ZEBRA battery

The ZEBRA battery is a type of rechargeable molten salt battery based on commonly available and low-cost materials – primarily nickel metal, the sodium and chloride from conventional table salt, as well beta-alumina solid electrolyte. It is technically known as the sodium–nickel–chloride battery, and sometimes as a sodium–metal–halide battery. The common name comes from its development under the Zeolite Battery Research Africa (ZEBRA) project, started in South Africa in 1985.

ZEBRA batteries need to be kept hot (300 °C is often used) because sodium metal melts at 98 °C and because the NaAlCl4-based electrolyte melts above 150 °C. Also such elevated temperature increases the ionic conductivity of beta-alumina solid electrolyte. Due to the thermal management reasons, ZEBRA batteries are only practical when built in large formats. They have been examined primarily for grid energy storage and to a lesser degree for electric vehicles. The ZEBRA is a simpler, safer and less expensive alternative to the otherwise similar sodium–sulfur battery, although it offers less energy density, about 90 to 120 Wh/kg compared to as much as 150 Wh/kg for sodium–sulfur. ZEBRA and sodium–sulfur both compete with better-known systems, like lithium–iron–phosphate and lithium–sulfur in these same roles.

The ZEBRA design saw on-and-off development since the 1980s, with major research being carried out in the AERE Harwell and AEG during the 1990s. After Daimler purchased AEG and then merged with Chrysler, the ZEBRA division was sold off.