Researchers advance micro-supercapacitor fabrication

By Gina Roos, editor-in-chief

A research team at the School of Energy and Chemical Engineering at UNIST  has developed a solid-state micro-supercapacitor (MSC) that can be integrated on a microchip. This makes the MSC attractive to IoT and wearable device manufacturers, along with its high-power delivery and longer life-cycle benefits compared to rechargeable lithium batteries.

Touted as a new class of ultra-high areal-number-density, solid-state MSCs (UHD SS–MSCs) that is fabricated on a chip using electrohydrodynamic (EHD) jet printing , the new supercapacitor can be manufactured as small as the width of a person’s fingerprint. The research team, led by Professor Sang-Young Lee, said that this is the first study to use EHD jet printing to manufacture MSCs.

Fig 1: The tiny MSC is as small as the width of a person’s fingerprint. (Image: UNIST)

A supercapacitor, also called an ultra-capacitor, can store more energy than traditional capacitors. Key advantages include a high-power delivery and longer cycle life compared to lithium-based secondary batteries. These devices could be considered a cross between a traditional capacitor and battery.

One of the biggest challenges faced by supercap manufacturers is the heat produced during manufacturing. This heat may deteriorate the electrical characteristics of the supercapacitors, which has been a challenge in terms of connecting them directly to electronic components, according to the researchers. Lower precision is another disadvantage due to the fabrication method that integrates the supercapacitors with electronic components via inkjet printing.

Fig. 2: Fabrication of the on-chip UHD SS–MSCs using EHD jet printing (Image: UNIST)

To address these challenges, researchers used EHD jet printing, a high-resolution patterning technique used in microelectronics, to fabricate the MCSes. It is similar to conventional inkjet printing, said researchers, but it can also control printed liquid with an electric field.

Fig. 3: UHD SS–MSCs — 36 unit cells on a chip and areal operating voltage of 65.9 V cm⁻² (Image: UNIST)

The team was able to fabricate 36 unit cells on a chip (area = 8.0 × 8.2 mm, 54.9 cells cm⁻² ) with an areal operating voltage of 65.9 V cm⁻² , which is a significant improvement compared to previously reported MSCs fabricated by printing techniques, said researchers.

Upon exposure to hot temperature (80°C), these cells maintained normal cyclic voltammetry (CV) profiles, proving that they can withstand excessive heat generated during the operation of an electronic component, said researchers. And because they can be connected in series or in parallel, they can produce custom power supplies or batteries.

“In this study, we have demonstrated on-chip UHD SS–MSCs fabricated via EHD jet printing,” said Professor Lee in a statement. “The on-chip UHD SS–MSCs presented here hold great promise as a new platform technology for miniaturized monolithic power sources with customized design and tunable electrochemical properties.”

This study was supported through the Mid-Career Researcher Supporting Program by the Ministry of Science and ICT (MSIT, Korea) and the Industry Technology Development Program funded by the Ministry of Trade, Industry and Energy (MOTIE, Korea). The findings have been published in the scientific journal Science Advances .