The electrons that make up our electricity are very light; however, batteries have historically been very heavy. I was wondering what the physics reason is for this, and whether we can look forward to much lighter batteries in the future?
traditional batteries produce electron flow by means of an electrochemical reaction that removes electrons from metal atoms as those atoms are dissolved into an acid solution. The most common battery like this is the lead-acid battery in your car. Lead is used here because it is possible to obtain two electrons for every lead atom that gets dissolved, but this means the amount of electricity the battery can provide is set by the mass of lead contained in it.
This in turn means that the mass of a battery is dominated by the mass of the metal it contains- even though the electrons themselves weigh very little in comparison.