KTH Royal Institute of Technology: Method recycles batteries faster, with less environmental impact

In a scientific article published by the journal Green Chemistry scientist Xiong Xiao, a postdoc at the Division of Polymeric Materials at KTH, explains how it works using ultrasound.

Portrait photo of Xiong Xiao.
Xiong Xiao, postdoc at KTH. Photo: Peter Ardell
“We perform the metal extraction in half the time it normally takes and we take out more metal ion than normally reported in scientific literature. In the extraction process we use mild acids such as acetic acid and citric acid instead of sulfuric acid, which is very beneficial from a work environment and sustainable development point of view,” says Xiong Xiao.

Ninety-nine percent recycled
The scientists have worked with the most common lithium-ion batteries in the world—the kind found in Tesla cars and iPhones. They go by the name NMC-batteries and besides lithium they contain nickel, cobalt and manganese. The scientists have been able to extract up to as much as 99 percent of the metal in the batteries.

“With ultrasound Xiong Xiao has discovered a way to eliminate the need for chemicals normally used, such as strong acids that are nearly unmanageable,” says Richard Olsson, scientist colleague and university lecturer at The Division of Polymeric materials at KTH.

“She has conducted extensive research to understand at what temperatures and concentrations of the more mild acids the ultrasound can help with the extraction in the best way.”

The significance of ultrasound
Olsson adds that the extraction is “residue layer migration controlled”, which means that it is in the interface of the grains in the crushed batteries where the bottleneck is located for the extraction. The implication is that this is where the ultrasound is of great significance.

“Going forward, now that we have reported this new method, scientists can focus on optimizing the ultrasound even further for this particular interface. For instance using different levels of intensity and frequency in order to reach even faster extraction of the important and expensive metals we want to recycle.”