Thermal Analysis Of Lithium-Ion Battery

With the increasing problems come from energy and environment, the rapiddeveloping of modern science and technology requires higher performance ofbatteries. Lithium ion batteries were concerned firstly owe to theirs favorableproperties of high voltage, high energy density, long cycling life and pollution-free.However, the major handicap of the batteries application is from theirs fire andexplosion hazards. The heat generation behavior of battery cells is critical to thedesignofthethermalcontrolportionofpowersystems.Lithium ion batteries require an adequately maintained thermal environment incase they are to work properly for long periods of time. If lithium ion batteries areallowed to get to warm, they can undergo accelerated degradation or explosion. Ifthey get too cold, their resistance can climb to unacceptablyhigh level. To ensure thesafe usage of lithium ion battery, it is necessary to fully disclose the heat generationinnerthecell.In this dissertation, a study of the heat parameter was conducted throughexperimental rate measurements in adiabatic condition. The heat dissipated of the cellin four different conditions was measured. A comparative heat beheaver wasconducted using auto-equipment of charging and discharging (ARBIN BT2000) fordifferent State-of-Charge and life in different current and temperature conditions. Theimpedance of cell was discussed by AC impendence or DC impulse.the major factorinfluenced thermal process was briefly summarized.and Inner and outer temperature ofcellwasmeasuredusingthermometerwrappedinnercell.The result shows that the resistance increased cause the change of heat. The heatdissipated during last of discharging is greater. During charging initial endothermiccooling and subsequent exothermic heating were observed. The heat dissipated isgreater in constant charging current than in constant charging voltage. The heatdissipatedbehaves endothermicwhenthecurrent under0.25Cduringconstantvoltagecharging phase. The thermal behavior of cell is influenced by current temperature orthe deep of charging. The more heat dissipated was discovered if too cold or biggercurrent or lower SoC or longer life. It is found that the heat dissipated of cell showsline relationship with current during discharge in room temperature. The heat dissipated of cell enhanced its inner temperature, so the discharge capacity andvoltage is not decreased with current and lower temperature. It founds that thedifference of inner and outter temperature in charging is smaller than discharging,lapse rate of them less then 0.19℃/Ah under 1C discharge current, the enhancingtemperature less then 1.25℃/Ah within cell,The quantity of heat inner cell will beaccumulated with cycle life,so the rationalization heat management is nessery to thebatteriesdesigin.