CATMAT researchers have made further major advances in understanding critical properties and limitations of lithium-rich layered oxide and disordered rock-salt cathodes, thereby developing novel solutions to maintain their high energy densities.

Increasing the range of electric vehicles demands battery materials that can store more charge at higher voltages in order to achieve a higher energy density. The CATMAT project is performing world-leading work on a research route involving storing charge on both transition metal ions and oxide ions (termed O-redox) observed in Li-rich layered oxide and disordered rocksalt materials.

CATMAT researchers at Bath and Oxford have used ab initio molecular dynamics modelling to show that on charging disordered rocksalt cathodes, transition metal migration is necessary for the formation of O2 trapped in the bulk, which is confirmed by resonant inelastic X-ray scattering (RIXS) data. The implications are that irreversible transition metal migration should be suppressed to prevent voltage loss and maintain high energy density (published in Nature Communications 2022). In parallel with this work, Oxford researchers have been the first to use an advanced 4D STEM technique (termed electron ptychography) to provide atomic-resolution imaging of key structural evolutions in Li-rich layered oxides that are critical in understanding the operation of these high energy density battery materials (published in Joule 2022).

Image: High-resolution resonant inelastic X-ray scattering (RIXS) map of Li2–xMnO2F charged to 5.0 V, showing the vibrational features corresponding to molecular O2 only, and an energy loss feature at ~7.5 eV (McColl, House, Islam et al., Nature Comms, 2022)

Case study published December 2022.