To increase driving range, electric vehicle (EV) batteries rely on high-nickel cathodes. However, this high nickel content has a critical drawback: battery performance degrades rapidly during charging and discharging. The primary cause has now been identified as internal structural distortion, which generates “oxygen holes“ that shorten the battery's lifespan—similar to how a warped pillar can crack a building's walls.
A research team from POSTECH (Pohang University of Science and Technology), led by Professor Kyu-Young Park of the Department of Battery Engineering (Graduate Institute of Ferrous & Eco Materials Technology) and the Department of Materials Science and Engineering, has confirmed that this structural distortion creates “double oxygen ligand holes” (simplified as “oxygen holes”), which shortens battery life. Crucially, the team discovered that adding a small amount of aluminum (Al) to the cathode dramatically extends its lifespan by preventing the formation of these holes. The study was published online in the international journal Advanced Functional Materials .
There is a growing trend to increase the nickel content in EV batteries to store more energy. However, while more nickel increases energy density, it also causes capacity to fade quickly over repeated charging and discharging cycles.
The research team theoretically identified the fundamental mechanism behind this capacity fading: lattice structural distortion, which intrinsically occurs during the charge/discharge process. When the structure distorts, significant oxygen holes form on the oxygen atoms, which destabilizes the lattice oxygen and shortens the battery's lifespan.
By substituting a small amount of nickel with aluminum, the team successfully suppressed the formation of these oxygen holes. The aluminum stabilizes the structure by improving the electronic environment around the oxygen atoms. This was confirmed to significantly enhance the battery's lifespan.
This research is significant for identifying the cause of degradation in high-nickel cathodes at the atomic level and proposing a strategy to simultaneously improve both energy density and lifespan. It is regarded as a core technology that can enhance both the performance and safety of EV batteries.
“This study, which identifies the capacity degradation caused by structural distortion in high-nickel cathodes for EVs, will help expand the design possibilities for next-generation, high-performance batteries,” said Professor Kyu-Young Park, who led the research. He added, “This achievement provides a key strategy that not only improves lifespan but can also mitigate thermal runaway, a critical issue in high-nickel cathodes. We expect it to have a significant impact on the entire rechargeable battery industry.”
This research was supported by the Ministry of Trade, Industry and Energy (MOTIE), the Ministry of Science and ICT (MSIT), and the Supercomputing Center of the Korea Institute of Science and Technology Information (KISTI).
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