Hanyang University's research team led by Professor Sun Yang-kook of the Department of Energy Engineering has succeeded in developing a cobalt-free cathode for lithium-ion battery, which has been considered as a challenge to be solved in the secondary battery industries for years. Batteries made of the cathodes are evaluated as future batteries in terms of its resolved stability, price, and performance. 

This study was published in Nature Energy, the world's most prestigious journal in the field of Energy. The new cathode is drawing attention from battery industry due to its advantage of increased battery stability and performance with lowered cost, if it is to be commercialized in the future.

Cobalt is considered as an essential element in configuration of battery cathode materials, such as NCM (nickel, cobalt, manganese) and NCA (nickel, cobalt, aluminum) whose demand in battery market has been surging. This is because cobalt plays an important role in the structural stability of lithium-ion cathodes. 

However, there have been attempts to eliminate cobalt from the next-generation lithium-ion battery cathodes throughout the science and industry fields due to the △ environmental pollution, △ high dependence of raw material on certain countries, and △ continuously increasing cost. As a result, the development of cobalt-free cathodes has become a serious challenge to dominate the next-generation electric vehicle market.

In order to succeed in cobalt-free cathodes development, Professor Sun's team first analyzed the effect of cobalt removal on the battery. The battery cathode from which cobalt was removed was structurally unstable, resulting in "crack" phenomenon during charging. The crack, which causes a dramatical decrease in battery-life characteristics and stability of cathodes, had to be suppressed.

The research team suggested two solutions to develop cobalt-free cathodes with stability and high performance. First, they deviced a cathode consisting of rod-shaped grains in a radial arrangement to suppress cracks during charging. Unlike the pre-existing crystal grains, these grains dissipate strains caused by the contraction of the cathode material and create paths in which lithium-ions could diffuse rapidly to prevent cracks during charging.

Then, the research team presented an "alternating arrangement" of lithium and transition metals to resolve the unstable crystal structure of cobalt-free cathodes. This arrangement enhances the stability of cathode structure by alleviating the stacking faults of the crystal structure caused by the absence of cobalt, as well as replaces the role of cobalt.

The new cobalt-free cathode with customized engineering design from nanostructure to microstructure showed high capacity retention and stability even  under the repeated fast charging. Electric vehicles applied to this technology is expected to drive 700 to 800 kilometers on a single charge and retain its performance even after 20 years of use. 

This study is one of the achievements from the High-level R&D workforce buildup (For graduate level) led by Korea Institute of Energy Technology Evaluation and Planning (KETEP) of the Ministry of Trade, Industry and Energy. Professor Sun Yang-kook's research team received 5.8 billion KRW for ten years since 2011 from the "GET-Future," a program to actively support the top-level R&D workforce. from 2021 to 2027, the research team is conducting research with 7.6 billion KRW of support from the Energy Innovation Research Center program.

Meanwhile, the study was led by professor Sun Yang-kook of the Department of Energy Engineering at Hanyang University, and professor Chong Seung-yoon of the Department of Materials Science & Engineering and Park Geon-tae, a Ph.D. in the Department of Energy Engineering jointly participated.