Solid-state supercapacitors (SSCs) consist of porous carbon electrodes and gel-polymer electrolytes and are used in novel energy storage applications. The current study aims to simulate the impedance of SSCs using a clearly defined equivalent circuit (EC) model with the ultimate goal of improving their performance. To this end, a conventional mathematical and a physicochemical model were adapted. The impedance was measured by electrochemical impedance spectroscopy (EIS). An EC consisting of electrical elements was introduced for each modeling approach. The mathematical model was purely based on a best-fit method and utilized an EC with intuitive elements. In contrast, the physicochemical model was motivated by advanced theories and allowed meaningful associations with properties at the electrode, the electrolyte, and their interface. The physicochemical model showed a higher approximation ability (relative error of 3.7%) due to the interface impedance integration in a more complex circuit design. However, this model required more modeling and optimization effort. Moreover, the fitted parameters differed from the analytically calculated ones due to uncertainties in the SSC’s microscale configuration, which need further investigations. Nevertheless, the results show that the proposed physicochemical model is promising in simulating EIS data of SSCs with the additional advantage of utilizing well-reasoned property-based EC elements.

Structural supercapacitors (SSCs) are multifunctional energy storage composites (MESCs) that combine the mechanical properties of fiber-reinforced polymers and the electrochemical performance of supercapacitors to reduce the overall mass in lightweight applications with electrical energy consumption. These novel MESCs have huge potentials, and their properties have improved dramatically since their introduction in the early 2000’s. However, the current properties of SSCs are not sufficient for complete energy supply of electrically driven devices. To overcome this drawback, the aim of the current study is to identify key areas for enhancement of the multifunctional performance of SSCs. Critical modification paths for the SSC constituents are systematically analyzed. Special focus is given to the improvement of carbon fiber-based electrodes, the selection of structural electrolytes and the implementation of separators for the development of more efficient SSCs. Finally, current SSCs are compared in terms of their multifunctionality including material combinations and modifications.

Carbon nanomaterials exhibit unique morphological and physical properties. When used as fillers in various matrices such as polymers, they can provide enhanced electrical, thermal and mechanical characteristics. The emerging field of sensing technologies has witnessed remarkable advancements, resulting from the integration of carbon-based nanocomposites. This paper presents a comprehensive review of the latest a developments in key carbon-based nanocomposite sensors. First, the unique properties of carbon nanomaterials are reviewed covering the full dimensional spectrum, followed by main synthesis routes addressing critical aspects such as morphology, surface functionalization, and doping strategies. Later, the synergistic effects arising from the combination of carbon nanomaterials with other components, such as polymers, are explored in detail, emphasizing the role of percolation levels in the overall sensing performance. The different sensing applications presented in this review cover a broad range, including strain, temperature, gas and biosensing. The mechanisms and principles governing the sensing capabilities of carbon-based nanocomposites are provided, shedding light on the interactions between analytes and nanocomposite surfaces. A critical analysis of current challenges and prospects is also presented, outlining potential avenues for further research and innovation. Finally, this review aims to serve as a valuable resource for researchers interested in carbon-based nanocomposites and their evolving role in advancing sensing technologies.

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.

Dynamically loaded structures made of thermoplastic polymers have been extensively exploited in several demanding industries. Due to the viscoelastic and thermal properties of thermoplastic polymers, self-heating is generally inevitable, especially during dynamic deformations at high frequencies. Therefore, the thermoplastic polyether ether ketone (PEEK), with its high temperature resistance and high specific strength, is a particularly ideal candidate for dynamically loaded applications. Using scanning laser Doppler vibrometry and infrared thermography, an experimental study of the vibration characteristics and the vibration-induced heating of flat-sheet PEEK specimens was carried out. The specimens were base-excited by means of a piezoelectric actuator at high frequencies in the range between 1 and 16 kHz. As a result, a maximum temperature rise of approximately 6.4 K was detected for the highest investigated excitation. A high correlation between the spatial distribution of the velocity along the beam’s axial direction and the resulting temperature increase was measured. To summarize, the occurring self-heating of PEEK due to the dissipation of vibrational energy has to be critically considered for dynamically loaded structural applications, especially areas with high displacement amplitudes, such as antinodes, which yield the highest temperature increase.