Structural Response of P2-Type Na sub( x)MnO sub( 2) against Na+ Intercalation

P2-type Na...MnO... (P6.../mmc, Z = 2) with a layered rock-salt structure is a promising cathode material for low-cost sodium ion secondary batteries (SIBs). Here, we performed an ex situ synchrotron radiation x-ray structural analysis of Na...MnO... (0.43 less than or equal to x less than or equal to 0.71) against Na+ concentration (x). We found that the thicknesses (d...) of the NaO... layer is nearly independent of x, in a sharp contrast to the rapid decrease observed in isostructural Na...CoO... In addition, the site energy differences ... is the site energy at Na1 (Na2)] in Na...MnO... are much smaller than those in Na...CoO... These observations are interpreted in terms of the screening effect of the Na+ charge in Na...MnO... (ProQuest: ... denotes formulae/symbols omitted.)