Bumpy battery surfaces can create signals that look like they show ion movement, possibly tricking researchers into thinking they understand how battery materials behave. A team from Korea Advanced Institute of Science and Technology (KAIST) has uncovered the source of these misleading signals and found a way to reduce them. Their research, published in the journal Small Methods, shows that rough surfaces can create signals similar to those from real ion movement, which could lead to incorrect interpretations in detailed battery studies. In batteries, lithium or sodium ions move during charging and discharging, and how fast and easily they move affects the battery’s performance and how long it lasts. To study this movement, scientists use a technique called electrochemical strain microscopy (ESM), which is based on atomic force microscopy (AFM). This method uses a very fine tip to scan a battery material’s surface and measures tiny changes linked to ion movement. However, when the surface of a battery material is uneven, similar signals can appear even without real ion movement. To investigate this, the team made tiny trenches on a single-crystal silicon sample that does not conduct ions. The results showed that differences in surface height can change how much the microscope tip touches the sample, creating signals that mimic actual ion movement. This same effect was observed in real battery materials like graphite anodes and a sodium solid electrolyte. As a solution, the researchers suggested making battery material surfaces as smooth and flat as possible. To do this, they used a technique called cooling cross-section polishing (CCP), which uses an argon ion beam to precisely polish the surface. This method allows for fine adjustments without significantly changing the material's properties. After smoothing, the surface roughness decreased, reducing the misleading signals caused by uneven surfaces. The team also looked at signals at grain boundaries—points where small crystals in the material meet. Before smoothing, strong ESM signals were detected at these boundaries. After polishing, those signals disappeared. This suggests that some signals thought to show "ion pathways" might have actually come from surface height differences, not real ion movement. This study is important because it shows how these misleading signals occur in detailed battery analysis and offers a practical way to reduce them by smoothing surfaces. The findings could lead to a better understanding of where ions move freely and where they are blocked within a battery. This knowledge could help in designing better battery materials that allow faster ion movement, improving charging speed and battery life. The team believes this method can be used not just for common lithium-ion batteries but also for newer battery types like solid-state and sodium-ion batteries. This approach could help researchers understand these batteries better and support the development of new materials. Additionally, accurate data from these studies could serve as high-quality training data for artificial intelligence and machine learning, helping to design better battery materials and predict their performance.