RESEARCH HIGHLIGHT - Sodium-ion cathode material could help improve battery lifetime for large-scale energy storage

Researchers have uncovered new details about how a promising sodium-ion battery material changes while charging, offering a potential route to longer-lasting batteries for storing renewable energy.

The work, carried out in collaboration between the Cavendish Laboratory - Department of Physics at the University of Cambridge and University of Cambridge Yusuf Hamied Department of Chemistry focuses on sodium nickelate (NaNiO2), the parent material for a type of “nickel-rich” cathodes that can store more energy than materials using other metals, but which breaks down quickly because of ordering phenomena. By gaining a better understanding of the structures that form in the most nickel-rich possible sodium-ion cathode material, the researchers hope to design cathodes that do not degrade as quickly. 

“Not a lot is known about the crystal structures present in many sodium-ion cathodes, and lessons from lithium-ion batteries do not always carry across,” said Dr James Steele, who led this research as a NanoDTC PhD student at the Cavendish Laboratory. 
“Because sodium-ions are bigger, they repel each other more strongly and tend to arrange themselves in special patterns, or “superstructures”, in a phenomena we call sodium-ion vacancy-ordering.”
 

For this study, the team identified the structures of the phases that form as sodium is electrochemically removed from sodium nickelate. To investigate how the cathode, or positive electrode, changes as sodium moves in and out during charging and discharging, the researchers used x-rays and neutrons in diffraction experiments to work out the crystal structures of the material and to see how those structures changed while the battery was charging. These phases show special arrangements of sodium-ions and different nickel oxidation states that result in stable structures. The live, in operando measurements also allowed the team to track how the structure evolves in real time and to identify additional “metastable” phases: unstable states that can’t be found by standard diffraction measurements, which are usually taken after a cell is charged and disassembled (giving it time to relax into stable structures).
 

Full article form the Cavendish Laboratory

Publication: James M. A. Steele et al., ‘Evolution of Charge and Orbital Ordering, and Cation Vacancy Ordering During Electrochemical Desodiation of NaxNiO2‘, J. Am. Chem. Soc. 2026, DOI: 10.1021/jacs.6c03074