Thermal safety management of lithium-ion battery energy storage systems for use in ocean-going and subsea applications

Increasing power demands for ocean and sub-sea sensors, unmanned and autonomous vehicles as well as requirements of power storage from ocean based generation sources, have led to newer energy storage technologies such as lithium-ion batteries being widely adopted for these purposes. One of the key challenges that operators and users face is the safe integration of these energy storage technologies into the current vehicles or equipment to mitigate or contain the consequences of unintended releases of the stored energy. A catastrophic failure of a battery pack can occur if one or more cells in the battery pack undergo a thermal runaway event rapidly releasing the stored energy in the battery. Thermal runaway can lead to a release of flammable gases, heat or explosions and can potentially result in a mission kill, loss of vehicle or sensor, or hazards to property and life. The objective of this paper is to discuss current research and techniques to measure and quantify the hazards posed by unintended release of stored energy from newer energy storage technologies, as well as mitigation of such hazards. In the present work, the combustion characteristics of vent gases produced due to thermal failure of lithium-ion cells are studied experimentally to assess potential flash fire and explosion hazards associated with venting of lithium-ion cells and packs during thermal runaway events. Gases vented from small format lithium-ion cells during thermal runaway are sampled and analyzed experimentally, and the explosion characteristics including maximum pressure rise, explosion severity and lower and upper flammability limit of the vent gas composition are also measured. Similar analysis can also be applied to larger format lithium-ion cells that may be used in subsea applications. Information obtained from such testing can be combined with thermal modeling and CFD to design, analyze and optimize systems with mitigation measures to prevent or minimize these unintended consequences.