The activation energy of solid-phase diffusion can be calculated by repeating GITT at different temperatures. This enables us to find the concentration/temperature dependency of solid-phase within the active material. The diffusion coefficients were analysed from the transients and steady-phase regions during GITT. The analytical approach involves evaluating changes in lithium concentration at the particle surface as a function of time. This can be described by an expression relating to the Sand equation: 49