Pack Level Estimations for Beyond Lithium-Ion Chemistries with High Theoretical Specific Energy and Energy Density

In response to the development effort of battery powered electric vehicles, the search for new battery chemistries with sufficiently high specific energy and energy density has been accelerated. The lithium-sulfur battery is one of the candidate chemistries that has gained significant attention over the several decades due to its much higher theoretical specific energy and energy density compared to today's Li-ion battery [1, 2].

                Theoretical specific energy and energy density, which are calculated considering only the active material mass and volume, are frequently used for the comparison of candidate chemistries; however the conclusions can be significantly different when one considers the system-level properties. In this study, the dependence of the system-level properties on the open-circuit voltage, theoretical specific energy, and area-specific impedance of the cell couple are discussed.

                The system-level specific energy and energy density are estimated for hypothetical cell chemistries with various open-circuit cell voltages and theoretical specific energies using the publically available Battery Performance and Cost (BatPaC) model [3, 4] for a 50 kWh, 100 kW and 360 V battery.

                The system-level energy density predictions can be seen in Figure 1 for various open-circuit voltage and theoretical specific energy couples. The dependence of the system-level specific energy on OCV is critical; at low OCVs systems with significantly higher specific energies show similar system-level properties. High theoretical specific energy systems continue to get lighter and smaller with increasing OCV whereas low theoretical specific energy systems do not because of the maximum electrode thickness limitation. System-level specific energy and fraction of the theoretical specific energy and energy density achieved on the pack level are also discussed as a function of OCV, theoretical specific energy and area-specific impedance. Finally, the Li-S battery, which has high theoretical specific energy but low OCV, is investigated.

Figure 1. The effect of open-circuit voltage on the system-level energy density for different theoretical specific energies. Theoretical energy density is not constant on constant theoretical specific energy curves.

Acknowledgments

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. The submitted abstract has been created by UChicago Argonne, LLC, Operator of Argonne National Laboratory (“Argonne”). Argonne, a U.S. Department of Energy Office of Science laboratory, is operated under Contract No. DE-AC02-06CH11357.

References

1.             Bruce, P.G., S.A. Freunberger, L.J. Hardwick, and J.-M. Tarascon, Nature Materials, 11, 19 (2012).

2.             Ji, X.L. and L.F. Nazar, Journal of Materials Chemistry, 209821 (2010).

3.             Nelson, P., K. Gallagher, I. Bloom, and D. Dees, Modeling the Performance and Cost of Lithium-Ion Batteries for Electric Vehicles, Chemical Sciences and Engineering Division, Argonne National Laboratory, ANL-11/32, Argonne, IL USA, (2011).

4.             Nelson, P.A., K.G. Gallagher, and I. Bloom, BatPaC (Battery Performance and Cost) Software, (2012).