Anatomy of a thermal runaway

Lithium-ion (Li-ion) batteries are now common in many data center applications, due in part to their increased use in other consumer, automotive and industrial applications. Li-ion technology continues to gain market share from lead-acid battery types such as valve-regulated lead-acid (VRLA). Some equipment vendors say most of their three-phase uninterruptible power supply (UPS) systems ship with Li-ion battery strings, although this ratio varies across vendors.

The business case for Li-ion batteries is undeniably strong: they take up a fraction of the space for the same energy capacity and have longer shelf lives. Cell health is less sensitive to temperature variations, and when the UPS system calls upon them, Li-ion cells can withstand deeper and many more discharge cycles without degradation in capacity. Furthermore, many end users of Li-ion batteries perceive them as sustainable because of their applications in electric vehicles (EVs), although this reputation does not account for the heavy environmental footprint of their production and the unsolved issue of their disposal (see EU battery regulations: what do the new rules mean?).