These fits are later used in the model and shown in Figure and S5. Figure also describes the change in diffusivity across the measured stoichiometric range as a function of temperature, demonstrating the Arrhenius-type behaviour of this parameter. The average value of solid-phase diffusivity of the 'fitted' curves for the graphite-SiOy is lower than the experimental average for about a factor of three, because we are fitting to the log10(D) rather than D. The reason not to fit to D directly is because that would not capture the features in low diffusivity zones, plus adds the risk of obtaining negative values for diffusivity. Fitting to to the log10(D) ensures diffusivity is always positive and captures the features at different orders of magnitude, at the expense of underestimating the average diffusivity (especially in the negative electrode). Therefore, a scaling factor of 3.03 for the graphite-SiOy diffusivity was introduced in the diffusivity used in the final model so the fitted average diffusivity matched the experimental average diffusivity across all temperatures, as shown in Figure (bottom right). An Arrhenius relationship (Eq. [6]) can be used to find the activation energies across the stoichiometric range of each electrode (Figure ). Similarly to the solid-phase diffusivity, the activation energies are influenced by thermodynamic phases and their transitions. For NMC the activation energy is in the range of 10 kJ mol -1 to 20 kJ mol -1 . This compares to reported values of 15 kJ mol -1 to 30 kJ mol -1 for the lower nickel content NMC electrodes. For graphite-SiOy the activation energy has a wider range of 5 kJ mol -1 to 60 kJ mol -1 . Similar to values up to 50 kJ mol -1 for graphite reported by Ecker et al. For graphitic materials the consensus is that values are generally between 20 kJ mol -1 and 40 kJ mol -1 . The range in reported values is attributed to the variability and high uncertainty for the analytical approaches used in determining the diffusion coefficients. Significant temperature dependence is observed for the diffusivity between stoichiometries of x=0.3 to 0.5 and at approximately x=0.8, corresponding to the plateau regions of graphite. Previously the exchange current density and its activation energy were evaluated at a single stoichiometry. Here, the exchange current density and its dependency were mapped on temperature and lithium concentration at various stoichiometries using a half cell (Figure ). The exchange current density 𝑗𝑗 𝑡𝑡 can be evaluated by measuring the charge-transfer resistance 𝑅𝑅 𝑐𝑐𝑡𝑡 during EIS: