A disruptive leap in energy storage: Indian scientists develop ultra-micro supercapacitors
Researchers from the Department of Instrumental and Applied Physics (IAP) of the Indian Institute of Science have designed a new type of ultra-micro supercapacitor,
a tiny device capable of storing large amounts of electric charge. It is also smaller and more compact than existing supercapacitors and could potentially
be used in many devices from street lights to consumer electronics, electric vehicles and medical equipment.
Currently, most of these devices are battery powered. However, over time, these batteries lose their ability to store electricity and therefore have a limited shelf life.
Capacitors, by virtue of their design, can store charge for longer periods of time. For example, a capacitor that operates at 5 volts will still be operating at the same voltage ten years later.
But unlike batteries, supercapacitors cannot be continuously discharged, such as to power a cell phone.
Advantages of supercapacitors
Supercapacitors, on the other hand, combine the advantages of batteries and capacitors—they can store and release large amounts of energy, making them highly sought after in the next
generation of electronic devices.
In a recent study published in ACS Energy Letters, the researchers used field-effect transistors (FETs) as charge collectors to create their supercapacitors, rather than using the metal electrodes
used in existing capacitors.
Abha Misra, professor at IAP and corresponding author of the study, said: "Using FETs as electrodes in supercapacitors is a new way to tune the charge of the capacitor.
Innovations in Capacitor Design
Current capacitors typically use metal oxide-based electrodes, but they are limited by low electron mobility. So the team decided to create hybrid field-effect transistors,
consisting of alternating a few-atom-thick layers of molybdenum disulfide (MoS2) and graphene to increase electron mobility, which were then connected to gold contacts.
A solid gel electrolyte is then used between the two FET electrodes to build a solid-state supercapacitor. The entire structure is built on a silica/silicon substrate.
The researchers say, "Design is the key part because you are integrating two systems. The two systems are two field-effect transistor electrodes and a gel electrolyte (an ionic medium),
which have different charge capacities. To make this Devices that obtain all the desirable properties of a transistor are challenging. Because these supercapacitors are so small, they are
impossible to see without a microscope, and the manufacturing process requires high precision and hand-eye coordination."
Performance and future plans
Once the supercapacitor was created, the researchers measured the device's electrochemical capacitance, or charge-holding ability, by applying various voltages. They found that under
certain conditions the capacity increased by 3,000%. In comparison, a capacitor containing only MoS2 without graphene only increased its capacity by 18% under the same conditions.
In the future, the researchers plan to explore whether replacing MoS2 with other materials can further improve the storage capacity of supercapacitors. They added that their supercapacitor
is fully functional and can be used in energy storage devices such as electric vehicle batteries or in any miniaturized system through on-chip integration. They also plan to patent the supercapacitor.
