Optimal Coin Cell Design for Operando Optical Characterisation of Lithium-Ion Batteries

Over recent decades, various operando techniques have been developed to probe battery mechanisms in real time. Optical approaches including Raman spectroscopy, reflection microscopy, and charge photometry are especially attractive because of their low cost, high throughput, and ease of use. Yet, limited attention has been given to designing operando optically-accessible cells that maintain electrochemical performance comparable to conventional coin cells. Here, we present four optically-accessible coin-cell geometries with: free-standing electrodes, electrodes cast on mesh, electrodes cast on perforated foil, and laser-drilled electrodes. We describe the steps needed to integrate these into coin cells and benchmark their performance. Rate tests on lithium cobalt oxide half-cells (0.1 C–2 C) show that free-standing and perforated foil electrodes match the performance of standard coin cells, even at areal loadings of 2 mAh cm −2 . Using the perforated foil design, we demonstrate charge photometry to capture lithiation and delithiation dynamics of lithium cobalt oxide with single-particle resolution. Our findings highlight that operando optical experiments can be performed without sacrificing electrochemical performance, crucial for ensuring conclusions are drawn from representative systems. This integration of optimized cell design with optical methods lays the groundwork for establishing charge photometry and other optical techniques as accessible tools for studying representative electrochemical systems.