Organic, metal

One of the problems with our ongoing shift toward renewable energy relates to the way we store it, with today's metal-laden lithium batteries currently serving us well but carrying sustainability issues of their own. Scientists are investigating alternative, more eco-friendly chemistries, and a team at Texas A&M University has just put forward an interesting candidate, demonstrating a metal-free battery that can be placed in acidic solutions to degrade on demand.

The increasing demand for electronic devices and electric vehicles means an increasing demand for lithium-ion batteries, which rely on heavy metals that aren't so easily sourced. Cobalt, for example, is plagued with ethical issues around mining practices involving child labor in Africa, as well as environmental degradation and the pollution of water supplies. Furthermore, it is difficult to separate and recover these materials at the end of the battery's life.

“The big problem with lithium-ion batteries right now is that they're not recycled to the degree that we are going to need for the future electrified transportation economy,” says Dr. Jodie Lutkenhaus, study author. “The rate of recycling lithium-ion batteries right now is in the single digits. There is valuable material in the lithium-ion battery, but it's very difficult and energy intensive to recover.”

These problems have driven researchers like Lutkenhaus to investigate metal-free battery architectures, with a saltwater prototype battery developed by IBM one notable example. The Texas A&M University scientists instead used electrochemically active chains of amino acids, called redox active polypeptides, to build the battery's two electrodes, which pass energy back and forth as the device is charged and discharged.

In testing, the organic battery ticked a couple of important boxes. First and foremost, these electrodes performed their role as active materials during operation, remaining stable throughout. And afterwards, the components were able to be degraded by subjecting them to acidic conditions, which left amino acids and other benign degradation products as a result, to be re-used or left to dissolve harmlessly in the environment.

“By moving away from lithium and working with these polypeptides, which are components of proteins, it really takes us into this realm of not only avoiding the need for mining precious metals, but opening opportunities to power wearable or implantable electronic devices and also to easily recycle the new batteries,” says study author Dr. Karen Wooley. “They [polypeptide batteries] are degradable, they are recyclable, they are non-toxic and they are safer across the board.”

While early days for the research, the scientists see it as a promising first step in the development of sustainable batteries, and they're now looking to improve the design further with the help of machine learning.

The research was published in the journal Nature.

Source: Texas A&M University

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