Professor Seo Dong-hwa, Department of Materials Science and Engineering
The most expensive material, which accounts for the highest percentage of the cost of lithium-ion batteries used in electric vehicles and smartphones, is the anode material, which contains large amounts of expensive and rare metals such as nickel and cobalt . An international joint research team has proposed a new strategy to increase both the energy density and price competitiveness of lithium-ion batteries .
Through joint research with UNIST and McGill University in Canada, Professor Seo Dong-hwa's research team from the Department of Materials Science and Engineering at our university has developed a high-performance next-generation lithium-ion battery anode with a 40% increase in energy density without the need for expensive nickel and cobalt, which are key minerals for lithium-ion battery anodes. It was announced on the 1st that it was developed .
The international joint research team focused on manganese - based cation -disordered rock-salt ( DRX) cathode material . This is because the DRX cathode material can use manganese and iron , which are cheap and have abundant reserves, and has a higher energy density ( approximately 1,000 Wh/kg) than the existing commercialized ternary cathode material ( approximately 770 Wh/kg) based on the weight of the cathode material. . Above all , it has the advantage of being able to design materials without expensive nickel and cobalt, so it is attracting attention as a cathode material for next-generation lithium-ion batteries .
However, in the case of manganese-based DRX cathode materials, when batteries were made with electrodes with a cathode material ratio of more than 90%, battery performance was very low and there was a problem of rapid deterioration . Therefore, DRX cathode materials researchers had to lower the cathode material ratio to 70% to create an electrode , but in this case , there was a problem of having a lower energy density ( about 700 Wh/kg) at the electrode level than the ternary system ( about 740 Wh/kg) .
The joint research team found that the higher the proportion of the manganese-based DRX cathode material in the electrode, the less well the electron transport network is formed , and the higher the volume change rate between charge and discharge, the more likely the network collapse occurs during charge and discharge, greatly increasing the resistance of the battery. . Even if high-performance next-generation cathode materials were used, the battery could not perform properly due to high resistance .
According to the joint research team's research , when manufacturing manganese-based DRX electrodes , multi-walled carbon nanotubes * were used to compensate for the low electronic conductivity of the DRX anode material and to withstand volume changes between charge and discharge, increasing the proportion of anode material in the electrode to 96%. Even when the temperature was increased, the electron transport network and battery performance did not deteriorate . Through this, we developed a next-generation lithium-ion battery anode that shows a high energy density of about 1,050 Wh/kg based on electrode weight without nickel or cobalt . This is the world's highest level among lithium-ion battery anodes , and the energy density is 40% higher than that of commercial ternary anodes .
* Multi-walled carbon nanotube : Nanoscale tube composed of several concentrated cylindrical graphene layers
Additionally , a correlation was found that the higher the manganese content in the DRX cathode material, the higher the electronic conductivity , but at the same time, the higher the volume change rate . Based on this understanding , the research team proposed a next-generation lithium-ion battery anode design strategy that suppresses volume change by lowering the manganese content and overcomes low electronic conductivity by using multi-walled carbon nanotubes .
Professor Seo Dong-hwa said, “ There are still problems that need to be solved for commercialization, but we can prepare for resource weaponization when developing next-generation anodes that do not require nickel and cobalt minerals, which are highly dependent on China, and our company can compete in the low-cost secondary battery market led by lithium iron phosphate anodes. “It is expected that our global competitiveness will be strengthened, ” he said .
In this study, Professor Jinhyuk Lee of McGill University participated as a co-corresponding author , and Eunryeol Lee, a postdoctoral researcher at UC Berkeley ( Ph.D. candidate in the Department of Energy and Chemical Engineering at UNIST at the time of the study ), and Daehyeong Lee , a doctoral candidate in the Department of Materials Science and Engineering at KAIST , participated as co- first authors . In addition , doctoral student Sangwook Park and master's student Hojun Kim of the Department of Materials Science and Engineering at KAIST participated as co-authors . The research was carried out with support from the National Research Foundation of Korea's basic research project in the field of science and technology , nano and material technology development project , original technology development project, and the energy human resources training project of the Ministry of Trade, Industry and Energy , and with the support of a supercomputer from the Korea Institute of Science and Technology Information. It was received and carried out .
The research results were published online on March 27th in the international energy journal ' Energy & Environmental Science ' and are scheduled to be published as the cover paper for the June issue . ( Paper title : Nearly all-active-material cathodes free of nickel and cobalt for Li-ion batteries).
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