Clay key to high-temperature supercapacitors

A composite of clay and an electrolyte allowed Rice University researchers to make sheets of material that can serve as both electrolyte and a separator in a new kind of high-temperature supercapacitor. Credit: Ajayan Group/Rice University Clay, an abundant and…

A composite of clay and an electrolyte allowed Rice University researchers to make sheets of material that can serve as both electrolyte and a separator in a new kind of high-temperature supercapacitor. Credit: Ajayan Group/Rice University

Clay, an abundant and cheap natural material, is a key ingredient in a supercapacitor that can operate at very high temperatures, according to Rice University researchers who have developed such a device.

The Rice group of materials scientist Pulickel Ajayan reported today in Nature’s online journal, Scientific Reports that the supercapacitor is reliable at temperatures of up to 200 degrees Celsius (392 degrees Fahrenheit) and possibly beyond. It could be useful for powering devices for use in extreme environments, such as oil drilling, the military and space.
“Our intention is to completely move away from conventional liquid or gel-type electrolytes, which have been limited to low-temperature operation of electrochemical devices,” said Arava Leela Mohana Reddy, lead author and a former research scientist at Rice.
“We found that a clay-based membrane electrolyte is a game-changing breakthrough that overcomes one of the key limitations of high-temperature operation of electrochemical energy devices,” Reddy said. “By allowing safe operation over a wide range of temperatures without compromising on high energy, power and cycle life, we believe we can dramatically enhance or even eliminate the need for expensive thermal management systems.”
A supercapacitor combines the best qualities of capacitors that charge in seconds and discharge energy in a burst and rechargeable batteries that charge slowly but release energy on demand over time. The ideal supercapacitor would charge quickly, store energy and release it as needed.
“Researchers have been trying for years to make energy storage devices like batteries and supercapacitors that work reliably in high-temperature environments, but this has been challenging, given the traditional materials used to build these devices,” Ajayan said.
In particular, researchers have struggled to find an electrolyte, which conducts ions between a battery’s electrodes, that won’t break down when the heat is on. Another issue has been finding a separator that won’t shrink at high temperatures and lead to short circuits. (The separator keeps the electrolyte on the anode and cathode sides of a traditional battery apart while allowing ions to pass through).

“Our innovation has been to identify an unconventional electrolyte/separator system that remains stable at high temperatures,” Ajayan said.
The Rice researchers led by Reddy and Rachel Borges solved both problems at once. First, they investigated using room-temperature ionic liquids (RTILs) developed in 2009 by European and Australian researchers. RTILs show low conductivity at room temperature but become less viscous and more conductive when heated.
Clay has high thermal stability, high sorption capacity, a large active surface area and high permeability, Reddy said, and is commonly used in muds for oil drilling, in modern construction, in medical applications and as a binder by iron and steel foundries.
After combining equal amounts of RTIL and naturally occurring Bentonite clay into a composite paste, the researchers sandwiched it between layers of reduced graphene oxide and two current collectors to form a supercapacitor. Tests and subsequent electron microscope images of the device showed no change in the materials after heating it to 200 degrees Celsius. In fact, Reddy said, there was very little change in the material up to 300 degrees Celsius.
“The ionic conductivity increases almost linearly until the material reaches 180 degrees, and then saturates at 200,” he said.
Despite a slight drop in capacity observed in the initial charge/discharge cycles, the supercapacitors were stable through 10,000 test cycles. Both energy and power density improved by two orders of magnitude as the operating temperature increased from room temperature to 200 degrees Celsius, the researchers found.
The team took its discovery a step further and combined the RTIL/clay with a small amount of thermoplastic polyurethane to form a membrane sheet that can be cut into various shapes and sizes, which allows design flexibility for devices.

Explore further:

Hybrid ribbons a gift for powerful batteries: Vanadium oxide – graphene material works well for lithium-ion storage

More information: www.nature.com/srep/2013/130903/srep02572/full/srep02572.html

Journal reference:

Scientific Reports

Provided by

Rice University

view popular

5 /5 (8 votes)

Related Stories

Hybrid ribbons a gift for powerful batteries: Vanadium oxide – graphene material works well for lithium-ion storage

Mar 25, 2013

Hybrid ribbons of vanadium oxide (VO2) and graphene may accelerate the development of high-power lithium-ion batteries suitable for electric cars and other demanding applications.

A simple slice of energy storage

Aug 01, 2011

Turning graphite oxide (GO) into full-fledged supercapacitors turns out to be simple. But until a laboratory at Rice University figured out how, it was anything but obvious.

Scientists create tiny bendy power supply for even smaller portable electronics

Aug 07, 2013

Scientists have created a powerful micro-supercapacitor, just nanometres thick, that could help electronics companies develop mobile phones and cameras that are smaller, lighter and thinner than ever before. The tiny power …

Sponge-like graphene makes promising supercapacitor electrodes

Oct 12, 2012

(Phys.org)—While most of today’s electric vehicles rely on batteries to store energy, supercapacitors have enjoyed significant improvements that have made them serious competitors to batteries. Batteries …

Engineers craft new material for high-performing ‘supercapacitors’

Apr 15, 2013

Taking a significant step toward improving the power delivery of systems ranging from urban electrical grids to regenerative braking in hybrid vehicles, researchers at the UCLA Henry Samueli School of Engineering …

Energy storage device fabricated on a nanowire array

Aug 01, 2011

In a vivid demonstration of the progress being made in miniaturizing energy storage devices, a team of engineers from Rice University in Houston, Texas, has fabricated an energy storage device where all essential …

Recommended for you

Robotics first: Engineering team makes artificial muscles that can lift loads 80 times their weight

18 hours ago

A research team from the National University of Singapore’s (NUS) Faculty of Engineering has created efficient artificial, or “robotic” muscles, which could carry a weight 80 times its own and able to extend to five times …

New strategically important hard metal developed in Finland

20 hours ago

Over the past three years VTT Technical Research Centre of Finland has been working with Finnish-based Exote Ltd to develop a new hard metal and the necessary manufacturing process. This material can be used to replace tungsten …

Microencapsulation produces uniform drug release vehicle

Sep 03, 2013

Consistently uniform, easily manufactured microcapsules containing a brain cancer drug may simplify treatment and provide more tightly controlled therapy, according to Penn State researchers.

Arylamine functionalization of carbon anodes for improved microbial electrocatalysis

Sep 02, 2013

Introduction of arylamine functional groups to graphite electrodes results in improved initial catalysis for acetate oxidation by microbial biofilms over that observed on unmodified anodes. Arylamine modified …

Water found to be an ideal lubricant for nanomachines

Sep 01, 2013

Researchers from the University of Amsterdam have discovered that machines just one molecule in size move far quicker if you add a ‘lubricant’ to their surroundings. To their surprise, water proved to be …

Breaking the code of royal purple

Aug 30, 2013

Royal purple, the color of robes swathing the emperors of Rome, ancient kings and high priests, and prized for its richness of hue and a brightness that wouldn’t fade, has long carried its own molecular mystery.

User comments : 0

More news stories

Robotics first: Engineering team makes artificial muscles that can lift loads 80 times their weight

A research team from the National University of Singapore’s (NUS) Faculty of Engineering has created efficient artificial, or “robotic” muscles, which could carry a weight 80 times its own and able to extend to five times …

Synthetic polymer could stop the spread of HIV

A precisely designed macromolecule that mimics the binding of HIV to immune system cells could be used to stop the virus from physically entering the body, according to a new study led by a materials scientist at Queen Mary …

New strategically important hard metal developed in Finland

Over the past three years VTT Technical Research Centre of Finland has been working with Finnish-based Exote Ltd to develop a new hard metal and the necessary manufacturing process. This material can be used to replace tungsten …

Water found to be an ideal lubricant for nanomachines

Researchers from the University of Amsterdam have discovered that machines just one molecule in size move far quicker if you add a ‘lubricant’ to their surroundings. To their surprise, water proved to be …

Fog harvesting: How to get fresh water out of thin air

In some of this planet’s driest regions, where rainfall is rare or even nonexistent, a few specialized plants and insects have devised ingenious strategies to provide themselves with the water necessary for …

Is mathematics an effective way to describe the world?

Mathematics has been called the language of the universe. Scientists and engineers often speak of the elegance of mathematics when describing physical reality, citing examples such as π, E=mc2, and even s …

Quantum steps towards the Big Bang

(Phys.org) —Present-day physics cannot describe what happened in the Big Bang. Quantum theory and the theory of relativity fail in this almost infinitely dense and hot primal state of the universe. Only …

Using harsh verbal discipline with teens found to be harmful

Many American parents yell or shout at their teenagers. A new longitudinal study has found that using such harsh verbal discipline in early adolescence can be harmful to teens later. Instead of minimizing teens’ problematic …

New evidence to aid search for charge ‘stripes’ in superconductors

(Phys.org) —Scientists at the DOE’s Brookhaven National Laboratory have identified a series of clues that particular arrangements of electrical charges known as “stripes” may play a role in superconductivity-the …

In longterm relationships, the brain makes trust a habit

(Medical Xpress)—After someone betrays you, do you continue to trust the betrayer? Your answer depends on the length of the relationship, according to research by sociologist Karen Cook of the University …