The Experimental And Numerical Research On The Thermal Response Of Lithium Nickel-cobalt-Manganese-oxide/Lithium Titanate Batteries

With the pressure of energy shortages and environmental pollution, lithium titanate batteries as the representative of power batteries have been gained the widespread concern. In this paper, the experimental and numerical investigations were performed to explore the thermal behavior of lithium titanate battery under different conditions. During the experimental, an Accelerating Rate Calorimeter combined with battery charging and discharging cycler was employed to study the electrical and thermal response of the1Ah lithium titanate battery under normal cycling, pulse discharge and high-temperature pulse discharge conditions in the adiabatic environment. The profile of voltage decreased quickly during pulse, and then increased to a special value in the stop time of5min. Due to the existence of pulse in the discharge process, the temperature and temperature rate were higher than that of the normal process. While the effect of the pulse process on the battery thermal response weakened as the temperature inside the battery increased.In the simulation, the heat generations of lithium titanate battery during different operating conditions were analyzed based on the verified electrical-thermal coupled model. For lithium titanate battery at0.5C, the discharging process generated more heat than that of charging which resulted in higher temperature rise, while the total heat value was slightly greater than zero during charging. It was the sharp increase in the irreversible heat generation that the temperature in pulse discharge were higher as shown in the simulation results. Due to the heat of polarization, two temperature peaks were observed during a constant-current discharge, constant-current and constant-voltage charge cycling under natural cooling condition. What’s more, the results of50Ah lithium titanate battery’s temperature and heat generation rate demonstrated that the higher the current, the faster the battery temperature was rising, the longer the times needed to reach thermal balance with the ambient temperature. Additionally, the effect of the current rate on the battery temperature rise was significantly greater than the environment temperature.The thermal abuse model was established considering the material decomposition heat obtained from C80micro calorimeter experiments. On the basis of the electrochemical thermal abuse model, thermal runaway could be simulated under extreme conditions. The thermal influence of the overheated cell on surrounding batteries in the3x7module was simulated. The result showed that the variation of temperature of the adjacent cells could be reached177℃where the separator melts, resulting in the short circuit inside the battery and followed by a sharp temperature rise till to the thermal runaway, leading to a chain reaction in the module and a potentially uncontrollable explosion in the module.This investigation interpreted the thermal behavior of lithium titante battery. The results could provide basic data for the thermal management of the battery pack during various discharging and charging processes as well as to ensure their thermal safety in hybrid electric vehicles applications.