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While the idea of electric vehicles might sound appealing, the idea of your electric vehicle’s battery combusting probably does not. As society shifts towards greener technology, many scientists and companies have looked into the potential of electric vehicles to reduce air pollution. However, society has been unable to integrate electric vehicles into daily life for various reasons. One major obstacle that scientists have been working to overcome is the lack of electric vehicle batteries that are both stable and easily produced.
Electron flow in batteries is facilitated through two electrodes, metal electrical conductors connected by a wire to form a circuit. These electrodes react with a surrounding electrolyte solution. As electrons flow through the circuit, the electrolyte offers a medium for positive ions to flow through, thus balancing the movement of electrons that is simultaneously occurring. An electrolyte has a high ionic conductivity if it allows for a high electron flow. The most conventional lithium batteries rely on organic liquid electrolytes—solutions made of organic elements. However, these easily catch on fire, making them unsuitable for extensive consumer use. The only current alternative, stabler solid-inorganic electrolytes, are also unsuitable candidates for consumer use due to their complicated manufacturing processes.
Georgia Tech’s Professor Seung Woo Lee and Michael Lee have been working to find a solution to this. Earlier this year, they published an article highlighting a new material as a candidate for batteries. “Rubber electrolytes are safer due to their flame retardancy, and the synthesis methods of rubber electrolytes is…highly possible to be adapted to the current roll-to-roll manufacturing process of battery production,” Michael Lee said.
So, what exactly is a rubber electrolyte? Seung Woo Lee’s rubber electrolyte uses lithium salt, a cross-linked elastomer (a polymer with elastic properties), and plastic crystals. No one thought rubber, a famous insulator, would make for a good battery electrolyte, not even Seung Woo Lee and Michael Lee. “We were actually not working on the lithium metal battery at first. It was a breakthrough that we tried to do the lithium metal batteries in the lab,” Michael Lee said. For him, coming up with the experimental design was the difficult part, while the subsequent experiments were relatively easy to execute.
The researchers use their materials to create a 3D structure with “a high ionic conductivity at room temperature (portion of plastic crystal) and great mechanical stability (portion of elastomer ),” Michael Lee said. This special 3D structure, which they refer to as a 3D interconnected plastic crystal phase, addresses the previous issue for rubber electrolytes in batteries: weak ionic conductivity. Furthermore, rubber’s elastic properties offer it increased adaptability compared to solid electrolytes.
Although the feasibility of large-scale rubber electrolyte production needs to be investigated further, Seung Woo Lee’s rubber electrolyte is promising for commercialization due to its relatively stable nature and the cheap cost of materials. “The ongoing research is basically [going in] two directions: one is to understand the 3D structures… all of the properties actually depend on the 3D structure. Trying to understand the structure and manipulate the structure is the first direction. The second direction is to scale up,” said Seung Woo Lee. If proven easy to manufacture, these batteries could revolutionize not only electric vehicles, but also countless other products.