Posted on 04/11/2015 6:43:06 PM PDT by concernedcitizen76
Aluminium ions are stored between layers of graphite when the battery is charged
A new rival to the lithium-ion battery has been created that charges in under a minute and still performs almost perfectly after being recharged thousands of times. The new battery is based on aluminium instead of lithium, which should make it both cheaper and safer than their lithium-ion competitors. The U.S. team behind the aluminium-ion battery say that the technology could find its way into the home, help store renewable energy for the power grid and even power vehicles.
The aluminium-ion battery is conceptually similar to the lithium-ion battery: when the battery is discharged atoms from a metal anode are oxidised, releasing electrons into the external circuit. When recharged, the electrons are driven back to the anode.
The aluminium-ion battery offers tantalising solutions to problems with lithium-ion ones. Aluminium, being the most abundant metal in the Earth's crust, is much cheaper than lithium and is also much less reactive so battery fires are unlikely to be a problem. Ionising aluminium also liberates three electrons compared with lithium's one, potentially giving the batteries a higher charge capacity. But aluminium-ion batteries have been plagued by numerous difficulties: the discharge voltages have often been as low as 0.55V and various cathodes trialled have disintegrated during repeated cycling, causing the lifetimes of the batteries of the batteries to drop to 85% or less within 100 cycles.
But now Hongjie Dai and colleagues at Stanford University in California unveil a prototype battery with a new graphite cathode that solves these problems. The group's discovery of the remarkable properties of graphite began with a stroke of luck. While investigating the potential of metal oxide films as cathodes, the researchers used graphite particles to increase their conductivity. When the composite films showed battery like behaviour, they decided to investigate further. In the Stanford team's aluminium-ion battery, aluminium chloride ions (AlCl4-) are stored at the cathode when the battery is charged. On discharge, the ions migrate to the anode where they combine with metallic aluminium to form Al2Cl7-. When the researchers investigated the graphite cathode’s chemistry they discovered that AlCl4- anions reversibly intercalate between the graphite layers.
Natural problem
However, natural graphite cathodes suffered from two problems: first, the battery's maximum charge and discharge rates were slowed by diffusion of the bulky AlCl4- ions between the atomic planes. Worse, when the ions did diffuse in, they caused 50-fold expansion of the graphite, pulling it apart into loosely-stacked atomic flakes. The team solved both problems with a graphitic foam they produced by depositing carbon onto nickel and then dissolving the metal in acid to produce a carbon structure with large atomic spaces that allowed the AlCl4- ions in and out rapidly with little or no damage.
Using their carbon foam cathode and ultra-dry electrolyte, the researchers produced a prototype battery with a discharge voltage of around 2V and an energy capacity similar to lead acid and nickel–metal hydride batteries. This battery lost very little of its storage capacity after 7000 cycles, making it far superior even to lithium-ion batteries, which last for about 1000 cycles. Perhaps most remarkably, the battery can safely be completely recharged in less than 60 seconds. This is nearly 100 times faster than the maximum charge rate for a lithium-ion battery. The battery can even be bent and folded safely, and the researchers drilled a hole through it while it was operating without causing a dangerous short circuit.
Dai reveals that commercial companies are interested. He believes the battery is a promising replacement for nickel–metal hydride rechargeable batteries in home appliances and, beyond this, for storing electricity for the grid. At present, he says, the battery's energy density is limited by the bulky AlCl4- ions. 'Hopefully this work can really open up more research in this area,' he adds.
Electrochemist Don Sadoway of the Massachusetts Institute of Technology, US, is excited. 'This is the first step to demonstrate that reversible cycling of aluminium is possible,' he says. 'The barrier to entry for lithium-ion in automobiles is not the energy density – at 150W/h/kg that's plenty already. The barrier is cost: lithium-ion is far too costly and will remain too costly. Most people in the battery world are working on the wrong problem and these people deserve credit for addressing the right problem.
"We have developed a rechargeable aluminum battery that may replace existing storage devices, such as alkaline batteries, which are bad for the environment, and lithium-ion batteries, which occasionally burst into flames," said Hongjie Dai, a professor of chemistry at Stanford. "Our new battery won't catch fire, even if you drill through it."
Durability is another important factor. Aluminum batteries developed at other laboratories usually died after just 100 charge-discharge cycles. But the Stanford battery was able to withstand more than 7,500 cycles without any loss of capacity. "This was the first time an ultra-fast aluminum-ion battery was constructed with stability over thousands of cycles," the authors wrote.
"Our battery produces about half the voltage of a typical lithium battery," he said. "But improving the cathode material could eventually increase the voltage and energy density. Otherwise, our battery has everything else you'd dream that a battery should have: inexpensive electrodes, good safety, high-speed charging, flexibility and long cycle life. I see this as a new battery in its early days. It's quite exciting."
Other co-lead authors of the study affiliated with Stanford are visiting scientists Mengchang Lin from the Taiwan Industrial Technology Research Institute, Bingan Lu from Hunan University, and postdoctoral scholar Yingpeng Wu. Other authors are Di-Yan Wang, Mingyun Guan, Michael Angell, Changxin Chen and Jiang Yang from Stanford; and Bing-Joe Hwang from National Taiwan University of Science and Technology.
Principal support for the research was provided by the U.S. Department of Energy, the Taiwan Industrial Technology Research Institute, the Stanford Global Climate and Energy Project, the Stanford Precourt Institute for Energy and the Taiwan Ministry of Education.
Well, let’s hope it works.
Sounds good. Lithium batteries are already a way better than Ni-Cads. Unfortunately they are also more expensive.
Cool! Let’s see how long it takes for the Chinese to put it in production.
Cue the luddites who are convinced anything that extends battery life is a commie plot and nothing will ever replace gasoline powered cars.
Kool, a beer can and campfire battery.
All the new battery technologies seem to have other problems, one is that high charge rates almost always imply high self-discharge rates. Also, you would have to plug in a nuclear power plant if you think you are going to charge a car battery of decent capacity as quickly as you fill a tank with gas (ok, an exaggeration, but still you would have to actually be at a substation to do this.
However, this is definitely worth a look - even if they are big and bulky and weigh a lot, they might make a nice compliment to stationary solar power, for example. Solar panels last 20 years or so. 7000 charge/discharges = about 20 years of day/night, for example, and the high self-discharge rates might not matter in relatively sunny areas. Aluminum is plentiful and not hard to recycle, also.
Okay, but who is this Al U. Minium guy? ;’) thanks RACPE.
According to the Royal Society article, the Stanford team developed a working prototype battery, and “commercial companies are interested.” Is “interested” the right word? Some of them might be shell shocked. In November 2014, Warren Buffett’s Berkshire Hathaway paid $4.7 billion to P&G in a stock transaction for cash-cow Duracell.
I will adopt a wait-and-see strategy. If it ever happens, fine. Being a skeptic does not make me a Luddite.
Ever the person who jumps to conclusions. Geez. Keep in mind this article is from the Royal Society of Chemists. That would be in London, England, wouldn’t it? In England, they spell aluminum as aluminium.
Ever the mouthy insulting snarky troll, you need to buy yourself a sense of humor.
This does sound like a possible game-changer for the near-future.
Just humbly offering you a dose of your own medicine.
See, if you were as clever as you make yourself out to be, you would have spelled it “humour.” lol
I'm inclined to agree that this sulphurous back-and-forth is unhealthy.
What does it all mean?
I don't recall seeing how fast it discharges. If it lasts twice as long as it takes to charge, you'd need to keep the 'battery powered' device plugged in.
He’s got a relative Stateside. His name is also Al. Al.U.Minum. When he crossed the Atlantic, he was offered $200 for a vowel. Being broke, he sold it to Pat and Vanna.
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