In the following chart, the instantaneous voltage change is due to cell Cell internal resistance $R_0$, and the exponentially slowing diffusion voltage change is due to diffusion processes:
Diffusion is also the cause of the Cell overpotential after periods of charge or discharge.
Randles model follows (imperfectly) the physics of the cell.
$Z_W$ is a Warburg impedance, it models slow diffusion processes (diffusion voltage).
Warburg impedance is impossible to write down in differential equations, therefore, it's replaced by series of parallel resistor-capacitor circuits.
The RC time constant of these circuits increases with temperature:
These time constants also depend on the State-of-charge.
See the Quick way to estimate diffusion resistance and capacitance in equivalent-circuit model of a cell.
Related:
‣ 2.1.4, 2.3.8