Originally developed by Alcan,
Now a private Company in Kingston Ontario,
They use a special grade of aluminum and salt water as the electrolyte. The problem is they are not storage batteries as we know them. They are designed as continuous power sources. They need oygen from the air or supplimental O2 supply, and they consume the aluminum plates. Once activated by adding the salt water they produce a contant energy/current flow until they run out of aluminum. The also produce Hydrogen gas as a by product. A concern in submarines of course, Oxygen supply and hydogen by product mmmmm BANG!
To this end the only way to shut them off, is drain the salt water out of them to stop the chemical reaction.
Some work has been done for use as back up to generators in arctic applications and as power sources for robot submarines by the Canadian Navy. There is also some experimental (Hush, it's a secret) work being done to create a portable electrical power source, for supplimental heating for divers in extreme cold environments.
regards
Mike D