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Posted: Aug 14, 2017
A multistable, shape-reconfigurable design for aluminum-air batteries
(Nanowerk News) Researchers propose a new, multistable, shape-reconfigurable design combined with a battery packing concept – which they term shape-reconfigurable batteries (SRBs) – that leads to 2D and 3D polymorphed states, while preserving the electrochemical functionality.
In this work, reported in Advanced Functional Materials ("Shape-Reconfigurable Aluminum–Air Batteries"), a team from Korea adopts aluminum– air battery cells as an ideal platform, which involve three-electron transfer during discharging reactions and, as a result, provide a specific capacity (2980 mA h g-1) that rivals that of the single-electron lithium–air battery (3582 mA h g-1 for an aqueous electrolyte).
The scientists chose porous cellulose as a substrate because of its high deformability, such that cellulose coated with a carbon composite served as the sole deformable current collector, whereas metal current collectors have struggled to achieve good deformability.
"Although the aluminum–air battery cell provides a geometric starting point for our research, our focus here is also on the reconfigurability of these structures and on the analysis of how this can lead to new designs for transformable batteries," the authors write.
This design provides advantages in terms of accessibility, disposability (low cost), deformability, and safety.
First, the carbon composite coupled with the porous cellulose scaffold offers a high-surface-area framework, and the oxygen-reduction reaction is promoted without a catalyst in the cathode electrode.
Second, because all cell components (graphite or the carbon–poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) composite, aluminum foil, and the cellulose substrate) are highly deformable, the resulting aluminum–air unit cell is provided with flexibility and even foldability.
For the electrolyte, the 'water-in-salt' electrolyte was used, which provides the safety advantages of an aqueous electrolyte when folded.
Third, owing to this foldability, a battery-pack design enabling aluminum–air batteries with a high voltage and high capacity is achieved.
Last, the researchers also demonstrate a concept of shape-reconfigurable architected materials capable of achieving packed aluminum–air batteries that tolerate significant morphological changes upon loading and resist rolling, expanding, stacking, and crumpling, while maintaining cell performance.
In their paper, the authors first describe the working mechanism and performance of the cellulose-based aluminum–air battery, and then demonstrate the integration of this cell into a stackable architecture for a potentially high-performance battery.