We present an analytic method to disentangle capacitive and diffusive rate limitations in battery electrodes using only standard capacity-rate data. Experimental capacity versus charge/discharge rate curves are fitted to extract the low-rate capacity, characteristic time τ and rate exponent n . We propose that n reflects the relative weights of capacitive and diffusive limitations, enabling the separation of τ into capacitive and diffusive timescales, τ C and τ D , for systems with 0.5 ≤ n ≤ 1. Applying the method to six literature datasets spanning common Li-ion storing materials over a range of electrode thicknesses, we find that τ C and τ D exhibit the thickness scaling expected from simplified transport models. The separated timescales further allow direct estimation of in-pore electrolyte conductivity and diffusion coefficients, giving realistic values without additional experiments. This approach offers a practical tool for diagnosing rate-limiting mechanisms and guiding design of faster-charging, higher-power electrodes. • Capacity–rate data are used to separate capacitive (τ C ) and diffusive (τ D ) timescales. • A simple analytic method extracts τ C and τ D from standard measurements. • Thickness scaling of τ C and τ D agrees with simplified transport models. • Electrolyte conductivity and diffusivity are estimated without extra experiments. • The method enables diagnosis of rate-limiting mechanisms in battery electrodes.
Jonathan N. Coleman (Thu,) studied this question.