Non-Equilibrium Lattice Heterogeneity As the Unified Kinetic Hurdle of Ni-Rich Layered Cathode for Ultrafast Lithium Ion Batteries

The significantly reduced capacity at a fast cycling rate is one of the most serious bottlenecks that prevent the large-scale application of Ni-rich layered oxide cathode for electrical vehicle batteries. Figuring out the capacity decline mechanism is crucial to addressing such hurdle and developing ultrafast lithium ion batteries. In this work, with operando synchrotron-based spectroscopy, we captured the formation of non-equilibrium separated phases during the extremely fast cycling of various Ni-rich layered oxides, in contrast to their solid-solution structural evolution pathway at slow cycling rate. Further, such non-equilibrium phase heterogeneity was demonstrated to be an effective capacity retention descriptor for Ni-rich layered oxide cathode: the capacity retention ratio is liner inversely proportional to the lattice heterogeneity at an extremely fast cycling rate (e.g., 10C), regardless of the composition and Ni content. Those detrimental non-equilibrium phase heterogeneity could be eliminated by raising the operation temperature, contributing to much higher lithium ion transport kinetics and better capacity retention during ultrafast cycling