Scientists find that fluorine may replace lithium for rechargeable batteries

With the increasing use of rechargeable batteries in modern technology (especially electric vehicles), researchers have been looking for alternative materials for lithium-ion for use in rechargeable batteries. According to foreign media reports, materials scientists at the McKelvey School of Engineering at Washington University in St. Louis have discovered a potential lithium substitute in fluorine. Fluorine is a relatively abundant light element.


What’s interesting is that fluoride ions are the opposite of lithium ions. They have the strongest attraction to electrons and are prone to electrochemical reactions. Researchers in Japan are also conducting tests to use fluorine-ion batteries as a possible alternative to lithium-ion batteries in automobiles. According to reports, using these batteries can make electric vehicles run 1,000 kilometers on a single charge. However, the cycle performance of the existing fluoride ion battery is poor, and it tends to be rapidly degraded after a charge-discharge cycle process.

Researchers Steven Hartman and Rohan Mishra adopted a new method to design fluoride ion batteries. They found that the two materials are easy to gain or lose fluoride ions, while achieving good circulation and little structural changes. Mishra, an assistant professor in the Department of Mechanical Engineering and Materials Science, said that these new battery materials are all layered Electronic compounds.

The electronic compound is a relatively new material that can conduct electrons like ordinary metals, but is different from the “electron sea” in metals (the electrons in the metal are dispersed throughout the crystal). In the electronic compound, the electrons reside in The specific gap position in the crystal structure is somewhat similar to an ion. Mishra said: “According to our prediction, fluoride ions can easily replace these interstitial electrons without causing significant deformation of the crystal structure, thereby achieving recyclability. In addition, due to the relatively open structure of layered electronic compounds, fluoride ions Can easily move or spread.”

Hartman, an alumnus of the School of Materials Science and Engineering, used quantum mechanics calculations to test dozens of potential battery candidates. Through computerized testing, fluoride is introduced into the gap between the layered electronic compounds calcium dicalcium nitride and yttrium carbide to make its energy storage capacity close to that of lithium ion batteries. Take dicalcium nitride as an example, which is composed of relatively abundant elements and helps overcome the current shortage of lithium-ion batteries.

The Hartman and Mishra teams compared each other’s research work. The latter used machine learning “big data” technology to filter thousands of candidates. Hartman said: “In principle, you can increase the charge storage by adding a large amount of fluoride ions to the conventional electrode. However, in fact, these theoretical capacities are difficult to control. When we add fluoride to the conventional electrode, they will charge and discharge. It expands and contracts rapidly at times, which may cause rupture and loss of electrical contact.”

For the manufacture of durable fluoride batteries, minimizing volume and shape changes is essential. Hartman said: “According to our speculation, in the layered electronic compound material, the addition and removal of fluoride ions can cause significantly smaller structural changes in the structure, which helps to extend the cycle life.”

Mishra’s laboratory is seeking to collaborate with other researchers to synthesize the electronic compounds found in this study and test them in prototype batteries.

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