Understanding the High‐Load Characteristics of Lithium‐ion Batteries Using a Combination of Three‐ and Two‐Electrode Measurements

To enhance control strategies for lithium‐ion batteries (LIBs) in vehicle applications, it is crucial to accurately understand their output behavior under high loads. However, conventional two‐electrode cells lack a reference electrode, making individually monitoring of positive and negative electrode potentials difficult and thereby limiting the analysis of overpotential and ohmic loss. In this study, LiCoO 2 and graphite were used as electrode materials and their single‐electrode characteristics and full‐cell performance were evaluated using a three‐electrode cell and a two‐electrode cell, respectively, under high‐load conditions up to 10C discharge and with electrolyte salt concentrations of 500, 1000, and 2000 mol/m 3 . Increasing the salt concentration improved the capacity of the LiCoO 2 but reduced that of the graphite. The full‐cell capacity was notably low at 500 mol/m 3 but similar between 1000 and 2000 mol/m 3 . The single‐electrode analysis results showed that the full‐cell capacities were dominated by LiCoO 2 at 500 and 1000 mol/m 3 and by graphite at 2000 mol/m 3 . These results indicate a latent reversal phenomenon not observable from full‐cell data alone. Electrochemical impedance and direct‐current resistance measurements, along with the reaction rate equation, enabled a theoretical interpretation of these behaviors. These findings highlight that high‐load LIB dynamics can only be fully understood through single‐electrode analysis. © 2026 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.