As a lithium ion battery wears out, the cathode material loses some of its lithium atoms. The cathode's atomic structure also changes, meaning that it’s less capable of moving ions in and out.
In order to address this, the team harvested the degraded cathode particles from a used battery. They then pressurised the cathode particles in a hot, alkaline, solution containing lithium salt. From there the particles went through an annealing process in which they are heated to 800°C, then slowly cooled.
The team claims to have built new batteries using cathodes regenerated through this technique; restoring the cathode's lithium concentration and atomic structure back to their original states. They also reported that charge storage capacity, charging time and battery lifetime were also restored to their original levels.
With less than 5% of used lithium ion batteries recycled today, this new technique could prove to be useful in terms of the environmental concern these batteries present.
"Think about the millions of tons of lithium ion battery waste in the future, especially with the rise of electric vehicles, and the depletion of precious resources like lithium and cobalt-mining more of these resources will contaminate our water and soil. If we can sustainably harvest and reuse materials from old batteries, we can potentially prevent such significant environmental damage and waste," said Professor Zheng Chen.
Prof Chen believes the work could also address economic issues related to battery waste."The price of lithium, cobalt and nickel has increased significantly. Recovering these expensive materials could lower battery costs," he said.
According to the team, this process can recover and restore a lithium ion battery cathode material called lithium cobalt oxide. The method is also said to work on NMC, which is used in most electric vehicles.
The process is said to use 5.9Mjoule to restore 1kg of cathode material; less than half the amount used by other cathode recycling techniques.
Prof Chen’s team aims to optimise this process for industrial scales and to refine the process so that it can be used to recycle any type of lithium ion battery cathode material. "The goal is to make this a general recycling process for all cathodes," he concluded.