Experimental Electrode Designs May Reduce Charging Times From Hours To Minutes

Researchers at Drexel University School of Engineering claim they have created a new highly conductive two dimensional material they call MXene that will permit faster battery charging. Led by professor Yuri Gogotsi, the team says electrodes made from MXene will allow ordinary batteries to charge as fast as supercapacitors but with the energy storage potential of a conventional battery.

“This paper refutes the widely accepted dogma that chemical charge storage, used in batteries and pseudocapacitors, is always much slower than physical storage used in electrical double-layer capacitors, also known as supercapacitors,” Gogotsi says. “We demonstrate charging of thin MXene electrodes in tens of milliseconds. This is enabled by very high electronic conductivity of MXene. This paves the way to development of ultrafast energy storage devices than can be charged and discharged within seconds, but store much more energy than conventional supercapacitors.”

Put simply, MXene has more places to store electrons than the electrodes in use today. More electron storage equals more electrical energy stored and transmitted. The team has recently published its work in the journal Nature Energy. Working with professors Patrice Simon and Zifeng Lin at the Université Paul Sabatier in France, the team developed a hydrogel electrode with greater volumetric performance, an important measure of a battery’s ability to store energy.

“In traditional batteries and supercapacitors, ions have a tortuous path toward charge storage ports, which not only slows down everything, but it also creates a situation where very few ions actually reach their destination at fast charging rates,” says Maria Lukatskaya, the lead author on the paper. “The ideal electrode architecture would be something like ions moving to the ports via multi-lane, high-speed highways instead of taking single lane roads. Our macro-porous electrode design achieves this goal, which allows for rapid charging — on the order of a few seconds or less.”

The primary advantage of MXene electrodes is their superior conductivity, which is equivalent to metals such as copper and aluminum. MXene was first created in Drexel labs in 2011 and researchers have been exploring its many and varied uses ever since — from energy storage to electromagnetic radiation shielding and water filtration.

“If we start using low dimensional and electronically conducting materials as battery electrodes, we can make batteries working much, much faster than today,” Gogotsi said. “Eventually, appreciation of this fact will lead us to car, laptop and cell-phone batteries capable of charging at much higher rates — seconds or minutes rather than hours.”

Henrik Fisker is also going down a similar path. He says his latest car, the Fisker EMotion, will use a proprietary system that is similar to a supercapacitor that will permit the car to have a 400 mile range and a 9 minute recharge time. Sitting idle waiting for an electric car to charge may be one of the biggest road blocks to mainstream acceptance of EVs.

Even Tesla, which has the largest high power charging network in the world, requires its drivers to wait 30 minutes of more to charge their batteries while travelling away from home. If someone could cut that wait time to a few minutes, the impact on the electric car market would be enormous.

The usual caveats apply. Researchers around the world on working on improvements that will make EV batteries, lighter, more energy dense, and less expensive while slashing charging times. Breakthroughs in battery technology are announced almost daily. But getting new tech out of the lab and into the real world is often fraught with danger.

More startups fail than succeed. So for the moment, this announcement from Drexel must be taken with the proverbial grain of salt. But if the promise shown in the Drexel lab can translate to reality? It’s game over for fossil fueled vehicles.

Source and photo credit: Drexel University via Science Daily

Nanowires Dramatically Increase Lithium Ion Battery Life

Battery life is of critical concern to car makers and energy storage companies. All of today’s lithium ion batteries degrade over time. The more times they are charged and discharged, the shorter their lifespan. Researchers at the University of California at Irvine (UCI) say they have discovered how to increase the tensile strength of nanowires. That breakthrough could be used to make lithium ion batteries that last virtually forever. Here’s the story.

UCI doctoral candidate Mya Le Thai holds a nanowire device. Credit: Steve Zylius/UCI

Researchers have tried using nanowires in batteries for years because the filaments, which are thousands of times thinner than a human hair, are highly conductive and have a large surface area for the storage and transfer of electrons. The problem is that nanowires are also extremely fragile. They don’t hold up well to repeated discharging and recharging, known as “cycling.” For example, in a typical lithium-ion battery, they expand and grow brittle, which leads to cracking.

The researchers, led by doctoral candidate Mya Le Thai, found a way to make nanowires less brittle. They coated a gold nanowire in a manganese dioxide shell and encased it in an electrolyte made of a Plexiglas-like gel called propylene carbonate. Capacitors made with uncoated nanowires have a useful life of between 2000 and 8000 cycles. Those with the coating are able to function through 200,000 cycles.

Reginald Penner, chairman of UCI’s chemistry department, says, “Mya was playing around, and she coated this whole thing with a very thin gel layer and started to cycle it. She discovered that just by using this gel, she could cycle it hundreds of thousands of times without losing any capacity. That was crazy because these things typically die in dramatic fashion after 5,000 or 6,000 or 7,000 cycles at most.”

The researchers believe the gel plasticizes the metal oxide in the battery and gives it flexibility, preventing cracking. Thai, the study’s leader, cycled the nanowire-enhanced electrode up to 200,000 times over three months without detecting any loss of capacity or power and without fracturing any nanowires. “All nanowire capacitors can be extended from 2000 to 8000 cycles to more than 100,000 cycles, simply by replacing a liquid electrolyte with a… gel electrolyte,” the researchers wrote in their paper.

“The coated electrode holds its shape much better, making it a more reliable option,” Thai said in a statement. “This research proves that a nanowire-based battery electrode can have a long lifetime and that we can make these kinds of batteries a reality.” If the research can be translated into viable commercial products, the result could be commercial batteries that last a lifetime in computers, smartphones, appliances, cars and spacecraft.

Source: Computerworld

World’s Fastest Charging Electric Bus Debuts in China

The world’s fastest charging electric bus is now operating in the eastern Chinese port city of Ningbo.

According to local transportation authorities, the public bus — which was manufactured in Ningbo and runs along a 24-stop, 11 kilometre route — takes as little as 10 seconds to charge up and be ready for the next leg of its journey.

Zhou Qinghe, president of Zhuzhou Electric Locomotive, said that, once charged, the bus can run for a distance of 5 kilometres.

While this may not appear to be a copious distance, the extremely rapid charging time combined with the fact that public transit vehicles tend to run along fixed routes mean that the bus can charge up whenever it’s stationary for just a brief period at designated locations – most obviously, passenger loading and disembarkation points.

In addition to its rapid charging ability, the bus is also capable of more efficient usage of its energy during its travel. While braking or negotiating slopes, the bus recycles over 80% of potential energy for storage and subsequent usage.

This translates into a reduction in electricity consumption of around 30–50% compared to its conventional peers.

Ningbo’s new electric bus makes use of supercapacitor technology that has already been trialled in nearby Shanghai for almost a decade.

The bus’s supercapacitors are manufactured from a cutting-edge carbon material that functions in all likely temperatures (from -40 degrees to 60 degrees Celsius).

The organic super capacitors are also extremely resilient, capable of charging and discharging on over a million occasions, conferring them with a service life of as long as 12 years.

Using only one tenth the energy of a standard diesel bus, this performance translates into fuel savings of as much as $200,000 over the full lifetime of the vehicle.

Ningbo now plans to add 1,200 more such buses to its public transportation fleet over the next 3 years.

Electric Superchargers Ready For Prime Time

After years of existing in the periphery of automotive performance tuning- and, quite literally, in the periphery of low-budget tuning magazines- electric superchargers are finally ready to hit the road for real under the hoods of Volkswagens, Audis, and Volvos.

A supercharger is a compressor that forces more air into the combustion chamber. The effect is like fanning the flames of a campfire to make it burn hotter. We get more ooomph from a supercharged engine when we press on the loud pedal. There is no free lunch, of course. It takes energy to spin a supercharger and connecting one to the engine through belts, or clutches can be an engineering nightmare. Exhaust driven turbochargers are more mechanically efficient, but they take time to build compression (or, “boost”). Most of us know this delay as “turbo lag”, the difference in time between when you mash the throttle and when the extra power kicks in.

Both Audi’s RS5 TDI and Volvo’s High Performance Drive-E use electric superchargers to supplement engines that are already turbocharged. The electric compressor can spin up from rest to 70,000 rpm in about a quarter of a second, providing instant boost on demand. Once engine revs rise, the electric supercharger shuts off and the turbo takes over. From the driver’s seat, the impression is of one long, continuous burst of power with no gaps. Using an electric supercharger also provides a significant boost to fuel economy because the engine can get more power out of a given amount of gasoline, as demonstrated by the HyBoost Ford Focus project.

Adding an electric supercharger is easy. All you need is a bracket to hang it from and an electric wire to the power source. And that’s where things get interesting. The true beauty of an electric supercharger is that it uses stored electricity harvested during normal driving. Because a regular battery is slow to charge and slow to release its energy, the key component is the supercapacitor – an energy storage device that charges and discharges almost instantaneously.

While it does not have the power density of a battery, it doesn’t need to, since the electric supercharger operates only for short intervals – usually 1 to 2 seconds -every once in a while. Supercapacitors cost more than a comparable battery at present, but prices are coming down rapidly, thanks in part to the use of graphene. Another key to using electric superchargers successfully  is the software that controls the complex relationship between it and the turbocharger so the driver feels only a seamless flow of power.

Turbochargers are already standard equipment on many cars today. As manufacturers struggle to meet ever tightening fuel economy standards around the world, look for electric superchargers to find their way under the hood of more and more mainstream automobiles.

Source | Images: Road & Track, via Popular Mechanics.