A brief description of the performance breakthrough of lithium batteries

Silicon anodes are of great concern in the battery community. Compared with lithium ion batteries currently using graphite anodes, they can provide 3-5 times more capacity. Greater capacity means that the battery is used longer after each charge. This can significantly extend the mileage of electric vehicles. Although silicon is abundant and cheap, the number of charge and discharge cycles of the Si anode is limited. During each charge and discharge cycle, their volume will greatly expand, and even the attenuation of their capacitance will cause the electrode particles to break or layer the electrode membrane. phenomenon.

Working principle of molecular pulley binder.

A molecular pulley adhesive for Silicon anode lithium-ion batteries was reported on 20 July by the KAIST research team led by Professor JangWook Choi and Professor AliCoskun.

The KAIST team integrated the molecular pulley(called polyrotaxane) into the battery electrode adhesive, including adding a polymer to the battery electrode to attach the electrode to the metal substrate. The ring in the polyrotaxane is twisted into the polymer skeleton and can be freely moved along the skeleton.

The ring in the polyrotaxane can move freely as the volume of the silicon particles changes, and the sliding of the ring can effectively maintain the particle shape of the Si so that it does not collapse during a continuous volume change. It is worth noting that since the polyrotaxane binder has high elasticity, even the pulverized silicon particles can remain in a coalesced state. The function of the new adhesive is in stark contrast to existing adhesives (usually simple linear polymers) which have limited flexibility and therefore do not hold the particle shape firmly. Previous adhesives scatter the comminuted particles, causing the silicon electrode to reduce or even lose its capacity.

The authors say this is an excellent demonstration of the importance of basic research, and Polyrotaxane won a Nobel Prize last year for the concept of "mechanical bonds." "Mechanical binding" is a newly defined concept that can be added to classical chemical bonds such as Covalent bonds, Ionic bonds, coordination bonds, and metal bonds. Long-term basic research is gradually addressing the long-standing challenges in the direction of battery technology at an unexpected rate. The authors also note that they are currently working with a large battery manufacturer to integrate its molecular pulleys into actual battery products.

Northwestern University's 2006 Nobel Laureate Prize in Chemistry Sir FraserStoddart also added: "Mechanical bonds recovered for the first time in an energy storage environment. The KAIST team cleverly used the mechanical binder in the sliding ring polystyrene, in the α-ring. The functional on the polyethylene glycol screw, This marks a breakthrough in the performance of lithium-ion batteries on the market. When pulley polymers with mechanical adhesives replace conventional materials with only single chemical bonds, this physical bond will have a very significant impact on the performance of materials and equipment. "

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