Stretchy plastic electrolytes could enable new lithium-ion battery design

September 09, 2019

The growing popularity of lithium-ion batteries in recent years has put a strain on the world's supply of cobalt and nickel - two metals integral to current battery designs - and sent prices surging.

In a bid to develop alternative designs for lithium-based batteries with less reliance on those scarce metals, researchers at the Georgia Institute of Technology have developed 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.

"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."

In a typical lithium-ion battery, energy is released during the transfer of lithium ions between two electrodes - an anode and a cathode, with a cathode typically comprising lithium and transition metals such as cobalt, nickel and manganese. The ions flow between the electrodes through a liquid electrolyte.

For the study, which was published Sept. 9 in the journal Nature Materials and sponsored by the Army Research Office, the research team fabricated a new type of cathode from iron fluoride active material and a solid polymer electrolyte nanocomposite. Iron fluorides have more than double the lithium capacity of traditional cobalt- or nickel-based cathodes. In addition, iron is 300 times cheaper than cobalt and 150 times cheaper than nickel.

To produce such a cathode, the researchers developed a process to infiltrate a solid polymer electrolyte into the prefabricated iron fluoride electrode. They then hot pressed the entire structure to increase density and reduce any voids.

Two central features of the polymer-based electrolyte are its ability to flex and accommodate the swelling of the iron fluoride while cycling and its ability to form a very stable and flexible interphase with iron fluoride. Traditionally, that swelling and massive side reactions have been key problems with using iron fluoride in previous battery designs.

"Cathodes made from iron fluoride have enormous potential because of their high capacity, low material costs and 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 researchers then tested several variations of the new solid-state batteries to analyze their performance over more than 300 cycles of charging and discharging at elevated temperature of 122 degrees Fahrenheit, noting that they outperformed previous designs using metal fluoride even when these were kept cool at room temperatures.

The researchers found that the key to the enhanced battery performance was the solid polymer electrolyte. In previous attempts to use metal fluorides, it was believed that metallic ions migrated to the surface of the cathode and eventually dissolved into the liquid electrolyte, causing a capacity loss, particularly at elevated temperatures. In addition, metal fluorides catalyzed massive decomposition of liquid electrolytes when cells were operating above 100 degrees Fahrenheit. However, at the connection between the solid electrolyte and the cathode, such dissolving doesn't take place and the solid electrolyte remains remarkably stable, preventing such degradations, the researchers wrote.

"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.

In the future, the researchers aim to develop new and improved solid electrolytes to enable fast charging and also to combine solid and liquid electrolytes in new designs that are fully compatible with conventional cell manufacturing technologies employed in large battery factories.
-end-
This material is based upon work supported by the Army Research Office under Grant No. W911NF-17-1-0053. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors.

CITATION: Qiao Huang, Kostiantyn Turcheniuk, Xiaolei Ren, Alexandre Magasinski, Ah-Young Song, Yiran Xiao, Doyoub Kim, and Gleb Yushin, "Cycle Stability of Conversion-Type Iron Fluoride Lithium Battery Cathode at Elevated Temperatures in Polymer Electrolyte Composites," (Nature Materials, Sept. 2019). https://doi.org/10.1038/s41563-019-0472-7

Georgia Institute of Technology

Related Lithium Articles from Brightsurf:

Preventing lithium loss for high-capacity lithium-ion batteries
A team of Korean researchers has developed a processing technology for maximizing energy densities of high-capacity batteries.

Using Jenga to explain lithium-ion batteries
Tower block games such as Jenga can be used to explain to schoolchildren how lithium-ion batteries work, meeting an educational need to better understand a power source that has become vital to everyday life.

Powering the future with revolutionary lithium extraction technique
An international research team, led by Australia's Monash University, has pioneered and patented a new filtration technique that could one day slash lithium extraction times and change the way the future is powered.

New lithium batteries from used cell phones
Research from the University of Cordoba (Spain) and San Luis University (Argentina) was able to reuse graphite from cell phones to manufacture environmentally friendly batteries.

Using neutrons and X-rays to analyze the aging of lithium batteries
An international team has used neutron and X-ray tomography to investigate the dynamic processes that lead to capacity degradation at the electrodes in lithium batteries.

Can lithium halt progression of Alzheimer's disease?
In a new study, a team of researchers at McGill University has shown that, when given in a formulation that facilitates passage to the brain, lithium in doses up to 400 times lower than what is currently being prescribed for mood disorders is capable of both halting signs of advanced Alzheimer's pathology and of recovering lost cognitive abilities.

MTU engineers examine lithium battery defects
Lithium dendrites cause poor performance and even explosions in batteries with flammable liquid electrolytes.

New technology for pre-replenishing lithium for lithium ion supercapacitors
Li3N containing electrode is prepared by a commercially adoptable route, using DMF to homogenate the electrode slurry.

Towards new lithium-ion batteries that are safer and more efficient
Researchers have studied 2 types of cathodes that are very similar in their composition, but which show completely different behavior: one of them suffers from the known loss of energy density in the first charge cycle, while the other does not.

Post-lithium technology
Next-generation batteries will probably see the replacement of lithium ions by more abundant and environmentally benign alkali metal or multivalent ions.

Read More: Lithium News and Lithium Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.