Tracking the structural evolution at atomic-scale in the spinel Mn3O4 induced by electrochemical cycling

Mn3O4 is a possible candidate for use as an electrode material and has been found to undergo structural transformation during electrochemical cycling. Clarifying the transformation process is important in developing methods for improving electrochemical performance. Here, using scanning transmission electron microscopy (STEM) combined with the electron energy loss spectroscopy (EELS) technique in aberration-corrected TEM, we succeeded in tracking the structural evolution at an atomic-scale and identified the intermediate stage as rock-salt-structured MnO. A reasonable route was deduced via which the spinel Mn3O4 was transformed firstly into MnO and then into MnO2.