Silicon anodes are an attractive alternative to graphite anodes currently in use in lithium-ion batteries, because they can deliver up to five times higher capacities. However, silicon anodes have a limited charge-discharge cycle number. Their volume expands during each cycle, leading to fracture of the electrode particles or delamination of the electrode, reducing its capacity.
Now a team from Korea Advanced Institute of Science and Technology (KAIST, Daejeon; www.kaist.edu), led by professors Jang Wook Choi and Ali Coskun, has reported a “molecular pulley” binder for high-capacity silicon anodes of lithium-ion batteries.
The team integrated molecular pulleys, called polyrotaxanes, into a battery electrode binder. A polyrotaxane is a molecule consisting of “strings and rings,” in which rings are threaded onto a molecular axle and prevented from dethreading by two bulky end groups. Polyrotaxanes can help build functional molecular machines.
The team included the polyrotaxanes in battery electrodes to attach the electrodes onto metallic substrates. The free-moving rings can follow the volume changes of the silicon particles. The rings’ sliding motion can hold silicon particles without disintegration during their continuous…