There’s no arguing that batteries are an essential element of today’s electronics landscape. Without them our mobile devices would be a lot less mobile and we might still be crank starting our cars. The explosion in mobile electronic devices enabled by batteries and miniaturization has a major downside in the form of discarded batteries, the majority of which contain toxic heavy metals. Chemists have now discovered a new way to pass electrons back and forth between two molecules that could see the development of organic batteries that are lightweight and work without the need for toxic heavy metals.
Batteries consist of electrochemical cells that store energy in the form of chemical energy, which is converted into electrical energy when connected to an electrical circuit in which an electrical current can flow. When molecules meet, they often form new compounds by exchanging electrons. In some cases, the electron transfer process creates one molecule with a positive charge and one molecule with a negative charge. Molecules with opposite charges are attracted to each other and can combine to form something new.
In their research, University of Texas at Austin chemists Christopher Bielawski and Jonathan Sessler created two molecules that could meet and exchange electrons but not unite to form a new compound.
Pull-push molecules"These molecules were effectively spring-loaded to push apart after interacting with each other," says Bielawski, professor of chemistry. "After electron transfer occurs, two positively charged molecules are formed which are repelled by each other, much like magnets held in a certain way will repel each other. We also installed a chemical switch that allowed the electron transfer process to proceed in the opposite direction."
Sessler adds, "This is the first time that the forward and backward switching of electron flow has been accomplished via a switching process at the molecular scale." Sessler is the Roland K. Pettit Centennial Chair in Chemistry at The University of Texas at Austin and a visiting professor at Yonsei University.
Bielawski says this system gives important clues for making an efficient organic battery. He says understanding the electron transfer processes in these molecules provides a way to design organic materials for storing electrical energy that could then be retrieved for later use.
Organic batteriesOrganic batteries made from organic materials instead of heavy metals could be lightweight, could be molded into any shape, have the potential to store more energy than conventional batteries, be safer and cheaper to produce and more environmentally friendly when being disposed of.
"I would love it if my iPhone was thinner and lighter, and the battery lasted a month or even a week instead of a day," says Bielawski. "With an organic battery, it may be possible. We are now starting to get a handle on the fundamental chemistry needed to make this dream a commercial reality."
Additionally, the molecular switch could also be a step toward developing a technology that mimics plants' ability to harvest light and convert it to energy through photosynthesis. With such a technology, fuel could be produced directly from the sun, rather than through a plant mediator, such as corn.
"I am excited about the prospect of coupling this kind of electron transfer 'molecular switch' with light harvesting to go after what might be an improved artificial photosynthetic device," says Sessler. "Realizing this dream would represent a big step forward for science."