Unveiling the Impact of Cross-Linking Redox-Active Polymers on Their Electrochemical Behavior by 3D Imaging and Statistical Microstructure Analysis

Polymer-based batteries offer potentially higher power densities and a smaller ecological footprint compared with state-of-the-art lithium-ion batteries comprising inorganic active materials. However, in order to benefit from these potential advantages, further research to find suitable material compositions is required. In the present paper, we compare two different electrode composites of poly(2,2,6,6-tetramethylpiperidinyloxy-4-yl methacrylate) (PTMA) and CMK-8, one produced with and one without cross-linking the PTMA. The influence of both approaches on the corresponding electrodes is comparatively investigated using electrochemical measurements and statistical 3D microstructure analysis based on synchrotron X-ray tomography. A particular focus is put on the local heterogeneity in the coating and how the cross-linking influences the interaction between PTMA and CMK-8. It is shown that cross-linked PTMA─compared to its non-cross-linked counterpart─exhibits a more heterogeneous microstructure and, furthermore, leads to better surface coverage of CMK-8, larger pores, and shorter transportation pathways through the latter. These changes improve the electrochemical properties of the electrode.