Scientists Finally Decipher Battery Breakdown Code to Make Electric Vehicles Last Longer

An international team of researchers led by Michael F. Toney, professor of chemical and biological engineering at the University of Colorado at Boulder, has determined the cause of battery capacity loss over time, also known as self-discharge, using powerful X-rays.

It is common knowledge that batteries lose capacity over time. Whether they are in a mobile phone or an electric vehicle, batteries lose their ability to hold a charge over time and need to be replaced.

Even after decades of experience designing and manufacturing different types of batteries, people still haven’t figured out what caused this phenomenon. “Having a better battery is very important in transitioning our energy infrastructure from fossil fuels to more renewable energy sources,” Toney said in a statement.

As a member of the Institute for Renewable and Sustainable Energy, Toney led a research group that studied this problem.

What is self-discharge?

In a lithium-ion battery, the world’s most widely used battery, lithium ions move from the anode, or positive terminal, to the cathode, or negative terminal, through an electrolyte solution. This creates a current that powers devices from phones to laptops and even electric vehicles.

Lithium ions are returned to the anode during the charging process, and the cycle can repeat. However, it was believed that not all lithium ions are returned to the anode, leading to a decrease in capacity over time or self-discharge.

As the use of the rare earth mineral cobalt in batteries has raised concerns about human rights and environmental costs, scientists have been working to develop batteries that don’t use cobalt, but nickel and magnesium. But these batteries are even more susceptible to self-discharge

Toney’s team used the Advanced Photon Source (APS), a powerful X-ray machine at Argonne National Laboratories in Illinois, to determine the cause of the self-charging. “The APS is a powerful and large (1.1 km circumference) machine outside of Chicago and it provides very intense X-ray beams,” Toney said. Interesting engineering in the email.

The main cause of self-discharge

The team found that hydrogen atoms are created by a reaction between the electrolyte and the cathode after the battery is fully charged. These atoms bind to the cathode, whereas lithium would otherwise bind during discharge.

This prevents the lithium from reaching the cathode, which reduces the electrical current produced and the battery’s overall capacity, the press release said. Now that scientists understand what causes self-discharge, they can direct efforts to prevent it.

Coating the cathode with a special material that blocks only hydrogen atoms could be an option. “Typically, you can use protective oxides like aluminum oxide (Al2O3) to coat the cathode,” Toney added in an email. “They’re not expensive, and there are coating processes, but we’re not sure how long the coating will last.”

Still, the research opens up new frontiers and could help develop better batteries. As the world moves to phase out fossil fuels, batteries that don’t lose charge capacity over their lifespan will be key.

It will promote renewable energy storage solutions and reduce the cost of storing excess energy. For electric vehicles, this would mean no loss of range or need to replace the battery even after years of use, thus increasing their adoption.

The research results were published in the journal Science Today.