Charge/discharge processes of organic radical batteries based on the radical polymer's redox reaction should be largely influenced by the structure and the composition of the composite electrodes. AC impedance measurement of the composite electrodes reveals a strong correlation between the overall electron transfer resistance of the composite electrode and the material of the current collector, and suggests that the electric conduction to the current collector through the contact resistance should be crucial. We also find that the adhesion and the contact area between the composite electrode and the current collector strongly influence the contact resistance rather than the work functions and the volume resistivities of the composite electrode and the current collector. It is also confirmed that the charge/discharge performance of the composite electrode is related to the overall electron transfer resistance of the composite electrode. These results indicate that the charge/discharge performance of the radical battery is dominated by the interfacial electron transfer processes at the current collector/carbon fiber interface. In fact, the composite electrode which has a high adhesion to the current collector shows a small overall electron transfer resistance and an excellent charge/discharge performance. The rate performance would be much improved by suitably designing the interfacial structure including adhesion and contact area.
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