Unveiling the Reference Electrode’s Artifacts: Competition between Polarization and Delay

Integration of reference electrodes (REs) in lithium-ion batteries is a critical step toward enabling in situ diagnostics, real-time monitoring of electrode potentials, and development of advanced battery management systems. However, practical implementation of REs remains hampered by the presence of artifacts that distort local potential measurements and compromise diagnostic accuracy. This study investigated the origin and impact of such artifacts through a combined experimental and simulation-based approach. Using six cell designs incorporating lithium foil or lithium iron phosphate (LFP) mesh REs, we show that the blocking effect of the RE induces (1) localized polarization due to increased local resistance, particularly pronounced for Li REs, and (2) delayed lithiation on the positive electrode (PE) and negative electrode (NE) areas facing the RE, highlighted by post-mortem analysis. A pseudo-3D Newman model elucidates the behavior of the RE and its surroundings. Polarization and delay phenomenon induced by the RE are shown to compete: the former leads to an underestimation of the NE potential, while the latter leads to its overestimation during charge. These findings provide a comprehensive understanding of the origin of RE artifacts, suggest design guidelines for minimizing them, and highlight the necessity of interpreting RE measurements with an awareness of such artifacts.