Speaker
Description
Battery materials can undergo a series of structural phase transitions during cycling that significantly change the ionic diffusion. In-operando $\mu$SR measurements provide a powerful new tool to investigate the ionic diffusion in these intermediate phases that affect both the performance and longevity of batteries.
Here we report in-operando $\mu$SR measurements of the battery cathodes LiNiO$_2$ and Na$_{2/3}$Li$_x$Ni$_{1/3}$Mn$_{2/3}$O$_2$ ($x = 0, 0.05$), materials that show multiple distinct phases on cycling and show large differences in the rate of ionic motion between successive phases related to the structural changes in each material. These measurements inform future materials design efforts to improve the performance of these battery cathodes.
In LiNiO$_2$ the internal field distribution changes in each of the four structural phases following the known transitions as a function of voltage. The hopping rate is nearly constant in two of the structural phases and changes smoothly in the other two phases. The observed behaviour shows how ionic motion relates to capacity fade at different voltages.
For Na$_{2/3}$Li$_x$Ni$_{1/3}$Mn$_{2/3}$O$_2$ ($x = 0, 0.05$) we show that adding a small amount of Li improves the diffusion properties. Similar to the previously studied Li-NMC811 cathode material [1], there is also a correlation between the fitted parameters and $\frac{dQ}{dV}$ measured electrochemically.
[1] I. McClelland et al., Chem. Mater. 2023, 35, 4149—4158.
| peter.baker@stfc.ac.uk |
