Supercapacitor Degradation Assesment by Power Cycling and Calendar Life Tests

Abstract

Degradation of Supercapacitors (SC) is quantified by accelerated ageing tests. Energy cycling tests and calendar life tests are used since they address the real operating modes. The periodic characterization is used to analyse evolution of the SC parameters as a whole, and its Helmholtz and diffusion capacitances. These parameters are determined before the ageing tests and during 3 × 10 5 cycles of both 75% and 100% energy cycling, respectively. Precise evaluation of the capacitance and Equivalent Series Resistance (ESR) is based on fitting the experimental data by an exponential function of voltage vs. time. The ESR increases linearly with the number (No) of cycles for both 75% and 100% energy cycling, whereas a super-linear increase of ESR vs. time of cycling is observed for the 100% energy cycling. A decrease of capacitance in time had been evaluated for 2000 hours of ageing of SC. A relative change of capacitance is ∆C/C0 = 16% for the 75% energy cycling test and ∆C/C0 = 20% for the 100% energy cycling test at temperature 25°C, while ∆C/C0 = 6% for the calendar test at temperature 22°C for a voltage bias V = 1.0 Vop. The energy cycling causes a greater decrease of capacitance in comparison with the calendar test; such results may be a consequence of increasing the temperature due to the Joule heat created in the SC structure. The charge/discharge current value is the same for both 75% and 100% energy cycling tests, so it is the Joule heat created on both the equivalent series resistance and time-dependent diffuse resistance that should be the source of degradation of the SC structure. The diffuse resistance reaches a value of up to 30 Ω within each 75% energy cycle and up to about 43 Ω within each 100% energy cycle.

Synthesis of a Very High Specific Surface Area Active Carbon and Its Electrical Double-Layer Capacitor Properties in Organic Electrolytes

“…The first ageing mechanism (presumably related to the degradation of electrolytes) is observed for most samples, while the second mechanism is significant only under harsh testing conditions, such as elevated temperature and/or increased operating voltage. The degradation rate due to the cycling ageing test is much higher than the degradation rate due to the calendar ageing test with equivalent voltage and temperature [60][61][62]. We presume that the second ageing mechanism is related to the electrode active area degradation caused probably by the decrease of potential barrier on the electrode/electrolyte interface.…”

A Comparative Review of Lead-Acid, Lithium-Ion and Ultra-Capacitor Technologies and Their Degradation Mechanisms

“…UC have high energy density, low self-discharge and relatively long lifetime, the last of which is affected by operating temperature, applied charge voltage as well as the charge/discharge current [34,193,194]. Their high cycle life can be attributed to the chemical and electrochemical inertness of the compositions of the electrodes and electrolyte.…”

“…All of these properties determine the capacity of the battery and there are many factors that contribute to, as well as ramifications that arise from, a reduction in the capacity [31]. The number of cycles is often used to determine the remaining capacity and, thus, the degradation of the battery [32,33]; this is shown in Figure 3 by P. Zhang et al [8] and in Figure 11 by V. Sedlakova et al [34].…”

An Overview on Electric-Stress Degradation Empirical Models for Electrochemical Devices in Smart Grids

“…Research on SC technology shows that overvoltage, deep-cycling, high temperature, and high charge/discharge current are the leading electrical stressors. Effects of degradation include capacitance fading, equivalent series resistance (ESR) increase, and leakage current [83,84]. Unfortunately, very few electrical stress models can be found in the literature.…”