Probing Electron Transfer Orbitals Selectively at LiCoO2/C Cathode Interfaces via Positron Annihilation Spectroscopy

Conductive carbon additives in lithium-ion battery cathodes significantly increase electron transport, facilitating rapid charging. However, quantifying this improvement remains challenging. Momentum distribution of annihilating electron-positron pairs offers a powerful approach to selectively probe the O 2p orbitals in LiCoO2 microparticles and the 2pz carbon orbitals in the conductive carbon additives. By analyzing this momentum distribution, we obtain the amplification of subtle electron momentum distribution signals from carbon pi bonds. Ab initio modeling of LiCoO2 and various topologies of carbon structures reproducing the experimental momentum distribution helps to quantify the fraction of positron annihilation occurring within the carbon structures. Our theoretical results combined with earlier experimental findings reveal potential charge transport pathways in the LiCoO2/C composite by quantifying the spectral contributions of electron transfer orbitals, which constitutes the nanoscale circuitry enabling efficient electron transport in battery cathodes.