Sulfonamides make robust cathode material for proton batteries
Proton batteries are an innovative and environmentally friendly type
of battery in which charge is carried by protons, which are positively
charged hydrogen ions. A team of researchers has now developed organic
sulfonamides as a robust and flexible material for cathodes in these
batteries. As the team explain in the journal Angewandte Chemie, sulfonamide cathodes also achieve a higher output voltage than conventional cathodes.
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In the constant search for alternatives to lithium-ion batteries,
proton batteries are proven to have great potential. Rather than storing
charge in the form of lithium ions, they transfer light, highly mobile
protons instead. As a result, this type of battery does not require the
environmentally harmful and unsustainable mining of lithium. In
addition, the mobile protons help achieve significantly shorter charging
times than for other battery types.
Despite these advantages, the performance of the electrodes in proton
batteries still requires improvement. To date, the cathodes (positive
electrodes) were only able to achieve a fairly low output voltage,
insufficient for most applications. Now, Bingan Lu and his team based at
Hunan University in Changsha (China) have improved this voltage by
replacing the chemicals making the cathode material. Instead of organic
carbonyl compounds or cyanide-based pigments, they used organic
sulfonamides.
Rather than storing the protons at the oxygen atoms, as is the case
in carbonyl compounds, sulfonamides store the protons at the nitrogen
atom of the sulfonamide group. The researchers explain why this is
beneficial: “the nitrogen atom has one more vacant site than the oxygen
atom that can accept foreign electrons, making it much more tailorable.”
By attaching electron-withdrawing groups to the molecular scaffold,
the researchers were able to increase the electric potential of the
material. At 1 V, the output voltage achieved was 20% higher than in the
next-best materials, and the researchers are confident there is even
further room for improvement with careful molecular design.
To assemble a complete proton battery, Lu and colleagues also
developed a gel-like electrolyte which was adapted to the sulfonamide
cathode material and enabled flexible construction. This malleable
battery pack retained capacity over 600 charge/discharge cycles.
The advantage of using sulfonamides does not end with their chemical
tailorability. Lu and colleagues report the new cathode material is also
easy to manufacture, stable under standard environmental conditions,
and virtually insoluble in water. The team highlights that
sulfonamide-based proton batteries of this type do not contain any heavy
metals and consist of non-toxic organic compounds, so they are readily
recyclable.
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About the Author
Dr. Bingan Lu is a Professor at the School
of Physics and Electronics at the State Key Laboratory of Advanced
Design and Manufacture for Vehicle Body and the Hunan Province Key
Laboratory of Multi-Electron based Energy Storage Devices, Hunan
University, Changsha, China. His research group explores low-cost energy
storage materials and devices, including potassium-based energy storage
devices.
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