A team of researchers at Harvard University claimed to have developed a new 'flow' battery that can store energy in organic molecules dissolved in PH-neutral water
The researchers claim that the technique may not only enable the development of safe, non-toxic batteries, but batteries that can last for as long as ten years.
The research was led by materials and energy technologies Professor Michael Aziz and Roy Gordon, Professor of Chemistry and Materials Science.
However, rather than solving the problem of exploding Samsung Galaxy Note 7s, the development, they suggest, would be more suitable used on a large scale for energy storage in the renewables sector.
Flow batteries used today, they add, often suffer degraded energy storage capacity after many charge-discharge cycles, requiring periodic maintenance of the electrolyte to restore the capacity.
By modifying the structures of molecules used in the positive and negative electrolyte solutions, and making them water soluble, the Harvard team claim that it was able to engineer a battery that loses only one per cent of its capacity per 1000 cycles.
"Lithium ion batteries don't even survive 1000 complete charge/discharge cycles," said Aziz. "[But] because we were able to dissolve the electrolytes in neutral water, this is a long-lasting battery that you could put in your basement," said Gordon.
He continued: "If it spilled on the floor, it wouldn't eat the concrete and since the medium is non-corrosive, you can use cheaper materials to build the components of the batteries, like the tanks and pumps."
The technique should also cut costs, which would help to make renewable energy more competitive, as well as more reliable.
The key to designing the battery was to first figure out why previous molecules were degrading so quickly in neutral solutions, said Eugene Beh, a post-doctoral fellow and first author of the paper. By first identifying how the molecule viologen in the negative electrolyte was decomposing, Beh was able to modify its molecular structure to make it more resilient.
Next, the team turned to ferrocene, a molecule known for its electrochemical properties, for the positive electrolyte. "Ferrocene is great for storing charge, but is completely insoluble in water," said Beh. "It has been used in other batteries with organic solvents, which are flammable and expensive."
By modifying the molecular structure of Ferrocene in the same way that the viologen molecule was modified, the researchers were able to turn an insoluble molecule into a highly soluble one that could be cycled stably. "Aqueous soluble ferrocenes represent a whole new class of molecules for flow batteries," said Aziz.
The neutral PH of the resulting liquid should also help to lower the cost of the ion-selective membrane that separates the two sides of the battery - it was defects in this membrane in the Samsung Galaxy Note 7 smartphone that was one of the causes of the spate of device fires.
Currently, this membrane needs to be expensively engineered to withstand the chemicals inside the battery, and can account for up to one-third of the total cost of the battery.
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