrolytes has been shown to effectively suppress interface resistance between solid and liquid electrolytes, leading to potential enhancements in energy density and roundtrip efficiency of Li-S or Li-O-2 batteries.