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

Depth-resolved X-ray absorption spectroscopy (DR-XAS) measurements were performed for the direct observation of the chemical state and local structure at the LiCoO(2) 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 LiCoO(2) electrode-solid electrolyte interface decreased with the introduction of a NbO(2) interlayer at the interface, while the resistance increased with ZrO(2) and MoO(2) interlayers. Using DR-XAS with a depth resolution of about 7 nm, the changes in electronic structure and local structure of the LiCoO(2) electrode were clarified. The extended X-ray absorption fine structure of DR-XAS revealed that the introduction of the NbO(2) 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 LiCoO(2) during delithiation and then decreased the activation energy for the charge transfer process.