According to foreign media reports, researchers from Ulsan National Academy of science and Technology (unist) in South Korea demonstrated a new solvent-free single lithium ion conductive covalent organic skeleton. The study was led by sang young Lee and sang kyu Kwak, professors of unist School of energy and chemical engineering. During the research, the research team demonstrated the new concept of “solid ion conductor”, which can selectively make lithium ions pass through ion channels. Because they are solid and can effectively transport lithium ions, they are expected to become raw materials for the next generation of batteries, such as high-voltage batteries or lithium metal batteries.

At present, lithium-ion batteries use highly flammable liquid electrolyte, which is very prone to fire or explosion. As an alternative, solid electrolytes are being developed, but their ionic conductivity is lower than that of liquid electrolytes. Especially in improving battery performance, many solid electrolytes have limitations, because the migration path of ions is tortuous and complex.

Professor Lee uses porous crystalline materials as ionic conductors, such as covalent organic framework (COF), to solve this problem. By arranging lithium ion channels regularly in the material, the ion conductivity is greatly improved. Dr. kihun Jeong, the first author of the study and from unist School of energy and chemical engineering, said: “the newly developed ionic conductor is a solid-phase carrier that does not use liquid at all to realize the conductive behavior of solid single lithium ions.”

The conduction behavior of single lithium ion means that ideally, only lithium ion is transmitted through electrolyte. Since lithium ions are cations, they are easy to move with anions. Unnecessary anion migration will cause side reactions on the electrode surface and reduce the performance of the battery. In this study, anions were fixed in the path of lithium ions, and organic skeleton structures were synthesized by anionic monomers paired with lithium ions. In this way, only lithium ions flow along the channel to achieve an ideal flow state. Researchers theoretically determined the use of computational chemistry. In computational science, lithium ions move along regularly arranged oxygen atoms in ion conductor channels.

Professor Lee said: “This research provides a new direction for the design of solid ion conductors and lays a foundation for the development of ‘high-performance solid electrolyte’. This is very important for the commercialization of the next generation of batteries, including all solid-state batteries. This conductor can selectively and effectively transport lithium ions without using explosive organic solvents. These ion conductors are of great significance The body is not only suitable as an electrolyte for solid-state batteries, but also can be applied to high activity lithium metal electrodes. “

     

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