Effect of Electrolytic Cations on a 3D Cd-MOF for Supercapacitive Electrodes

Abstract

A cadmium-based metal−organic framework (Cd-MOF) is synthesized in a facile manner at ambient temperature by an easy slow diffusion process. The three-dimensional (3D) structure of Cd-MOF is authenticated by single-crystal X-ray diffraction studies and exhibits a cuboid-shaped morphology with an average edge length of ∼1.13 μm. The prepared Cd-MOF was found to be electroactive in nature, which resulted in a specific capacitance of 647 F g −1 at 4 A g −1 by maintaining a retention of ∼78% over 10,000 successive cycles in the absence of any binder. Further, to distinguish the efficiency of Cd-MOF electrodes, different electrolytes (NaOH, KOH, and LiOH) were explored, wherein NaOH revealed a higher capacitive response due to its combined effect of ionic and hydrated ionic radii. To investigate the practical applicability, an asymmetric supercapacitor (ASC) device is fabricated by employing Cd-MOF as the positive electrode and activated carbon (AC) as the negative electrode, enabling it to light a commercial light-emitting diode (LED) bulb (∼1.8 V). The as-fabricated ASC device delivers comparable energy density and power density.

Insights on Effect of Different Electrolytes on Electrochemical Performance of CoNi Nanoflower‐Based Supercapacitors

“…The ionic radii of Li + ion lower than that of Na + and K + ions, that is, Li + (0.069 nm) < Na + (0.102 nm) < K + (0.138 nm), which leads to high diffusion probability, result in high electrochemical performance in case of LiOH electrolyte. [ 48,49 ] Furthermore, to check the specific capacitance and rate capability of CoNi nanoflowers, the GCD measurements were executed at different current densities within potential window 0–0.42 V with 3 m KOH, NaOH, and LiOH electrolytes, as shown in Figure 1B. The specific capacitance was calculated using equation [ 50 ] where C s , I , Δ t , Δ V , and m denote specific capacitance, discharge current, discharge time, potential window, and mass of electrode material, respectively.…”

“…[71] The calculated R ct value for Nyquist circuit is low in case of LiOH than other two electrolytes, that is, NaOH and KOH, which confirms the fast charge transfer rate. [48,72] The details of electrolyte diffusion and ionic diffusion at interior sites of active material are estimated via Warburg resistance (low-frequency region). The overall internal resistance parameters are declined, which offer higher mobility of ions and hence enhanced electrochemical behavior of CoNi nanoflowers in LiOH electrolyte.…”

“…Further, the charge-discharge curves showed 66.61 F g À1 at 1 A g À1 , as depicted in Figure 3D,E, and the capacitance at different current densities was plotted (Figure 3F). Further, with the help of discharge curves, the energy (E) and power (P) densities were calculated using the formulae [48] E ¼ CðΔVÞ 2 3.6 Â 2 ¼ CðΔVÞ 2 7.2 (5)…”

Covalent Organic Frameworks (COFs)/MXenes Heterostructures for Electrochemical Energy Storage

“…Figure a illustrates energy storage mechanisms with various types of electrode materials . An EDLC SC stores electrochemical energy at the electrode–electrolyte interface (depends largely on the surface area), whereas a pseudocapacitive material follows a fast surface redox reaction or intercalation mechanism to store energy with kinetics similar to that of an EDLC system. − Among different classes, a pseudocapacitor is ranked between non-Faradaic EDLC and Faradaic rechargeable batteries in their energy density and power throughput (high energy capacitance but short cycle life than EDLC) . Sustained cyclic efficiency without compromising high capacitance is the bottleneck to strategize an efficacious pseudocapacitor.…”

Upcycling rust and plastic waste into an Fe MOF for effective energy storage applications: transformation of trash to treasure

“…The GCD pattern has a characteristic pseudocapacitive nature with symmetrical charging/discharging time, which implies a higher Coulombic efficiency. 42 Subsequently, the specific capacitance was calculated at different current densities with the help of eqn (S1), as shown in Fig. S8 †.…”