While my previous article on flexible Lithium-ion batteries focused on wearables as a driving force in flexible battery development, this article is focused on a new type of flexible Lithium-ion battery technology being developed at the Georgia Institute of Technology that aims to help relieve the dependency current Lithium-ion batteries have on nickel and cobalt, two metals that are becoming more volatile in the world’s markets. I previously published an article that details why those metals are becoming more scarce every year, and I highly recommend reading it before continuing on with this one.


Gleb Yushin, a professor in Georgia Tech’s School of Materials Science and Engineering and Kostiantyn Turcheniuk, research scientist in Yushin’s lab, inspect a battery using a new cathode design that replaces expensive metals and traditional liquid electrolyte with lower-cost transition metal fluorides and a solid polymer electrolyte. (Credit: Allison Carter)


“Electrodes made from transition metal fluorides have long shown stability problems and rapid failure, leading to significant skepticism about their ability to be used in next-generation batteries,” said Gleb Yushin, a professor in Georgia Tech’s School of Materials Science and Engineering. “But we’ve shown that when used with a solid polymer electrolyte, the metal fluorides show remarkable stability – even at higher temperatures – which could eventually lead to safer, lighter and cheaper lithium-ion batteries.”


The team at Georgia Tech developed a new type of cathode using an iron fluoride active material and a solid polymer electrolyte nanocomposite. This is significant because iron fluorides more than double the energy storage capacity of nickel or cobalt-based cathodes. An added bonus is that iron is more than 150 times cheaper than nickel, and over 300 times cheaper than cobalt.


“Cathodes made from iron fluoride have enormous potential because of their high capacity, low material costs and the very broad availability of iron,” Yushin said. “But the volume changes during cycling as well as parasitic side reactions with liquid electrolytes and other degradation issues have limited their use previously. Using a solid electrolyte with elastic properties solves many of these problems.”


The new design is based on a prefabricated iron fluoride electrode that is filled with a solid polymer electrolyte and then heated and pressed to increase its density as well as to remove any remaining air pockets. The benefit of using a solid polymer electrolyte is its ability to flex and move as the iron fluoride swells and shrinks during cycling, an issue that has plagued iron fluoride-based lithium-ion designs in the past.


After testing several different designs using this new concept, researchers analyzed the data of more than 300 high-temperature charging cycles per battery and discovered that this new solid-polymer electrolyte design was far superior to previous iron fluorite lithium-ion battery designs.  The culprit in the previous designed was thought to be that the metallic ions migrated to the surface of the cathode and eventually dissolved into the liquid electrolyte, causing a capacity loss, particularly at elevated temperatures as low as 100 degrees Fahrenheit. The new design was stable at a steady temperature of 122 degrees Fahrenheit throughout the testing.


A lithium-ion battery is shown using a promising new cathode and electrolyte system that replaces expensive metals and traditional liquid electrolyte with lower-cost transition metal fluorides and a solid polymer electrolyte.
(Photo Credit: Allison Carter)


“The polymer electrolyte we used was very common, but many other solid electrolytes and other battery or electrode architectures – such as core-shell particle morphologies – should be able to similarly dramatically mitigate or even fully prevent parasitic side reactions and attain stable performance characteristics,” said Kostiantyn Turcheniuk, research scientist in Yushin’s lab and a co-author of the manuscript.


While the flexible lithium-ion battery design I wrote about previously is revolutionary for its improvement in making this technology more environmentally friendly, this design has a serious advantage in both cost improvement and increased capacity. Doubling the capacity of current lithium-ion batteries will have a major impact on everything from smartphones to spaceships, and everything in between. It’s going to take major leaps in cost performance and storage capacity to fule the switch to renewable energy, and being able to replace our dependence on nickel and cobalt are huge steps in that direction.



Source: https://www.news.gatech.edu/2019/09/09/stretchy-plastic-electrolytes-could-enable-new-lithium-ion-battery-design