Phase transition behavior of NaCrO2 during sodium extraction studied by synchrotron-based X-ray diffraction and absorption spectroscopy

The structural evolution of layered NaCrO2 cathodes for sodium-ion batteries during charge was investigated using synchrotron-based in situ X-ray diffraction and ex situ X-ray absorption spectroscopy. Three solid solution phases with expanding 'c' and contracting 'a'/'b' lattice parameters were observed. The coordination changes of Cr and Na during sodium extraction were also studied.