In operando powder X-ray diffraction data reveals an unexpected structural evolution in a layered P2 type NaxCo0.7Mn0.3O2 material during cycling.
The population of single crystallographic sites sometimes increases even though sodium ions are being extracted from the structure, implying a highly cooperative diffusion mechanism. The structural evolution is shown to proceed through a series of metastable structures that cannot be predicted by thermodynamics.
Received 25 Nov 2016, Accepted 20 Dec 2016
First published online 21 Dec 2016