The Progress and Comprehensive Analysis of Supercapacitors for Alternating Current Line Filtering: A Review

Abstract

To address the potential application of supercapacitors (SCs) in the field of alternating current filtering, this review summarizes the working mechanism toward ultrafast response, the progress of SCs in electrode materials, electrolytes (aqueous, organic electrolyte, and ionic liquids), current collectors, as well as device configuration. The performance of SCs is compared comprehensively with that of the commercial aluminum electrolyte capacitor (AEC) from the viewpoint of operating temperature, voltage, response time, impedance phase angle, and capacitance. Especially, there exists a big gap between AECs and SCs in terms of the operating temperature and operating voltage. And we give insights into future research focus for high‐frequency SCs, in terms of mechanism, structural design, and application management.

Whole Landscape of the Origin and Evolution of Gassing in Supercapacitors at a High Voltage

“…27 The Nyquist plot (Figure 2d) is fitted through the equivalent circuit shown in the illustration of Figure 2e and is recorded in Figure 2e and Table S1. The fitting circuit of SCs consists of three parts, 27 all of which increase in different degrees after floating, especially at 3.0 V. R s (Ohmic impedance) is the Z′-axis intercept at high frequencies, 28,29 which is caused by the electrode and electrolyte resistance. Compared to the initial R s value (16.47 mΩ), it increased by 3.35 and 10.10 mΩ after the floating charge at 2.7 and 3.0 V, respectively, confirming that the electrodes and electrolytes in SCs may be susceptible to high voltages.…”

“…Compared to the initial R s value (16.47 mΩ), it increased by 3.35 and 10.10 mΩ after the floating charge at 2.7 and 3.0 V, respectively, confirming that the electrodes and electrolytes in SCs may be susceptible to high voltages. The semicircle corresponds to the charge-transfer impedance at the middle–high frequencies, defined by the contact resistance ( R ct ) and capacitance ( C c ) between materials, which include activated carbon (AC) particles, AC-conductive particles, and AC–Al foils . The semicircle appears only after the floating charge at 3.0 V, indicating that operating at high voltages can damage the contact between the components, leading to an increase in the contact impedance.…”

“…The angle between the sloped line and the Z ′-axis increases, particularly at 3.0 V, representing that the ion diffusion to the electrode might be affected by gas generation during the floating charge. At lower frequencies, the perpendicular line represents the behavior of an ideal EDLC related to the charge storage by surface chemistry. , The decrease in the curve slope and the increase in Z w at the lowest frequency represent a decrease in C dl , further signifying that the porous carbon electrode may be damaged, resulting in restricted diffusion of electrolyte ions into the internal pores. Also, these results are more pronounced at a higher voltage.…”

“…The semicircle corresponds to the charge-transfer impedance at the middle−high frequencies, defined by the contact resistance (R ct ) and capacitance (C c ) between materials, which include activated carbon (AC) particles, AC-conductive particles, and AC−Al foils. 29 The semicircle appears only after the floating charge at 3.0 V, indicating that operating at high voltages can damage the contact between the components, leading to an increase in the contact impedance. The transition from midhigh to low frequencies, characterized by a line segment at an angle of nearly 45°to the Z′-axis denoting the Warburg impedance (W), is associated with the diffusion of electrolyte ions within the electrode pores.…”

MoS2 Nanoflakes based Kilohertz Electrochemical Capacitors

“…Various electrode structures, [1b,5] including graphene, carbon nanotube, carbon nanofiber, and other carbon based, as well as other conductive and chemically inert nanomaterials such as conductive polymers, MXene, [6] conductive transition metal nitrides, [7] 2D transition metal dichalcogenides (TMDCs), [8] and many others, [9] have been employed to fabricate HF‐ECs for ripple filtering. In addition to a very low resistance, these structures typically have a common feature of open pores to strike a balance between capacitance and response frequency [10] .…”