Lightweight Electric/Hybrid Vehicle Design

Electrolyte
discharge
Electrolyte
inlet
Cell frame
GDE
Screw
Cathode
support
frame
Fig. 2.5 Exploded view of aluminium/air bipolar battery (courtesy Eltech Systems).
Viable energy storage systems 35
Cathode
current
collector
Anode
assembly
The development of advanced battery chemistries with increased power and energy density will
place even greater demands on cell packaging in the future and a new family of optimum proportions
needs to be designed for the job.
2.3 Status of the aluminium battery
In 1997, patents were filed in Finland for a new aluminium secondary battery. The inventor was
Rainer Partanen of Europositron Corporation who claims major improvements in power density
and energy density for the new cell based on a 1.5 V EMF2 . The author is interested in this
problem because it represents one of the last major barriers to be overcome before the widespread
introduction of electric and hybrid vehicles. In recent years, significant effort has been directed at
improving secondary battery performance and this effort is beginning to bear fruit. We can now
see advanced lead acid, nickel metal hydride and Lithium Ion products out in the market place
with performance of up to 100 Wh/kg and 200 W/kg.
Market requirements fall into two distinct categories: (a) small peak power batteries of 500 Wh
(2 kWh for hybrids) and (b) 30–100 kWh for pure electric vehicles. Each of the cell types has its
own distinctive attributes but none has so far succeeded in making the breakthrough required for
mass market EV implementation. The fundamental problem is one of weight. At the factory gate,
vehicle cost is almost proportional to mass, as is vehicle accelerative and gradient performance.
Consequently it will take at least 300 Wh/kg and 600 W/kg to achieve the performance/weight
ratio for long range electrics we really desire. This would make one type of hybrid particularly
attractive – the small fuel cell running continuously together with a large battery.