Cobalt-free cathodes could enhance lithium-ion batteries

Researchers at the US-based Oak Ridge National Laboratory (ORNL) have developed a new family of cathodes with the potential to replace the costly cobalt-based cathodes typically found in today’s lithium-ion batteries that power electric vehicles and consumer electronics.

Cobalt is a metal currently needed for the cathode that makes up the significant portion of a lithium-ion battery’s cost. But cobalt is rare and largely mined overseas, making it difficult to acquire and produce cathodes. As a result, finding an alternative material to cobalt that can be manufactured cost-effectively has become a lithium-ion battery research priority.

The NFA (nickel, iron and aluminium) cathode, developed by ORNL scientists, is a derivative of lithium nickelate and can be used to make the positive electrode of a lithium-ion battery. The novel cathode is designed to be fast-charging, energy dense, cost-effective and long lasting.

The scientists tested the performance of the NFA class of cathodes and determined they are promising substitutes for cobalt-based cathodes. The researchers used neutron diffraction, Mossbauer spectroscopy and other advanced characterisation techniques to investigate NFA’s atomic and micro structures as well as electrochemical properties. The results were published in Advanced Materials and the Journal of Power Sources.

“Our investigations into the charging and discharging behaviour of NFA showed that these cathodes undergo similar electrochemical reactions as cobalt-based cathodes and deliver high enough specific capacities to meet the battery energy density demands,” said Ilias Belharouak, ORNL’s scientist leading the NFA research and development.

Although research on the NFA class is in the early stages, Belharouak said his team’s preliminary results to date indicate that cobalt may not be needed for next-generation lithium-ion batteries, claiming the new cathode “has similar or better electrochemical characteristics than cobalt-based cathodes while utilising lower cost raw materials”.

Belharouak added that not only does NFA perform as well as cobalt-based cathodes, but the process to manufacture the NFA cathodes can be integrated into existing global cathode manufacturing processes.

“Lithium nickelate has long been researched as the material of choice for making cathodes, but it suffers from intrinsic structural and electrochemical instabilities,” he said. “In our research, we replaced some of the nickel with iron and aluminium to enhance the cathode’s stability. Iron and aluminium are cost-effective, sustainable and environmentally friendly materials.”

Future research and development on the NFA class will include testing the materials in large-format cells to validate the lab-scale results and further explore the suitability of these cathodes for use in electric vehicles.

Image caption: ORNL researchers have developed a new class of cobalt-free cathodes that is being investigated for making lithium-ion batteries for electric vehicles. Image credit: Andy Sproles/ORNL, US Dept of Energy.

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