14500 is a battery size, not a battery chemistry. An alkaline battery has a nominal voltage = 1.5 volts. A NiCad or NiMH battery has a nominal voltage = 1.2 volts. A LiPo battery has a nominal voltage = 3.6 volts, and a LFP battery has a nominal voltage =3.3 volts.
A system designed to operate with 4 AA batteries is designed to operate at 6 volts. 5 AA NiCad or NiMH batteries is an equivalent match, but most systems designed to run on 6 volts will operate at 4.8 volts which is what you get with 4 AA NiMH or NiCad batteries. 2 AA Li batteries are the closest equivalent to 4 Alkaline AA batteries producing either a nominal 7.2 volts or 6.6 volts. When using Li batteries, a load will attempt to draw a higher current in proportion to the voltage ratio or 7.2/6.0 = 120% which is 20% higher than with the alkaline batteries, or 6.6/6.0 = 110% or 10% higher with LFP batteries. If you use 4 batteries, the load will attempt to draw more than twice the design current because the supply current is more than twice the design current. (It's simply ohm's law, I=V/R, in practice.) The power drawn by the load is proportional to the current squared, so the power draw using 4 Li batteries is 4 times that of the alkaline batteries.
If the battery has a low enough impedance so it can supply the current draw required by the lot without difficulty, the battery will be happy. If the current and power delivered due to the higher voltage simply causes an igniter to active quicker, that's also good. But if the current is high enough to over heat the wiring, or burn out a lamp filament or LED, than it's not good.
The bottom line is you should do some very simple specification checks and ohm's law calculations before you change the battery chemistry.
Bob