An Impedance Behavior Study of Commercial NCA Cylindrical Battery Cells at Different SOCs

Abstract

The impedance behavior of a commercial Nickel-cobalt-aluminum(NCA) cylindrical cell was studied in this work. A series of impedance experiments was designed to explore the impact of battery state of charge (SOC) and other operating conditions. Our results indicated the impedance response of this cylindrical battery varies with the state of charge in both charge and discharge process. Experimental results also showed the SOC dependent impedance existed in different operating temperatures and C-rates. An impedance model was developed to explore the potential mechanisms behind experimental observations. Model results showed that the operating temperature and charge-discharge rate could significantly influence the impedance response of the battery but could not directly cause the variation of the impedance response at different SOC conditions. Results also showed that the contact resistance variation, resulted from the expansion and contraction of cell electrodes during charge and discharge, could lead to a SOC dependent impedance behavior of the commercial cell and influence battery output performance.

Data science accelerates energy device development

“…[29][30][31][32][33][34] Kinetic degradation can be probed through pulse power tests or electrochemical impedance spectroscopy. [35][36][37][38] Those low rate and impedance tests are best known for being non-destructive, and because of this, many introduce low-rate cycles and pulse tests periodically to their testing process to track changes in both thermodynamic and kinetic properties. [39][40][41][42] By building data-driven models with fitted physicsbased degradation parameters as input, and device performance, such as battery cycle life as output, we can correlate the device degradation with physic-based parameter change like resistance rise or electrode capacity drop while achieving low prediction errors.…”

Data science accelerates energy device development

“…[29][30][31][32][33][34] Kinetic degradation can be probed through pulse power tests or electrochemical impedance spectroscopy. [35][36][37][38] Those low rate and impedance tests are best known for being non-destructive, and because of this, many introduce low-rate cycles and pulse tests periodically to their testing process to track changes in both thermodynamic and kinetic properties. [39][40][41][42] By building data-driven models with fitted physicsbased degradation parameters as input, and device performance, such as battery cycle life as output, we can correlate the device degradation with physic-based parameter change like resistance rise or electrode capacity drop while achieving low prediction errors.…”