An Alkynyl-Based Olefin-linked Covalent Organic Framework as an Anode Material for Potassium-ion Batteries

Rechargeable batteries, particularly lithium-ion batteries (LIBs), have become the preferred choice for high-performance energy storage systems powering portable electronics. However, potassium-ion batteries (KIBs) are emerging as a viable alternative due to lithium's limited availability and high cost. Covalent organic frameworks (COFs), an advanced class of crystalline porous polymers, have become attractive electrodes for KIBs thanks to their great chemical stabilities and tunable electrochemical properties. In this study, an olefin-linked alkynyl-based COF containing 1,3,5-tri(arylethynyl)benzene (TAEB) and 2,4,6-trimethyl-1,3,5-triazine (TMT) units was utilized as a bulk anode material for KIBs. The TAEB-TMT-COF demonstrated a reversible capacity of 124 mAh g^-1 after 300 cycles with an efficiency of ∼ 99 %. TAEB-TMT-COF also exhibited a reversible capacity of 105 mAh g^-1 after 300 cycles at a high current density of 500 mA g^-1 with ∼ 99 % efficiency. The excellent performance is attributed to the chemical stability of olefin-linkage and the presence of the alkynyl groups, which aid in enhancing the binding of K-ions.