A single-particle model serves as the simplest representation emphasizing active material intercalation of the electrode. This model captures interplay between active material reaction and diffusion processes . For simplicity, we assume the system is reaction limited , allowing us to neglect solid state diffusion in the particles. The system consists of a single active material particle in an idealized electrolyte bath, corresponding to a half cell electrode only. We define ϕ = ϕ s -ϕ + as the difference between the solid and electrolyte potential, which is the electrical potential difference applied to the kinetic interface. Within this single-particle model, the electrolyte potential applied to the single particle is denoted as ϕ, while the current is i, representing the rate of lithium-electron pairs intercalating or deintercalating into the active material. The relationship between the current and potential is dictated by the reaction kinetics, modeled by the coupled-ion electron transfer kinetics. To account for the complexities of a full cell, further extensions to the model are required as discussed below.