Researchers at the American Association for the Advancement of Science (AAAS) have developed a method for using molecular 'pulleys' that expand and contract to improve battery performance.

The method yields a performance in silicon anode-based lithium batteries that is similar to commercialized lithium-ion batteries with other types of anodes. As researchers look to improve lithium batteries, one appealing option is to use silicon anodes that enable batteries to achieve high volume and energy densities sufficient for electric vehicles.

However, the volume changes that silicon undergoes during charging causes the battery components to fail. AAAS researchers included an anchored polymer containing rings along its backbone, known as polyrotaxane (PR), which binds material used to hold together the particles in a silicon anode. The mechanical properties of the PR allows for a sliding movement of the backbone through the rings.

The polymer acts as a pulley system to relieve stress on the anode, allowing it to expand and contract more easily. The method allowed researchers to create a silicon anode with the same capacities of current commercial lithium-ion batteries.

The full-cell showed decent cyclability such as 98 percent retention of the original capacity after hundreds of cycles.