A Tohoku University research group has produced fresh insights about the release of oxygen in lithium-ion batteries, paving the way for more robust and safer high energy density batteries. As rechargeable batteries get more powerful, the chance of batteries overheating – thermal runaway – increases.

Seeking a way to make batteries safer, researchers have investigated one of thermal runaway’s main triggers: oxygen release. The team’s study paper has been published in Advanced Energy Materials.

Next-generation batteries that store more energy are critical if society is to achieve the UN’s Sustainable Development Goals and realize carbon neutrality. However, the higher the energy density, the higher the likelihood of thermal runaway – the overheating of batteries that can sometimes result in a battery exploding.

Oxygen release from battery materials which can cause thermal runaway. Image Credit: ⒸTakashi Nakamura at Tohoku University. Click image for the largest view.

Oxygen released from cathode active material is a trigger for thermal runaway, yet our knowledge of this process is insufficient.

The researchers from Tohoku University and the Japan Synchrotron Radiation Research Institute (JASRI) investigated the oxygen release behavior and relating structural changes of cathode material for lithium-ion batteries LiNi1/3Co1/3Mn1/3O2 (NCM111). NCM111 acted as a model oxide-based battery material through coulometric titration and X-ray diffractions.

The researchers discovered NCM111 accepts 5 mol% of oxygen release without decomposing and that oxygen release induced structural disordering, the exchange of Li and Ni.

When oxygen is released, it reduces the transition metals (Ni, Co and Mn in NCM111), lessening their ability to keep a balanced charge in the materials.

To evaluate this, the research group utilized soft-Xray absorption spectroscopy at BL27SU SPring-8 – a JASRI operated large-scale synchrotron radiation facility in Japan.

They observed selective Ni3+ reduction in NCM111 at the beginning stage of oxygen release. After the Ni reduction finished, Co3+ decreased, while Mn4+ remained invariant during 5 mol% of oxygen release.

Takashi Nakamura, coauthor of the paper said, “The reduction behaviors strongly suggest that high valent NI (Ni3+) enhances oxygen release significantly.”

To test this hypothesis, Nakamura and his colleagues prepared modified NCM111 containing more Ni3+ than the original NCM111. To their surprise, they discovered the NCM111 exhibited much severe oxygen release than expected.

Based on this, the research group proposed that the high valent transition metals destabilize lattice oxygen in oxide-based battery materials.

Nakamura concluded the press release noting, “Our findings will contribute to the further development of high energy density and robust next-generation batteries composed of transition metal oxides.”


This is very, very welcome news. For those watching, there is quite list of battery fires and explosions littering technical news, providing considerable worthy concern. It looks like this team’s efforts will assist in development of not just stronger batteries, but those batteries just might be much safer. The need to park an EV a distance from things flammable might not last so long.


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