Scientists at Korea University of Science and Technology (KAIST) have successfully developed a lithium-ion high-capacity battery with silicon as the anode using molecular pulley binders.

　　Silicon anodes have received great attention in the battery industry. Compared with the current lithium-ion batteries using graphite anodes, they can provide 3-5 times larger capacity. The larger capacity means that the battery is used after each charge. The time is longer, which can significantly extend the mileage of electric vehicles. Although silicon is abundant and cheap, the number of charge-discharge cycles of Si anodes is limited. During each charge-discharge cycle, their volume will greatly expand, and even the attenuation of their capacitance will cause electrode particles to break or electrode film delamination. .

　　The ring in the polyrotaxane can move freely with the volume change of the silicon particles, and the sliding of the ring can effectively maintain the shape of the Si particles, so that it will not disintegrate during the continuous volume change. It is worth noting that, due to the high elasticity of the polyrotaxane binder, even the crushed silicon particles can remain agglomerated. The function of the new adhesive is in sharp contrast with the existing adhesives (usually simple linear polymers), which have limited elasticity and therefore cannot firmly maintain the particle shape. The previous binder will scatter the crushed particles, which will cause the silicon electrode to reduce or even lose its capacity.

　　The author thinks this is an excellent demonstration of the importance of basic research. Polyrotaxane won the Nobel Prize for the concept of "mechanical bonds" last year. "Mechanical bonding" is a newly established concept that can be added to classic chemical bonds, such as covalent bonds, ionic bonds, coordination bonds and metal bonds. Long-term basic research is gradually solving the long-standing challenges in the direction of battery technology at an unexpected speed. The author also mentioned that they are currently working with a large battery manufacturer to integrate their molecular pulleys into actual battery products.