Flexible Solid-State Aqueous Sodium-Ion Capacitor Using Mesoporous Self-Heteroatom-Doped Carbon Electrodes

Abstract

Supercapacitors find numerous applications such as in consumer electronics, peak power demands, capturing surge power, etc. Various types of carbon materials are explored as electrode material. In this work, disordered mesoporous carbon was synthesized from expired medicinal capsule covers by sulfonation and subsequent chemical activation was carried out with KOH. Powder X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, Brunauer−Emmett−Teller studies, and X-ray photoelectron spectroscopy were utilized to characterize the generated carbon which confirmed the disordered carbon had a large surface area with stratified pores. The testing for electrochemical charge storage was conducted on a three-electrode setup comprising an aqueous 1 M NaClO 4 electrolyte that exhibited a high 324 F g −1 specific capacitance at 0.4 A g −1 , revealing suitability for sodium-ion ultracapacitor. Consequently, CR2032 coin-type sodium-ion capacitors were fabricated using both aqueous and nonaqueous electrolytes. The laboratory prototype capacitor with the aqueous electrolyte delivered 42 Wh kg −1 specific energy at 179 W kg −1 specific power. Besides, the capacitor with the nonaqueous electrolyte showed a remarkable 54.3 Wh kg −1 specific energy at 540 W kg −1 specific power. The Coulombic efficiency exhibited by both devices was about 99% even at the 10000th charge−discharge cycle. The amplified charge storage performance of the disordered carbon was ascribed to the presence of homogeneous mesopores that led to enhanced accessibility of the electrode/electrolyte contact area. According to the results of the power law and Dunn's approach, the mesoporous carbon electrode was found to have a considerable diffusive charge storing mode involving Na + intercalation in the sodium-ion nonaqueous ultracapacitor. A green-light-emitting diode could run continuously for 16 min on a single charge using the laboratory prototype CR-2032 coin-type nonaqueous ultracapacitor. Interestingly, a homemade solid-state flexible sodium-ion ultracapacitor was also fabricated that impressively manifested 13.7 Wh kg −1 specific energy at 180 W kg −1 specific power in 180°bent angle.

Deconvolution of capacitive and diffusive charge/lithium storage in lyophilized NiCo2S4–NiCo2O4 composite for supercapattery and lithium-ion battery

“…This is how the capacitive and the diffusive contributions in the CV profile are given in the current literature. 57,58 This high capacitive contribution is attributed to the nanostructured feature associated with the freezedried NCS-NCO composite. The presence of the carbon matrix seems to contribute to the capacitive storage.…”

Freeze-Drying-Assisted ZIF-67 Template-Derived Co@NCS Porous Composite as Sulfur Cathode Host for Improved Li–S Battery Performance: Deconvolution of Diffusive and Capacitive Li+ Storage

“…Using the Power law, it is possible to qualitatively state whether the charge storage in an electrode is dominated by the capacitive-type or the diffusive-type process from the current response of a CV profile recorded at different scan rates. According to the Power law, the peak current response of a CV profile is related to the scan rate, as shown below 17,35…”

“…Using the Power law, it is possible to qualitatively state whether the charge storage in an electrode is dominated by the capacitive-type or the diffusive-type process from the current response of a CV profile recorded at different scan rates. According to the Power law, the peak current response of a CV profile is related to the scan rate, as shown below , i peak ( V ) = a ν b goodbreak0em1em⁣ or goodbreak0em1em⁣ log ( i peak ) = log ( a ) + b nobreak0em0.1em⁡ log ( ν ) where i peak represents the response of the peak current observed in the CV curves, ν is the scan rate, and a and b are two parameters that could be obtained by mathematical operation. The value of parameter b gives insights into the Li + charge storage kinetics: if the value of parameter b is ∼0.5, it is considered that the mode of charge storage is dominated by diffusion-limited processes (Faradaic), whereas parameter b ∼ 1 indicates the capacitive dominance due to surface electrosorption.…”

“…Thus, using Dunn’s approach, quantitatively, the percentage of diffusive and capacitive contributions in the current response of the CV profile was deconvoluted as described below. According to Dunn’s equation, the current response at any chosen potential of a CV profile and the scan rate can be related using the equation shown below i ( V ) = k 1 ν + k 2 ν 1 / 2 or equivalently ( i false( V false) ν 1 / 2 ) = k 1 ν 1 / 2 + k 2 where k 1 v [the first term in eq ] is the contribution from the capacitive current, k 2 v 1/2 [the second term in eq ] is the contribution from diffusive current, and i ( V ) represents the overall current response registered at a specific potential ( V ) in the CV profile. To derive the values of k 1 and k 2 , a linear plot between ( i false( V false) ν 1 / 2 ) and (ν 1/2 ) was constructed, known as Dunn’s plot, as per eq .…”

Transition Metal Oxides as the Electrode Material for Sodium-Ion Capacitors

“…Scientists have made several attempts to create new and renewable energy sources, such as solar power, wind power, and wave energy driven by frequent and harmful indications of environmental deterioration, such as smog, and significantly diminished fossil fuel supplies. Yet, climate and sunlight frequently result in intermittent and fluctuating energy supply [Yang et al, 2023;Halder et al, 2023;Peng et al, 2023;Thirumal et al, 2023]. Therefore, the demand for electrochemical energy storage systems has grown in the market globally.…”