At Carnegie Mellon University’s Mellon College of Science and College of Engineering, researchers have created a novel semiliquid lithium metal-based anode that signifies a new example in battery design.
Lithium batteries developed with this new kind of electrode would be relatively safer and also have a higher capacity when compared to standard lithium metal-based batteries that generally utilize lithium foil as an anode. The interdisciplinary group of researchers reported their findings in the latest issue of Joule.
One of the most standard types of rechargeable batteries used in contemporary electronics are lithium-based batteries, because of their potential for storing high amounts of energy. Conventionally, such batteries include combustible liquid electrolytes as well as a pair of electrodes—a cathode and an anode—which are isolated by a membrane.
Repeated charging and discharging of a battery causes strands of lithium known as dendrites to grow on the electrode’s surface. The dendrites can penetrate via the membrane separating the two electrodes. This promotes contact between the cathode and anode, which can lead to short circuits in the battery and, in the worst-case scenario, cause a fire.
Incorporating a metallic lithium anode into lithium-ion batteries has the theoretical potential to create a battery with much more capacity than a battery with a graphite anode. But, the most important thing we need to do is make sure that the battery we create is safe.
Krzysztof Matyjaszewski, J.C. Warner University Professor of Natural Sciences, Department of Chemistry, Carnegie Mellon University
One recommended solution is to replace the volatile liquid electrolytes utilized in existing batteries with solid ceramic electrolytes. Such electrolytes are non-combustible, highly conductive¸ and sufficiently strong to resist dendrites.
Conversely, scientists have noted that the contact between a solid lithium anode and the ceramic electrolyte is not enough for storing and delivering the amount of power required for a majority of electronics.
Han Wang, a doctoral student in the Department of Materials Science and Engineering at Carnegie Mellon University, and Sipei Li, a doctoral student in the Department of Chemistry at Carnegie Mellon University were able to overcome this problem by developing a novel class of material that can be utilized as a semiliquid metal anode.
Wang and Li worked with Jay Whitacre, Trustee Professor in Energy in the College of Engineering and director of the Wilton E. Scott Institute for Energy Innovation at Carnegie Mellon, who is known for his work in creating innovative technologies for storage and generation of energy, and Matyjaszewski, a leader in polymer chemistry and materials science at Mellon College of Science, and ultimately developed a dual-conductive polymer/carbon composite matrix in which lithium microparticles were uniformly distributed throughout.
At room temperatures, the matrix continues to be flowable and this enables it to promote an adequate level of contact with the solid electrolyte. When the researchers integrated the semiliquid metal anode with a garnet-based solid ceramic electrolyte, they found that they can cycle the cell at 10x higher current density when compared to cells containing a conventional lithium foil anode and a solid electrolyte. In addition, this cell was noted to have a relatively longer cycle-life when compared to conventional cells.
This new processing route leads to a lithium metal-based battery anode that is flowable and has very appealing safety and performance compared to ordinary lithium metal. Implementing new material like this could lead to step change in lithium-based rechargeable batteries, and we are working hard to see how this works in a range of battery architectures.
Jay Whitacre, Trustee Professor in Energy, College of Engineering, Carnegie Mellon University
According to the researchers, their approach could have major implications. For instance, it can be used for producing specialized batteries for application in wearable devices that demand flexible batteries and for creating high-capacity batteries for electric vehicles.
The investigators also believe that in addition to lithium, their techniques could also be extended to other rechargeable battery systems, such as potassium metal batteries and sodium metal batteries and could be utilized in grid-scale energy storage.
The National Science Foundation (1501324) and the National Institutes of Health (021533) funded the study. Additional study authors include Tong Liu and Julia Cuthbert from the Department of Chemistry at Carnegie Mellon University.