Probing Electron Transfer Orbitals Selectively at LiCoO 2 / 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 LiCoO_{2} microparticles and the 2p_{z} carbon orbitals in the conductive carbon additives. By analyzing this momentum distribution, we obtain the amplification of subtle electron momentum distribution signals from carbon π bonds. Ab initio modeling of LiCoO_{2} 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 LiCoO_{2}/C composite by quantifying the spectral contributions of electron transfer orbitals, which constitutes the nanoscale circuitry enabling efficient electron transport in battery cathodes.