BATTERIES
NANOTECHNOLOGY IS INSPIRING NEXT-GEN BATTERIES Liam Critchley*
Rechargeable batteries are an important part of many modern-day technologies.
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esearchers, manufacturers and end-user companies are always looking to improve the efficiencies of batteries, making them safer, smaller and more lightweight to fit in the requirements of new technologies — that is, the consumer desire to have higher-powered, smaller and more lightweight electronic devices. Conventional fabrication methods, electrochemistries and materials will take batteries technologies only so far, so a lot of interest in recent years has been around using nanomaterials within the electrodes. Nothing is wrong with current battery technologies — as showcased by the 2019 Nobel Prize in Chemistry, which honoured the scientists behind the Li-ion battery — but change is inevitable. Without an everchanging electronics industry, technological advances made in the past few decades would not have been possible. While lithium-ion (Li-ion) batteries are ubiquitous nowadays, their efficiencies aren’t overly impressive. They are much safer than other batteries while still having a good energy density, so there is room for improvement. Other types of batteries are gaining traction at both fundamental and commercial levels, but a drive to improve the already-established Li-ion batteries
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by incorporating nanomaterials into them has begun.
Why nanomaterials? The switch to trialling nanomaterials over bulkier materials is for many of the same reasons that other industries have made the switch (or have looked to make the switch). A number of properties can be harvested for a small amount of nanomaterials being included in a device (or within another material). Not all nanomaterials are suitable for batteries, as some nanomaterials are inherently insulating in nature. Rather, it is the conductive nanomaterials that are of use in battery systems, such as those of solid-state nature, or those which are incredibly thin (for example, some 2D materials). Luckily, the use of nanomaterials in electrodes is not a completely new invention. It is merely a natural progression to make systems more effective without altering the internal workings of the technology. While the inclusion of nanomaterials might slightly alter the specific mechanisms of how the ions move into the electrodes (because of different-sized/geometry atomic holes) via different architectures, the general operational mechanism of the batteries remains
the same. This means that any safety or efficiency issues that arise can be pinpointed much easier than trying to develop a new type of battery from scratch. Sometimes, improving the status quo is better than trying to develop something completely novel. Many of the nanomaterials trialled have high electrical conductivity, and with this comes a high charge carrier mobility. These properties stem from nanomaterials having a very active surface — and a very high surface area — compared to bulkier materials. In some cases, the active surface is the whole nanomaterial (2D materials). Given that nanomaterials are inherently thin, they are a lot more flexible — even the inorganic materials — than bulk materials, meaning that they are more useful for the batteries used in flexible and wearable technologies (Figure 1). Despite their small size, a lot of nanomaterials are very stable and are resistant to high temperatures, harsh chemicals and high physical stresses. While this can’t be said for all nanomaterials, enough of them are stable and conductive enough for battery electrodes. One disadvantage of nanomaterials is their higher cost because of the more complex fabrication methods required to make them. However, because only a small
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