A team at the Korea Advanced Institute of Science and Technology has found why some nanoscale battery tests can show a signal that looks like ions moving when no ions are moving at all. The misleading signal can come from an uneven material surface.
The researchers tested an ionically inactive silicon sample with small trenches, then checked the same effect in a graphite anode and a sodium solid electrolyte. Changes in surface height altered the contact between the microscope tip and the sample, creating signals that resembled ion transport.
The team used a cooling cross-section polisher to make battery-material surfaces smoother. After polishing, the unusually strong signals at the boundaries between tiny crystals disappeared, showing that the surface roughness had been creating the illusion.
More trustworthy measurements could help researchers understand how ions move through lithium-ion, solid-state, and sodium-ion batteries. That knowledge may support future designs for batteries that charge faster and last longer. The study appeared in Small Methods.
