Tour and his colleagues discovered that magnetic properties can facilitate the separation and purification of spent battery materials. They use a method known as solvent-free flash Joule heating (FJH). This technique involves passing a current through a moderately resistive material to rapidly heat and transform it into other substances.

Using FJH, the Rice engineers heated battery waste to 2,500 Kelvin within seconds, creating unique features with magnetic shells and stable core structures. The magnetic separation allowed for efficient purification.

During the process, cobalt-based battery cathodes—commonly used in EVs and associated with high financial, environmental and social costs—unexpectedly showed magnetism in the outer spinel cobalt oxide layers, allowing for easy separation. This approach resulted in a high battery metal recovery yield of 98 percent, with the value of battery structure maintained.

“Notably, the metal impurities were significantly reduced after separation, while preserving the structure and functionality of the materials,” explains Tour. “The bulk structure of battery materials remains stable and is ready to be reconstituted into new cathodes.”