Li_xMn₂O₄-graphite lithium-ion batteries are promising candidates for the electric vehicles and energy storage systems because of their relative high specific energy and power comparing with other commercial rechargeable batteries. However, the thermal management of a Li_xMn₂O₄-graphite lithium-ion battery pack is still a challenge due to the temperature rise and uneven temperature distribution within the pack during EV /HEV operation. The systematic investigation of the electrochemical and thermal behaviors of Li_xMn₂O₄-graphite single lithium-ion battery was therefore conducted in this work first, which aims at providing guidance for single battery design with better performance under different thermal environment. Moreover, the simulation was extended to battery pack level, and...[ Read more ]

Li_xMn₂O₄-graphite lithium-ion batteries are promising candidates for the electric vehicles and energy storage systems because of their relative high specific energy and power comparing with other commercial rechargeable batteries. However, the thermal management of a Li_xMn₂O₄-graphite lithium-ion battery pack is still a challenge due to the temperature rise and uneven temperature distribution within the pack during EV /HEV operation. The systematic investigation of the electrochemical and thermal behaviors of Li_xMn₂O₄-graphite single lithium-ion battery was therefore conducted in this work first, which aims at providing guidance for single battery design with better performance under different thermal environment. Moreover, the simulation was extended to battery pack level, and the thermal analysis of the battery pack under forced air cooling condition was also conducted so as to have a better battery pack design and air cooling solution.

Specifically, a 1D electrochemical model was developed based on Newman's Porous Electrode Theory to investigate the interaction between the electrochemical behaviors and the heat generation rate of Li_xMn₂O₄-graphite lithium-ion batteries. The impacts of various battery cell design parameters, such as the thickness of the porous electrode, the radius of the active solid particles and so on, were investigated using the developed models. Simulation results showed that the simulated discharge curves were in close agreement with the published experimental data, which verified the accuracy of the output of the heat generation rate from the model. The average heat generation rate was chosen to serve as the link to connect the electrochemical model and thermal model of the single battery. Finally, the temperature profile of the battery pack under natural convection and forced air flow were analyzed and discussed. It turned out that the battery pack under natural convection suffered serious temperature rise with value of 15.7K at 4C discharge and the temperature variance could be enlarged to 2.3K at 4C discharge. After applying forced air cooling, the maximum temperature rise of the pack was reduced to only 4.22K at 4C discharge. Two forced air cooling methods were discussed. Among them, the serial cooling strategy enjoyed the relatively lower maximum temperature rise and the paralleled air cooling method resulted in lower temperature variation between batteries within the pack.