Direct imaging of oxygen shifts associated with the oxygen redox of Li-rich layered oxides

Li-rich metal oxides deliver larger specific capacities in Li-ion batteries than conventional oxides resulting from redox of lattice O^2- ions and cations, although they suffer from the voltage hysteresis and degradation of the voltage and capacity.  Atomic-resolution imaging on the structural evolutions of Li-rich oxides in oxygen redox is critical to understand the problems.

Imaging oxygen distortion is particularly important, but in conventional electron microscopy it is challenging to achieve.  In the paper 'Direct imaging of oxygen shifts associated with the oxygen redox of Li-rich layered oxides', published in Joule, the team from Oxford Materials, The Faraday Institution and The Royce Institute used an advanced 4D scanning transmission electron microscopy technique (known as electron ptychography) to image the oxygen shift in an archetypal Li_1.2Ni_0.13Mn_0.54Co_0.13O₂ upon the first charge-discharge cycle.  

The picometer-scale precision measurement points out distinct oxygen shifts in the bulk and surface regions, implying different redox mechanisms.  The team concluded that the results of oxygen shifts aid the building of understandings on oxygen redox and the associated problems.