As fast charging of electric vehicles and smartphones becomes more commonplace, concerns about reduced battery life are growing. Amidst this, a domestic research team is attracting attention for developing a next-generation cathode material that can address this issue.

A joint research team led by Professor Seok-Joo Kang of the Department of Energy and Chemical Engineering at Ulsan National Institute of Science and Technology (UNIST), Professor Sang-Kyu Kwak of Korea University, and Dr. Seok-Hoon Ahn of the Korea Institute of Science and Technology (KIST) announced on the 24th that they have developed a hybrid cathode material combining graphite and curved nanographene.

This material has a structure that can stably maintain battery performance and lifespan even during fast charging.

Battery charging is the process by which lithium ions move and are stored within the cathode material. However, during fast charging, lithium ions cannot fully penetrate and accumulate on the surface in the form of metallic lithium, a phenomenon known as "dead lithium," which reduces battery capacity and lifespan.

The research team evenly distributed commercial graphite particles (MCMB) into a curved nanographene (Cl-cHBC) layered structure to implement a 'sequential insertion' path in which lithium ions move through the nanographene layers into the graphite. Curved nanographene has a bow-like twisted structure, wide interlayer spacing, and abundant nano-spaces, which increases the movement speed of lithium ions.

Experimental results showed that the hybrid cathode had a capacity more than four times higher than that of conventional graphite under fast charging conditions (4 Ag¹).

Furthermore, in tests combined with a single-crystal NCM811 cathode for electric vehicles, the battery maintained 70% of its initial capacity after over 1,000 charge/discharge cycles, and operated stably for over 2,100 cycles based on pouch cells. Charge/discharge efficiency reached 99%.

The research team explained, "This material is compatible with existing battery manufacturing processes, and by leveraging the structural scalability of curved nanographene, it can be applied not only to lithium batteries but also to sodium battery cathodes." They added, "The sequential insertion structure can be utilized as a next-generation cathode design strategy that simultaneously ensures fast charging and long-term stability."

The results of this study were published online on September 11 in the international academic journal in the field of materials science, 'Advanced Functional Materials', and were conducted with support from the National Research Foundation of Korea (NRF), UNIST, and the Korea Institute for Science and Technology Promotion (KOIST).