AsianScientist (Aug. 1, 2017) - In a study published in Science, a research team from the Korea Advanced Institute of Science and Technology (KAIST) have created high-capacity silicon anodes by integrating molecular pulleys into the electrode binders of lithium ion batteries.
Silicon anodes are receiving a great deal of attention from the battery community. They can deliver three- to five-times higher capacities compared with the graphite anodes used in lithium ion batteries today. A higher capacity means longer battery use per charge, which is particularly critical in extending the driving mileage of all-electric vehicles.
Although silicon is abundant and cheap, silicon anodes have a limited charge-discharge cycle number and can tolerate recharging less than 100 times. Their volume expands enormously during each charge-discharge cycle, leading to fractures of the electrode particles or delamination of the electrode film which also decays its capacity.
The KAIST team integrated molecular pulleys, called polyrotaxanes, into a battery electrode binder which is a polymer included in battery electrodes to attach the electrodes onto metallic substrates. In a polyrotaxane, rings are threaded into a polymer backbone and can freely move along the backbone. The free moving of the rings in polyrotaxanes can follow the changes in volume of the silicon particles.
Importantly, the rings’ sliding motion can efficiently hold silicon particles without disintegrating, even as the volume of the silicon particles continues to change. Even pulverized silicon particles can remain coalesced because of the high elasticity of the polyrotaxane binder. Read more...
Silicon anodes are receiving a great deal of attention from the battery community. They can deliver three- to five-times higher capacities compared with the graphite anodes used in lithium ion batteries today. A higher capacity means longer battery use per charge, which is particularly critical in extending the driving mileage of all-electric vehicles.
Although silicon is abundant and cheap, silicon anodes have a limited charge-discharge cycle number and can tolerate recharging less than 100 times. Their volume expands enormously during each charge-discharge cycle, leading to fractures of the electrode particles or delamination of the electrode film which also decays its capacity.
The KAIST team integrated molecular pulleys, called polyrotaxanes, into a battery electrode binder which is a polymer included in battery electrodes to attach the electrodes onto metallic substrates. In a polyrotaxane, rings are threaded into a polymer backbone and can freely move along the backbone. The free moving of the rings in polyrotaxanes can follow the changes in volume of the silicon particles.
Importantly, the rings’ sliding motion can efficiently hold silicon particles without disintegrating, even as the volume of the silicon particles continues to change. Even pulverized silicon particles can remain coalesced because of the high elasticity of the polyrotaxane binder. Read more...