Exploration of aqueous electrolyte on the interconnected petal-like structure of Co-MOFs for high-performance paper-soaked supercapacitors

Abstract

The electrolyte is a crucial component in supercapacitors (SCs), along with the electrode material, which can affect the electrochemical parameters, such as specific capacitances (Cs), energy density (ED), cyclic stability, and potential window. Therefore, the present work explores the effect of different electrolytes on the performance of Co-MOFs/FSS electrodes for SCs. The Co-MOFs/FSS electrode was synthesized on a flexible stainless-steel (FSS) substrate using the reaction-diffusion framework method, and its structural, morphological, and compositional characteristics were analyzed. The SCs performance of Co-MOF/FSS was examined across multiple electrolytes (1M KOH, 1M LiOH, and 1M NaOH). The SCs performance of Co-MOFs/FSS increased in the following sequence: 1M LiOH > 1M NaOH > 1M KOH. Furthermore, the dependence of concentration variation of LiOH electrolyte on Co-MOFs/FSS for SCs was studied. In 2M LiOH electrolyte, the Co-MOFs/FSS demonstrated a maximum Cs of 650 F g− 1 and specific capacity (Csp) of 262 C g− 1 at 5 mV s− 1. Furthermore, it exhibited a favourable retention rate of 71 % over 5000 GCD cycles at 10 mA cm−2. It also possessed higher ED and Power Density (PD) of 14.10 Wh kg−1 and 666 W kg−1 at 1 mA cm−2 respectively. Further, a flexible symmetric paper-soaked Co-MOFs/FSS//Co-MOFs/FSS device was fabricated, and its electrochemical performance was assessed. The fabricated device exhibited a higher Cs of 122 F g− 1 and Csp of 171 C g− 1 at 10 mV s− 1. Additionally, it showed good retentivity of 46 % after the 3000th cycle at 15 mA; and exhibited higher ED of 6.78 Wh kg−1 and PD of 1500 W kg−1 at 6 mA. This study highlights the importance of selecting the appropriate electrolyte for enhancing the electrochemical performance of Co-MOFs/FSS electrode material.