Novel Insoluble Organic Cathodes for Advanced Organic K‐Ion Batteries

Abstract Organic redox‐active molecules are inborn electrodes to store large‐radius potassium (K) ion. High‐performance organic cathodes are important for practical usage of organic potassium‐ion batteries (OPIBs). However, small‐molecule organic cathodes face serious dissolution problems against liquid electrolytes. A novel insoluble small‐molecule organic cathode [ N , N ′‐bis(2‐anthraquinone)]‐perylene‐3,4,9,10‐tetracarboxydiimide (PTCDI‐DAQ, 200 mAh g −1 ) is initially designed for OPIBs. In half cells (1–3.8 V vs K + /K) using 1 m KPF 6 in dimethoxyethane (DME), PTCDI‐DAQ delivers a highly stable specific capacity of 216 mAh g −1 and still holds the value of 133 mAh g −1 at an ultrahigh current density of 20 A g −1 (100 C). Using reduced potassium terephthalate (K 4 TP) as the organic anode, the resulting K 4 TP||PTCDI‐DAQ OPIBs with the electrolyte 1 m KPF 6 in DME realize a high energy density of maximum 295 Wh kg −1 cathode (213 mAh g −1 cathode × 1.38 V) and power density of 13 800 W Kg −1 cathode (94 mAh g −1 × 1.38 V @ 10 A g −1 ) during the working voltage of 0.2–3.2 V. Meanwhile, K 4 TP||PTCDI‐DAQ OPIBs fulfill the superlong lifespan with a stable discharge capacity of 62 mAh g −1 cathode after 10 000 cycles and 40 mAh g −1 cathode after 30 000 cycles (3 A g −1 ). The integrated performance of PTCDI‐DAQ can currently defeat any cathode reported in K‐ion half/full cells.