Now, University of Texas at Dallas researchers have discovered that the problem isn’t inside the battery materials.
“It turns out only the surface of the battery cathode materials is the problem,” said Dr. Kyeongjae Cho, professor of materials science and engineering in the Erik Jonsson School of Engineering and Computer Science. “The inside is ok - this gives us great hope we can figure out how to stabilise the surface and make really high-capacity batteries a reality.”
But, according to Dr. Cho, high-energy-density batteries come at a high price: increased volatility.
"When a battery is constantly charged and recharged, the material begins to degrade. Released energy causes heating and the battery catches fire. That's essentially the safety problem."
The good news is that "only the surface of the battery materials is unsafe and unstable," said Dr. Cho. "If that can be addressed, it can be fixed."
During the constant cycles of charging and recharging, oxygen gases are released from the surface of battery materials. During that process, the pathway for lithium-ion transportation from the interior to the exterior can get blocked by metallic nickel dust, which is generated along with gas releasing, Dr. Cho explained.
“When there is a blockage, there’s no way to transfer lithium-ions at the surface that want to come in and out. This leads to rapid decrement of battery capacity. As the amount of heat increases, the chances of fire and explosions also increase," he added.
The team believe that that discovery at the surface of the battery materials might change the way manufacturers build them. Dr. Cho suggests that a well-designed oxide coating could be added on the battery surface.
Solving the heating conumdrum could lead to a 20-30 per cent higher capacity. "Modifications could lead to maintaining a charge for a longer period of time," Dr. Cho continued.
Based on the new findings, the team says there is some industry interest in working with the UT Dallas group on next-generation cathode materials for electric vehicle batteries. The group is also collaborating with the U.S. Naval Research Laboratory on a follow-up research project to increase the capacity and safety of cathode materials.
