Pleated graphene is found to have extraordinary energy storage capacity

When someone crumples a piece of paper, it usually means he has to throw it. But researchers have now discovered that a piece of pleated graphene paper—a material that is bonded together by a two-dimensional layer of carbon atoms—has a new property that can be used to create extraordinary retractable super capacitors. A capacitor can store energy for a flexible electronic device. Zhao Xuanhe, assistant professor of mechanical engineering and civil and environmental engineering at the Massachusetts Institute of Technology, and four other authors published the findings in the journal Scientific Reports. The research team said that the new flexible super capacitor should be easier to manufacture and less expensive to manufacture.

Two-dimensional "carbon paper" can form a retractable super capacitor that provides power to flexible electronic devices.

In order to form pleated graphene, a layer of polymer material is first stretched in two dimensions, and then graphene is bonded to the stretched polymer material.

In order to form pleated graphene, a layer of polymer material is first stretched in two dimensions, and then graphene is bonded to the stretched polymer material. When stretching in one dimension is released, regular wrinkles appear on the graphene, as shown in the lower left figure, which is obtained by scanning electron microscopy (SEM). Finally, when the stretching in the other dimension direction is released, mixed pleats appear on the graphene (as shown in the upper left figure). The SEM image of the upper right panel shows that the graphene is in a slightly pleated state. The SEM image of the lower right panel shows the flattened pleated graphene. The picture is provided by the researcher.

Pleated graphene super sensor diagram

Pleated graphene super sensor diagram (top left part of the figure). The upper and lower layers are polymers used as substrates, the black two layers are pleated graphene, and the white intermediate layer is a hydrogel used as an electrolyte. The illustration shows the actual product of a super capacitor, which proves that it does not affect its conductive properties anyway. The picture is provided by the researcher.

When someone crumples a piece of paper, it usually means he has to throw it. But researchers have now discovered that a piece of pleated graphene paper—a material that is bonded together by a two-dimensional layer of carbon atoms—has a new property that can be used to create extraordinary retractable super capacitors. A capacitor can store energy for a flexible electronic device.

Zhao Xuanhe, assistant professor of mechanical engineering and civil and environmental engineering at the Massachusetts Institute of Technology, and four other authors published the findings in the journal Scientific Reports. The research team said that the new flexible super capacitor should be easier to manufacture and less expensive to manufacture.

Zhao Xuanhe said: "Many people are studying graphene paper: Since graphene has a very large surface area per unit mass, it has become a good material that can be used to make super capacitors." He also pointed out that today's flexible electronic devices The development requires flexible electrical energy storage systems such as wearable, implantable biomedical sensors or monitoring devices.

Like a battery, a super capacitor can store electrical energy, but a super capacitor stores electrical energy primarily in the form of static electricity rather than storing it in the form of chemical energy, so super capacitors deliver electrical energy faster than batteries. Zhao Xuanhe and his team demonstrated that a super capacitor that can be bent or stretched to 8 times its original size can be made by making a layer of graphene paper into a mixed fold. For the proof of principle, the research team has used this method to create a simple super capacitor.

The team demonstrated that the material did not show a significant drop in performance after being repeatedly creased and flattened 1,000 times. Zhao Xuanhe said: "Graphene paper is very durable, it can withstand many rounds of large deformation." Graphene is a hexagonal pure carbon structure with only one carbon atom thickness, it is one of the most powerful materials known. .

In order to make pleated graphene paper, a layer of material is first placed on a mechanical device to compress the layer of material in one direction to form a series of mutually parallel pleats, which are then compressed in the other direction to form a mixed pleat. surface. This layer of material is easily flattened when stretched.

Two capacitors are required to form the capacitor. In this example, two layers of pleated graphene paper are required. An insulating layer is required between the two layers of capacitors. In this example, the insulating layer is made of a hydrogel. Like pleated graphene, hydrogels have strong deformability and ductility. Therefore, even if it is bent or stretched, the three layers can remain in contact.

Li Dan, a professor of materials engineering at the University of Monash in Australia who did not participate in the study, said: "I am really excited and surprised by this work. He pointed out that the research team provided an extremely simple but efficient concept of a retractable electrode for making super-capacitors by controlling the folds of multilayer graphene films. He added: "At a time when other teams have already made flexible super capacitors, manufacturing retractable super capacitors is a huge challenge. This article proposes a clever way to meet this challenge, and I believe it will bring wearable energy storage devices to everyone. "

The research team also includes Qi Jianfeng from Huazhong University of Science and Technology, Cao Changyang, Feng Yaying and Liu Jie from Duke University. This work was funded by the National Naval Office, the National Science Foundation, and the China National Thousand Talents Program.

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