Fig. 3
From: Environmentally stable interface of layered oxide cathodes for sodium-ion batteries
Chemical/electrochemical/thermal stability of the NM and NMTN samples. a Structural evolution of the NM samples exposed to humid air for 3 days. The results show the phase transition process (O′3-Birnessite) caused by H2O insertion; the vertical purple and yellow-green shadings indicate the Na-inserted and H2O-inserted layered structures, respectively. b Structural evolution of the NMTN samples exposed to humid air for 3 days. The results indicate a stabilized layered-structure independent of air exposure. c DSC results of the desodiated NM and desodiated NMTN electrodes. d–f Impedance evolution of the NM and NMTN electrodes during cycling. The results show the severely diminished electrochemical properties for the NM electrode and negligible electrochemical evolution of the NMTN electrode
