Elucidation of the mechanism by which lithium-ion batteries deteriorate
Lithium-ion batteries, which are used as power sources for smartphones and electric vehicles, are known to lose capacity as they continue to be used. A research team at Stanford University has elucidated the mechanism of battery deterioration.
Persistent and partially mobile oxygen vacancies in Li-rich layered oxides | Nature Energy
Scientists discover how oxygen loss saps a lithium-ion battery's voltage | SLAC National Accelerator Laboratory
According to the research team, the deterioration of lithium-ion batteries is caused by the leakage of oxygen contained in lithium-ion batteries. However, the amount of oxygen leaked in 500 charge cycles is 6% of the total, and the amount of oxygen leaked in each charge cycle is too small, so the mechanism has not been observed. Therefore, in this study, we indirectly observed the mechanism of oxygen leakage by observing the chemical properties and structures of surrounding particles that change due to the loss of oxygen.
The research team disassembles a lithium-ion battery that has undergone various charging cycles and uses a special X-ray microscope from Lawrence Berkeley National Laboratory to construct a lithium-ion battery on a one-billionth-meter scale. I observed the structure of the nanoparticles.
According to the research team, it has been thought that oxygen in lithium-ion batteries leaks from the surface of nanoparticles. However, as a result of this observation, it was found that oxygen first leaks from the surface of the nanoparticles and then leaks from the inside of the nanoparticles. In addition, it was revealed that when nanoparticles form agglomerates, the amount of oxygen leaked out is small.
In addition, the research team predicted that 'nanoparticles that have lost oxygen will collapse inward to form a close-packed structure ,' and analyzed the structural changes of nanoparticles after losing oxygen by computer simulation. As a result, it was found that, contrary to expectations, 'the metal ions that make up the nanoparticles move, but the structure of the nanoparticles does not change.'
'This rearrangement of metal ions is caused by a lack of oxygen, which reduces battery voltage and efficiency over time. We outline this phenomenon,' said Will Chue, a member of the research team. I've known it for a long time, but the mechanism was unknown. '
'The scientific understanding of this study could lead to the development of new ways to reduce oxygen loss and its damaging effects,' said Chue, motivated by research to mitigate the deterioration of lithium-ion batteries. Is talking about.
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