Inspenet, July 29, 2023.
Scientists from several universities, including Birmingham, Cambridge, Warwick and the Faraday Institution at Didcot, have developed new research and have made significant progress in understanding and overcoming the challenges associated with nickel-rich cathode materials used in batteries. lithium ions.
These materials have great potential to achieve high voltages and capacities in batteries. However, its practical application has faced challenges due to problems of structural instability and oxygen loss.
The study has revealed that the formation of “oxygen holes”, where an oxygen ion loses an electron, plays a crucial role in the degradation of LiNiO 2 cathodes, which accelerates oxygen release and can lead to further degradation. of the cathode material.
This new research reveals the behavior of oxygen
In their research, the team used a variety of advanced computational techniques on regional supercomputers in the UK. They observed the behavior of the LiNiO 2 cathodes during the charging process and found that the oxygen in the material undergoes changes, while the nickel charge remains largely unchanged.
“We found that the charge on nickel ions stays around +2, regardless of whether it is in its charged or discharged form. Meanwhile, the charge on oxygen varies from -1.5 to around -1. This is unusual, the conventional model assumes that oxygen remains at -2 during charging. However, these changes show that oxygen is not very stable and we have discovered a way for it to escape from the nickel-rich cathode.” Andrew J. Morris, study co-author, University of Birmingham.
The results of the research agree with the experimental data collected. Scientists have proposed a mechanism that explains how oxygen loss occurs during this process, which involves the combination of oxygen radicals to form a peroxide ion that is converted to oxygen gas, thereby creating voids in the material. This process releases energy and produces singlet oxygen, a highly reactive form of oxygen.
“We can improve the stability and longevity of this type of lithium-ion batteries, paving the way for more efficient and reliable energy storage systems.” Dr. Annalena Genreith-Schriever, University of Cambridge.
Lithium-ion batteries are commonly used in various applications due to their high energy density and rechargeability, but problems related to the stability of cathode materials have restricted their overall performance and durability. This research provides a new perspective to address these challenges and improve the efficiency of such batteries.
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