Energy, which plays a significant role in the economies of developing countries, has always been a primary concern for governments. Among these concerns, ensuring that energy is not only clean and sustainable but also stored and distributed efficiently is of utmost importance. Additionally, the increasing use of mobile devices in recent years, driven by technological advancements, highlights the growing need for energy storage systems. Various electrochemical energy storage devices, such as fuel cells, batteries, and lithium-ion batteries, have been used to date for energy storage. The primary goal of these devices is to convert the chemical energy of a reaction into electrical energy. However, the storage capacity, production costs, and non-toxic material content of today's commercialized energy storage systems are still not at the desired level. Moreover, improving parameters such as charge/discharge times, lifespan, and energy density of these devices remains a key focus for researchers.

The specific power-energy density distribution of various energy storage devices used to date is shown in the Ragone plot (Figure 1). According to this graph, supercapacitors fill the gap between commercial capacitors and batteries in terms of power density. Supercapacitors are advanced versions of traditional capacitors and hold promise for the future of energy storage systems. Their rapid charge/discharge times offer a significant advantage, and their long shelf and cycle life are superior to that of conventionally used batteries.

A supercapacitor device consists of two electrodes (anode and cathode), a membrane (separator), and an electrolyte (Figure 2). Supercapacitors are categorized into two main groups based on their operating mechanisms. The first group includes electric double-layer capacitors, which store electrical charge through charge accumulation and diffusion between the electrode and electrolyte. The second group comprises pseudocapacitors, which are managed through rapid and reversible Faradaic redox reactions occurring on the electrode surface. Understanding the properties of the electrode materials used in a supercapacitor is crucial for producing high-efficiency and high-capacitance devices. Specifically, the high surface area, pore size, and rapid electron/ion exchange within the circuit are key factors in the energy storage performance of supercapacitors. Therefore, for a high-performance and low-cost supercapacitor device, the electrode materials should possess high conductivity, high surface area, good corrosion resistance, operational stability across a wide temperature range, controlled pore structure, and ease of processing.

References

[1] Vandeginste, Veerle. "A Review of Fabrication Technologies for Carbon Electrode-Based Micro-Supercapacitors." Applied Sciences 12.2 (2022): 862.

[2] Choudhary, N., Li, C., Moore, J., Nagaiah, N., Zhai, L., Jung, Y., & Thomas, J. (2017). Asymmetric supercapacitor electrodes and devices. Advanced Materials, 29(21), 1605336.