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Researchers Uncover the Nature of Oxygen in a Potential Next-Generation, Lithium-Rich Battery Material

October 17, 2020 by Stephanie Leonida

The latest research concerning battery technology brings a collaborative team of researchers closer to a better understanding of the nature of oxidized oxygen in a well-known battery material known as lithium-rich nickel manganese cobalt oxide (Li-rich NMC).

Nickel has high specific energy but can have poor stability, while manganese forms a spinel structure which offers low internal resistance but also allows specific energy. Combining the two makes Li-rich NMC a battery material that has been considered for use in powering e-bikes, power tools, and other electric powertrains. 

 
Li-rich NMC is a promising battery material for powering electric vehicles.
Li-rich NMC is a promising battery material for powering electric vehicles.

 

The use of the battery material might even be able to extend driving ranges of electric vehicles or increase power capacity for a range of applications concerning robotics. The prospect of using Li-NMC as a favorable battery material, appears to be growing with more promise considering the research findings highlighted here. Further research and technological development in this area may offer benefits and solutions for the power electronics community in the future. 

 

The Nature of the Research

Hysteresis time-based dependence of a systems output based on past and present inputs. The output value does not necessarily result as a strict function of the input, which engenders a delay or lag. In the study mentioned in this article, researchers investigate the hysteresis of the OR reaction for the battery material Li-NMC. The researchers used resonant inelastic X-ray scattering (RIXS) and an NMR spectroscopy technique to understand more about the link between OR and the substantial loss of voltage and by extension, energy density during the first charge/discharge cycle of Li-NMC. 

"Our current work focuses on the Li-rich material Li1.2Ni0.13Co0.13Mn0.54O2. The key findings as before show the formation of free O2 molecules inside the materials, which has not been appreciated before in the community. This is a very important discovery as the material has higher TM-O covalency which was thought to suppress formation of molecular O2 ”, said Kejin Zhou, a scientist at Diamond Light Source in a recent news release.

 

Researchers unveil the nature of oxidized oxygen in battery material Li-rich NMC.
Researchers unveil the nature of oxidized oxygen in battery material Li-rich NMC. Image used courtesy of Diamond Light Source

 

The research was able to reveal the fine structure attributed to the vibrations of O2 molecules which allowed RIXS features to be assigned. Within the bulk of the cathode material, O2 molecules were found to be trapped. During discharge researchers found that they could be reformed back into oxide ions. This happened at a lower voltage than on the initial charge. 

In another news release, Zhou expressed that he believes the “work will have huge impact in future battery cathodes designs to minimise the unstable honeycomb structure. Our work also has important consequences for tackling other issues associated with Li-rich NMC, such as voltage fade, which hinder their commercialisation and ultimately discovering new materials which may be able to harness O-redox more reversibly.”