Reaction and Space Charge Layer Formation at the LiCoO2-LiPON Interface: Insights on Defect Formation and Ion Energy Level Alignment by a Combined Surface Science Simulation Approach

In this contribution, we investigate the formation and evolution of LiCoO2-LiPON interfaces upon annealing using photoelectron spectroscopy. We identify interlayer compounds related to the deposition process and study the chemical reactions leading to interlayer formation. Based on the structure of the pristine interface as well as on its evolution upon annealing, we relate reaction layer and space charge layer formation to chemical potential differences between the two materials. The results are discussed in terms of a combined Li-ion and electron interface energy level scheme providing insights into fundamental charge transfer processes. In constructing the energy level alignment, we take into account calculated defect formation energies of lithium in the cathode and solid electrolyte.