Depth-resolved X-ray absorption spectroscopic study on nanoscale observation of the electrode–solid electrolyte interface for all solid state lithium ion batteries

Abstract

Depth-resolved X-ray absorption spectroscopy (DR-XAS) measurements were performed for the direct observation of the chemical state and local structure at the LiCoO₂ electrode–solid electrolyte model interface, which can contribute towards the enhancement of the power density in all solid-state lithium batteries. The charge transfer resistance, measured by AC impedance spectroscopy, of the LiCoO₂ electrode–solid electrolyte interface decreased with the introduction of a NbO₂ interlayer at the interface, while the resistance increased with ZrO₂ and MoO₂ interlayers. Using DR-XAS with a depth resolution of about 7 nm, the changes in electronic structure and local structure of the LiCoO₂ electrode were clarified. The extended X-ray absorption fine structure of DR-XAS revealed that the introduction of the NbO₂ layer is effective for restricting the large Co–O bond change at the interface during delithiation. This interlayer relieved the stress at the interface due to the volume change of LiCoO₂ during delithiation and then decreased the activation energy for the charge transfer process.