Hierarchical implementation of electrochemical techniques to provide a reliable diagnosis of commercial lithium-ion pouch cells under selected operational conditions

Abstract

Understanding the performance of commercial Lithium-Ion batteries (LIBs) under various operational conditions is a paramount concern for ensuring their long-term stability. While numerous methodologies exist from a materials perspective to enhance comprehension of fundamental phenomena, electrochemical engineers often rely only on charge/discharge curves. Although these curves provide valuable insights, their information can be enriched through the systematic implementation of electrochemical protocols. This approach offers more nuanced data that can facilitate swift diagnostics of LIB conditions and enable in-depth analysis of underlying physicochemical processes. In this study, a comprehensive methodology is proposed for assessing the reversibility, stability, dominant processes, and degradation effects of LIBs. This involves combining charge/discharge curves with complementary electrochemical techniques and specific methodologies to extract maximum information from the data; for this purpose the following strategies are sequentially applied: Galvanostatic Cycling with Potential Limitation (GCPL), Galvanostatic Electrochemical Impedance Spectroscopy (GEIS), Distribution of Relaxation Time protocols (DRT), and Differential Capacitance (DC) analysis to a range of commercial pouch cell LIBs under diverse conditions. By correlating the results obtained through these techniques, we established meaningful interpretations of battery performance, thorough specialized protocols based on DRT and DC analysis, under various operational case scenarios, the effect of temperature, C-rate, and extended cycling. These protocols yielded crucial electrochemical parameters and relevant characteristics, enabling advanced diagnostics. The proposed framework serves as a guide for methodologically analyzing commercial batteries, it underscores that traditional characterization techniques can be augmented with additional analyses to comprehensively grasp the performance of commercial LIBs.