Interactions at the electrode-electrolyte interfaces in batteries studied by quasi-in-situ soft x-ray absorption spectroscopy

The pursuit of high capacity rechargeable batteries which utilize strong oxidizing cathodes and reducing anodes create significant challenges on the electrochemical stability of the electrolyte. A viable rechargeable Li-ion battery system is realized through an in-situly formed passivation layer on the anode-electrolyte interface. Additionally, the surface and interface properties of the cathode determine the stability, rate, and voltage of the battery. Therefore, understanding and controlling reactions at the electrode-electrolyte interfaces is essential for developing high-capacity, long-lasting and safe battery system. In this review, we discuss some of the recent soft x-ray absorption spectroscopic results on electrode-electrolyte interfaces. By virtue of the sensitivity of soft x-ray to both low-Z elements and transition metals and its short probing depth, the spectroscopic results provide insight into the complex interactions between electrode and electrolyte, as well as the surface evolutions of the electrodes during electrochemical operations.