Nanotechnology's Impact on Energy Storage Devices

(Source: Love Employee - stock.adobe.com)

For many years, scientists and engineers have tried to devise ways of making energy storage systems more efficient. This has manifested in a several ways, including trying to increase the storage capacity of energy storage devices, a reduction in the size of the devices, developing energy storage devices that can rapidly charge, and even manufacturing hybrid devices that take the best properties of multiple devices into a single device—one example being hybrid battery-ultracapacitor modules.

The need for greater efficiencies, smaller sizes, and faster charging rates manifested in recent years due to societal changes that have meant we are now more reliant on electronic devices throughout our daily lives. So, developers constantly strive to improve these devices and provide more power while maintaining or reducing the size.  Many conventional manufacturing methods limit how small and efficient developers can make these with bulk materials, so many academic scientists and industrial manufacturers are now turning nanomaterials to solve these challenges. The impact of nanotechnology on these devices over the last few years has been so great that we are now starting to see a number of commercial energy storage devices on the market that use nanomaterials, many of which are in consumer products.

Nanomaterials exhibit properties that make them ideal for a wide range of energy storage devices. Because nanomaterials can have very different properties from each other, developers have endless possibilities for improving energy storage devices, as well as in other application areas.

One of the main benefits for energy storage devices is the high electrical conductivity and charge carrier mobility of some nanomaterials, which enable electrons to travel and be stored more effectively. This can also be enhanced in some nanomaterials by the quantum effects seen at the nanoscale. Some nanomaterials possess quantum wells—energy potential wells—in which electrons can tunnel between if the wells are close enough together. This means that in some nanomaterials, the electrons can pass through the material without being impeded by any of the chemical bonds that make up the device, which, in turn, means that they don’t lose energy.

Nanomaterials are also inherently small and/or thin, enabling them to construct the miniature devices that society wants without compromising on the efficiency of the device. Nanomaterials also have a very large and active surface area compared to bulk materials that can be used for storing charge and/or ions, depending on the storage device.

Some other nanomaterials are also incredibly insulating and can withstand high heat—much higher than the heat given off by high-power electronic devices. In a world where electronic devices are continually producing more heat as each technology generation passes, these insulating nanomaterials not only help to protect the electrical properties of the device; they can often dissipate heat within the device, meaning that it is less likely that heat spots and localized damage will occur, lengthening the usable lifetime of the device.

Different nanomaterials have had an impact on the properties of energy storage devices, and it’s not uncommon to use more than one nanomaterial to improve multiple properties of the device and/or induce synergistic effects between the nanomaterials that contribute to a more efficient device. So, developers can use more than one nanomaterial in conjunction with each other to provide enhanced benefits. One example is stacking electrically insulating (dielectric) nanomaterials on top of highly conductive nanomaterials to reduce energy loss to the surroundings, protect the electronic charge carriers, and in some cases, help to manipulate the direction of an electron.

Nanomaterials are now being used in a number of energy storage systems. Of these, batteries are the most common, with commercial batteries now being produced that contain nanomaterials. Given that Li-ion batteries present the biggest market to manufacturers, this is where the most impact has been made, but they have also been used to produce commercial lithium-sulfur (Li-S) batteries. While the most use of nanomaterials within batteries has been in the electrode, they are also used in solid and gel forms as the electrolyte within some batteries.

Aside from batteries, some nanomaterials are also being used to construct the next-generation of supercapacitors and some modules are being developed which are a hybrid of both batteries and supercapacitors to try and exploit the beneficial properties of both (while simultaneously trying to remove the issues associated with both).

These energy storage systems are used in many different modern-day technologies, and the use of nano-inspired energy storage devices has potential across small-scale (handheld) systems as well as larger energy storage systems, such as electric vehicles. In fact, nanomaterials have been touted as one of the most promising ways of improving the relatively poor charging and energy storage capabilities of many of the batteries currently used in electric vehicles.

While nanotechnology-inspired energy storage devices have capabilities in larger systems, they are currently more prevalent in portable and handheld devices. A prime example includes a smartphone, used in the Internet of Nano Things (IoNT). The IoNT means smaller sensors are needed, and nanotechnology-based batteries offer a way of powering such devices—with typical application areas spanning from medical sensing to environmental monitoring.

Another key area where the small size of such batteries has become useful is in the ever-evolving area of flexible and wearable electronic devices. In addition to stand-alone devices, there are a number of e-textiles which are being developed that use energy storage—and energy-harvesting devices)—that power the device, and these devices are only possible due to the small size and efficiency of the nanomaterials used in them.

A number of nanomaterials have properties that are highly suited to improving the performance, size, and charging capabilities of many energy storage devices. As the demand for smaller, yet more efficient devices continue to grow, nanomaterials are going to play an even bigger part in these devices than they already do now. We’re already starting to see commercial systems hitting the market across a range of handheld consumer products, and these markets are likely to grow in the future as more end-user manufacturers adopt these technologies.