A surfactant-assisted strategy to tailor Li-ion charge transfer interfacial resistance for scalable all-solid-state Li batteries

Solid-state batteries with Li anode present a promising design to achieve high energy density and safe batteries that meet today's growing demands for portable electronics, electric vehicles, and grid-scale energy storage. Garnet-type solid Li-ion electrolytes exhibit desired physical and chemical properties, including high total (bulk + grain-boundary) Li-ion conductivity, chemical stability with elemental Li, and high electrochemical stability window (6 V vs. Li⁺/Li), which make them a unique candidate membrane for all-solid-state batteries. A significant challenge with all-solid-state batteries is the high area specific resistance (ASR) in the solid electrolyte/Li anode interface. Although a substantial reduction in interfacial ASR has been achieved recently with Li-stuffed garnets and Li anode, the equipment and techniques used present massive challenges in both cost-effectiveness and scalability. Here, we show a surfactant-assisted wet chemical method to deposit a ZnO layer on Li-stuffed Li_6.5La_2.9Ba_0.1Zr_1.4Ta_0.6O₁₂ (LLBZT) that increases the contact area between Li/LLBZT and reduces interfacial ASR from 70 to 10 Ω cm² at room temperature. Microstructural analysis reveals the uniform distribution of nano ZnO, which causes an excellent Li wetting on the garnet electrolyte and improvement in the contact area between the electrolyte and electrode. Electrochemical characterization and galvanostatic cycling confirm stable Li plating/stripping for more than a hundred cycles at 0.1 mA cm^-2, demonstrating a compelling strategy to solve the Li/solid electrolyte interface problem in all-solid-state Li batteries.