In situ electropolymerization of 2,7-Di(thienyl)pyrene-4,5,9,10-tetraone for superior lithium-ion battery cathodes

The dissolution of organic materials in electrolytes and their low electrical conductivity pose significant challenges to their application as electrode materials of batteries. To address these limitations, an electropolymerizable molecule, 2,7-di(thienyl)pyrene-4,5,9,10-tetraone (PTO-2TH), with a high theoretical capacity of 377mAh g- 1, was proposed, synthesized, and fabricated as a cathode material for lithium-ion batteries. Leveraging an effective, streamlined, and efficient in situ electropolymerization strategy, the thiophenes on PTO2TH smoothly undergo electro-oxidative coupling reactions during the initial cycles within battery electrode. The resulting polymer, PPTO-2TH, affords a reliable and high specific capacity of 372 mAh g- 1@0.2 A g- 1 and a high energy density of 1078.8 Wh kg- 1 under ambient conditions. It also exhibits outstanding rate capability and exceptional cycling stability, retaining a high capacity of 98mAh g- 1 even at high current density of 5 A g- 1, with an average capacity decay of only 0.001 % per cycle observed between the 1000th and 4000th cycles. PPTO-2TH even exhibits good performance under low-temperature conditions, delivering a reversible capacity of 141mAh g- 1@0.2 A g- 1 at 2 degrees C. The charge storage sites and mechanisms, as well as the polymerization process, are elucidated through electrochemical testing, DFT simulations, and ex situ characterizations (XRD, SEM, UV-vis, FTIR, XPS).