Researchers at the University of Michigan have found that a network of aramid nanofibers, recycled from Kevlar, can enable lithium-sulfur batteries to overcome their Achilles heel of cycle life—the number of times they can be charged and discharged. This means the car will be able to run for more cycles - essentially lasting longer.
Leading up to their discovery, the researchers were faced with a challenge; they had to stop small molecules of lithium and sulfur attaching themselves to the battery’s lithium and reducing the battery’s capacity. They had to figure out how to allow lithium ions to flow from the lithium to the sulfur and back, as well as block the lithium and sulfur particles, known as lithium polysulfides. This process is known as ion selectivity.
To solve the problem, the researchers mimicked pores in biological membranes. They added an electrical charge to the pores in the battery membrane. The nanofibres the researchers added to the lithium polysulfides were negatively charged, which repelled the lithium polysulfide ions that continued to form at the sulfur electrode. Positively charged lithium ions, however, could pass freely.
Several other benefits of the battery include:
- Capabilities to handle extreme temperatures, from the heat of charging in direct sunlight to cold and ‘chilly’ winters.
- An extended life-cycle. Even with fast charging, the battery is predicted to last for up to 1,000 charges, which is roughly the equivalent of a 10-year lifespan.