World news – GB – The best conditions for getting the most out of high nickel batteries

IMAGE: Effects of ambient air storage on the surface of NMC-811
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It is well known in the battery manufacturing that many cathode materials are sensitive to moisture. However, with the increasing popularity of battery components that contain a high content of nickel, researchers from WMG, University of Warwick found that the drier conditions in which these cathodes are stored and processed, a significant improvement in battery performance is achieved..

High nickel (nickel) batteries are getting more and more popular around the world, as more car companies are investigating the use of high nickel batteries for electric cars. However, high nickel cathode materials are prone to reaction and instability are exposed to moisture, so how they are stored in order to provide optimum performance is critical..

In the paper titled “Effects of ambient storage conditions on the structural and electrical properties of NMC-811 batteries for Li-ion batteries” published in Electrochimica Acta, researchers from WMG, University of Warwick proposed the best method for storing high nickel cathodes in order to mitigate early degradation.

The researchers exposed NMC-811 (a high nickel cathode material) to different temperatures and humidity, then measured the material’s performance and deterioration in the battery over a period of 28 days, and analyzed it using a combination of physical, chemical and electrochemical tests.. This included high-resolution microscopy to determine the morphological and chemical changes that occurred at the micron and semi-micron scale during charging and discharging of the batteries..

Storage conditions included oven drying, exposed (to moisture) and a control measure. The researchers looked for surface impurities, which include carbonate and H2O, and found that there are three processes that could be responsible for the impurities, including:

They found that, in all conditions, (oven drying and when exposed to light) they showed specific capacity when emptying first and lower riding performance compared to the control.. However, measurement on exposure to moisture showed that after 28 days of exposure to ambient moisture, H2O and CO2 interact with Li ions in the battery cell, forming lithium carbonate and hydroxide species..

The formation of carbonates and oxides on the surface of NMC-811 contributes to a loss of electrochemical performance during material aging, due to poor ionic and electronic conductivity, as well as the electrical insulation of the active particles. This means that they can no longer reverse-store the lithium ions to transport the « charge ».. SEM analysis confirmed the porosity between the granules and the microcracks on these aggregate particles, 28 days after ambient exposure.

So they can conclude that the drier conditions, at dew points of around -45 ° C, are the best for storing and handling materials, in order to produce the best battery performance. . Moisture and exposure conditions at junctions along the manufacturing process will lead to materials and components being tried; This results in a shorter battery life.

“While moisture is well known to be an issue here, we set out to define the optimum storage conditions required to mitigate unwanted early deterioration in battery performance.. These measures are essential to improving processing capacity and ultimately maintaining performance levels. This also has relevance to other nickel-rich systems. G. NCA material.

“Large global research efforts will continue to focus on these materials, including how to protect their surfaces to eliminate the risks of parasitic reactions before incorporating them into the electrodes.. In the United Kingdom, pioneering research by Faraday has a consortium entirely dedicated to uncovering degradation mechanisms for such industry-related materials..

https: // warwick. a. UK / Services / Communications / Medical Library / Pictures / Oct_2020 / the_effects_of_ambient_air_storage_on_the_surface_stability_of_nmc-811. jpg
(1) Caption: Effects of ambient air storage on the surface of NMC-811
Credit: WMG, University of Warwick

https: // warwick. a. Uk / services / communications / medialibrary / images / october_2020 / post-mortem_nmc811_particle. jpg
(2) Caption: a-b) Postmortem NMC811 particle, without prior exposure to moist air, analyzed by FIB-SIMS, with the aim of detecting lithium. c-d) Post-mortem NMC811 particle, after 28 days of exposure to moist air, analyzed by FIB-SIMS, with the aim of detecting lithium.
Credit: WMG, University of Warwick

https: // warwick. a. Uk / services / communication / medialibrary / images / october_2020 / schematic. jpg
(3) Caption: Schematic diagram of particle breakdown during battery discharging
Credit: WMG, University of Warwick

For more information, contact:
Isn’t Scott
Media Relations Manager – Science
University of Warwick
Phone: 44 (0) 7920 531 221
Email: Alice. J. Scott @ Warwick. a. United kingdom

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