Linkage Engineering Boosts Battery Performance of Two-Electron Phenothiazine-Based Polyamide Cathodes

Organic cathode materials based on redox-active p-type phenothiazine have attracted considerable interest for lithium-organic batteries (LOBs) due to their high operating voltage and tunable chemical structures. Nevertheless, their practical application is often limited by low capacity resulting from single-electron transfer per molecule, as well as poor cycling stability caused by solubility issues. In this work, we report three phenothiazine-based polyamides and demonstrate a straightforward linker engineering strategy to synergistically overcome these challenges. The linker motif serves not only as a structural bridge to suppress solubility, but also as a functional design element that governs optoelectronic properties and electron/ion transport kinetics. Among the series, the benzene-bridged polymer MPT-AB exhibits the most balanced optoelectronic performance and transport kinetics, resulting in the best battery performance. When employed as a cathode in LOBs, MPT-AB exhibits two reversible redox processes, a high average voltage of 3.7 V, and a reversible capacity of 150 mAh g^-1 at 0.2 A g^-1. It also demonstrates excellent rate capability and outstanding cycling stability, achieving 90 % and 72% capacity retention after 2000 and 5000 cycles at 5 A g^-1. The potential application has also been demonstrated with satisfactory performance in an MPT-AB//graphite full battery.