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 KPF6 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 (K4TP) as the organic anode, the resulting K4TP||PTCDI-DAQ OPIBs with the electrolyte 1 m KPF6 in DME realize a high energy density of maximum 295 Wh kg(cathode)(-1) (213 mAh g(cathode)(-1) x 1.38 V) and power density of 13 800 W Kg(cathode)(-1) (94 mAh g(-1) x 1.38 V @ 10 A g(-1)) during the working voltage of 0.2-3.2 V. Meanwhile, K4TP||PTCDI-DAQ OPIBs fulfill the superlong lifespan with a stable discharge capacity of 62 mAh g(cathode)(-1) after 10 000 cycles and 40 mAh g(cathode)(-1) 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.