Supercapacitors: Materials, Design, and Commercialization

Supercapacitors: Materials, Design, and Commercialization provides a comprehensive overview of the latest research trends and opportunities in supercapacitors, and particularly in terms of novel materials and electrolytes.The book will address the transformation in supercapacitive technology from double layer capacitance to battery-type capacitance, providing a clear understanding of the conceptual differences between various charge storage processes for supercapacitors, charge storage based on materials and electrolytes, and calculation for capacitance for these charge processes. Detailed chapters discuss recent developments in materials, such as carbons, chalcogenides, MXene and phosphorene, various polymer nanocomposites, and polyoxometalates for supercapacitors. This is followed by in-depth coverage of electrolytes, including the evolution of electrolytes from aqueous to water-in-salt electrolytes and their role in improving the energy density of supercapacitors. The final part of the book examines the role of artificial intelligence in the design of supercapacitors, and latest developments in translating novel supercapacitor technologies from laboratory-scale research to a commercialization.This is a valuable resource for advanced students, researchers, and scientists in the fields of energy storage, electrical engineering, materials science, and chemical engineering, as well as engineers and R&D personnel working with supercapacitors or energy storage in an industrial setting.

• Brings together the latest developments in supercapacitor materials and electrolytes
• Discusses cutting-edge charge storage concepts and methods for supercapacitors
• Addresses the role of machine learning and the scale-up from laboratory to commercialization

• Language: English
• Publisher: Elsevier Science
• Release date: Mar 20, 2024
• ISBN: 9780443154775

Book preview

1

Introduction to supercapacitors, materials and design

Syam G. Krishnan¹*, Hong Duc Pham² and Deepak P. Dubal³,    ¹Department of Chemical Engineering, Faculty of Engineering and Information Technology, The University of Melbourne, Victoria, Australia,    ²Centre for Future Materials, University of Southern Queensland, Toowoomba, QLD, Australia,    ³Centre for Materials Science, School of Chemistry and Physics, Queensland University of Technology, Brisbane, QLD, Australia*, Corresponding author. e-mail address: [e-mail]

Abstract

Supercapacitors are power devices whose energy storage capability is lower than batteries. These supercapacitors are broadly divided into two types: electric double-layer capacitors and pseudocapacitors. Recently, battery-type electrodes are also used as supercapacitor electrodes to increase energy density. These various categories of supercapacitors are differentiated based on the selection of materials, electrolytes, and their design. Commercial supercapacitors offer various designs such as cylindrical and stacked layers for improving the energy storage capability of supercapacitors. This chapter serves as an introduction to this book, where a glimpse of materials and supercapacitor designs are compiled.

Keywords

Supercapacitors; electric double-layer supercapacitor; asymmetric supercapacitor; device design; material realm

1.1 Introduction

The social and economic importance of energy storage devices and their related markets are on an exponential rise due to the push for a sustainable world. Different energy harvesting technologies based on renewables such as solar, wind, thermal, and water were explored [1]. Basically, this energy-harvesting process involves the conversion of mechanical energy to electrical energy. To store the harvested electrical energy, energy storage devices are required. Currently, different types of batteries and fuel cells are used to store these energies [2]. Furthermore, the use of batteries especially lithium-ion batteries (LIBs) for the portable wireless communication devices and internet of things devices revolutionized the world. Different commercial companies developed LIBs with various energy storage capabilities. Hence, a significant rise in research for materials and other parts of these devices such as separators and electrolytes were performed to increase the energy storage performance of LIBs [3].

Although LIBs possess higher energy storage capability or energy density, the power density of the device is poor [4]. Hence, merging the gap between energy and power density is researched by designing a supercapacitor with appreciable energy density. Supercapacitors, also known as electrochemical capacitors, are energy storage devices, and unlike batteries, which store energy through chemical reactions, they store energy through the separation of charge in an electric double layer [5]. This allows for quick charging and discharging times, high power density, and a long cycle life. Supercapacitors have a relatively low energy density compared to batteries, but they have a higher power density.

The power density of a supercapacitor refers to the amount of power it can deliver per unit of weight or volume, while energy density refers to the amount of energy it can store per unit of weight or volume. The power density of a supercapacitor can range from 1 to 10 kW/kg, or even higher for some advanced materials and designs [6]. Hence, supercapacitors release high power quickly, making them ideal for applications that require rapid energy discharge, such as in electric vehicles (EVs) or regenerative braking systems. On the other hand, the energy density of a supercapacitor is lower (1–30 Wh/kg). With some advanced materials and designs, it could be extended to 60 Wh/kg [7]. However, this is significantly lower compared to batteries whose energy densities are 500 Wh/kg or more. Apart from this drawback, high power density and long cycle life of supercapacitors suit applications that require frequent charge and discharge cycles, such as in hybrid vehicles or renewable energy systems.

The design and materials used in supercapacitors play a crucial role in their performance and efficiency. Some common materials used in supercapacitor electrodes include carbon-based materials, metal oxides, chalcogenides, graphene, MXene, polyoxometalates (POM), etc. [8–10]. The performance of these materials will differ as the redox state, electrical conductivity, morphology, and surface area of these materials differ with synthesis techniques. Various synthesis techniques such as hydrothermal method, coprecipitation technique, electrospinning, and electrodeposition technique are used in developing these materials [11]. These innovations in the material realm of supercapacitors are well detailed in separate chapters of this book. Hence, a detailed approach regarding these is avoided in this chapter.

Along with these materials, different designs for supercapacitor fabrications are employed such as planar parallel-plate design, cylindrical design, asymmetric design, three-dimensional design, and hybrid design [12]. These designs have their advantages and disadvantages and will be briefed in this chapter. Apart from the design, factors such as the choice of electrolytes and electrode configurations can significantly impact their performance.

A Scopus search has showed that researches are on increasing trends in the past two decades in supercapacitors (Fig. 1.1A). The main countries contributing to supercapacitors research these periods were China and India (Fig. 1.1B). Furthermore, it can be observed from Fig. 1.1C that the main research focus on the material realm on the supercapacitors were various metal oxides, showing that the research attempts were to improve the capacitance and energy density of the devices. Also, a lot of carbon materials were also researched during these two decades. Regarding the electrolytes, the main research focused on aqueous ones, as they are economical and easy to operate at room temperature (Fig. 1.1D). In recent years research attempts focused on improving the energy density using ionic and polymer electrolytes owing to their improved voltage window and hence increasing the energy density of the supercapacitor. Hence, it is important to update these research through a book dedicated to materials, electrolytes, and its commercialization aspects.

Figure 1.1 A Scopus data search for the period 2003–2022, showing (A) the supercapacitor research publications from 2003 to 2022; (B) the first 20 countries on supercapacitor research based on publications; (C) main materials realm for supercapacitors; (D) main categories of electrolytes for supercapacitors.

This introductory book chapter aims to provide a brief overview of the current state of the art in supercapacitor technology. It will discuss the various materials used in supercapacitors and their properties, the design considerations for optimizing performance, and the potential applications of supercapacitors in energy storage, EVs, and portable electronics.

1.2 Materials realm for supercapacitors

The materials along with their synthesis technique and performance evaluation used for supercapacitors are detailed in the following chapters of the book. Hence, this chapter serves as an outlook for these chapters and a detailed description is avoided. Supercapacitors can be made from a variety of materials that are chosen based on their electrochemical properties and their ability to store charge efficiently. Some common materials used in supercapacitor electrodes is shown in Fig. 1.2 which includes the following:

1. Carbon-based materials: Carbon materials, such as activated carbon, graphene, and carbon nanotubes, are widely used in supercapacitor electrodes due to their high surface area, excellent conductivity, and low cost. These carbon materials store energy in an electric double layer between electrode and electrolyte interface and also known as electrochemical double-layer capacitor (EDLC) electrode materials [13].

2. Metal oxides: Metal oxides, such as ruthenium oxide, manganese oxide, and titanium oxide, can also be used as electrode materials in supercapacitors. These materials can provide high capacitance and high stability, but they are often more expensive than carbon-based materials. These materials allow the formation of electric double layer along with surface redox reaction due to the interaction with metal oxides causing faradic reactions [14]. This increases the charge storage capability of metal oxides compared to carbon-based materials.

3. Conducting polymers: Conducting polymers, such as polypyrrole and polyaniline, are organic materials that can be used as electrode materials in supercapacitors. These materials can provide high capacitance and good stability, but they can be more difficult to process and have lower conductivity compared to carbon-based materials. Although these materials increase the cycling stability of metal oxides, some researchers report that the lower conductivity of polymers will decrease the faradic reaction, lowering the capacitance of the composite materials [15].

4. Composite materials: Composite materials, which combine two or more different materials, can also be used in supercapacitor electrodes. For example, a composite of carbon and metal oxide can provide both high surface area and high capacitance. These composite materials combine both EDLC and pseudocapacitive property of the material, increasing the capacitance of the material. Also, different binary and ternary composites of metal oxides, metal oxide-carbon composites, metal oxide-graphene composites, etc., were explored as supercapacitor electrodes [16–18].

Figure 1.2 Various electrode materials for supercapacitors.

The choice of electrode material depends on various factors, such as the desired power and energy density, the operating voltage, the cost, and the specific application. In recent years, there has been increasing interest in exploring new materials and designs to improve the performance and efficiency of supercapacitors. Fig. 1.2 compiles various materials used for supercapacitor research under different categories. Apart from these materials, metal chalcogenides, polyoxometalates, MXene, graphene, ternary metal cobaltites, ternary metal oxide composites, and other materials were also tested [19–22]. The main criteria for the metal oxides and their composites as a pseudocapacitor or battery-type electrode are its higher theoretical capacitance, various redox states, and appropriate active sites for charge storage. Hence, different morphologies of these materials in nano- and microscale were synthesized using different techniques to tailor the active sites and the surface area of these materials [23]. Hence, the synthesis techniques and performance evaluation of the materials are detailed in other chapters of this book.

1.3 Electrolytes for supercapacitors

A typical supercapacitor device consists of two electrodes separated by an electrolyte, which is a key component that determines the performance and characteristics of a device. The energy density and power density of the supercapacitor depend on the type of electrolytes used. The key factors such as voltage window, solvated ion size, and the device resistance depend on the selection of electrolytes [24]. Hence, an understanding of the categories of electrolytes available for the supercapacitors (Fig. 1.3) and majorly used electrolytes is briefed in the following subsections.

Figure 1.3 Different categories of electrolytes for supercapacitors.

1.3.1 Aqueous electrolytes

Aqueous electrolytes are commonly used due to their low cost and high ionic conductivity, but they have a limited electrochemical stability window, which limits the operating voltage (~1.2 V) and energy density of the supercapacitor [25]. They are mainly composed of water and dissolved ions such as potassium, sodium, and lithium. The most popular aqueous electrolytes in supercapacitors are as follows:

1. Potassium hydroxide (KOH): KOH is one of the most widely used electrolytes in supercapacitors due to its high ionic conductivity, low cost, and environmental friendliness. It is typically used in concentrations ranging from 1 to 6 M. Usually these are used to test the electrochemical properties of metal oxides as the solvated ion size for KOH is lower and can intercalate to the surface sites of metal oxides.

2. Sodium hydroxide (NaOH): NaOH is another commonly used aqueous electrolyte due to its high conductivity and low cost. It is typically used in concentrations ranging from 1 to 6 M. These neutral electrolytes are often used in testing carbon materials as electrodes for supercapacitors.

3. Sulfuric acid (H2SO4): H2SO4 is a strong acid that is used as an electrolyte in supercapacitors due to its high ionic conductivity and low cost. It is typically used in concentrations ranging from 0.1 to 2 M.

4. Hydrochloric acid (HCl): HCl is another strong acid that is used as an electrolyte in supercapacitors due to its high ionic conductivity and low cost. It is typically used in concentrations ranging from 0.1 to 2 M.

1.3.2 Nonaqueous electrolytes

Nonaqueous electrolytes are typically based on organic solvents, which are less polar than water and can dissolve a wide range of electrolytes. These electrolytes can be either inorganic salts, such as lithium perchlorate or tetraethylammonium tetrafluoroborate (TEABF4), or organic salts, such as imidazolium-based salts [26]. The choice of electrolyte will depend on several factors, including the desired operating voltage and energy density of the supercapacitor, as well as the compatibility of the electrolyte with the electrode materials.

1.3.2.1 Organic electrolytes

Organic electrolytes are a type of nonaqueous electrolyte that has been widely used in supercapacitors due to their high conductivity, low viscosity, and wide electrochemical windows. The electrochemical windows of organic electrolytes are typically larger than those of aqueous electrolytes, which makes them suitable for high-voltage supercapacitors [27]. Common organic electrolytes are based on organic solvents such as acetonitrile, propylene carbonate (PC), and ethylene carbonate (EC). These solvents are mixed with various types of salts such as lithium perchlorate, TEABF4, and tetraethylammonium perchlorate to form the electrolyte [28].

1.3.2.2 Ionic liquids

Ionic liquids are a type of nonaqueous electrolyte that consists of organic cations and inorganic or organic anions. They have several advantages over organic electrolytes, such as a wide electrochemical window, low volatility, and good thermal stability. Ionic liquids have been used in supercapacitors due to their high conductivity and low toxicity [29]. The main ionic liquids in supercapacitors are based on imidazolium, pyridinium, and pyrrolidinium cations, and bis(trifluoromethanesulfonyl)imide, tetrafluoroborate, and hexafluorophosphate anions [30].

1.3.2.3 Deep eutectic solvents

Deep eutectic solvents (DESs) are a type of nonaqueous electrolyte that consists of a eutectic mixture of two or more compounds, typically a hydrogen bond donor and a hydrogen bond acceptor [31]. DESs have several advantages over other types of nonaqueous electrolytes, such as low cost, low toxicity, and easy preparation. DESs have been used in supercapacitors due to their high conductivity and wide electrochemical window. The most commonly used DESs in supercapacitors are based on choline chloride, ethylene glycol, and urea [32].

1.3.2.4 Polymer electrolytes

Polymer electrolytes are a type of nonaqueous electrolyte that consists of a polymer matrix and a salt. Polymer electrolytes have several advantages over other types of nonaqueous electrolytes, such as high mechanical strength, good thermal stability, and low flammability. The most commonly used polymer electrolytes in supercapacitors are based on polyethylene oxide, poly(vinylidene fluoride), and poly(acrylonitrile) [33].

1.3.2.5 Hybrid electrolytes

Hybrid electrolytes are a type of nonaqueous electrolyte that combines two or more types of electrolytes, such as organic electrolytes and ionic liquids. Hybrid electrolytes have several advantages over single-component electrolytes, such as improved conductivity, wider electrochemical window, and improved stability [24]. The most used hybrid electrolytes in supercapacitors are based on organic solvents and ionic liquids.

The most used nonaqueous hybrid electrolytes in supercapacitors are as follows [27]:

1. Acetonitrile (CH3CN): CH3CN is a commonly used organic solvent in nonaqueous electrolytes due to its high dielectric constant, low viscosity, and wide electrochemical window. It is typically used in combination with lithium salts such as lithium perchlorate.

2. PC: It is another commonly used organic solvent in nonaqueous electrolytes due to its high dielectric constant, low viscosity, and wide electrochemical window. It is typically used in combination with lithium salts such as lithium perchlorate.

3. EC: It is a cyclic carbonate that is commonly used in nonaqueous electrolytes due to its high dielectric constant, low viscosity, and wide electrochemical window. It is typically used in combination with lithium salts such as lithium perchlorate.

4. TEABF4: It is a commonly used salt in nonaqueous electrolytes due to its high solubility, high stability, and low viscosity. TEABF4 is typically dissolved in organic solvents such as acetonitrile, PC, and EC to form the nonaqueous electrolyte. These solvents are chosen because of their high solubility for TEABF4 and their good compatibility with the electrodes. The concentration of TEABF4 in the electrolyte can vary depending on the specific application, but it is typically in the range of 0.1–1 M.

These nonaqueous electrolytes have several advantages over aqueous electrolytes, including a wider electrochemical stability window, which allows for higher operating voltages and energy densities, as well as higher ionic conductivity, which can improve the performance of the supercapacitor [34]. However, they also have some disadvantages, including a higher cost and lower environmental friendliness than aqueous electrolytes, and a greater potential for electrolyte decomposition at high voltages, which can lead to reduced performance and safety issues. Despite these challenges, nonaqueous electrolytes continue to be an active area of supercapacitor development and have shown great promise in improving the performance and energy density of these devices. A detailed performance evaluation of these electrolytes is compiled in the following chapters of this book.

1.4 Separators for supercapacitors

Separators are another important component of supercapacitors as they physically separate the two electrodes to prevent electrical contact while allowing the ions to flow between the electrodes [35]. The choice of separator depends on the specific application and performance requirements of the supercapacitor. Some factors to consider when selecting a separator include its mechanical strength, chemical stability, porosity, and electrical conductivity.

Various separators are available for supercapacitors and are used depending on the practical utility of the supercapacitor. The main categories of separators researched are as follows [36]:

1. Polymeric separators: Polymeric separators are commonly used in supercapacitors due to their high mechanical strength, flexibility, and thermal stability. They are typically made of materials such as polyethylene, polypropylene, and polyvinylidene fluoride [37]. Also, there are research reports on using electrospinning techniques on developing polymer and polymer-based separators for supercapacitors.

2. Ceramic separators: Ceramic separators are characterized by their high thermal stability and resistance to chemical degradation. They are often used in high-temperature applications and can be made of materials such as alumina, zirconia, and silicon carbide [38].

3. Carbon-based separators: Carbon-based separators are characterized by their high surface area, high conductivity, and low resistance. Materials such as graphene and carbon nanotubes are commonly used as carbon-based separators in supercapacitors [39]. These separators can increase the performance of the supercapacitor device due to the increase in conductivity of the separator.

4. Hybrid separators: Hybrid separators are made by combining two or more types of materials to achieve specific performance characteristics. For example, a hybrid separator made of polymeric material and carbon-based material can offer both flexibility and high ion conductivity [12]. There is increased research on developing hybrid separators for supercapacitors, especially polymer-based metal oxide and carbon-material research.

5. Ion gel separators: Ion gel separators are made by incorporating an electrolyte into a gel matrix, which is then sandwiched between two electrodes. This type of separator offers high ion conductivity and low resistance, making it suitable for high-power applications [40]. Also, this will serve both as an electrolyte and as a separator for the device, reducing the charge transfer resistance of the device.

The choice of separator for a supercapacitor depends on various factors such as the desired performance characteristics, the operating environment, and the cost of production. Researchers continue to explore new materials and technologies to improve the performance and cost-effectiveness of supercapacitor separators.

1.5 Categories and design of supercapacitors

There are several categories of supercapacitors researched to increase the energy storage performance of supercapacitors. The below-mentioned categories of supercapacitors are well explained in other chapters of this book. However, for a general introduction, these categories are mentioned here at a glance.

There are several categories of supercapacitors, including the following:

1. EDLCs: These supercapacitors have high capacitance and energy density and operate based on the electrostatic attraction between the charged electrodes and the electrolyte [41]. Usually, the electrode material of these capacitors is made up of activated carbon.

2. Pseudocapacitors: These supercapacitors have a high energy density and operate through reversible redox reactions on the surface of the electrode material, which allows for faster charging and discharging compared to EDLCs [42]. Metal oxides such as RuO, MnO2, and their carbon-based composites are used as electrode material.

3. Hybrid supercapacitors: These supercapacitors combine the high power density of EDLCs with the high energy density of batteries by using both electrochemical double-layer capacitance and pseudocapacitance. For this category, the electrode materials consist of both pseudocapacitive or battery-type metal oxides in a single electrode utilizing both EDLC, pseudocapacitive, and battery-type charge storage [43].

4. Asymmetric supercapacitors: These supercapacitors use different electrode materials with different capacitances to achieve a higher energy density. A typical asymmetric supercapacitor consists of a battery-type or pseudocapacitive electrode as positive electrode and activated carbon as negative electrode with aqueous or ionic electrolytes and a paper separator [44]. Also, research on asymmetric supercapacitors also reports the use of reduced graphene oxide, carbon nanotubes, and MXenes as negative electrodes for asymmetric supercapacitors.

5. Symmetric supercapacitors: These supercapacitors have the same electrode material and geometry and are used mainly for high-power applications. Most of the commercial supercapacitors available are symmetric supercapacitors [45]. A symmetric capacitor consists of activated carbon as electrodes with aqueous or ionic electrolytes.

These supercapacitors are fabricated in various designs for commercialization aspects [46]. The various designs of supercapacitors are briefly mentioned here.

1. Coin cell: These are small supercapacitors designed for low-power applications, such as backup power for electronic devices. They have a coin-shaped design and typically have low capacitance and voltage ratings.

2. Cylindrical: Cylindrical supercapacitors are commonly used in hybrid EVs and other high-power applications. They have a cylindrical shape and are available in different sizes and capacitance ratings. And most of commercial supercapacitors are cylindrical in shape.

3. Prismatic: Prismatic supercapacitors have a rectangular shape and are used in high-power applications where space is limited. They offer high energy density and can be stacked to increase the voltage.

4. Flexible: Flexible supercapacitors are designed to be bendable and flexible, making them suitable for wearable devices and other flexible electronics. They are typically made using thin film technology.

5. Module: Supercapacitor modules consist of multiple supercapacitors connected in series or parallel to achieve the desired voltage and capacitance. They are used in applications such as regenerative braking systems in electric vehicles and backup power systems for data centers.

These various designs are detailed in the following chapters of the book and their performance evaluation is also detailed.

1.6 Machine learning and supercapacitors

In the present supercapacitor research, experiments are performed with the optimization of different parameters such as volume/weight/molarity of precursors, volume of solvents, their solvent to precursor ratio, reaction temperature, and voltage. Mostly, these parameters are optimized by using trial and error approaches. This creates lag in finalizing the electrode materials and confirming its phase and morphology. Hence, artificial intelligence or machine learning could be utilized in different aspects of supercapacitor research [47]. Machine learning can be used to improve the performance of supercapacitors by predicting the optimal materials and design parameters for the device.

One way machine learning can be applied to supercapacitors is using computational modeling. Researchers can use machine learning algorithms to train models that can simulate the behavior of supercapacitor materials and predict their performance characteristics [47]. These models can help identify the optimal electrode and electrolyte materials, as well as the best design parameters such as the electrode thickness and pore size, to achieve high energy density and power density [48].

Another approach is to use machine learning to analyze large amounts of experimental data on supercapacitor performance. By inputting data on various materials and design parameters into a machine learning algorithm, researchers can develop models that can predict the performance of new supercapacitors with high accuracy [49]. This can significantly reduce the time and cost required to develop new supercapacitors and optimize their performance. Software such as design of experiments use such type of analysis in delivering the predicted results.

Machine learning can also be used to optimize the charging and discharging cycles of supercapacitors. By analyzing real-time data on supercapacitor performance, machine learning algorithms can adjust the charging and discharging cycles to maximize the energy and power density of the device while minimizing the risk of damage or degradation [50]. This could increase the cycling stability of the supercapacitors providing a longer, safer, and optimized supercapacitor performance.

Overall, machine learning has the potential to significantly improve the performance and efficiency of supercapacitors, making them a more viable alternative to traditional batteries for energy storage applications. The various techniques of these machine learning on the material design and their performance evaluation are detailed in the dedicated chapter of this book.

1.7 Future of supercapacitors as energy storage devices and their commercial markets

Supercapacitors are considered a promising alternative to batteries for applications that require high power output, such as electric vehicles, renewable energy systems, and portable electronics. The future of supercapacitors as energy storage devices looks promising, as researchers continue to develop new materials and designs that improve their energy density, charge-discharge efficiency, and overall performance [51]. One of the key areas of research is developing new electrode materials that can increase the specific capacitance of supercapacitors, which is the amount of charge that can be stored per unit of mass or volume. Another area of research is in the development of hybrid energy storage systems that combine the benefits of supercapacitors with those of batteries. For example, a supercapacitor–battery hybrid system could provide both high power output and high energy density, making it suitable for a wider range of applications [52].

The future of supercapacitors as energy storage devices is promising, and as research in this area continues, we can expect to see improvements in their performance, efficiency, and cost-effectiveness. However, it is important to note that supercapacitors are still relatively new technology, and there are challenges that need to be addressed, such as their limited energy density compared to batteries and their relatively high cost. Furthermore, with the research progress in design of materials and electrolytes for improving the energy density of supercapacitors without much reduction in its power density, high voltage supercapacitors will be available in future markets.

Considering these research improvements, plenty of exciting opportunities for the future commercial prospects of supercapacitors are available. The future commercial markets of supercapacitors are vast, and there are a number of industries that could benefit from their high power density, long cycle life, and high charge-discharge efficiency. Some of the potential markets for supercapacitors and applications where they could be used are given below.

1. Electric vehicles

One of the most promising markets for supercapacitors is EVs. EVs require energy storage systems that can deliver high power output for acceleration and braking, and traditional batteries have limited power density. Supercapacitors could be used in conjunction with batteries in EVs to provide the necessary power output for acceleration and braking, while the batteries provide the necessary energy density for longer range. This could save the battery life and the power performance of EVs.

2. Renewable energy systems

Renewable energy systems, such as wind and solar power, require energy storage devices that can store energy when it is available and release it when it is needed. Supercapacitors could be used as an intermediate energy storage device in renewable energy systems, providing fast response times and high charge-discharge efficiency.

3. Consumer electronics

Consumer electronics, such as smartphones and tablets, require energy storage devices that can be charged quickly and last a long time on a single charge. Supercapacitors could be used in consumer electronics to provide fast charging and long battery life, improving the user experience. Although the energy density of supercapacitors is poor, it could be useful in high intense mobile gaming applications where intense power is required, saving the battery life.

4. Aerospace and defense

Aerospace and defense applications require energy storage devices that are lightweight, reliable, and durable. Supercapacitors and flexible supercapacitors could be used in aerospace and defense applications, such as satellites and spacecraft, to provide high power output and long cycle life.

5. Medical devices

Medical devices, such as implantable devices and wearable sensors, require energy storage devices that are small, lightweight, and safe. Supercapacitors could be used in medical devices to provide high power output and long cycle life, improving the performance and reliability of these devices.

6. Industrial automation

Industrial automation applications, such as robotics and automation systems, require energy storage devices that can provide high power output and fast response times. Supercapacitors could be used in industrial automation applications to provide the necessary power output and response times, improving the efficiency and productivity of these systems.

7. Smart grids

Smart grids require energy storage devices that can store excess energy generated during low-demand periods and release it during high-demand periods. Supercapacitors could be used in smart grids to provide fast response times and high charge-discharge efficiency, improving the efficiency and reliability of the grid.

The future commercial markets of supercapacitors are vast, and there are a number of industries that could benefit from their high power density, long cycle life, and high charge-discharge efficiency. The advancements in supercapacitor technology, such as the development of new electrode materials and the improvement of supercapacitor design, make them increasingly attractive for a wide range of applications. As research in this area continues, we can expect to see improvements in the performance, efficiency, and cost-effectiveness of supercapacitors, making them an even more viable alternative to traditional batteries in a variety of industries. An elaborated commercialization detail for supercapacitors and prospects is discussed in a detailed chapter of this book.

1.8 Conclusion

In conclusion, this chapter has provided a comprehensive overview of supercapacitors, including their materials and design. Supercapacitors are essential energy storage device that offers higher energy density and faster charge-discharge rates compared to traditional batteries. This chapter has introduced the materials used in supercapacitors, including various types of electrodes, electrolytes, and separators, and their properties. Furthermore, it has discussed the design considerations for supercapacitors, including their geometric design, device configuration, and the impact of operating conditions on their performance. Overall, this chapter has demonstrated the potential of supercapacitors as highly efficient energy storage devices and highlighted the need for further research in developing new materials and designs for enhancing their performance.

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