Ethynyl/Thienyl-Functionalized Porphyrin Complexes as High-Performance Cathodes for Electrochemical Energy Storage

Organic molecules are promising candidates for next-generation energy storage; however, it still faces challenges of high solubility and low electronic conductivity. Here, we propose two functionalized porphyrin complexes, [5,15-bis(2-thienyl)–10,20-bis(5-ethynyl-2-thienyl)porphinato]copper(II) (CuDET4P) and its metal-free analogue DET4P, as high-performance cathodes for lithium organic batteries. The introduction of ethynyl and thienyl substituents effectively suppresses active material dissolution, thereby enhancing cycling stability. CuDET4P delivers a high stabilized reversible capacity of 216 mAh g–1 after 100 cycles, with a maximum capacity of 221 mAh g–1 at the 69th cycle, while DET4P exhibits a lower reversible capacity of 180 mAh g–1 under comparable conditions. Remarkably, at a high current density of 1 A g–1, both cathodes maintain excellent long-term stability, with capacity retentions of 89.1% and 88.2% for CuDET4P and DET4P, respectively, over 500 cycles. Furthermore, copper coordination is found to significantly boost rate capability, making CuDET4P a superior performer. This study demonstrates that the synergistic effects of ethynyl and thienyl functionalization, combined with metal ion coordination, offer a promising molecular design strategy for developing durable and high-energy organic electrodes.