Manganese cathodes could boost performance of lithium-ion batteries

Rechargeable lithium-ion batteries are increasingly adopted for devices such as smartphones and laptops, electric vehicles and energy storage systems. But supplies of nickel and cobalt, commonly used in cathodes for these batteries, are limited. New research led by the Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab) reveals the potential for a low-cost, safe alternative in manganese, the fifth most abundant metal in the Earth’s crust.

Researchers have shown that manganese can be used effectively in new cathode materials called disordered rock salts, or DRX. Previous research suggested that DRX materials would need to be ground into nano-sized particles in an energy-intensive process to perform well. But the new study found that manganese-based cathodes can actually be successful with particles about 1,000 times larger than expected. The study was published Sept. 19 in the journal Nature Nanotechnology.

“There are many ways to generate power with renewable energy, but the key lies in how you store it,” says Han-Ming Hau, a doctoral student at UC Berkeley who researches battery technology as part of Berkeley Lab’s Ceder Group. “By applying our new approach, we can use a material that is both abundant on Earth and low-cost, requiring less energy and time to produce than some commercial Li-ion battery cathode materials. And it can store the same amount of energy and perform just as well.”

The researchers used a new two-day process that first removes lithium ions from the cathode material and then heats it at low temperatures (about 200 degrees Celsius). This contrasts with the existing process for manganese-based DRX materials, which require more than three weeks of processing.

The researchers used cutting-edge electron microscopes to capture atomic-scale images of the manganese-based material in action. After applying their process, they found that the material forms a nanoscale semi-ordered structure that allows it to store and deliver energy at a high density, which actually improves battery performance.

The team also used different techniques with X-rays to study how battery cycling causes chemical changes in manganese and oxygen at the macroscopic level. By examining how the manganese material behaves at different scales, the team offers different methods for making manganese-based cathodes and insights into the nanoengineering of future battery materials.

“We now have a better understanding of the material’s unique nanostructure,” Hau said, “and we have a synthesis process that creates this ‘phase change’ in the material that improves its electrochemical performance. This is an important step that brings this material closer to real-world battery applications.”

This research used resources at three DOE Office of Science user facilities: the Advanced Light Source and Molecular Foundry (National Center for Electron Microscopy) at Berkeley Lab and the National Synchrotron Light Source II at Brookhaven National Laboratory. The work was supported by DOE’s Office of Energy Efficiency and Renewable Energy and the Office of Science.