Li-ion microbatteries produced via 3D printing

The technique is used in a range of fields, from producing crowns in dental labs to rapid prototyping of aerospace, automotive and consumer goods. Lewis' group has greatly expanded the capabilities of 3-D printing. They have designed a broad range of functional inks with useful chemical and electrical properties. And they have used those inks with their custom-built 3D printers to create precise structures with the electronic, optical, mechanical or biologically relevant properties they want.

To print 3D electrodes, the group first created and tested several specialised inks. Unlike the ink in an office inkjet printer, which comes out as droplets of liquid that wet the page, the inks developed for extrusion-based 3-D printing must fulfil two difficult requirements. They must exit fine nozzles like toothpaste from a tube, and they must immediately harden into their final form.

In this case, the inks also had to function as electrochemically active materials to create working anodes and cathodes, and they had to harden into layers that are as narrow as those produced by thin-film manufacturing methods. To accomplish these goals, the researchers created an ink for the anode with nanoparticles of one lithium metal oxide compound, and an ink for the cathode from nanoparticles of another. The printer deposited the inks onto the teeth of two gold combs, creating a tightly interlaced stack of anodes and cathodes. Then the researchers packaged the electrodes into a tiny container and filled it with an electrolyte solution to complete the battery.

Lastly, they measured how much energy could be packed into the tiny batteries, how much power they could deliver, and how long they held a charge.

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