A “matter–antimatter sensor” for lithium batteries
An international team led by Prof. Rafael Ferragut from the Department of Physics at Politecnico di Milano, in collaboration with Meiying Zheng - PhD and European partners, has developed a new method to “see” how electrons move inside lithium-ion battery cathodes. The study, published in Physical Review Letters, addresses a key challenge in fast battery charging: understanding the role of “buried” interfaces between oxide cathode microparticles (LiCoO₂) and conductive carbon additives.
The innovative solution uses positron annihilation spectroscopy, a technique that emploits positrons as a quantum probe, the antimatter counterparts of electrons. After slowing down inside the material, a positron annihilates with a local 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 oxide–carbon interface (LiCoO₂/carbon), the Coincidence Doppler Broadening mode distinguishes the “π bonds” of carbon (2pz) from the oxygen (2p) orbitals in the oxide, which are involved in the electrochemical redox processes underlying the operation of lithium batteries.
Combining experiments and ab initio simulations (DFT – Density Functional Theory), the study introduces a new parameter quantifying how much of the signal comes from the carbon phase.
By linking these quantum fingerprints to carbon morphology, the method makes the cathode’s nanoscale “circuitry” visible and can guide the design of more effective additives and coatings for faster charging, with applications also in the next generation of solid-state batteries.
Rafael Ferragut, Department of Physics
Zheng M., Kuriplach J., Makkonen I., Ferragut R., Laakso E., Pagot G., Di Noto V., Barbiellini B.
Probing electron transfer orbitals selectively at LiCoO2/C cathode interfaces via positron annihilation spectroscopy.
Phys. Rev. Lett., Jan 2026