Organic Electrodes: A Promising Development For The Energy Transition

A Chinese team has now introduced a new Organic Electrode Materials (OEM) for aqueous organic high-capacity batteries that can be easily and cheaply recycled. Right now our modern rechargeable batteries, such as lithium-ion batteries, are anything but sustainable.

The team has introduced their results in the journal Angewandte Chemie. Modern rechargeable batteries, such as lithium-ion batteries, are anything but sustainable. One alternative is organic batteries with OEMs, which can be synthesized from natural 'green' materials.

Graphical display of the Huazhong University redox organic electrode battery material function. Image Credit: Angewandte Chemie. Click either the press release or study paper abstract links for a larger image.

Traditional inorganic electrode materials in commercial batteries involve a whole spectrum of problems: limited resources, toxic elements, environmental problems, partly unacceptable mining conditions, limited capacity, difficulties in recycling, and high costs. No sustainable batteries can be developed on a large scale based on these electrodes, though they are needed for an energy transition.

Organic batteries with OEMs are still at the very beginning of their long road toward practical application. A team led by Chengliang Wang at Huazhong University of Science and Technology has now taken a significant step in this direction. The goal is to use OEMs in batteries with aqueous electrolytes. These are "greener," more sustainable, and less expensive than the conventional organic electrolytes in lithium-ion batteries.

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The team chose to use azobenzene, a material that can be produced inexpensively on a large scale and is insoluble in water while being highly soluble in organic solvents. Whereas most other functional groups can only transfer one electron, the azo group (-N=N-) in this molecule is able to reversibly transfer two electrons, which contributes to a high capacity. Comprehensive analyses demonstrated that, during the discharge process, the azobenzene is converted to hydroazobenzene after absorbing two of the electrons - through the rapid, reversible binding of two protons (H+). Prototype coin cells and laminated pouch cells of various sizes with azobenzene OEMs and zinc counter-electrodes reached capacities on the scale of ampere hours, which were retained over 200 charge/discharge cycles.

In contrast to polymeric OEMs, the small azobenzene molecules can be inexpensively recycled with a simple extraction using commercial organic solvents. The electrode material is air stable in both its charged and discharged states and can be recycled in yields of over 90% in every state of charge. The recycled products could be directly reused as OEMs with no loss of capacity.

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This looks like it might be a technological breakthrough. But the abstract and graphical data is really thin. Most of what is disclosed is about the electrolyte. One of the electrodes is mentioned as a zinc compound while the other is not revealed. That's kind of understandable, keeping one proprietary data private is a logical thing. There is some cause to believe that the journal's editors have been told and anyone seeking to replicate might have some documentation to sign.

There is quite some interest that this technology gets more attention. There isn't a notice of exotic or dangerous or rare materials involved and the lab device has cleared the 200 cycles mark.

This looks pretty good. It would be a very good thing if a non or low toxic rechargeable battery chemistry got competitive the various metallic chemistries. But 'green or organic' can still be very toxic.

We're going have to wait some more. Power per weight and volume aren't noted or operating voltage and the other needed data. But the baby has just been born, alive, it will be interesting to see how it grows.

By Brian Westenhaus via New Energy and Fuel

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