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According to the report of the World Technology News website Phys.org, American scientists recently discovered that by migrating paper-based lithium-ion batteries in Miura-ori, their energy density and capacity per unit area will increase by 14 times.
In a recent issue of Nano Letters, Arizona Cheng University scientist Qian Cheng and other researchers jointly published a paper describing their use in folding paper-based lithium-ion batteries. Latest research results.
"Folding batteries can be very helpful for equipment with limited space on the power board," said Candace Chan, an assistant professor and co-author of the paper at the School of Materials Science and Engineering at Arizona State University. In addition, recent research by other research groups on collapsible paper-based electronic devices has shown that it is important to integrate a power source and other components into a single, fully foldable mobile device. A foldable battery pack is important.
In the current study, scientists used lithium ion batteries made of carbon nanotube (CNT) inks as current collectors, traditional lithium powders as electrodes, and thin and porous Kimwipes as paper substrates. The researchers also added polyvinylidene fluoride (PVDF) coatings to it to improve the adhesion of CNT inks in paper substrates. The resulting battery has good electrical conductivity and relatively stable energy.
The researchers tried to use a simple half-fold and a more complicated Miura-ori fold method. The researchers found that when using a simple half-fold method, the energy density and capacity per unit area can be increased by 1.9, 4.7, and 10.6 times compared to flat cells, once, twice, and three times.
The Miura-ori folding method is more efficient: folding a 6 cm by 7 cm battery into 25 layers can increase the energy density and capacity per unit area by a factor of 14 and reduce its total area to 1.68 square centimeters.
“We use the energy density per unit area to express the increase in energy density,†Chen explained. “This is different from the energy density per unit of weight because the battery is unfolded and unfolded with constant mass.â€
In general, in a simple folding mode, the folded cell has electrochemical properties similar to those of a flat cell. The coulombic efficiency of the folded battery is higher than those of the unfolded battery, which may be due to the increased contact between the electrode material and the carbon nanotube after the battery is folded.
Relative to flat cells, some of the properties of cells folded with the Miura-ori method are slightly reduced, including reductions in discharge capacity and permittivity. The researchers believe that these losses may be due to the delamination of the intersection of vertical folds, because these batteries contain 16 vertices. To prevent the battery, the researchers used a flexible insulating film between layers: Parylene-C.
The results of this research made it possible for the first time to see the potential of using folds to increase the energy density and capacity per unit area of ​​lithium-ion batteries. In the future, with the advances in geometric folding algorithms, computational tools, and robotic manipulation techniques, more complex folding patterns may occur, and the emergence of large-scale batteries for commercial use becomes possible.
Because of the low cost, simple manufacturing methods and flexibility, paper-based batteries have become quite attractive to people. If the performance of the paper-based battery can be further provided by folding, this may result in the production of high-performance batteries for various applications.
"Using folding and origami concepts can create new geometric shapes, geometric designs, and new features for paper-based energy storage devices. This area has unlimited potential," said Chen.
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