Temperature Analysis and Behavior of Individual Supercapacitors and Supercapacitor Packs for Development of Sustainable Energy Storage Systems

This study investigates the temperature-dependent electrical behavior of 400 F/2.7 V supercapacitors, both at the single cell level and in packs of six cells connected in series (6S configuration), over the temperature range of −20 °C to 58 °C, for further development of sustainable energy storage systems (ESSs). In the context of the increasing share of renewable energy sources and the development of low-environmental-impact storage systems, supercapacitors represent a viable technology due to their high power density, energy efficiency, and extended operational lifespan. The work is motivated by the critical influence of temperature on the Equivalent Series Resistance (ESR), voltage stability, and charge–discharge dynamics in real energy storage applications. Experimental characterization was performed using controlled Constant-Current (CC) and Constant-Voltage (CV) charge–discharge cycles with automatic data acquisition, complemented by temperature regulation via thermal chambers. Different parameters like ESR, Open-Circuit Voltage (OCV), and transient current profiles were extracted for each cell, while the pack-level behavior was derived by analyzing the experimental data. Additional investigations have included voltage recovery analysis. The results showed that the capacitance remains largely stable over the entire temperature range investigated, while the ESR exhibits a strong nonlinear dependence, increasing significantly at low temperatures and contributing to a reduced efficiency. A common transition region was identified around the 20–25 °C range, where the system performance is optimal. The voltage recovery increases with temperature, indicating increased ionic mobility and faster charge redistribution. Significant non-uniformity was observed between cells connected in series, with some cells exhibiting higher thermal sensitivity and instability. Optimizing the use of supercapacitors within their operating temperature range may contribute to increasing energy efficiency, to extending system lifespan, and to developing sustainable solutions for modern ESSs. In conclusion, the 6S supercapacitor pack exhibits a strongly temperature-dependent electrochemical dynamics, governed mainly by the ESR and diffusion processes. These findings highlight the need for thermal modeling and integration of balancing strategies in series-connected supercapacitor packs, which can be used for the expansion of the environmental-friendly ESSs.