Model and experimental studies: Understanding aging mechanisms under high-voltage operation

Model and experimental studies: Understanding aging mechanisms under high-voltage…

Presenter: Jing Ying Ko
Title: Model and experimental studies: Understanding aging mechanisms under high-voltage operation
Affiliation: KTH Royal Institute of Technology

Abstract

To fulfill the demand of long driving range for electric vehicles without compromising the weight and cost of battery is to increase its energy density, i.e. by extending its voltage window. In this work, we intend to examine the aging phenomena under high-voltage operation of a NMC/graphite cell.

When cycled up to 4.5 V, a rapid performance degradation is observed. Aging stems from the NMC electrode rather than graphite. The severe NMC impedance rise causes an inaccessibility of utilizing its capacity, thus inducing cell failure. Therefore, an extended physics-based impedance model is developed to fit electrochemical impedance spectroscopy data from NMC symmetric cells.

The model indicates the particle surface layer, an electrode layer near separator and current collector resistance as the main causes of impedance rise. Higher temperature enhances the rate of degradation. Experimental evidences from scanning electron microscopy and Raman spectroscopy support these model findings.

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Jing Ying Ko
Jing Ying Ko
Jing Ying Ko graduated as a chemical engineer from Friedrich-Alexander-University in Erlangen-Nuremberg, Germany. Now, she is pursuing a doctoral study in battery modeling in the group of Applied Electrochemistry at KTH Sweden, led by Göran Lindbergh. Her work focuses mainly in the modeling of the performance and aging in lithium-ion batteries.