A type of energy storage system that has garnered the attention of a growing number of industry professionals in recent years is known as a supercapacitor. These devices are also referred to as ultracapacitors, double-layer capacitors, or electrochemical capacitors. In layman’s terms, you can think of them as a combination of a regular capacitor and a battery; however, they are not the same.

Before we get into the specifics of whether or not supercapacitors can make a difference on their own in terms of how energy can be stored in the future, it is essential to understand how they function and how they are distinct from lithium-ion batteries. This will allow us to answer the question: “Can supercapacitors make a difference on their own in terms of how energy can be stored in the future?”

Batteries and supercapacitors are both examples of different storage technologies. When we look at lithium-ion batteries, we see that they rely entirely on chemical reactions. They have a positive and negative electrode, referred to by their respective technical names: the anode and the cathode. These two electrodes are then separated by a micro-perforated separator and placed in a liquid electrolyte before submerging. Ions are the only particles that can pass through the separator. Therefore, ions tend to move back and forth between the anode and cathode of a battery while it is being charged and discharged. When this ion transfer process is taking place, the battery will heat up, expand, and finally contract. Because of these reactions, a battery will gradually lose its capacity, which will result in a shorter battery lifespan. On the other hand, batteries possess a very high specific energy or energy density, which allows them to store energy for use at a later stage and is one of its most significant advantages.

However, supercapacitors are not like regular batteries because their operation does not depend on chemical reactions. Instead, they are capable of storing energy within them via electrostatic means. The negative and positive charges are separated by an insulator or dielectric sandwiched between supercapacitor electrode plates. Because of this separation, the device is able to store energy and then release it in a very timely manner. It does this by storing the static electricity that is generated for later use. The most significant benefit is that a capacitor can keep the same voltage rating for more than 20 years. On the other hand, the voltage capacity of a battery can degrade over time and with continued use. This can happen both when the battery is not in use, and when it is.

In contrast to a battery, supercapacitors have a higher power throughput, indicating that they can charge and discharge in a much shorter time. Despite this, their specific energy is relatively low compared to batteries. Therefore, the most effective use for supercapacitors is delivering very brief surges of power.

Table 1.1. Features of supercapacitors in comparison with batteries. Adaptaded from (E.S. Steigerwalt, G.A. Deluga, D.E. Cliffel, C.M. Lukehart, J. Phys. Chem. B 105 (2001) 8097.)

When it comes to applications that require a high power density as well as a large number of charge/discharge cycles or a longer life, supercapacitors have many benefits to offer. These devices find applications across a variety of industries, including wind turbines, mobile base stations, electronic devices, and various manufacturing processes. Since they are superior to lead-acid batteries, they have also begun to be used in uninterruptible power supplies (UPS), electric vehicles, and various power electronics applications. In recent years, supercapacitors have been used as energy storage devices in renewable and hybrid energy storage systems to regulate the source and the grid. Voltage stability is achieved through the use of these devices. A supercapacitor can help keep the power supply stable when the load constantly shifts. In addition, they can provide power for portable speakers and flashes, both of which can quickly be recharged. Braking energy recovery has the potential to reduce both overall energy consumption and CO2 emissions, which are two of the primary challenges faced by transportation today. Supercapacitors can meet the requirements for a wide variety of applications in all types of vehicles because they can store and deliver energy quickly. Consumer electronics, tools, power supply, voltage stabilization, microgrid, renewable energy storage, energy harvesting, street lights, medical applications, military and automotive applications, and energy recovery are just some of the applications for supercapacitors. You can see some of these examples illustrated in the figure that can be found below.

The layer of active material that makes up the electrodes in supercapacitors can range in thickness from just a few nanometers to several micrometres. Although carbon-based materials have low specific capacitance, they are typically utilized as electrodes in supercapacitors because they satisfy the electrode requirements. A wide range of carbon-based materials, including activated carbon, templated carbon, carbon nanotubes, graphene, carbon onions, and carbide-derived carbon, have been utilized. Because these carbon materials have a large surface area, they are able to provide a significant amount of specific energy and power.

The application of slot die coating is widespread in the field of industrial electrode coating for energy storage devices. The advantages of this coating method, including scalability of the process, high layer uniformity, reproducibility, and a low total cost of ownership, are the primary drivers behind its widespread adoption. As a result, we at FOM technologies have developed slot die coating tools specifically for electrode coating at both the R&D and pilot scale.