Monday 4 November 2024

New research tackles battery performance in electric vehicles

New research on the enhancement of the lifespan and performance of lithium-ion batteries in electric vehicles has been published by experts at WMG, the University of Warwick.

The paper, published in Joule – a leading sustainable energy journal - explores charge compensation in Li-ion battery cathodes by assessing the electronic structure.

WMG scientists in collaboration with academic partners in the Faraday Institution’s Degradation and FutureCat projects have experimentally demonstrated that oxygen (rather than the transition metal, as previously believed) is the redox active species, and is responsible for the energy storage mechanism.

Matthew Ogley, PhD Researcher at WMG, who led the project together with Dr Ashok S. Menon, explained: “This work highlights the bulk stability of NMC811 cathodes within high voltage cycling windows. By now focusing on surface stabilisation to minimise degradation, our research highlights practical strategies for the creation of longer-lasting batteries, which is crucial for electric vehicles.”

Li-ion batteries move Li-ions between an anode and a cathode to store energy. Nickel-rich transition metal oxide cathode materials, like NMC811, allow lots of Li-ions to be extracted. However excessive removal at high voltages causes structural changes at the surface which trap the Li-ions and reduce the amount of energy that can be stored.

Higher voltage, longer lifespan, cost savings

Matthew added: “We used advanced techniques at the Diamond Light Source and ISIS Neutron and Muon Source to investigate how high-mass-loading NMC811 cathodes change during charge and discharge. We found that oxygen, which is part of the cathode’s transition metal oxide structure, is responsible for allowing the lithium to move in and out, helping us to redefine how these materials work.

 

“With facilities at WMG, we manufactured the high-quality electrode coatings using our Battery Scale-Up facility and incorporated them into full-cell pouch cells. These designs are highly representative of those used in the industry, which allows our operando X-ray results performed at the Warwick X-ray diffraction RTP to have a direct impact on current practices.

 

“Using all this information, we can propose strategies to stabilise the cathode particle surface and limit the reaction between reactive oxygen and the organic liquid electrolyte. This should allow these materials to withstand higher voltages, last longer and with cost savings too.”

This builds on previous WMG research published in Joule in July 2023 (in collaboration with the University of Birmingham and the University of Cambridge), and PRX Energy in March 2023 and January 2024.

Find out more about WMG’s battery research here: Battery Materials and Cells Group - WMG

Read the paper in full here: Metal-ligand redox in layered oxide cathodes for Li-ion batteries: Joule

This work was supported by the Faraday Institution's FutureCat project (FIRG065). The Research Pouch Cell Manufacture (FIRG062) and Degradation (FIRG060) projects are also acknowledged.