TABLE OF CONTENTS In the sodium-nickel chloride battery (sometimes known as the Zebra or Beta battery), the liquid sulphur positive electrode of the sodium-sulphur battery is replaced by a nickel chloride positive electrode, otherwise the construction is very similar (see Figure 5.5). The sodium salt electrolyte is modified to sodium chloroaluminate which has a lower melting point, at 160 C, than the sodium electrolyte of the previous battery. It also becomes a powder rather than a solid on freezing, making reactivation easier and avoiding the mechanical stress problems which occur on freezing in the sodium-sulphur battery.
The battery operates at a slightly lower temperature (300 C) than sodium-sulphur, has a similar energy density of 100 Wh/kg, and the same maximum power density of 150 W/kg. If damaged it is potentially less dangerous than sodium-sulphur due to the relatively harmless nature of the potential nickel chloride-sodium contact. Another advantage it has over the sodium-sulphur battery is that the cells fail to a short-circuit condition rather than open circuit. This permits the use of single series chains of cells so avoiding the circulating currents present in parallel chains. The cells can also be assembled without the corrosive liquid sodium negative electrode which can be added later.
The Daimler-Benz subsidiary AEG-ZEBRA is now the principal manufacturer having merged in 1987 with the original developers BETA R&D, a subsidiary of the Anglo-American Corporation. The battery is being tested by a number of vehicle manufacturers and there are plans for high-volume...
