Fabrication of flexible and aqueous hybrid supercapacitors with diffusion channels contained copper cobalt bi-Metal Organic Framework nanosheets and ionic conductivity optimized semi-solid electrolyte

Abstract

Metal-Organic Frameworks (MOFs) have established as important energy storage materials owing to their tunable pore diameter, high specific surface area, low density, easily accessible metal active centers, tunable morphology, and high catalytic activity. Supercapacitor electrode materials should be specifically needed some properties like high specific surface area, electrochemically active, and high electrical as well as ionic conductivity. Copper has high electrical conductivity, and cobalt has high electrochemical activity. Using their advantages in this work, copper and cobalt are used as metal active centers for bi-Metal Organic Framework (bMOF). The morphology of bMOF is tuned by temperature-assisted solvothermal synthesis method, and a perfect nanosheet-like structure is obtained at 140 °C. It exhibited a high specific capacity of 1049.5 C g−1 at 1 A g−1. Aqueous and flexible hybrid supercapacitor devices are fabricated using bMOF and activated carbon. Aqueous hybrid supercapacitor device provides a maximum specific energy of 91.3 W h kg−1 and a maximum specific power of 14.14 kW kg−1. For a flexible hybrid supercapacitor device (FHSD), semi-solid electrolyte's ionic conductivity is optimized by injecting water with various weight ratios. FHSD exhibits a maximum specific energy of 82.3 W h kg−1 and a maximum specific power of 16.23 kW kg−1 in an optimized semi-solid electrolyte. It retains 82.9 % of its initial specific capacity after 12,000 charge-discharge cycles. The flexibility of FHSD is investigated by cyclic bending and stretching of it during charge-discharge.