Imaging Sodium Dendrite Growth in All-Solid-State Sodium Batteries Using ²³Na T₂-Weighted Magnetic Resonance Imaging

Two-dimensional, Knight-shifted, T ₂-contrasted ²³Na magnetic resonance imaging (MRI) of an all-solid-state cell with a Na electrode and a ceramic electrolyte is employed to directly observe Na microstructural growth. A spalling dendritic morphology is observed and confirmed by more conventional post-mortem analysis; X-ray tomography and scanning electron microscopy. A significantly larger ²³Na T ₂ for the dendritic growth, compared with the bulk metal electrode, is attributed to increased sodium ion mobility in the dendrite. ²³Na T ₂-contrast MRI of metallic sodium offers a clear, routine method for observing and isolating microstructural growths and can supplement the current suite of techniques utilised to analyse dendritic growth in all-solid-state cells.