The Influence of the Entropic Effect on Battery Performance

摘要

1. The entropy is an interesting property to characterize electrodes and full cells 2. The measurement of the entropy is time consuming and needs well defined test methods 3. The heat effect by the entropy can be used in some systems for battery state determination 4. The operation of cells and parallel connected cells is influenced by the entropic effect, especially for systems with flat ocv curves. 5. Parallel cells show depending on the slope of the ocv, the voltage hysteresis and the entropic effect inhomogeneous current distribution. For LFP-Gr cells up to 20% SOC inhomogeneity (at 15℃ temperature difference) was monitored. 6. Within cells we find accelerated aging at partial soc cycling, strongly depending on the soc window and the dod. 7. The reason for this effect seems to be a horizontal Lithium displacement. 8. The mechanism is not totally understood, but we think it is caused by an entropic effect in combination with overhanging anode areas and flat ocv potentials.