Bridging the gap between electrolytic capacitors and rechargeable batteries, supercapacitors are finding a home in a growing number of applications.
What are supercapacitors used for?
Supercapacitors are cutting-edge energy storage devices that offer a wide range of desirable features, including high capacitance, high power density, and extended cycle times. Also known as ultracapacitors, supercapacitors effectively span the gap that currently exists between electrolytic capacitors and rechargeable batteries.
A typical double-layer supercapacitor is different from a conventional capacitor in two important ways. A supercapacitor's metal plates present a much larger surface area than in an ordinary capacitor, and the distance between the plates is significantly smaller, since the separator between them works in a different way than a conventional dielectric.
In a battery, charge and discharge are electrochemical reactions. Supercapacitors store charge electrostatically on their high surface-area plates. The devices store less energy, but they can charge or discharge in seconds. Therefore, supercapacitor applications are primarily used to supply short bursts of power. For at least the foreseeable future, batteries will remain the preferred choice for storing large amounts of energy over long periods of time.
Supercapacitors applications and their multiple benefits
Over the past few decades, supercapacitors have evolved from being an exotic, unique design choice to a routinely relied upon technology that's suitable for applications ranging from battery backups to preventing accidental storage memory loss. Engineers are drawn to supercapacitors by the technology's multiple benefits, including excellent performance and reliability.
A key supercapacitor attribute is that it can be charged and discharged hundreds of thousands of times under normal conditions. Unlike an electrochemical battery, which has a defined cycle life, little wear and tear is created by cycling a supercapacitor. Additionally, supercapacitors offer faster charge/discharge cycles than batteries.
Supercapacitors are prized for their current handling capabilities at levels that alternative devices cannot provide due to ESR. Supercapacitors are also able to handle wider temperature ranges than batteries.
When used for battery support, supercapacitor technology can significantly extend primary/secondary battery lifetime, usually by a minimum of 2X.
Safety is an important consideration in many different types of product designs, particularly mobile and wearable devices. Unlike some battery types, such as lithium-ion (li-ion), which pose a fire and explosion risk when punctured, overcharged, overheated or short circuited, supercapacitor failures are never catastrophic. They are also environmentally friendly in that they do not require the same precautions when being disposed of contrary to batteries.
Supercapacitor types
Supercapacitor performance depends to a large extent on its electrode material and electrolyte. A supercapacitor's high-surface area electrodes are formed out of a porous material. Charge is typically stored close to the boundary that exists between the electrolyte and the electrode material. For double-layer capacitors, electrodes are commonly created out of carbon aerogel, carbon cloth or carbon black.
Some supercapacitors incorporate an aqueous electrolyte while others feature an organic electrolyte. Commonly used organic electrolytes include acetonitrile and propylene carbonate.
Cylindrical supercapacitors are the technology's basic workhorse. The devices are designed to provide a wide range of industrial and consumer technology engineers with a solution that delivers optimal pulse power handling characteristics and significantly outperforms the competition while remaining cost-competitive.
AVX offers cylindrical supercapacitors in a wide range of mount configurations, including two-to-four terminal planar mounts, through-hole mounts, extended stand-off through hole mounts and wire lead mounts. Series-connected modules are also available.
Multiple applications
Although supercapacitors are a relatively new technology (at least when compared to traditional capacitors), the devices are now ready for use in a wide range of applications. One of the earliest supercapacitor applications was as a backup to primary batteries in order to bridge brief power interruptions or to smooth electrical flow. In this still widely used role, supercapacitors can be found in uninterruptable power supplies (UPSs), wireless alarm systems, smart meters, and even solid-state drives (SSDs).
Supercapacitors are also widely used to provide power in pulse applications, telemetry, peak power assist and electronic locks. Additionally, many engineers turn to supercapacitor technology as the best way to start backup generators during power outages and provide power until the switch-over gets up to full speed. In Japan, large supercapacitors are frequently installed in commercial buildings to reduce grid consumption at peak demand times and to ease loading.
Supercapacitors are also now commonly used as energy harvesters to capture and store collected energy from solar cells, wind turbines, ocean waves and other external sources to power low-energy electronics. Supercapacitors, which can operate in harsh environments across a wide range of operating temperatures while offering high-power density and high reliability, are also ideal for use in Internet of Things (IoT) sensor and communication designs.
A growing number of engineers are now turning to supercapacitors as high-performance energy storage devices that can contribute to the rapid growth of low-power electronics. Portable electronic devices, such as smart phones, smart watches, GSM/GPRS modules and wearable medical devices, can all benefit from supercapacitor technology. Honeywell, for example, now offers a supercapacitor-powered, battery free UPC scanner that fully recharges within seconds. The manufacturer promises an eight-plus year lifespan, approximately six times longer than standard lithium-ion batteries.
The automotive sector is emerging as another leading supercapacitor adopter, integrating the technology into various vehicle systems. Start/stop functions and power steering can benefit from the technology's performance and temperature tolerance attributes. Down the road, supercapacitors promise the ability to rapidly charge hybrid vehicle batteries, operating in conjunction with the car or truck's gasoline engine. Installing supercapacitors in hybrid vehicles will allow them to travel longer distances with high power control and efficiency.
The rail industry has also started to appreciate the energy harvesting potential of supercapacitor technology. Spanish rail company CAF, for instance, offers Greentech Evodrive, an on-board supercapacitor-based energy harvesting system designed for street trams. The technology recovers kinetic energy released in braking, thereby improving upon the tram's overall energy efficiency.
The AVX advantage
AVX offers the widest variety of standard cylindrical-type supercapacitors, offering the ability to satisfy custom design requests. AVX provides a diverse range of part offerings focused on maximizing energy storage, low ESR and minimal leakage current.
The company's SCC and SCM series of cylindrical electrochemical double-layer capacitors, for instance, offers excellent pulse power handling characteristics based on the combination of very high capacitance and very low ESR. Used individually or in conjunction with primary or secondary batteries, the devices provide extended back up time and longer battery life, as well as instantaneous power pulses when needed.
The BestCap supercapacitor in AVX's BZ series is a low ESR pulse supercapacitor that's based on the non-hazardous proton activated polymer system. The product competes directly with devices made with organic electrolytes, but has a far wider voltage range, from 3.6V to 20V (organics are typically limited up to around 3V per cell). BestCap has a temperature range of -20°C to +70°C—wider than batteries—and also offers select values available between -40°C to +75°C. BestCap offers the most "capacitor-like" frequency response of all supercapacitors and features low ESR and low profile characteristics.
AVX’s PrizmaCap prismatic supercapacitors, featured in the SCP series, provide the lowest profile and widest operating temperature range available in AVX supercapacitors. Used by themselves, or in conjunction with primary or secondary batteries, the devices offer an extended backup time with longer battery life and instantaneous power pulses when needed. The devices are targeted at applications requiring pulse power handling, energy storage, energy/power holdup and battery assist.
All AVX supercapacitor series are available for customization in the areas of lead orientation, wire harness leads, packaging and non-standard offerings in voltage, capacitance, and other key areas. For higher voltage supercapacitor applications, AVX can design and build custom module assemblies, complete with enclosure, balancing and health monitoring support.
Supercapacitors grow in popularity
Supercapacitors are a rapidly growing energy storage technology that has become an increasingly popular design choice for a growing number of applications. Despite the fact that li-ion batteries are now used in a wide range of personal and commercial devices, the technology will never be able to compete against supercapacitors in terms of power density and number of charge/discharge cycles.
As supercapacitor adoption grows and new applications are envisioned, researchers worldwide are striving to increase performance and compatibility by investigating new forms of dielectric materials, such as carbon nanotubes, polypyrrole and barium titanate, all of which promise to improve capacitance and energy density.
Stay tuned—the supercapacitor story has just begun.
To view AVX’s entire supercapacitor product line, and to select the devices that most closely match your design needs, click here.
