Risk is inherent in all United States Navy operations, training exercises, and missions, no matter how routine. The Navy reduces or offsets these risks by systematically identifying hazards and assessing and controlling the associated risks allowing decisions to be made that weigh risks against mission or task benefits. For systems like munitions, petroleum fuels and even nuclear fuel, the degradation and decomposition mechanisms are clearly understood. However, the stochastic nature of high energy density lithium-ion battery failures make certification and implementation of these systems on Navy platforms problematic. Recent battery safety incidents in the commercial sector with e-cigarettes, hoverboards and even electric vehicles highlight these challenges. The mission of our group at the Naval Research Laboratory (NRL) is to understand the basic science of lithium battery safety to identify key material, chemical and electrochemical signatures of instability that lead to catastrophic failure. One of the most realistic threats to battery safety is internal short circuits caused by metallic lithium dendrites that act as electrical pathways for high current draw, leading to thermal runaway. We have found the morphology and subsequent physical properties of these structures to be temperature-dependent. This talk will focus on temperature-induced degradation effects under isothermal condition and more catastrophically, under an imposed external thermal gradient. We leverage a well understood phenomenon in the field of physical metallurgy, undercooling, to draw an electrochemical parallel to describe the nucleation and growth of lithium dendrites and the underpinnings of short circuits in lithium-ion batteries. Lastly, I will present materials design and battery diagnostic considerations to help steer future battery technology towards high performance and safety and away from catastrophic failure and harm to Sailors, Marines and Navy platforms.