From the Scifi.com blog:
...a new battery created by Japanese inventor Susumu Suzuki gets its power from an even cooler source: water. The size of a AA battery, the little energy source gets juiced up with just a tiny amount of water — even licking it will do the trick. The thirsty batteries can last far longer without degrading than normal batteries and could cost a mere 1/10th the price of their alkaline cousins if they were to be mass produced. And the best part? The mostly carbon-based batteries are much less damaging to the environment when they get tossed in the trash. Sounds good to us, but time will tell if these guys will replace the copper top.