AGING MECHANISM ANALYSIS IN NICKEL-COBALT-MANGANESE TERNARY BATTERIES BASED ON DRT TECHNOLOGY

Abstract

This study investigates 18650-type LiNi0.5Co0.2Mn0.3O2(NCM523)/graphite lithium-ion batteries, systematically collecting electrochemical impedance spectroscopy (EIS) data across various cycle numbers (CN20 to CN240) and SOC(3.0–4.2 V), and employs equivalent circuit models and distribution of relaxation times (DRT) techniques to reveal the multiscale dynamic behaviors and aging mechanisms within the battery. The results indicate that the ohmic resistance of the battery increases significantly with cycle number (2.6-fold from CN20 to CN240), independent of the state of charge, whereas the charge-transfer resistance is closely related to the state of charge but exhibits no significant overall aging trend, suggesting distinctly different aging mechanisms for the two. DRT analysis successfully deconvoluted five polarization processes: SEI/CEI film formation, positive/negative electrode charge transfer, and solid-phase diffusion, with polarization behavior dominated by diffusion control (P5). The impedance of positive/negative electrode charge transfer (P3/P4) and solid-phase diffusion (P5) is highly dependent on the state of charge, exhibiting variations in magnitude ranging from 10- to 740-fold within the same cycle, highlighting the heterogeneity of various dynamic processes. This study provides theoretical insights and data support for optimizing battery performance and extending battery lifespan.