Quantifying the electrochemical kinetics of battery positive-electrode crystal facets

Improving the reaction kinetics of LiNi_0.8Mn_0.1Co_0.1O₂ is of great importance for realizing batteries with both high energy and power density. The promotion of electrochemical kinetics, i.e. exchange current density of LiNi_0.8Mn_0.1Co_0.1O₂ materials, is a significant strategy. Because there is great variation in exchange current density of different crystal facets, it is critical to fundamentally understand the intrinsic exchange current density of crystal facets for designing high-rate electrode materials. To quantitatively analyze the intrinsic exchange current density of six representative crystal facets on LiNi_0.8Mn_0.1Co_0.1O₂ particles, we develop a quantitative single-particle method based on the combination of the electrochemical impedance spectrum and three-dimensional geometric reconstruction on the single-particle scale. Here we show, compared to the exchange current density of (003) facet of LiNi_0.8Mn_0.1Co_0.1O₂ particles, interestingly, the exchange current density of (201) facet exhibits a 25-fold higher value (~1.50 mA/cm²), which is used to guide the nano-structure design of anisotropic core-shell LiNi_0.8Mn_0.1Co_0.1O₂ particles with improved rate performance (500 cycles) at discharge rate of 10 C (6 min).