Operando XRD-CT of commercial sodium-ion batteries

Sodium-ion batteries have emerged as a promising alternative to conventional lithium-ion systems for specific applications. Although their lower nominal voltage results in reduced gravimetric energy density, they are well suited to grid-scale energy storage. Currently, sodium-ion cells are in early stages of commercialisation. In this work, operando XRD-CT is applied for the first time to investigate phase changes and heterogeneities within a commercial sodium-ion cell. The sodiation behaviour is compared with that of an aged cell cycled 2000 times and exhibiting 50% state of health. Previous studies on lithium-ion systems have identified ageing-induced defects, providing a basis for comparison with new experimental data. Operando measurements are complemented by high-resolution ex situ electrode-level analyses to characterise defects within the cathode. This combined approach provides insight into ageing mechanisms and defect formation in commercial sodium-ion cells.