Performance and operando failure analysis of laser-perforated Li–Cu reference electrodes in lithium-ion pouch cells

The potential of reference electrodes in future-oriented battery technologies relies critically on their design optimization. Previous studies show that locating reference electrodes within the effective stack region, while maintaining a minimally invasive geometry, is essential for precise and artifact-free electrochemical sensing. Here, we fabricated a highly porous (93%) microscale Li–Cu reference electrode by in-situ Li deposition on a laser-perforated Cu substrate. Since Li reference electrodes remain intrinsically unstable, we implemented a three-stage workflow to evaluate their performance and failure behavior. First, galvanostatic deposition of 0.5 mAh cm −2 Li delivered a stable reference potential for over 3000 h. A subsequent parametric study showed that Li stability depends on both deposition parameters and operating conditions. Accelerated failure during operation was linked to active Li consumption into inactive species, as revealed by coupled thickness–potential monitoring and supported by complementary analyses. Finally, benchmark testing confirmed that the perforated design enables reliable potential tracking with negligible blocking effects under the investigated conditions, supporting diagnostic measurements such as differential analysis and EIS. This work advances the understanding of Li-based reference electrodes and highlights perforated designs as a promising strategy for reliable sensing in battery systems.