COMPARISON OF MODELING PREDICTIONS WITH EXPERIMENTAL-DATA FROM PLASTIC LITHIUM ION CELLS

Modeling results for a lithium-ion battery based on the couple LixC6 \ LiyMn2O4 are presented and compared to experimental data. Good agreem ent between simulation and experiment exists for several different exp erimental cell configurations on both charge and discharge. Simulation s indicate that the battery in its present design is ohmically limited . Additional internal resistance in the cells, beyond that initially p redicted by the model, could be described using either a contact resis tance between cell layers or a film resistance on the negative electro de particles. Modest diffusion limitations in the carbon electrode ari sing at moderate discharge rates are used to fit the diffusion coeffic ient of lithium in the carbon electrode, giving D-s,D-- = 3.9 x 10(-10 ) cm(2)/s. Cells with a 1 M (mol/dm(3)) LiPF6 initial salt concentrati on become solution-phase diffusion limited at high rates. The low-rate specific energy calculated for the experimental cells ranges from 70 to 90 Wh/kg, with this mass based on the composite electrodes, electro lyte, separator, and current collectors. The peak specific power for a 30 s current pulse to a 2.8 V cutoff potential is predicted to fall f rom about 360 W/kg at the beginning of discharge to 100 W/kg at 80% de pth of discharge for one particular experimental cell. Different syste m designs are explored using the mathematical model with the objective of a higher specific energy. Configurations optimized for a Bh discha rge time should obtain over 100 Wh/kg.