  Ultrahigh rate performance of active particles used in lithium-ion battery
electrodes has been revealed by single-particle measurements, which indicates a
huge potential for developing high-power batteries. However, the
charging/discharging behaviors of single particles at ultrahigh C-rates can no
longer be described by the traditional electrochemical kinetics in such
ion-intercalation active materials. In the meantime, regular kinetic measuring
methods meet a challenge due to the coupling of interface reaction and
solid-state diffusion processes of active particles. Here, we decouple the
reaction and diffusion kinetics via time-resolved potential measurements with
an interval of 1 ms, revealing that the classical Butler-Volmer equation
deviates from the actual relation between current density, overpotential, and
Li+ concentration. An interface ion-intercalation model is developed which
considers the excess driving force of Li+ (de)intercalation in the charge
transfer reaction for ion-intercalation materials. Simulations demonstrate that
the proposed model enables accurate prediction of charging/discharging at both
single-particle and electrode scales for various active materials. The kinetic
limitation processes from single particles to composite electrodes are
systematically revealed, promoting rational designs of high-power batteries.
