Batteries are getting better at a steady pace, but the technology is far from perfect – they are still quite short-lived, and have real trouble delivering bursts of power. Now, researchers at Drexel and the Paul Sabatier universities have managed to embed mini supercapacitors directly inside a microchip to enable electronics that are even smaller, last longer, and have more power to feed on.
The study was led by Yury Gogotsi and Patrice Simon and is the culmination of a more than five-year effort in which the scientists, after developing their tiny energy storage devices, have now managed to fit them inside silicon chips using methods that they say can easily integrate with existing chip manufacturing techniques.
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"We set a lofty goal of not just making an energy storage device as small as a microchip," said Simon, "but actually making an energy storage device that is part of the microchip and to do it in a way that is easily integrated into current silicon chip manufacturing processes."
The scientists opted to store on-chip energy on micro-supercapacitors rather than miniature batteries. Current supercapacitors store less than a tenth the energy per unit volume of lithium-ion batteries, but they provide higher power outputs and are much more durable. For most applications, the team's vision is not to replace batteries with supercapacitors altogether, but rather to combine the two to get the best out of both worlds.
"What kills batteries is the high power delivery that induces mechanical and chemical stresses," Simon told Gizmag. "Supercapacitors, when associated with batteries, can deliver the power while the battery delivers the energy. In that way, you improve the lifetime of the battery and you do not need to oversize it with respect to the power demand."
The tiny supercapacitors are made from thin, porous carbon films deposited directly on top of a silicon wafer, with current collectors made of titanium carbide (TiC). Characteristics like resistivity, thickness and mechanical stress of the carbon film can be tweaked by changing manufacturing parameters to fit specific applications and chip designs.
According to the researchers, the result is much more promising for a wide range of applications than the more common route of focusing on micro-batteries.
"Going down to the micro-scale, you need high power in smartphones and other electronic devices, and micro-batteries suffer to meet this power demand," said Simon. Our micro-supercapacitors can do it. Moreover, now that we developed a fabrication process that can be integrated on a chip, compatible with the processes of the semiconductor industry, it becomes easy to place micro-supercapacitors in electronic devices, making the power source more compact – or, you can put more in the same volume."
The earliest applications of this technology could include RFID tags, remote sensors and other devices with a low energy requirement. Outside the world of electronics, the carbon films used to make the supercapacitors – which feature molecule-sized pores – could also find use for gas filtration or water desalination and purification.
A study detailing the findings appears in a recent edition of the journal Science.
Source: Drexel University