STRUCTURE OF MATERIALS

132 ESRF

Fig. 115: a) Scatter plots of XRD point measurements, colour-coded by depth, showing LixC6 for 6C charge. Illustration showing the depths to which colours correspond. b) (Top) Colour map of Li wt% as a function of

depth and time for the 6C charge and (bottom) Li wt% plotted for different depths.

Fig. 114: a) Photograph showing the operando coin cell in place during the

experiment. b) Illustration showing the internal assembly. c) Illustration showing a magnified

view of the graphite electrode. The coloured illustration shows a qualitative example of a

lithiation gradient.

conditions of up to 6C (full charge in 10 min) in a thick (101 μm) graphite electrode (Figure 114). With a depth resolution of 3 μm and point measurements taken at 100 Hz, the state of lithiation, concurrent fractions of graphite s lithiation stages, and Li plating and stripping, are quantified. This provides the first spatial and

temporal description of depth-heterogeneities of Li plating, current densities, and state of charge during fast-charge and discharge conditions.

The evolution of the distinct lithiation stages was quantified at each depth, providing insight into the lithiation state distribution (Figure 115).