Factors Determining the Manufacturing Costs of Lithium-Ion Batteries for PHEVs

In this study, we developed a model for calculating the costs of lithium-ion batteries supporting electric drive in light duty passenger vehicles (LDVs). The model calculates the annual materials requirements from design criteria for the battery pack including power, capacity, number of cells, and cell chemistry parameters. The costs of capital equipment, plant area and labor for each step in the manufacturing process were estimated for a baseline plant. These costs are adjusted for each battery pack studied by comparing the processing rate pertinent for each step (area to be coated, number of cells to be tested, etc.) with that of the baseline process and applying correction factors. We applied the cost modelling method to batteries with four lithium-ion cell chemistries and for several levels of capacity and power. For quality assurance purposes, electrode coating thicknesses are limited to 100 microns by the model. The result of this restriction is that as the capacity of the cells is increased to achieve longer range under electric power, the electrode area and the cell power are also increased and the power of the entire battery pack is also increased. In simulations of our reference chemistry for 16, 32 and 48 -km PHEVs there is almost no cost increase for increasing the pack power from 40 to 60kW; for PHEVs with 48- and 64 km electric range, there was almost no additional cost for power up to 90 kW. For a set value of pack energy storage, a small number of high capacity cells are much less expensive to manufacture than a large number of low-capacity cells. The useable fraction of the state-of-charge range for a battery system is shown to be an important cost factor. In view of cost similarities, the choice of cell chemistry will probably depend more on proven safety, reliability, and long life rather than on initial cost.