An international team of scientists has found a material that could enable lithium ion batteries to hold far more energy without sacrificing battery lifetime. The team discovered antimony crystals spontaneously and reversibly hollow out during the charge-discharge cycle, a much-desired characteristic that can facilitate greater energy density without compromising on safety.

Lithium-ion batteries produce electricity by shuttling ions back and forth between two electrodes, the negatively-charged cathode and the positively-charged anode. But in their current state they are stretched to their limits. Efforts to increase this flow of lithium ions have been held back by the deterioration of the anode material, which tends to swell and shrink during charging and discharging, resulting of greater stress that reduces the lifetime of the battery.

Scientists see a solution in “yolk-shell” particles that improve cycling ability thanks to hollow voids that can accommodate volume changes as the battery charges and discharges, while offering a stable outer surface. Swapping out the metal alloy anode material for these particles has long been seen as a pathway forward, but manufacturing them in a cost-effective way has proven problematic.

“Intentionally engineering hollow nanomaterials has been done for a while now, and it is a promising approach for improving the lifetime and stability of batteries with high energy density,” says study author Matthew McDowell from the Georgia Institute of Technology. “The problem has been that directly synthesizing these hollow nanostructures at the large scales needed for commercial applications is challenging and expensive. Our discovery could offer an easier, streamlined process that could lead to improved performance in a way that is similar to the intentionally engineered hollow structures.”