Impedance characterization of lithium-ion batteries aging under high-temperature cycling: Importance of electrolyte-phase diffusion.

Lithium-ion batteries experiences impedance rise and therefore power fade during aging. Current understanding toward the impedance rise is yet qualitative, leaving quantification of multiple contributions a challenging gap. To fill in this gap, we combine the distribution of relaxation times method and physics-based modeling to analyze the electrochemical impedance spectroscopy of lithium-ion batteries aged by cycling at 45 °C. We find that the oft-neglected low-frequency diffusion is the largest sole source to the impedance rise. Furthermore, thanks to the advanced physics-based impedance model, we distinguish electrolyte- and solid-phase diffusion, identifying that the former dominates over the latter. This piece of understanding implies novel insights into improving battery lifetime, and the methodology developed is flexible to other battery chemistries. • DRT quantifies different polarization losses in a wide frequency range. • Causes of impedance rise during aging are identified. • The oft-neglected diffusion polarization is emphasized. • Model enables separation of electrolyte- and solid-phase diffusion. • Electrolyte-phase diffusion dominates over solid-phase diffusion. [ABSTRACT FROM AUTHOR]