An Experimental Study of a Lithium Ion Cell Operation at Low Temperature Conditions

Lithium-ion (Li-ion) batteries are widely used for various applications such as telecommunication, automotive, and stationary applications. With their wide range of safe operating temperatures (i.e. -10 °C to 50 °C), the Li-ion is preferred over other types of matured battery technologies such as lead acid and nickel-cadmium (NiCd). Nevertheless, operating the Li-ion batteries at cold climate conditions can potentially harm the batteries and lead to issues such as degradation and reduction in their capacity and power density. This paper aims to experimentally investigate the behavior of a Li-ion cell operating at low temperatures (i.e. -15 °C to 25 °C) with respect to its charging and discharging behavior. It was observed that at sub-zero temperatures (i.e. -5 °C, -10 °C and -15 °C) the Li-ion cell's capacity is reduced due to the impedance effect which then increases the cell's internal resistance. Moreover, at such low temperatures the best state of charge (SOC) of the cell (i.e. during charging mode) has reduced to about 7-23% of its maximum initial SOC (i.e. 100%). To complement the experimental finding, an existing simplified adaptive thermal model was used to obtain the discharge curves at various current rates based on the function of extracted charge (Qout). The discharge curve of equilibrium potential (Eeq) is then extrapolated towards zero current in order to obtained the overpotential heat generation curve based on the discharge current of the cell. The result showed a good agreement to the discharge curves that were obtained experimentally. Likewise, with the finding of cell voltage (E), current (I) and temperature (T) that were obtained experimentally, the thermal behavior of the cell in respect of its internal temperature is predicted and represented by comparing both the simulated and experimental cell internal temperatures.