Ethynyl functionalized porphyrin complex as a new cathode for organic alkali metal batteries with excellent cycling stability

Organic materials, featuring low cost, structural diversity, and environmental friendliness, have emerged as promising electrode materials for rechargeable batteries in recent years. However, they suffer from unstable cycling performance due to their high solubility in liquid electrolytes. Herein, we demonstrated a novel functionalized porphyrin [5,15-bis(ethynyl)- porphinato]copper(II) (CuDEP) as the stable organic cathode for organic alkali metal batteries. Owing to the in-situ electropolymerization and multiple electron transfer capability, CuDEP showed highly reversible capacity, long-term cycling stability (106 mAh/g at 1 A/g after 5000 cycles), and superior rate performance in organic lithium battery. N atoms act the charge storage sites where both cations and anions are alternatively stored during the charge and discharge. In organic sodium and potassium batteries, CuDEP cathode also demonstrated stable cycling and high rate capability. This result suggests that ethynyl group functionalized small porphyrin molecule would be a promising cathode for long-term organic alkali metal batteries for green and stable energy storage.