All-solid-state batteries offer a safer and more powerful way to run electric vehicles, power electronics, and store renewable energy from the grid. However, their key ingredient, lithium, is both costly and scarce, and mining it often causes serious environmental harm. Sodium presents a much cheaper and more abundant alternative, and it is far less damaging to extract. Yet, sodium-based solid-state batteries have long struggled to match lithium's performance at typical temperatures. "It's not a...