Study of LiCoO₂+C₆₀ hybrid cathode using neutron and ion-beam profiling methods

Thin films of a hybrid cathode designed for all-solid-state Li-ion batteries (ASSLIBs), based on a combination of LiCoO₂ (LCO) and C₆₀ phases, were prepared by simultaneous ion beam sputtering of LiCoO₂ and thermal evaporation of C₆₀. The sub-micrometer-thick films were analyzed using the Neutron Depth Profiling (NDP) and Rutherford Back Scattering (RBS) methods (in the Center of Accelerator and Nuclear Anlytical Methods - NPI CANAM infrastructure) to measure the depth distribution of lithium, cobalt, and other building elements. Both NDP and RBS analytical methods used provided essential information about the profiling of elements in the hybrid layer and showed the influence of the fullerene phase and the charge collector metal on their distribution. It was confirmed that the presence of C₆₀ leads to the higher accumulation of Li on the surface and their slight but broad decrease below the surface. Uneven distribution was also observed for Co, C and O. After depositing the top current collector, a significant decrease in Li and changes in concentrations of other elements occurred in the surface region. It is assumed that the uneven distributions of structural elements in the hybrid LCO + C₆₀ mixtures are due to the difference in electrochemical potentials of the deposited elements.