High energy sodium-nickel battery cell for EV application

The aim is to demonstrate the performance of, and develop manufacturing processes for, an advanced sodium-nickel chloride battery cell with a capacity 200 Wh/kg and power rating 200-300 W/kg, capable of mass production at a cost of $550/kWh by 2015, and ultimately at a cost of $130/kWh. This represents an increase of more than 50% in capacity and power over the state-of-the-art 'Zebra' battery cell that has a good safety record in EVs but is complex and costly to manufacture; the tubular solid electrolyte results in performance limitations due to the high cathode resistance especially at low state of charge, and is operated vertically which is inconvenient for EVs due to the 28 cm height requirement.
We propose a novel slim-line battery cell concept incorporating a thin layer cathode, a flat solid electrolyte manufactured by plastic forming, and a novel hermetic sealing method. The number of cell components + weld operations is thereby reduced from 20 to 10. A composite glass-ceramic-metal seal replaces the Zebra cell's complex and costly header cap. Long cell life is promoted by the use of 2 different glass seals which are corrosion-resistant to the respective electrode materials. The slim-line cell is flexible for battery stacking and can result in an EV battery height of less than 12 cm. Enhanced performance projections have been verified by cathode modelling studies. Raw materials are abundant and low-cost, except for nickel for which the cell requires only 1.5 g/Wh (cf. 6.8 g/Wh in nickel metall hydride cells). No handling of liquid sodium is required since cells are manufactured in the discharged state.