Novel Insoluble Organic Cathodes for Advanced Organic K-Ion Batteries

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.