Applications of Soft X-ray Spectromicroscopy in Energy Research from Materials to Batteries

Scanning transmission X-ray microscopy (STXM) and X-ray photoemission electron microscopy (X-PEEM), operated under soft X-rays with photon energy below 2500 eV, integrates X-ray microscopy and X-ray absorption near edge structure spectroscopy (XANES). This integration, also denoted as soft X-ray spectromicroscopy, affords chemical imaging in varieties of applications including energy materials, environmental fields and magnetic materials through revealing spatially resolved bonding and electronic structure information. This chapter focuses on its applications in energy materials and aims on providing an overview of this technique to non-experts. It begins on instrumentation details of STXM and X-PEEM. Then, the bulk of this chapter provides a survey of STXM and X-PEEM applications in energy materials studies and is organized into three subgroups: (1) soft X-ray chemical imaging of energy nanomaterials with the focus on electronic structure and chemical interaction in hybrid nanomaterials; (2) soft X-ray chemical imaging applications in battery research with the focus on interface phenomena such as transport behaviors and interactions among multiple electrode components; (3) future developments on the 4th generation synchrotron sources. The purpose is to demonstrate the recent growth of soft X-ray chemical imaging employing STXM/X-PEEM-XANES to probe complex chemical interactions and their impacts in energy materials.