A new technique for studying interfaces in lithium battery cathodes
How do electrons move within lithium-ion battery cathodes?
A new method for analysing their behaviour has been developed by Rafael Ferragut, professor in the Department of Physics, in collaboration with Meiying Zheng, PhD, and European partners. The study focuses on the role of “buried” interfaces between the oxide microparticles that make up the cathode (LiCoO₂) and conductive carbon additives.
What the study consists of
The new approach is based on positron annihilation spectroscopy, a technique that uses positrons as a quantum probe. Positrons are the antimatter counterparts of electrons: when a positron stops in the material, it annihilates with an electron, producing two gamma rays.
By precisely measuring the velocity distribution of the electron-positron pair, the researchers obtained a fingerprint of the orbitals involved. At the interface between oxide and carbon (LiCoO₂/carbon), the Coincidence Doppler Broadening mode distinguishes the π bonds of carbon (2pz) from the oxygen orbitals (2p) in the oxide, linked to the redox electrochemical processes underlying the functioning of lithium batteries.
The result obtained
By combining experimental data with theoretical simulations based on the DFT (Density Functional Theory) technique, the research group introduced a new parameter capable of quantifying which fraction of the measured signal comes from the carbonaceous phase.
The study was published in Physical Review Letters.