Seawater (or sodium hydroxide)
Aluminum
Nickel Manganese
I'm reading about it here: http://www.zpenergy.com/modules.php?name=News&file=article&sid=717
It says it will transfer three ions per Aluminum atom
Also other company working on varient of this:
www.europositron.com
Stats
Energy density : 2100 W.h/litre or 1330 W.h/kgr
Cycle times : 3000+ cycles
Working temperatures : ?40 C to +70 C
Lifetime battery : 10 to 30 years