Oxygen ‘holes’ could hold the key to higher performing EV batteries

Nickel is already used in lithium-ion batteries, but increasing the proportion of nickel could significantly improve battery energy density, making them especially suitable for electric vehicles and grid-scale storage.

Oxygen ‘holes’ could hold the key to higher performing EV batteries. Photo: Kumpan Electric/Unsplash

However, practical applications for these materials have been limited by structural instability and the tendency to lose oxygen atoms, which cause battery degradation and failure.

The researchers, led by the University of Cambridge and the University of Birmingham, found that ‘oxygen hole’ formation – where an oxygen ion loses an electron – plays a crucial role in the degradation of nickel-rich battery materials.

These oxygen holes accelerate the release of oxygen that can further degrade the battery’s cathode, one of its two electrodes.

The researchers examined the behaviour of nickel-rich cathodes as they charged. They found that during charging, the oxygen in the material undergoes changes while the nickel charge remains essentially unchanged.

The researchers proposed a mechanism for how oxygen is lost during this process, involving the combination of oxygen radicals to form a peroxide ion, which is then converted into oxygen gas, leaving vacancies in the material. This process releases energy and forms singlet oxygen, a highly reactive form of oxygen.

“Potentially, by adding compounds that shift the electrochemical reactions from oxygen more to the transition metals, especially at the surface of the battery materials, we can prevent the formation of singlet oxygen,” said first author Dr Annalena Genreith-Schriever from the Yusuf Hamied Department of Chemistry.

“This will enhance the stability and longevity of these lithium-ion batteries, paving the way for more efficient and reliable energy storage systems.”

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