Advanced Self-Discharge Measurements of Lithium-Ion Cells and Comparison to Modeling

Abstract

Lithium-ion batteries (LIBs) are currently the most relevant energy storage solution for a wide field of applications starting from mobile communication and going to high power applications in electric vehicles. To assess the quality of a LIB either during production or in post-production, its self- discharge rate is an important parameter. Here we present a new method for precise potentiostatic self-discharge measurements (SDMs) that is very sensitive and considerably faster than other currently available methods. We validated the new SDM by measuring ten commercial 3000 mAh 21700 LIBs resulting in roughly 3 μA self-discharge current with a noise level of 0.1 μA, at 60% state of charge (SoC). Higher self- discharge currents of about 40 μA were observed at a higher SoC of 80%. To model the SDM, the electrochemical processes are coupled with a 3D temperature FEM and an electric circuit model of the cell self-discharge, resulting in a good overlap and a quantitative value of the LIB self-discharge resistance. Furthermore, we tested a realistic physical self-discharge scenario of the formation of Lithium dendrites by comparing experimental and modelled self-discharge resistance values.