Quinone-Enriched Conjugated Microporous Polymer as an Organic Cathode for Li-Ion Batteries

Among various organic cathode materials, C═O group-enriched structures have attracted wide attention worldwide. However, small organic molecules have long suffered from dissolving in electrolytes during charge-discharge cycles. π-Conjugated microporous polymers (CMPs) become one solution to address this issue. However, the synthesis strategy for CMPs with rich C═O groups and stable backbones remains a challenge. In this study, a novel CMP enriched with C═O units was synthesized through a highly efficient Diels-Alder reaction. The as-prepared CMP exhibited a fused carbon backbone and a semiconductive characteristic with a band gap of 1.4 eV. When used as an organic electrode material in LIBs, the insoluble and robust fused structure caused such CMPs to exhibit remarkable cycling stability (a 96.1% capacity retention at 0.2 A g^-1 after 200 cycles and a 94.8% capacity retention at 1 A g^-1 after 1500 cycles), superior lithium-ion diffusion coefficient (5.30 × 10^-11 cm² s^-1), and excellent rate capability (95.8 mAh g^-1 at 1 A g^-1). This study provided a novel synthetic method for fabricating quinone-enriched fused CMPs, which can be used as LIB cathode materials.