I'm writing a story where in the future bullets have become obsolete as batteries have become cheap and very energy dense, so much that making defensive lasers that are able to vaporize bullets before they touch you its plausible. So the question is, is this even possible? How much energy you could pack in something the size of a cellphone battery? Given a lot more space, say the size of a car, could you change the course of the bullet so the vapor doesn't hit you?
A 'box' of perfect mirror containing photons in a vacuum might be your best bet here, since you're using the energy to produce a laser anyway you can instead just open up a pinhole in the 'box' to extract the energy. such a system can approach E=MC^2 though you won't need nearly that much for the desired application. unlike antimatter suggested by alexander (though good on him for pointing it out) this doesn't produce harmful and hard to harness gamma rays.
the specific energy by mass of such a system is as previously stated E=MC^2, they specific energy by volume is just slightly less than the swartzchild radius.
that being said this is very much overkill for the application given and if your civilisation has energy storage this good they have much better options available to them than bullets and well war. the enthalpy of vaporisation of lead is 178 KJ/mol or 860J/gram in other words even if someone threw a tonne of bullets at you it would take only 9 micrograms worth or energy about 860MJ to get rid of them all meaning you need no where near ideal energy storage to do it.
Finally if you did do this I am afraid the lead oxide fumes will immediately kill everyone on the battle field from exposure and if this technology is available then bullet have been made obsolete last century. other than that this technology is totally viable.