The US Navy has a mechanical battery based on spinning flywheels, which store energy as they spin and can discharge it in a quick burst when stopped. It could be used to power laser weapons or railguns, or even to store energy for homes.
Generators provide sustained power, but can’t be cranked up for the short bursts of high power that are needed for directed energy weapons and railguns. For these, the US Navy currently uses banks of lithium-ion batteries. These can …