In-situ induced self-solidification and activation of ultra-high energy density organic cathode

•We have developed a method of in situ electrochemical polymerization that the terminal-acetylene coupling occurs at high operating voltage (4.5 V vs. Li/Li+) without Cu elements. This is a very effective method to show that the kinetic performance and the long-term stability of the molecular cathode are greatly improved.•Utilization of the general approach, the assembly engineering of organic battery is unprecedentedly simplified, and the cathode based on 2,7-diethylnylpyrene-4,5,9,10-tetraone delivers an ultrahigh capacity of 411 mAh/g with a robust retention in 1000 cycles. The energy density is raised up to 955 Wh/kg. Our results demonstrate that such a method has broad application prospects in organic batteries with high energy density.•Significantly, this approach activates the new positions of the diyne linkage for storing anions, efficiently compensating the capacity decline caused by the introduction of nonactive unit in the polymerization approach.•PTO-diyne providing a high reversible capacity of 411 mAh/g over 1000 cycles.