Interfacial Engineering with a Nanoparticle-Decorated Porous Carbon Structure on β″-Alumina Solid-State Electrolytes for Molten Sodium Batteries.

We present a novel anode interface modification on the β″-alumina solid-state electrolyte that improves the wetting behavior of molten sodium in battery applications. Heat treating a simple slurry, composed only of water, acetone, carbon black, and lead acetate, formed a porous carbon network decorated with PbOx (0 ≤ x ≤ 2) nanoparticles between 10 and 50 nm. Extensive performance analysis, through impedance spectroscopy and symmetric cycling, shows a stable, low-resistance interface for close to 6000 cycles. Furthermore, an intermediate temperature Na-S cell with a modified β″-alumina solid-state electrolyte could achieve an average stable cycling capacity as high as 509 mA h/g. This modification drastically decreases the amount of Pb content to approximately 3% in the anode interface (6 wt % or 0.4 mol %) and could further eliminate the need for toxic Pb altogether by replacing it with environmentally benign Sn. Overall, in situ reduction of oxide nanoparticles created a high-performance anode interface, further enabling large-scale applications of liquid metal anodes with solid-state electrolytes.