Imagine a battery that can be charged in seconds
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Fitness tracking watch, smartwatches, clever earphones and extra implausible wearables are the primary upsurge in a new age in electronics. Most are confined by partial battery power, so the next wave – an army of tiny sensors that autonomously transfer data to other devices, better known as the Internet of Things (IoT) – will rely on a revolution in battery technology. Cue 3D micro batteries.
How do batteries work?
Batteries have a negative (cathode), and a positive (anode) electrode finished through metal, with a non-conducting electrolyte in amongst that encourages electrically charged atoms, usually lithium ions, traveling between one and the other. When all those atoms are on the positive side, the battery needs reviving, after which the atoms (now with a supply of electrons) then travel the other way.
Given the size inadequacies of the normal lithium-ion batteries originated in nearly all portable electronics, from phones and cameras to Bluetooth earphones and wearables, scientists are continuously on the quest for smaller and more efficient designs.
About 3D battery
A 3D battery is a comprehensive redesign of how current batteries are built, in order to make them either more powerful, or smaller. Instead of a coating of the anode, the electrolyte, then a layer of the cathode, a 3D battery has 3D-shaped anode and cathode that are more like puzzle pieces. Such a design raises the surface area of the cathode and anode and can either hold more lithium ions, and so offer more power, or be many times smaller than an outdated battery. Efficiently, 3D designs increase the energy degree of batteries.
What has UCLA done?
Investigators at the University of California, Los Angeles (UCLA) have created a powerful 3D lithium-ion battery no bigger than 100 grains of salt. In their paper High Areal Energy Density 3D Lithium-Ion Micro batteries published in Joule in May of this year, they outlined not only a 3D battery, but a new way of constructing it by means of similar methods used to manufacture electronic circuits – that’s key, since though improved in theory, 3D batteries have so far proved difficult to construct.
As an alternative of layers, the UCLA team’s ‘concentric-tube’ design uses 3D anode posts protected by a thin layer of a photo-patternable polymer electrolyte, with the area between the poles filled by the cathode material. The end result had an energy density of 5.2 milliwatt-hours per square centimeter, which is pretty good for a 3D battery. Nevertheless, even more, significant for use in small strategies was its small size: just 0.09 square centimeters. Wow.
How significant is this?
More work is desired on mechanisms, gathering, and packaging, but it could mean 3D micro batteries for IoT applications are cooler to create. “For small sensors, you need to re-design the battery to be like a skyscraper in New York instead of a ranch house in California,” said Bruce Dunn, professor of materials science and engineering at UCLA and senior author of the report, about the team’s use of cathode posts.
“That’s what a 3D battery does, and we can use semiconductor processing and a conformal electrolyte to make one that is compatible with the demands of small internet-connected devices.”
The battery that charged rapidly
The sum of power a battery can store becomes less important if it can be recharged very quickly. Think about Apple AirPods and other ‘true wireless’ earphones; if they could be recharged in under a minute, would anyone care how long the battery actually lasted? And what if those batteries could be recharged in less than a second?
There are other ways of making 3D batteries that could mean wearables and IoT devices could be recharged almost rapidly, as proven by a team at Cornell University, which sought to intertwine the components inside a battery. In place of the standard cathode-electrolyte-anode design, they designed a 3D gyroidal structure with thousands of nanoscale pores filled with all the battery’s usual components.
“This is truly a revolutionary battery architecture,” said Ulrich Wiesner, professor of engineering in the Department of Materials Science and Engineering. “This three-dimensional architecture basically eliminates all losses from a dead volume in your device.” He also pointed out that by shrinking everything to the nanoscale, you get orders of magnitude higher power density. “So you can access the energy in much shorter times than what’s usually done with conventional battery architectures.”
So how fast will its 3D battery recharge? “By the time you put your cable into the socket, in seconds, perhaps even faster, the battery would be charged,” said Wiesner. The team’s paper Block Copolymer Derived 3-D Interpenetrating Multifunctional Gyroidal Nanohybrid for Electrical Energy Storage was published in Energy and Environmental Science in May 2018.
The compliant battery for wearables
Both of these 3D batteries are a challenge to blow new life into the lithium-ion battery, but some think a whole new kind of battery is needed for flexible (and even stretchable) wearable devices – think smart clothes for fitness pursuits that constantly collect and send data on all kinds of body metrics.
Lithium-sulfur (Li–S) batteries are one option that’s been investigated by a team of researchers in Korea, in a paper published in the Journal of Materials Chemistry. The team exhibited a new class of battery that uses an all-fibrous cathode–separator and carbon nanotubes to create a metallic foil form aspect. As well as special enhancements in energy density, that power-driven deformability means the batteries can be creased without being disturbed.
With the IoT growing at an exponential rate, and with the wearable fitness tracker market alone considered to be worth $48.2 billion by 2023, there’s going to be a massive and increasing demand for tiny batteries that boast higher capacity, can be enormous quickly, and can even bow and move – and more power to whoever can make them commercially possible initially.