Next-generation lithium-ion batteries may hold more charge for a greater number of cycles thanks to a new material derived from natural silk. Scientists at the Beijing Institute of Technology found that not only does their regenerated silk fibroin material work for over 10,000 cycles but it also stores five times more lithium than graphite, which is the most common choice for the anode (negative electrode) in lithium-ion batteries.

Scientists and battery manufacturers have tried all sorts of possible graphite replacements to boost performance, including high-quartz sand, which tripled performance in coin-sized batteries. But nothing has yet made it to widespread use.

The Beijing-based researchers challenged themselves to find a sustainable biorenewable source that would outperform graphite. They found that natural silk could be processed to create carbon-based nanosheets, which they then incorporated in prototype batteries and supercapacitors.

The resulting batteries had a capacity of 1,865 mAh/g – five times greater than the theoretical capacity of graphite (372 mAh/g) – at a current density of 0.1 A/g and they retained a high cycle stability of around 92 percent after 10,000 cycles. In other words, they take a much longer time to run out and they can be charged and discharged many times more than conventional lithium-ion batteries and the performance boost is comparable across a large range of current densities.

The researchers believe that their method could easily be scaled up for commercial use, and they note that their material could also find use in sodium-ion batteries, hydrogen storage, and other hybrid energy storage devices.

A paper describing the research was published in the journal ACS Nano.