Lithium-sulfur batteries are theoretically ideal for powering gadgets. They have more than twice the energy density of lithium-ion packs, but at a much lower cost thanks to sulfur's dirt-cheap price. There's just one problem: sulfur dissolves, giving the battery a short lifespan. That's where Berkeley Lab might help. It recently discovered that a derivative of red seaweed, carrageenan, can stabilize a lithium-sulfur battery and make it practical for more devices. If you use the seaweed derivative as a binder (the "glue" that keeps a battery's active materials together), it reacts with the sulfur and prevents it from dissolving. The ultimate goal is to produce cells that last for "thousands" of charging cycles, or better than many batteries you see today.