Lithium-ion batteries can be made using metals such as aluminum, nickel and stainless steel.
But they are not currently used in electric vehicles because of a number of problems, including a lack of corrosion resistance, high operating temperatures and high levels of pollution.
The problem with aluminum, on the other hand, is that it can break down into toxic compounds.
A team of researchers led by the University of California, Davis, has now created an aluminum alloy that is nearly entirely free of these toxic compounds, making it a viable alternative to lithium-metal batteries.
The research was published in the journal Advanced Materials.
“Aluminum is a very good conductor, but we are now finding that it’s actually the worst conductor for a number the metals we are currently using,” said lead author Rachael C. Jones, a professor of mechanical engineering at UC Davis.
“There is a lot of information that has been done on the conductivity of aluminum, and we are not yet aware of all the effects of that on the chemistry of these batteries.”
The aluminum alloy was found to have an electrical conductivity similar to copper, a good conductor that has a low level of toxicity.
It also had high conductivity at temperatures up to 695 degrees Fahrenheit, well above the temperatures used in most lithium-sulfur batteries.
While the researchers did not measure any of the aluminum’s properties directly, they did use data from a battery that was designed to run at temperatures of 2,000 degrees Fahrenheit.
The researchers found that aluminum had the ability to deliver a voltage of 1.2 volts per square meter (5 milliamps) while at room temperature.
“The fact that it is so stable at these temperatures is quite remarkable,” said Jones.
“It is very, very low.”
Aluminium-Aluminum Alloy Materials used in batteries have long been used for this type of technology, but it was not until the early 2000s that researchers were able to create a metal with such high conductivities.
“We wanted to see if it would work at higher temperatures,” Jones said.
In 2008, the team was able to get a 1.5 volt per square centimeter (1 milliamp per square foot) aluminum battery up to 1,000 volts.
The result was a device that was able do more than just charge a lithium-cell battery, though.
“What this does is make the batteries that we are building and testing today, which are about 10 times more energy dense, much more efficient,” Jones added.
In the past, batteries were typically made of aluminum and magnesium.
But the researchers discovered that this material is also the best conductor for other metals, including copper, which is also known to be toxic.
Jones and her colleagues created an alloy of aluminum with nearly all of the elements found in the Earth’s crust.
The aluminum has high electrical conductivities and low toxicity, making aluminum an attractive material for batteries.
However, the researchers found a problem with this material.
It was not only that it was extremely corrosive to the lithium electrodes, but also that it has a high melting point, meaning it is prone to breaking down into many toxic compounds during the manufacturing process.
So the researchers added some additives to the aluminum to help prevent these compounds from forming.
“These compounds would normally have been created during the fabrication process, and then would have broken down in the manufacturing processes, and would have produced toxic compounds,” Jones explained.
“So we added some chemicals that would be able to keep these toxic materials out of the metal.”
Jones and colleagues also used the aluminum-aluminum alloy to create batteries that were 20 percent more energy density than the lithium-aluminium alloy, but the results are still not conclusive.
But it is still encouraging that the researchers were not only able to increase the electrical conductance of the alloy, they were also able to reduce the toxicity.
“For a long time, it was assumed that aluminum would be a bad conductor for lithium-iron battery technology,” said study co-author Matthew L. Ritz, a chemical engineer at UC Berkeley.
“However, we now know that the aluminum has a much lower toxic content than lithium-titanium.
So, we think that aluminum has the potential to be an ideal conductor for battery technology, especially for applications that use lithium as a store of energy.”
A new approach for aluminum Alumina is a material that has unique properties that make it more attractive than other aluminum alloys, Jones said, including the fact that the material has a higher surface area than other alloys.
This surface area means the aluminum will not simply stick to a battery electrode.
Instead, the aluminum particles will adhere to the metal surface and bond with it.
In order to bond with the aluminum, the electrode has to be heated and this can cause problems, Jones explained, because it can create a thermal imbalance.
However the team found a way to reduce these problems, by bonding aluminum to the electrodes themselves.