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Lithium-ion batteries might be the go-to technology today, but the next generation of energy storage devices — which has the potential to be safer and last longer — might be here sooner than you think.
Battery innovations are needed to enable a renewable electricity grid and to decarbonize heavy-duty transportation, like long-haul trucking, marine shipping and aviation. Among those leading the innovation charge is the Joint Center for Energy Storage Research (JCESR), a U.S. Department of Energy (DOE) Innovation Hub led by DOE’s Argonne National Laboratory.
Since 2013, JCESR researchers have invented a wide and diverse range of technologies in the “beyond lithium-ion” space. The primary focus has been on flow, lithium-sulfur, multivalent and solid-state batteries, and has yielded more than 30 patents that are now available for licensing.
“The portfolio of intellectual property we’ve developed illustrates our fundamental understanding of how to build, from the atomic level up, molecules that interact and create stable, functioning battery materials,” said Argonne materials engineer and JCESR researcher, Brian Ingram.
Why beyond lithium technologies are needed
All batteries include three key parts: an anode, the negative side of the battery; a cathode, the positive side of the battery; and an electrolyte, a chemical material that allows the flow of current or charge between the anode and cathode.
In the case of lithium-ion, when the battery is turned on, chemical reactions occur that cause negatively charged particles known as electrons and positively charged particles of lithium, known as lithium ions, to be released. The lithium ions move through the electrolyte to get from the anode to cathode. Meanwhile, electrons from the anode pass through a separate circuit to get to the cathode, and their movement creates an electric current that powers devices. When these batteries are recharged, the ions and electrons are pushed back to the anode, ready to start the cycle all over again.
Though highly useful, lithium-ion batteries have some drawbacks. They require extra physical protection to maintain safe operations, are costly to produce and have limits to how long they can last. Research on next generation batteries focuses on creating new designs and materials that can overcome these limitations and expand uses for batteries.
Redox flow batteries
Particularly in the electric grid space, redox flow batteries are considered a valuable beyond lithium-ion technology. Compared to lithium-ion batteries, which are able to deliver lots of energy over a short period of time, flow batteries are better suited to deliver lower amounts of energy over longer durations.
Research from JCESR has revealed ways to make flow batteries even more energy dense and efficient than they are today. Within their intellectual property are patents that address some of the limitations in existing flow batteries and non-aqueous flow batteries, an emerging technology.
Multivalent-ion battery technologies
Batteries with multivalent metals are another emerging technology researchers are JCESR are exploring. Relative to lithium, which can have only a single charge, multivalent metals can realize a higher charge density.
Anodes made from multivalent metals, like magnesium and calcium, have the potential to match and even surpass the energy density of lithium and typically are more abundant, which could make them cheaper and more sustainable to engineer. But to advance their development, researchers still have a range of scientific challenges to overcome. JCESR’s intellectual property, in particular, addresses challenges associated with making a stable electrolyte that works in a multivalent battery, which is needed to maintain performance over time.
“The electrolytes that have existed within this space are stable only under a very narrow scope of conditions. With JCESR, we’ve done a lot to expand that stability range,” said Ingram.
In transportation, lithium-sulfur (Li-S) batteries, another beyond lithium-ion technology, have shown great potential. Due to their chemistry and the fact that sulfur is cheap and more abundant than other commonly used cathode materials (such as cobalt, nickel and manganese), Li-S batteries could store more energy at a cost lower than conventional lithium-ion technologies. However, today, when a Li-S battery is discharged, unintended reactions can occur that cause materials known as polysulfides to accumulate in the battery, which can shorten its cycle life.
JCESR scientists have developed materials and processes to address this and other challenges limiting the development of Li-S technologies. Their intellectual property includes patents for binding materials to prevent polysulfide material from diffusing throughout the battery, as well as for making cathodes made of sulfur.
“How sulfur is spread out within the cathode is extremely important. You want the sulfur particles not to be in big chunks but rather smaller pieces so that you can have more interfaces where reactions can happen,” said Lei Cheng, Argonne chemist and JCESR researcher. “In our patent we’ve put forward a process for making the sulfur in a way that maximizes the number of interfaces or active sites in the material.”
Solid-state and lithium metal batteries
Amid the push to extend the life of electric vehicles, scientists around the world are also studying solid-state batteries. These batteries use solid electrolytes, which are nonflammable, in place of the flammable liquid electrolytes found in conventional batteries.
By replacing the liquid electrolyte, solid-state batteries are more stable and thus potentially safer. One type in particular — solid-state lithium metal batteries — have been found to have a high energy density and the potential to offer more range, and faster charging compared to the lithium-ion batteries found in vehicles today.
Despite their potential, these batteries tend to form long, branching needles of lithium, called dendrites, which limit battery life span and safety. Among their intellectual property, JCESR researchers have a patented coating for their anodes that can suppress the formation of dendrites. Additionally, they’ve developed novel processes and battery designs for enhancing their efficiency and extending their life cycle. Collectively, this and their other work in the “beyond lithium-ion” space illustrate the exciting opportunities that are here now to improve energy storage for decades to come.