Who makes li-ion for UPS for AI data centers

Lithium-ion has displaced lead-acid in new UPS installations for reasons that are mostly about floor space and life. It stores far more energy per unit of volume and weight, so the battery room shrinks or disappears into the UPS lineup, and it tolerates many more charge cycles, so it lasts closer to the life of the equipment rather than being replaced several times over. The engineering that comes with it is the battery management system, and it is not optional. Lithium cells need monitoring and balancing at the cell level, thermal management, and a protection scheme that isolates a fault before it propagates. The failure mode everyone plans around is thermal runaway, which is why lithium UPS installations bring their own fire detection, suppression and ventilation requirements, and why some jurisdictions treat a lithium battery room as a different occupancy from a lead-acid one. AI sites make the trade sharper because they need more stored energy in less space, on a schedule where a battery room is floor area not holding compute. Chemistry within lithium matters here — iron phosphate cells give up energy density for better thermal behaviour, which is often the right trade for a UPS that discharges rarely. What to look for is which chemistry a system uses, how the battery management system is integrated with the UPS, and what the local code requires for the room.