150 nano meters wide, the nano battery 6 times smaller than a bacterium, couple a hundreds times thinner than a human hair and more than 60,000 times smaller than a AAA batter, which all means u cannot see it in naked eye.
Then battery is being developed in Rice University. The tiny battery is merged between a super-capacitor and the battery it self, super-capacitor stores electric charge which give out jolts of power at once. The battery is made in thousands of arrays where each battery is is a nano wire where one wire is the positive and the other a negative.. This battery could power all kinds of large and tiny electronic devices, in medical and chemical fields and microscopic wireless networks.
The battery is still a prototype and a lot of research is still required, which means it is going to take some time for commercial use.