October 28, 2020
Elements of the Future
Researchers investigate the foundations and applications of forgotten elements in energy storage.
The development of powerful lithium-ion batteries was a blessing, but they also contribute to significant problems in many parts of the world. Questionable sourcing and economic bottlenecks in the supply of the elements they contain, as well as ever-growing demands for energy storage, require new research and ideas for how to innovate the design of batteries. Stefan Freunberger at the Institute of Science and Technology Austria (IST Austria) is now tackling these questions.
Batteries are crucial to our world of modern electronics, but they are in trouble. Several factors complicate their future production and use, especially of the widely used lithium-ion batteries. You can find this kind of batteries in any mobile phone, laptop, and electric car, but their parts bring up some economic, technical, and ethical difficulties. The newly established research group of Stefan Freunberger at the Institute of Science and Technology Austria (IST Austria) is now addressing these problems with basic research in electrochemistry.
But first of all, how does such a battery work? In its most simple form, a battery consists of a container filled with a solution where ions can move—the electrolyte—in which two separate pieces of electrochemically active material such as metals are inserted, called anode and cathode. When these pieces are connected via a wire in an external electric circuit, for example your phone, the battery provides electricity. This happens because the material in the anode is oxidized releasing positively charged metal ions into the electrolyte, where they can move to the other electrode, the cathode. In turn, negatively charged electrons flow as current through the external circuit to the cathode. There, they recombine with the positively charged ions that travelled through the electrolyte. More generally, a battery is a combination of electrode materials, where negative or positive ions that are mobile in the electrolyte are absorbed or released at different electric potentials–creating the cell voltage.
Collecting Free Electrons
Nowadays, the lithium-ion batteries in our devices contain the elements lithium, cobalt, and nickel in various chemical compounds. Their development provided an enormous increase in energy density compared to the classic zinc and manganese batteries, the cylinders you put into the remote of your TV. But increasing global demand for batteries, especially for electric vehicles, calls for new innovations in their construction. A key problem of lithium-ion batteries is that they rely on scarce, toxic, and heavy elements from the group of the so-called transition metals such as cobalt. Moreover, they only release at most one electron per atom, which limits the achievable energy density. Researchers are, therefore, looking into many different combinations of chemical compounds and how they interact with each other.
The approach of Stefan Freunberger and his group at IST Austria is to use compounds composed of so-called main group elements such as oxygen, nitrogen, sulfur, phosphorous, carbon, or iodine. Next to being highly abundant, cheap, and light, they also may absorb or release multiple electrons per atom. This way, more electrons in the battery are freed to flow through the external wire, and thus, more energy can be stored.
This year, the researchers started to investigate phosphorous as a promising candidate to improve batteries. In their laboratory, they are studying how to make phosphorous atoms accept up to five electrons. Similarly to releasing electrons, accepting more of them at the cathode also increases the provided current. Previously, applications had each atom accept only up to three electrons. In another study they analyze the use of sulfur, which can release even up to eight electrons per atom.
Another innovation is a new way of structuring the internal parts of the battery. In a newly published paper in Nature Communications co-authored by Stefan Freunberger, the researchers discuss how carbon with tiny pores of a few nanometers (a billionth of a meter) can slow down self-discharging in iodine batteries. The iodine is deposited in the pores and therefore retains the desired chemical qualities.
In order to make these chemical reactions work as intended, many individual steps have to be investigated. The researchers have to find the right elements and molecular compounds as well as specific catalysts—other chemicals enabling the reactions. This research will continue in the new chemical laboratories of IST Austria’s most recent building, Lab 5, which is currently under construction and will be opened in 2021.
Searching for Sustainable Atoms
Stefan Freunberger cites his concerns about sustainability as a motivation for his research: “For me, both the study of the foundations of electrochemistry as well as the possible development of an application are interesting, especially if they help to establish more sustainable products.”
The transition to sustainable energy sources requires more and stronger batteries for various electric vehicles, but also for stationary electric storage facilities at home or on industrial scales. The number of available lithium deposits in the world would not restrict the production of lithium-ion batteries. Still, their concentration in a few areas—mainly South America, Australia, and China—may pose economic difficulties for a steadily increasing demand in the future.
Cobalt deposits are even more concentrated, mostly in the Democratic Republic of Congo (DRC). Similarly to lithium, the production of this element suffers not only from economic but also massive environmental and ethical problems. The DRC produces more than half of the world’s cobalt supply, often in artisanal non-industrialized mines with dire employment and safety standards, some even using child labor.
Both the production of cobalt and lithium, among other elements, also causes enormous environmental harm by pollution through chemicals and waste, as well as by claiming major parts of the local water supply for their industrial processes. Switching out cobalt and lithium for more abundant elements like phosphorous or sulfur could not only bolster the energy stored in the batteries but also decrease the economic incentives for exploitative and harmful practices.
After studying chemistry in Vienna, Zurich, and Canada, Stefan Freunberger worked as a scientist in the UK and France and became a group leader at the Technical University Graz. At IST Austria, he will continue his research on the foundations of electrochemistry in batteries and other applications such as electrosynthesis. The innovations investigated by him and his group could lay the foundations for a more sustainable energy system and an environmentally friendly production.