Engineering news
At Massachusetts Institute of Technology, researchers have developed a new kind of self-assembling battery material that breaks apart when submerged in an organic liquid. In a paper published this week in
Nature Chemistry, the research team demonstrated that the material can be used as an electrolyte in a solid-state battery and then revert back to its original molecular components.
The approach could serve as an alternative to shredding the battery, which is how they are currently disposed of, making them hard to recycle. “So far in the battery industry, we’ve focused on high-performing materials and designs, and only later tried to figure out how to recycle batteries made with complex structures and hard-to-recycle materials,” says the paper’s first author Yukio Cho. “Our approach is to start with easily recyclable materials and figure out how to make them battery-compatible. Designing batteries for recyclability from the beginning is a new approach.”
Recycling batteries today requires harsh chemicals, lots of heat and complex processing. To simplify the process, the researchers decided to try to make a more sustainable electrolyte, which shuttles lithium ions between the negatively charged electrode and the positively charged cathode.
They used aramid amphiphiles, a class of molecules that self-assemble in water, and designed them to contain polyethylene glycol, which can conduct lithium ions. When the molecules are exposed to water, they spontaneously assemble into nanoribbons that can conduct lithium ions.
“The material is composed of two parts,” Cho explains. “The first part is this flexible chain that gives us a nest, or host, for lithium ions to jump around. The second part is this strong organic material component that is used in the Kevlar, which is a bulletproof material. Those make the whole structure stable. Within five minutes of being added to water, the solution becomes gel-like, indicating there are so many nanofibres formed in the liquid that they start to entangle each other. What’s exciting is we can make this material at scale because of the self-assembly behaviour.”
When they immersed a battery cell including this new material in organic solvents, the material immediately dissolved – like candy floss submerged in Water, Cho says – with each part of the battery falling away for easier recycling. “The electrolyte holds the two battery electrodes together and provides the lithium-ion pathways,” Cho says. “So, when you want to recycle the battery, the entire electrolyte layer can fall off naturally and you can recycle the electrodes separately.”
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