Lim Won-bin, a professor from the School of Materials Science and Engineering at Hanyang University, has developed a technology that can synthesize lithium-ion batteries at low temperatures using water vapor.

The cathode material is one of the core materials in batteries and is used to store lithium ions that generate electricity when discharged. Specifically, cathode materials are core materials that determine battery capacities, lifespan, and charge/discharge. However, the existing research on battery cathode material synthesis requires a lot of energy due to the high heat treatment during solid-phase synthesis and has difficulty in controlling the shape of the material due to high-temperature heat treatment. In addition, although liquid synthesis can be controlled in shape, it requires a large amount of solvent (distilled water and organic solvents).

Professor Lim Won-bin's research team developed a solid-phase synthesis method based on a sub-micro droplet reactor, which injects vapor into solid-phase raw materials and induces phase synthesis from its surface to interior at 80 degrees celsius. In particular, the size and shape of the material can be easily controlled by synthesizing the material in water vapor. Previous synthesis methods used high-temperature conditions, toxic organic solvents and expensive materials, resulting in environmental pollution and high energy consumption. However, the new synthesis method can replace toxic solvents with very small amounts of water vapor and synthesize materials at low temperatures, which is eco-friendly and economical.

In this study, Li3VO4 cathode materials doped with Ca (calcium) were synthesized by the ultrafine liquid reaction. Ca-doped Li3VO4, which is synthesized in water vapor, controls the size of the material reactor to nanometers, increasing the non-surface area by about 30 times compared to the material synthesized by high-surfaced synthesis. Synthesized cathode materials have excellent electrochemical properties, and Ca-doped Li3VO4 cathode materials and NCM622 (LiNi0.6Mn0.2Co0.2O2) anode materials are used to complete the cell form, resulting in a capacity of 543 mAhgg-1.

(left) Professor Lim Won-bin (right) Dr. Tran Huu Ha

Professor Lim Won-bin said, "The low-temperature ultra-fine liquid reaction method can improve surface control and electrochemical performance of lithium battery cathode materials. Hence, it is expected it will be widely used in various energy storage materials in the future through eco-friendly synthesis."

The results of the study were published in the international journal, "Nature Communications" on May 26. The theme of the paper is "Sub-micro droplet reactors for green synthesis of Li3VO4 anode materials in lithium-ion batteries"."

The research was carried out with the support of the National Research Foundation's fourth stage Brain Korea 21 (BK21) project, the support project for middle-sized researchers, and the support project for the European Research Council (ERC).