Abuse response of lithium-ion batteries has been extensively studied over several decades. Most studies on the onset and propagation of battery fires following mechanical deformation are focused on understanding the onset of thermal events following quasi-static loading. Using an array of cylindrical lithium-ion cells as example, we report results from ultra-high strain-rate deformation mechanical events (> 100 /s) that result in electrochemical short-circuits followed by thermal events. We present a methodology that takes stock of gas compositions as a function of state of charge and compute flammability limits. Finally, we discuss implications for flame lengths and propensity for propagation of thermal events.