Comprehensive Study on Dynamic Parameters of Symmetric and Asymmetric Ultracapacitors

Abstract

Electrical storage components such as ultracapacitors (UC) have received significant attention from various industrial sectors, from electric vehicles to renewable power plants. This article presents the investigations on dynamic properties of asymmetric Li-ion hybrid (CPQ2300S: 2300 F, 2.2-3.8 V, JSR Co., Tokyo, Japan) and symmetric double-layer (BCAP3400: 3400 F, 2.85 V, Maxwell Technologies Co., San Diego, CA, USA) ultracapacitors. The internal resistance and capacitance of both UCs were slightly changed with respect to current and voltage alterations, but these changes were more prominent for the Li-ion UC. The internal resistance of the Li-ion UC became five times larger and its capacitance decreased significantly when the temperature decreased from +25 • C to −20 • C. More importantly, the double-layer UC exhibited nearly constant capacitance for a wide range of temperature changes (0 • C to −40 • C), although internal resistance increased somewhat. Electrochemical impedance spectroscopy analysis of both UCs was performed for the frequency range of 1 Hz-1 kHz and in the temperature range from −15 • C to +30 • C. It was observed that the temperature effects were much more pronounced for the asymmetric Li-ion UC than that of the symmetric double-layer UC. This work also proposes an improved equivalent circuit model based on an infinite number of resistance-capacitance (r-C) chains. The characteristic behavior of symmetric UCs can be explained precisely by the proposed model. This model is also applicable to asymmetric UCs, but with less precision. similar asymmetric UCs are also applicable to pulsed electric power sources [12,13]. Piórkowski et al. presented a case study about the application of UCs in hybrid systems including an engine start module (ESM), a photovoltaic (PV) module, a battery, and an internal combustion engine (ICE) [14]. In continuation, the hybrid model control strategy was proposed for a double active bridge-based supercapacitor energy storage system [15]. More importantly, the service lifetime of UCs is three times higher compared to electrochemical storage batteries (e.g., Li-ion or lead-acid) although UCs are relatively bulky and voluminous [16]. Consequently, there is a lack of accurate information regarding the ability of Li-ion UCs to provide voltage and current during charge-discharge cycles. Previously, a significant number of experimental investigations were carried out [16][17][18][19][20][21][22] in order to understand the characteristic behavior of UCs. Different direct measurement methods for the evaluation of UC parameters were also proposed [16][17][18][19][20]. A comprehensive review of characterization methods for supercapacitor modeling and general parameter identification techniques were also discussed [21,22].A significant amount of effort has been made to describe dynamic UC behavior using different types of equivalent circuits [23][24][25][26][27][28][29][30]. Some works presented modeling approaches based on electrochemical explanations of UC performance [31][32][33...

Studies on Dynamic Properties of Ultracapacitors Using Infinite r–C Chain Equivalent Circuit and Reverse Fourier Transform

“…Currently, ultracapacitors (UCs) are considered as an efficient energy storage system for electrical devices [9]. Electric double-layer capacitors (EDLCs) or symmetric double-layer UCs have attracted attention as plausible electrical energy storage devices [10][11][12][13][14]. EDLCs are a complex of two identical porous electrodes, electrolytic solution, and a separator, which is used as an ion conductor.…”

“…The parameters responsible for the dynamic behavior of UCs have not been studied for the applicable range. In very recent work, we studied the dynamic behavior of a double-layer UC [13]. The capacitance remained nearly constant for a wide range of temperatures (+25 • C to −40 • C), but the internal resistance increased~1.5 times as the temperature decreased to −40 • C [13].…”

“…In very recent work, we studied the dynamic behavior of a double-layer UC [13]. The capacitance remained nearly constant for a wide range of temperatures (+25 • C to −40 • C), but the internal resistance increased~1.5 times as the temperature decreased to −40 • C [13]. The equivalent electrical circuit models are required to simulate the device parameters for the development and design of electrical appliances.…”

“…The equivalent electrical circuit models are required to simulate the device parameters for the development and design of electrical appliances. Previously, different types of equivalent circuit models have been proposed in order to understand the dynamic characteristics of UCs [13,[15][16][17][18][19][20]. Importantly, the electrochemical analysis-based modeling approaches have also been employed to study the performance of UCs [21][22][23][24].…”

“…These methods could not explain exact changes in the UC parameters during their functionality since equivalent circuits do not have a rigorous physical base. In a previous article, we proposed that the infinite r-C chains-based equivalent circuit model could describe the behavior of double layer UCs [13]. The multibranch r-C circuit modeling approach was also studied by other researchers [27][28][29][30][31][32][33].…”