Research priorities for next-generation batteries -Lithium - Ion Battery Equipment
Keeping track of the latest scientific literature is an important part of a scientist's job, from which scientists can generate insights that may translate into major advances in the future.
This figure shows the aggregates of the battery electrolyte. (Image courtesy of Argonne National Laboratory)
In 2018, Lei Cheng, a battery chemist at the U.S. Department of Energy's (DOE) Argonne National Laboratory, stumbled across some studies on battery electrolytes that described the existence of nanoaggregate structures. These are clusters of tens to hundreds of charged particles, called ions, with an overall diameter greater than one nanometer. Until now, most battery electrolyte research has focused on smaller structures.(Lithium - Ion Battery Equipment)
"An important goal of the research is to find when aggregates are beneficial and when they are not," said Larry Curtiss, a senior chemist at Argonne and Distinguished Scholar. "When aggregates are adversely affected, they are eliminated from the electrolyte." "
An electrolyte is a chemical solution that plays an important role in battery operation. The electrolyte contains positive charged ions that can move back and forth between the positive and negative electrodes of the battery.
Cheng is the technical lead at the Joint Energy Storage Research Center (JCESR), an Energy Innovation Hub, initiated by the Department of Energy and led by Argonne. The Joint Energy Storage Research Center brings together more than 150 researchers from 20 institutions, including national laboratories, universities and companies, to design and manufacture the materials that will enable the next generation of batteries. Such batteries help enable significant energy conversions in cars, power grids and even electric aircraft.
Cheng and several other JCESR researchers agreed that aggregates deserve further study. After all, the research team is fully aware that the structure of an electrolyte can significantly affect its properties and ultimately play a large role in the performance of the battery. For example, in order to develop better lithium batteries, researchers have found that adding small amounts of salt can make them more stable.
"Aggregates are not a big problem," Cheng said. "Scientists don't talk too much about how to affect the properties of the electrolyte. That's why we decided to start a research project to investigate further."
From 2018 to 2021, researchers at the research center have accumulated enough research results that aggregates are a very important emerging topic with a potentially significant impact on the performance of next-generation batteries. To alert the battery science community, the researchers published a survey and analysis of aggregate studies in American Chemical Society's Energy Letters. The article brings together the results of 60 studies by researchers at the research center and other scientists.
Effects on Electrolyte Properties
This article explores how aggregates have unique effects on electrolyte properties, including stability and ion transport.
Stability affects many key aspects of battery performance. These include lifetime (number of charge-discharge cycles), safety, energy density, and charge-discharge rate. For example, unstable electrolytes are easily decomposed. This may shorten battery life and lead to safety issues.
Ion transport refers to the speed at which ions move through an electrolyte. This characteristic can affect the charge-discharge rate of the battery. Fast ion transport could allow electric vehicles to charge more quickly, while also allowing grid-scale batteries to discharge more quickly. Another potential benefit is to improve the performance of electrolytes made from macromolecular polymers. This electrolyte is safer than liquid electrolytes.
Aggregates of electrolytes may have beneficial or detrimental effects on battery performance. Therefore, aggregates may slow or accelerate ion transport.
"An important goal of research is to find out when aggregates are beneficial and when they are not," said Larry Curtiss, an experienced Argonne chemist and one of the authors of the article. When adverse effects occur, it should probably be removed from the electrolyte."
One known beneficial effect of aggregates occurs in lithium-oxygen batteries. The new generation of batteries works by delivering oxygen to the cathode through the electrolyte. The aggregates react with lithium to form lithium peroxide. Lithium-oxygen batteries have a higher energy density than lithium-ion batteries and have the potential to be used for long-distance trucking and transportation.