Materials for Energy, Efficiency and Sustainability: TechConnect Briefs 2015Materials for Energy, Efficiency and Sustainability TechConnect Briefs 2015

Energy Storage Chapter 1

Degradation Mechanisms in Electric Double Layer Capacitors Subjected to Voltage and Temperature Stress Testing

A.S. Peter, M.H. Azarian, M. Pecht
University of Maryland, United States

pp. 33 - 36

Keywords: EDLC, supercapacitor, ultracapacitor, failure, mechanisms, SEI, exfoliation

Due to their high power densities, electric double layer capacitors ¬¬(EDLCs) are used to supplement high energy density power sources (such as lithium ion batteries and fuel cells) in applications such as automotive kinetic energy recovery systems. At the other end of the spectrum, EDLCs are also used in data storage technologies such as redundant array of independent disks (RAID). Such applications demand high reliability from the EDLCs used. To ensure that the EDLCs are capable of satisfying these reliability requirements, original equipment manufacturers (OEMs) need to be able to test and screen samples from several suppliers. In order to achieve this, the test conditions would need to accelerate degradation in EDLCs being evaluated without over-stressing them. In this paper, we subject EDLC samples from different manufacturers to voltage and temperature step stress testing while monitoring each sample’s capacitance and DC (internal) resistance. The variation of these electrical parameters with the applied stress levels is used to identify margins outside the rated temperatures and voltages, within which accelerated testing can be performed. We also identify the failure modes associated with increasing and voltage and temperature stresses. The underlying failure mechanisms causing degradation in EDLCs are determined using post-test analyses.