Stepwise Structural Relaxation in Battery Active Materials.

Whenever the cycling of Li-ion batteries is stopped, the electrode materials undergo a relaxation process, but the structural changes that occur during relaxation are not well-understood. We have used operando synchrotron X-ray diffraction with a time resolution of 1.24 s to observe the structural changes that occur when the lithiation of graphite and LiFePO electrodes are interrupted.

(De)sodiation Mechanism of BiMoO in Na-Ion Batteries Probed by Quasi-Simultaneous Operando PDF and XAS.

Operando characterization can reveal degradation processes in battery materials and are essential for the development of battery chemistries. This study reports the first use of quasi-simultaneous operando pair distribution function (PDF) and X-ray absorption spectroscopy (XAS) of a battery cell, providing a detailed, atomic-level understanding of the cycling mechanism of BiMoO as an anode material for Na-ion batteries. This material cycles via a combined conversion-alloying reaction, where electrochemically active, nanocrystalline Na Bi particles embedded in an amorphous Na-Mo-O matrix are formed during the first sodiation.