Study On Lithium-ion Batteries Thermal Runaway Propagation Characteristics And Blocking Techniques

Lithium-ion batteries are well-suited for electric vehicles and ships, due to their high specific energy and power. However, safety issue has become the main barrier for lithium-ion batteries to be applied in these fields. Thermal runaway(TR) propagation blocking techniques can prevent thermal runaway events initiated in one cell from propagating to adjacent cells. As a result, battery pack damages as well as collateral damages and personnel hazards are minimized. Through experiments, this thesis studies the characteristics of thermal runaway(TR) propagation within lithium-ion battery modules. TR propagation blocking techniques are also investigated. This thesis mainly comprises the following sections:1) Characteristics of TR propagation both in open circumstances and adiabatic circumstances are investigated. Experiment results show that TR does not easily propagate in open circumstances. While in adiabatic circumstances, heat generated by triggered cells hardly transfers to the environment. Nevertheless, flame and core materials released from exploded cells in adiabatic circumstances have greater influences on adjacent cells. Thus, the TR in adiabatic circumstances propagates more easily.2) In adiabatic circumstances, TR propagation characteristics of lithium-ion batteries with different capacities are investigated at different intervels. The closer batteries are, the more easily TR propagates. The larger capacities of cells are, the more easily TR propagates. Because batteries with larger capacities have poor tolerance to higher temperatures and release more energy and core materials when they explode.3) Maximum safe specific energies of battery modules constituted by cells with different capacities are investigated. Experiment results show that modules constituted by cells with lower capacities have higher safe specific energies than modules constituted by larger capacities cells.4) TR propagation blocking effects of different thermal insulation materials are studied. Aerogel boards can isolate the flame and core materials released from the exploded cells and decrease the heat transfer by weakening convection and thermal radiation. Thus, applying aerogel boards between cells can pvevent the TR events initiated in the triggered cells from propagating to adjacent cells. Mica tapes twined on the cell surface can block heat transfer through metal connections in modules and decrease heat transfer by weakening convection and thermal radiation. Therefore applying mica tapes on cell surfaces can also pvevent TR events initiated in the triggered cells from propagating to adjacent cells.5) TR propagation blocking effects of venting passageways are investigated. Venting passageway can isolate the flame and core materials released from exploded cells. Thus, applying venting passageway in battery modules can pvevent the TR events initiated in the triggered cells from propagating to adjacent cells.6) Effects of applying liquid nitrogen to TR propagation blocking are assessed. When thermal runaway occurs, applying liquid nitrogent to target cells or adjacent cells can decrease explosion temperatures and create low-temperature and inert circumstances to quench the flame and cool the core materials released from exploded cells. As a result, propagation of TR between the cells can be prevented.