Researchers have created printable solid-state batteries that can be printed in any conceivable shape and can be seamlessly embedded into a variety of surfaces. To demonstrate the technology, the scientists printed a working heart-shaped battery onto a cup, another onto a paper eyeglass and even one in the form of the letters "PRISS", all of which were capable of powering LEDs.

Conventional Li-on batteries come in set shapes and sizes because of the way they’re constructed. You need separator membranes to prevent the electrodes within the battery from coming into contact with each other. And the battery as a whole needs a robust case that doesn’t leak because of the combustible liquid electrolyte within.

The researchers achieved their breakthrough by eliminating the need for traditional separator membranes. To do this, they created printable solid-state electrolytes that function as an ion-conducting medium.

"The new solid-state electrolytes are printable and also solidify after exposure to UV irradiation, eventually acting as an alternative separator membrane," Sang-Young Lee, a Professor at the Ulsan National Institute of Science and Technology (UNIST) in South Korea, told Gizmag.

The printable electrolyte in paste form, encases the electrodes, effectively acting as separator membrane. The electrodes themselves are composed of printable slurry. Once they’re both printed onto a surface they are cured by exposing them to ultraviolet right. Additionally, the process removes the need for other processing steps like injecting the liquid electrolyte and drying the solvent.

The resulting printable solid-state battery (PRISS), can be printed in any arbitrary shape, and integrated seamlessly into curved objects or others with complex geometries to create battery-embedded surfaces. For instance, the frame of a mobile phone could itself be a battery.

When tested, the performance of the printed battery was found to be on par with other flexible batteries. It was shown to have a 90 percent capacity retention after 30 cycles, with no significant loss in charge or discharge capacities. The researchers plan to further improve the battery’s life and increase its energy density by tweaking either the battery’s thickness or increasing the overall printed area.

Currently, they are working on a new battery that can be printed directly onto clothes. They're also exploring new battery applications based on ink-jet and 3D printing technologies. The goal is to adapt the batteries to these technologies in such a way that they don’t impact the battery’s electrochemical properties.

"We are trying to find unprecedented application fields that we have not yet encountered, most of which have difficulties using traditional batteries due to shape/design limitations," Lee told us. "One of most promising application fields is wearable electronics and the IOT (Internet of Things)."

Going forward, they plan to make the rest of the battery components, such as current collectors and packaging materials, printable, enabling them to to create fully-printable batteries. They expect to launch shape-conformable totally printable PRISS batteries on the market within three to five years.

The team's paper describing the research was recently published in the journal Nano Letters.

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