A Kinetic Indicator of Ultrafast Nickel-Rich Layered Oxide Cathodes

Elucidating high-rate cycling-induced nonequilibriumelectrodereactions is crucial for developing extreme fast charging (XFC) batteries.Herein, we unveiled the distinct rate capabilities of a series ofNi-rich layered oxide (NRLO) cathodes by quantitatively establishingtheir dynamic structure-kinetics relationships. Contrary toconventional views, we discovered electrode kinetic properties obtained ex-situ near equilibrium states failed to assess the effectiverate capability of NRLOs at ultrafast C rates. Further, the kineticphase heterogeneity, characterized by the dynamic separations in in-situ X-ray diffraction patterns and deviations in NRLO c-axis lattice parameters, exclusively correlated with thecapacity reduction under XFC and became an effective indicator ofthe NRLO rate capability. Enhancing the cycling temperature boostedthe rate capability of studied NRLOs by similar to 10%, which was furtherverified to mitigate the kinetic phase heterogeneity during XFC. Overall,this study lays the groundwork for tuning the kinetic phase heterogeneityof electrodes to develop ultrafast batteries.