he USC organic redux flow battery (not pictured) replaces metals with water-soluble organic materials
Lithium-ion batteries have made portable, rechargeable electronics commonplace. Unfortunately, they do have some glaring drawbacks, including heat issues, being made with rare, toxic elements, and the fact the technology doesn't scale up very well, which limits applications. A team of scientists at the University of Southern California (USC) is working on an alternative in the form of a water-based organic battery that is not only cheaper and more environmentally friendly, but also holds the potential for scaling up for use in wind and solar power plants as a means to store large amounts of energy.
The technology developed by the USC team is what’s called an organic redux flow battery. It’s a bit like a fuel cell, and a similar one was developed for NASA’s Helios electric-powered drones. It consists of two tanks containing solutions of electroactive chemicals. These are pumped into a cell, which is divided by a membrane. The solutions interact through the membrane and electricity is produced.
According to the team, the tanks can be of any size in comparison to the cells, so the total amount of energy that the system can store depends on how large the tanks are, which is one up on conventional batteries. The flow battery also has a better life span than lithium-ion batteries and its variants.
"The batteries last for about 5,000 recharge cycles, giving them an estimated 15-year lifespan," says Sri Narayan, professor of chemistry at the USC Dornsife College of Letters, Arts and Sciences. “Lithium ion batteries degrade after around 1,000 cycles, and cost 10 times more to manufacture.”
The key to the new flow battery is the electroactive materials used. Instead of metals or other toxic materials, the USC team used organic compounds. By trial and error, the researchers were able to develop materials based on oxidized organic compounds called quinones, which are found in plants, fungi, bacteria, and some animals and involved in photosynthesis and cellular respiration.
Specifically, the quinones used in the new battery are anthraquinone-2-sulfonic acid or anthraquinone-2,6-disulfonic acid on the negative side, and 1,2-dihydrobenzoquinone- 3,5-disulfonic acid on the positive side of the cell.
The team sees the technology as one day leading to large “mega-scale” battery banks that are cost-effective and environmentally friendly. The quinones used in the flow battery are currently produced from naturally occurring hydrocarbons, but the team hopes one day to derive them directly from carbon dioxide. However, the immediate goal of the team is to scale up the technology to make it more practical.
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