Improving the Low-Temperature Performance of Electric Vehicles by Hybrid Energy Storage Systems

Electric vehicles based on high-energy Li-ion batteries often show a substantial loss in performance at cold temperatures: Due to slower electrochemical kinetics, internal resistances of the battery rise and available power and capacity diminish. In order to overcome these weaknesses, a selection of hybrid energy storage systems (HESS) is investigated here: Different hybrid systems combine a high-energy Li-ion battery with either a double-layer capacitor or a Li-ion capacitor or a high-power Li-ion battery. For these three types of HESS, experimental studies performed at various temperatures reveal available energy under realistic driving conditions. At temperatures of 0 ^oC and below, an increased driving range can be achieved with two of the three HESS combinations. Depending on the available space for the energy storage system, either the HESS utilizing a Li-ion capacitor or the HESS utilizing a high-power Li-ion battery is found to be the most promising solution for electric vehicle applications.