Demand is booming for batteries that are faster, thinner and cheaper. We want electric cars and bikes that travel further, devices that last longer, charge quicker and cost less. Today, lithium-ion batteries (LIBs) set the benchmark. But after decades of research, this technology is approaching its limits, and each new gain is harder to achieve.

Lithium–sulfur (Li–S) batteries are a promising next-generation technology. They store far more energy than LIBs by weight and are made from cheap, readily available materials.

But here’s the catch. Current Li–S batteries take up around 1.5 to 2.0 times more space than LIBs. In other words, their volumetric capacities are much lower. That’s a serious bottleneck because in many real-world applications, space matters more than weight. From portable electronics, electric vehicles to aerospace systems, every inch of space matters.