“Lithium-ion batteries are everywhere! They power cell phones, laptops, cameras, cars, and pacemakers. In the future, these devices may store energy from renewable resources like solar and wind to help provide reliable green energy. From the outside, a lithium-ion battery often simply looks like a little (black) box but the inside is full of chemical reactions.

Most present applications use a compound called LiCoO 2 as the cathode or positive electrode and graphite, like that found in pencils, as the anode or negative electrode. In addition to these solid electrodes, most batteries contain a liquid electrolyte, which allows lithium-ions to flow between the electrodes. To make this solution, a lithium salt like Li+[PF 6 ]– is dissolved in an organic liquid—usually a combination of the molecules ethylene carbonate and dimethyl carbonate are used. When you use a device, you discharge the battery and both electrons and lithium-ions flow from the negative electrode to the positive electrode; the electrons go through a circuit to do work for you while the lithium-ions go through the electrolyte to balance the charge of the electrons. This is a chemical reaction!

2Li 0.5 CoO 2 + LiC 6 ↔ 2LiCoO 2 + C 6 (graphite)

When you charge up your device from the outlet or collect energy from the sun or wind, the reaction goes backwards. In addition to this reaction, a lot more chemistry can occur inside the battery. These “side reactions” are the reason that your phone battery doesn’t last as long after a year as it did when new. For example, the electrodes and electrolyte might react to form compounds such as LiF, polymers, and gases like CO 2 or H 2 .

Lithium cobalt oxide (LiCoO 2 ) and graphite are not the only materials that will store lithium ions and provide energy. In my work, I am interested in discovering new compounds that can take in and give out Li+ much more rapidly. Oxides with metals like titanium (TiO 2 ) and niobium (Nb 2 O 5 ) and mixtures (TiNb 2 O 7 ) are able to charge and discharge in as little as one minute in contrast to several hours for conventional materials. This means that new applications can arise with fast charging and/or high power capabilities. Other new battery materials like silicon (the main element of beach sand) or phosphorus (plentiful in soil) can store a lot more energy for their size and thus might lead to batteries that can last longer without needing a charge. Finally, we could replace the Li+ with Na+, which is cheap and easy to find in the form of salt (NaCl). Sodium-ion batteries use the same principles as their lithium analogues and could be much cheaper, which would be great for storing renewable energy, but they require new electrode materials. My research into these new battery areas—fast charging/high power, long lasting, and cheap (Na+)—involves understanding all these new chemistries and the side reactions that are associated with each type. This is all with the goal of improving battery technology to enable these truly transformative chemical devices to reach new applications for humanity!”

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References & Further Reading