Molecular pulleys to boost battery performance

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In the search for ways to improve lithium batteries, one option is to use silicon anodes, which according to the research team would enable batteries to achieve high volumetric and energy densities sufficient for electric vehicles.

However, the dramatic volume changes silicon undergoes during charging causes the battery components to fail.

To solve this issue, the researchers included an anchored polymer containing rings along its backbone, known as polyrotaxane (PR), to the binder material used to hold together the particles in a silicon anode.

The PR is said to have unusual mechanical properties that arise from the sliding movement of the backbone through the rings. The PR acts as a pulley system that relieves stress on the anode, allowing it to expand and contract more easily.

The researchers claim this technique allowed them to create a silicon anode with the same areal capacities within the range of current commercial lithium-ion batteries. Furthermore, the full-cell showed decent cyclability, with 98% retention of the original capacity after hundreds of cycles.