UC Davis Institute of Transportation Studies

This paper is concerned with the testing and evaluation of various battery chemistries for use in PHEVs. Test data are presented for lithium-ion cells and modules utilizing nickel cobalt, iron phosphate, and lithium titanate oxide in the electrodes. The energy density of cells using NiCo (nickelate) in the positive electrode have the highest energy density being in the range of 100-170 Wh/kg. Cells using iron phosphate in the positive have energy density between 80-110 Wh/kg and those using lithium titanate oxide in the negative electrode can have energy density between 60-70 Wh/kg. The situation regarding the power capability (W/kg) of the different chemistries is not as clear because of the energy density/power capability trade-offs inherent in battery design.

Simulations of Prius plug-in hybrids were performed with Advisor utilizing lithium-ion batteries of the different chemistries. The UC Davis test data were used to prepare the battery input files needed in Advisor. Simulations were made for battery packs weighing 60 kg and 120 kg. The simulation results show that the selection of the battery chemistry for plug-in hybrids is closely linked to the details of the vehicle design and performance specifications and expected driving cycle. Economic factors such as cycle life and battery cost and battery management and safety issues must also be considered in selecting the most appropriate battery chemistry of plug-in hybrids.