Lithium in a battery sometimes behaves like ivy on a building facade: instead of a uniform layer, it sprouts thin, sharp tendrils. These needles can pierce the separator inside the battery and cause a short circuit. So engineers are looking for ways to make lithium grow calmly.

One trick they've found is to put a thin silver film under the lithium. The authors of a new study zoomed in to the atomic level and saw exactly how silver helps. On a silver surface, lithium prefers to align in the same crystal lattice as the silver itself. It's like building a wall with bricks that perfectly match the size of the foundation bricks. The joint is tight and gap-free.

But there's a flip side. Once lithium has covered the silver with a few layers, alloying slows down. New lithium atoms are not as eager to mix with the silver, and the risk of branching returns. The authors suggest improving the alloy by adding a bit of magnesium to the silver. Magnesium slightly expands the silver's crystal lattice, making it easier for lithium to penetrate.

This approach could lead to batteries that withstand repeated charging without growing dangerous needles. That means electric cars and phones could become safer and last longer.