Advanced Lithium-Ion Batteries for Plug-In Hybrid-Electric Vehicles

In this study, electric-drive vehicles with series powertrains were configured to utilize a lithiumion battery of very high power and achieve sport-sedan performance and excellent fuel economy. The battery electrode materials are LiMn2O4 and Li4Ti5O12, which provide a cell area-specific impedance of about 40% of that of the commonly available lithium-ion batteries. Data provided by EnerDel Corp. for this system demonstrate this low impedance and also a long cycle life at 55C. The batteries for these vehicles were designed to deliver 100 kW of power at 90% opencircuit voltage to provide high battery efficiency (97-98%) during vehicle operation. This results in battery heating of only 1.6C per hour of travel on the urban dynamometer driving schedule (UDDS) cycle, which essentially eliminates the need for battery cooling. Three vehicles were designed, each with series powertrains and simulation test weights between 1575 and 1633 kg: a hybrid electric vehicle (HEV) with a 45-kg battery, a plug-in HEV with a 10-mile electric range (PHEV10) with a 60-kg battery, and a PHEV20 with a 100-kg battery. Vehicle simulation tests on the Argonne National Laboratory’s simulation software, the Powertrain System Analysis Toolkit (PSAT), which was developed with MATLAB/Simulink, showed that these vehicles could accelerate to 60 mph in 6.2 to 6.3 seconds and achieve fuel economies of 50 to 54 mpg on the UDDS and highway fuel economy test (HWFET) cycles. This type of vehicle shows promise of having a moderate cost if it is mass produced, because there is no transmission, the engine and generator may be less expensive since they are designed to operate at only one speed, and the battery electrode materials are inexpensive.