Lawrence Berkeley National Laboratory

Understanding electronic structure is crucial to enhance the battery performance. Soft X-ray spectroscopy (SXS) is one of the most effective methods to provide direct probe of electronic states. Here, spectroscopic measurements of transition metal 3d and oxygen 2p states are simply reviewed. Then, we mainly focus on the perspective of the development direction of modern SXS techniques. Although the true power of recently developed high efficiency mapping of resonant inelastic X-ray scattering (mRIXS) has been apparent for materials and chemistry studies, great challenges remain for mRIXS spectroscopic interpretation, and the understanding of the battery materials on novel redox activities remains elusive.