Foreign media reported that a joint research team led by professors Nam soon Choi and sang kyu Kwak of the school of energy and chemical engineering of the National Academy of science and technology in Ulsan, South Korea, developed an ion concentrated electrolyte using fluorine-containing atomic solvents.

The electrolyte can uniformly form a protective film on the positive and negative electrodes of the lithium metal battery, prolong the service life of the battery and increase its energy output.

(image source: greenarchongress.com)

Lithium metal anode and high nickel anode with high reversible capacity are considered to be one of the best material systems for manufacturing high energy density batteries. However, the low first effect Coulomb of lithium metal anode, the generation of lithium dendrites and the unstable performance of high nickel cathode hinder the practical application of these electrodes.

When lithium ion moves between the positive and negative poles of the battery, lithium metal battery or lithium ion battery will be charged and discharged. At this time, the channel of lithium ion movement is the electrolyte, and the electrolyte itself will react on the surface of the electrode (negative / positive) to form a protective film. However, when the protective film formed is not uniform, problems will appear.

At that time, lithium metal will appear in the negative pole significantly, that is, dendrites will be generated, resulting in short circuit of the battery, or the positive pole will be changed, which will reduce the performance of the battery. Therefore, it is very important to manufacture an ideal protective film. Therefore, the composition of electrolyte must be effectively controlled.

In this regard, Professor Nam's research team has developed a new type of fluorine-containing electrolyte, which can protect the negative and positive electrodes at the same time and increase the battery output. When fluorine reacts with lithium, a protective film is formed on the surface of the lithium electrode. When the protective film is partially damaged, it will also be repaired.

Professor Kwak's team used theoretical calculations to determine the reaction trend and reaction mechanism of fluorinated solvents. Compared with conventional fluorine, fluorinated ether solvent with easier reduction reaction has the property of easy release of fluorine, so as to form a protective film (fluorination interface) on the positive electrode.

Specifically, this fluorocompound can be used as an interface modifier to expand the applicable voltage range of ether based electrolytes.

The electrolyte has been specially used to charge lithium metal batteries with cut-off voltage lower than 4 V (vs. Li)/ Li ）。

The complementary electrolyte design of using 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether and fluoroethylene carbonate simultaneously in concentrated ether based electrolyte can significantly improve the capacity retention rate (99.1%) in Li | lini0.

8co0.1mn0.1o2 full cell, after 100 cycles at 25 ° C, the coulomb efficiency is as high as 99.98%.

Therefore, the improved electrolyte system is expected to be used to solve the reduction and oxidative decomposition of unstable ether based electrolytes in high energy density lithium metal batteries with high nickel cathode.

It is expected that this calculation principle will contribute to the development of functional electrolyte materials and additives to achieve high performance of lithium metal batteries. The electrode interface stabilization mechanism will be used to design the electrolyte system developed for high energy density batteries.

Article source:High tech lithium power grid