Anthraquinone-Enriched Conjugated Microporous Polymers as Organic Cathode Materials for High-Performance Lithium-Ion Batteries

Extended pi-conjugated microporous polymers (CMPs) are useful as organic anode or cathode materials in lithium-ion batteries (LIBs), overcoming the issue of small organic molecules becoming soluble in the electrolytes during charge-discharge cycles. In this study, we constructed two CMPs (Py-A-CMP, TPE-A-CMP) containing anthraquinone (A) moieties (as redox-active units and sources of C = O groups) and applied them as organic cathodes in LIBs. We synthesized the Py-A-CMP and TPE-A-CMP through Sonogashira-Hagihara couplings of 2,6-dibromoanthraquinone (A-Br-2) with tetraethynylpyrene (Py-T) and tetraethynyltetraphenylethene (TPE-T), respectively. The TPE-A-CMP displayed high thermal decomposition temperatures (up to 539 degrees C) and char yields (up to 53 wt %). Electrochemical tests revealed that Py-A-CMP and TPE-A-CMP delivered discharge capacities (196.6 and 164.7 mAh g(-1) at a C-rate of 0.1C, respectively) higher than those of other CMP materials. The capacity retention of TPE-A-CMP was 163 mAh g(-1) (99.3%) over 400 cycles. The corresponding cells incorporating Py-T-CMP and TPE-T-CMP also exhibited excellent rate capability performance, maintaining discharge capacities of approximately 79 and 49 mAh g(-1), respectively, at a high charge/discharge rate of 5C. Scanning electron microscopy confirmed the superior stability of both CMPs, revealing that these electrode materials remained intact, without any surface crack formation, during long-term cycling.