Energy storage systems (ESSs) have gained increased attention over the years due to our dependency on energy in daily life executions. The eco-friendly type of energy storage is desired to help combat global warming. Rechargeable batteries, especially lithium-ion batteries (LIBs) have become one of the most popular high-performance energy storage systems used as a power source for portable electronics. Potassium-ion batteries (KIBs) are slowly becoming an alternative to LIBs due to Lithium's scarcity and high cost. A high KIB performance greatly depends on the anode electrode material and the right type of electrolyte that compliments it. Covalent organic frameworks (COFs), an organic polymers with distinctive qualities such as high stability, high porosity, easy synthesis, and high crystallinity are used for gas adsorption, catalysis, optical properties, and as an anode in KIB. Herein, alkynyl-based (containing 1,3,5-tri(arylethynyl)benzene (TAEB)) and non-alkynyl-based (containing 1,3,5-tris(4-formylphenyl)benzene (TFPB)) olefin-linked COFs have been used as bulk organic anode materials in a low concentrated electrolyte (LCE) for KIB. Aldol condensation reaction in a solvothermal condition was used in the synthesis of these COFs. The olefin-linked TAEB COF gave a high capacity performance of 124 mAh g^-1 after 300 cycles at 98% coulombic efficiency and the olefin-linked TFPB COF gave a capacity performance of 29 mAh g^-1 after 300 cycles at 99 % coulombic efficiency on a current loading of 50 mAh g^-1. The high-performance olefin-linked alkynyl-based COF can be attributed to the high stability of the olefin linkages that extend their pi-conjugation along the x and y planes of the 2D COF and the alkynyl groups that allow K ion storage at the anode. To boost performance, TAEB COF is effectively synthesized onto the outer surface of multi-walled carbon nanotubes (MWCNTs). This composite is then utilized as an anode material for potassium-ion batteries (KIBs). The stratified arrangement of the COF on the MWCNTs facilitates greater exposure of active sites and rapid K ion storage, resulting in enhanced performance.

Psaras McGrier

The Ohio State University

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