Some DJI drones uses LiPo, some uses Li-Ion, but as others have said they are all Lithium-Ion batteries.
The Mavic 4 uses LiNiMnCoO2 - Lithium nickel manganese cobalt oxides - which is also a Li-Ion.
The takeoff altitude (service ceiling) specification is quite conservative. For example the Mavic 3 has 6000 meters max service ceiling, but people have taken off from the top of Mt. Everest with it, and ascended to over 9000 meters above sea level.