Researchers from Stanford University have developed the first high-performance, fast-charging, and long-lasting aluminum battery which is economical as well. The new battery technology is a safe substitute for many of the widely used commercial batteries today.
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. Our new battery won't catch fire, even if you drill through it.
Hongjie Dai, a professor of chemistry at Stanford.
Stanford University Professor Hongjie Dai and colleagues have developed a high-performance aluminum battery (Courtesy - MARK SHWARTZ)
Since aluminum is economical, features high storage capacity and low flammability, it has been an appealing material choice for batteries for years. However, so far researchers have not been successful in constructing a commercially feasible aluminum-ion battery. One of the main challenges they faced was finding materials which were able to generate adequate voltage following repeated charging and discharging cycles.
A positively charged cathode and a negatively charged aluminum anode constitute an aluminum ion battery.
People have tried different kinds of materials for the cathode. We accidentally discovered that a simple solution is to use graphite, which is basically carbon. In our study, we identified a few types of graphite material that give us very good performance.
Hongjie Dai, a professor of chemistry at Stanford
The Stanford researchers used an aluminum anode and graphite cathode for the trial battery and placed it within a flexible polymer-coated pouch along with an ionic liquid electrolyte.
"The electrolyte is basically a salt that's liquid at room temperature, so it's very safe," said Stanford graduate student Ming Gong, co-lead author of the Nature study. Aluminum batteries are safer than conventional lithium-ion batteries used in millions of laptops and cell phones today, Dai added. "Lithium-ion batteries can be a fire hazard," he said. He explained how United and Delta airlines have banned bulk lithium-battery consignments on passenger planes.
"In our study, we have videos showing that you can drill through the aluminum battery pouch, and it will continue working for a while longer without catching fire," Dai said. "But lithium batteries can go off in an unpredictable manner – in the air, the car or in your pocket. Besides safety, we have achieved major breakthroughs in aluminum battery performance."
The Stanford team stated that their novel aluminum battery prototype was capable of exceptional charging times of just about a minute. The ultra-fast charging will be a key attraction as smartphone owners know the hours it takes to charge a lithium-ion battery.
Another appealing factor is the prototype’s durability. Most aluminum batteries built in various laboratories have not worked over 100 charge-discharge cycles. However, the Stanford battery could endure beyond 7,500 cycles with no loss in capacity. "This was the first time an ultra-fast aluminum-ion battery was constructed with stability over thousands of cycles," the authors wrote.
A basic lithium-ion battery can endure for around 1,000 cycles in comparison. "Another feature of the aluminum battery is flexibility," Gong said. "You can bend it and fold it, so it has the potential for use in flexible electronic devices. Aluminum is also a cheaper metal than lithium."
Dai states that apart from using these aluminum batteries in small electronic devices, these batteries can also be applied for storing renewable energy on the electrical grid.
The grid needs a battery with a long cycle life that can rapidly store and release energy. Our latest unpublished data suggest that an aluminum battery can be recharged tens of thousands of times. It's hard to imagine building a huge lithium-ion battery for grid storage.
Hongjie Dai, a professor of chemistry at Stanford
Moreover, aluminum-ion technology provides an eco-friendly option to disposable alkaline batteries, Dai stated.
"Millions of consumers use 1.5-volt AA and AAA batteries," he said. "Our rechargeable aluminum battery generates about two volts of electricity. That's higher than anyone has achieved with aluminum."
However, additional improvements are vital to match lithium-ion battery voltage, Dai explained.
"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 Normal University.
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.
Dai and team illustrate their new aluminum-ion battery in ‘An ultrafast rechargeable aluminum-ion battery’, which is published in the April 6 advance online edition of the journal Nature.