Illustration of the change of hoop stressσ_θwith timetin a spherical particle, which contains a moving two-phase boundary between the pristine core (white) and lithiated shell (grey).^[30](a)–(c)σ_θin a representative material element A near the surface. As the phase boundary moves toward the center of the particle, progressive lithiation results in a gradual expansion of the particle, leading to the reversal of hoop compression in panel (b) to hoop tension in panel (c). (d) Schematic plot ofσ_θversustin element A.