Thermo-electrochemical coupled modeling of solid-state supercapacitors

Solid-state supercapacitors (SSC) are pivotal in modern energy storage technologies due to their high power density, rapid charge–discharge cycles, and extended lifespan. They can be used in both structural and flexible configurations with innovative applications across industries. For practical applications, SSCs need to preserve their electrochemical performance at elevated service temperatures. Therefore, the interplay and effect of high temperatures on the electrochemical performance of SSCs need to be investigated. In this work, for the first time, a multiphysics thermo-electrochemical coupled continuum modeling framework is developed to capture the effect of temperature on the frequency-dependent behavior of SSCs. This novel approach employs finite element analysis (FEA) instead of conventional equivalent circuit methods, enabling more detailed insights into the internal structure effects of temperature on performance parameters such as resistance, diffusion, and double-layer capacitance. The model is numerically solved by means of finite element analysis (FEA). To validate the simulations, a sustainable solid-state supercapacitor was fabricated using biocarbon and chemical vapor deposition. The use of biowaste-derived biocarbon as a novel sustainable electrode material aligns with global sustainability goals. The temperature-dependent impedance of the supercapacitor was measured at temperatures within 20 to 50 °C. The results showed that the model is able to predict the cell impedance behavior at various elevated temperatures. Furthermore, a sensitivity study was conducted to examine the effects of various coupling parameters. Key findings reveal the substantial impact of high temperature on resistance, diffusion, and double-layer capacitance. The system response trend was changed at 50 °C due to polymer electrolyte degradation. This thermo-electrochemical framework provides valuable insights for the design and optimization of next-generation solid-state supercapacitors, contributing to the development of sustainable energy storage solutions.