The relevant science is "Conservation of energy", one of the most fundamental principles.
If you want to heat a certain mass of something by a certain number of degrees, whether it's a complex chemical or pot of water, you have to put the appropriate number of watt-seconds of power (= joules) in to it, regardless of the power source.
That can be slow or fast, high wattage for a short time or lower wattage for a longer time, but the amount of power or energy needed must come from somewhere.
You can boil a jug or cup of water with a low voltage element - 12V ones have been available for many years.
They are normally intended to run from a vehicle "cigar lighter" power connection, but there is no reason they could not be used from a 12V battery pack, if it were big enough.
Example:
**broken link removed**
You would need a battery pack that can provide 12 to 15V at a minimum of ten amps for probably 10 - 15 minutes, to boil each cup quantity of water.
A large four cell drone battery pack (eg 5AH) could run it and make two or three cups of coffee.
It's possible, just not convenient. That's why gas is so often used for small heating appliances and tools, as the energy "storage" in a small can of gas is vastly higher than the best similar size battery made so far.