News

CeO₂ significantly enhances the oxygen evolution reaction (OER) activity of CoOx, although the mechanism behind this synergy is still unclear. Here, operando hard X-ray absorption spectroscopy (hXAS) is applied to monitor the Co-K edge and Ce L3 edge in CoOx/CeO2 to shed light on the evolution of Co and Ce oxidation states during OER. In addition, ex situ soft XAS (sXAS) characterizations provide information on the irreversible surface-specific transformations of the Co L3 edge as well as the O K edge.

Identification of gaseous decomposition products from irreversible side-reactions enables understanding of inner working of rechargeable batteries. Unlike for Li-ion batteries, the knowledge of the gas-evolution processes in Na-ion batteries is limited.  Our study revealed that Na-ion cells develop a less stable solid-electrolyte interphase (SEI) compared to Li-ion cells due to higher solubility of SEI constituents in Na-electrolytes.