It is found that folded graphene paper can be used to prepare flexible supercapacitors

When we crumple a piece of paper, it usually means we throw it away. But researchers have found that wrinkling a sheet of graphene paper, a layered material made of two-dimensional carbon bonded together, could lead to new properties for making flexible supercapacitors that store energy in flexible electronic devices.

The discovery was reported in ScientificReports by xue anhezhao of the Massachusetts institute of technology in mechanical and civil engineering. Zhao's team says the new flexible supercapacitors are easy to make and cost less.

"Many researchers are exploring graphene paper, which is a good choice for making ultracapacitors because of its large specific surface area," zhao said. He said the development of flexible electronic devices, such as wearable or implantable biomedical sensors or detection devices, requires flexible energy storage systems.

Like batteries, supercapacitors can store electricity, but they mostly store static rather than chemical electricity, which means they can transfer energy faster than batteries. Now professor zhao and his team have discovered that crumpling a sheet of graphene paper into a very messy state can be used to make flexible and foldable supercapacitors that stretch up to 800% of their original size. To demonstrate this, the team has used the method to produce a simple supercapacitor.

Zhao's team showed that the material could be crumpled and flattened 1,000 times without significant loss of performance. "The material is very strong," says zhao. "Graphene, a six-membered ring composed of a single carbon atom, is the strongest material known.

To get a pleated graphene paper, a piece of material is placed in a mechanical device, compressed in one direction to make a series of flat or live pleats, and then made into a surface of messy pleats in the other direction. When stretched, the material can be easily restored to its original flat shape.

Capacitors require two conductive layers -- in this case, an insulating layer between two layers of folded graphene paper, the hydrogel material used in this experiment. Hydrogels can also be highly deformed and stretchable, so the three layers stay together while bending and stretching.

Although the initial demonstration was to make a supercapacitor, the same folding technique could be applied to other applications, zhao said. For example, pleated graphene could be used to make electrodes for flexible batteries, or to make stretchable sensors for specific chemical or biological molecules.

"This work is very exciting for me," said DanLi, a materials engineer at monash university in Australia, who was not involved in the research. He said zhao's team has provided a very simple but effective method for fabricating stretchable electrodes for supercapacitors by controlling the pleating of multilayer graphene films. While other teams are building flexible supercapacitors, he said, "making them scalable is a big challenge, and this graphene paper provides a very clever way to address this challenge, which I believe will lead to the development of wearable energy storage devices." "

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