To pave the way for stronger, safer energy-dense batteries, during a new study, researchers created new perspectives on the release of oxygen in lithium-ion batteries.
Next-generation batteries that store more energy are critical if societies are to achieve the UN’s Sustainable Development Goals and become aware of carbon neutrality. However, the higher the energy density, the greater the probability of thermal leakage – heating the batteries can sometimes cause the battery to explode.
The oxygen released from the active material of the cathode is the cause of thermal leakage, however, knowledge of this process is insufficient.
Researchers at Tohoku University and the Japan Institute of Synchrotron Radiation Research (JASRI) have investigated the behavior of oxygen release from the cathodic material of lithium-ion batteries LiNi1 / 3Co1 / 3Mn1 / 3O2 (NCM111) and the associated structural changes. NCM111 functioned as an oxide-based battery material by coulometric titer and X-ray diffraction.
The researchers found that NCM111 supports 5 mol% of oxygen without decomposing and that oxygen release causes a structural imbalance, the exchange of Li and Ni.
When oxygen is released, it reduces transition metals (Ni, Co, and Mn in NCM111), reducing the ability to maintain a balanced charge in materials.
To evaluate this, the research team used XX soft absorption spectroscopy on the BL27SU SPring-8 – JASRI in Japan in a large-scale synchrotron radiation installation.
In NCM111 a selective reduction of Ni3 was observed at the beginning of oxygen release. After the completion of the I reduction, Co3 decreased, while Mn4, on the other hand, decreased oxygen by 5 per cent.
“The restrictive behaviors are very reminiscent of the fact that high Valent NI (Ni3) significantly improves oxygen release,” said Takashi Nakamura, author of the paper.
To test this hypothesis, Nakamura and his colleagues prepared modified NCM111s with more Ni3 than the original NCM111. To his surprise, they found that NCM111 showed much more severe oxygen release than expected.
Based on this, the research team proposed that high transition metals in Valent destabilize the oxygen in the network in oxide-based battery materials.
“Our findings will help us further develop next-generation solid batteries made of high-density, transition-grade metal oxides,” Nakamura said.