PNNL

Abstract

Wetting liquid metal on the solid electrolyte of a liquid-metal battery determines the battery’s operating temperature and performance. Liquid sodium electrodes are particularly attractive because of their low cost, natural abundance, and geological distribution, but wet poorly on a solid electrolyte near its metaling temperature, limiting their widespread suitability for low-temperature batteries used for large-scale energy storage systems. Herein we develop an isolated metal island strategy that can improve sodium wetting in sodium-beta alumina batteries that allows operation at lower temperatures. Our results suggest that in situ heat treatment of a solid electrolyte followed by bismuth deposition effectively eliminates oxygen and moisture from the surface of the solid electrolyte, preventing the formation of an oxide layer on liquid sodium, leading to enhanced wetting. We also show that employing isolated bismuth islands significantly improves cell performance, retaining 94% charge after the initial cycle, an improvement over cells without bismuth islands. These results suggest that coating isolated metal islands is a promising but simple strategy for the development of low-temperature sodium-beta alumina batteries.