Isotropic Microstrain Relaxation in Ni-Rich Cathodes for Long Cycling Lithium Ion Batteries.

Developing isotropic-dominated microstrain relaxation is a vital step toward the enhancement of cyclic performance and thermal stability for high-energy-density Ni-rich cathodes. Here, a microstructure engineering strategy is employed for synthesizing the elongated primary particles radially aligned Ni-rich cathodes only by regulating the precipitation rates of cations and the distributions of flow field. The as-obtained cathode also exhibits an enlarged lattice distance and highly exposed (003) plane. The high aspect ratio and favorable atomic arrangement of primary particles not only enable isotropic strain relaxation for effectively suppressing microcrack formation and propagation, but also facilitate Li-ion diffusion with greatly reduced Li/Ni mixing. Consequently, it shows obvious superiority in the high-rate, long-cycle life, and thermal stability compared with the conventional counterparts. After modification, an exceptionally long life is achieved with a capacity retention of 90.1% at 1C and 84.3% at 5C after 1500 cycles within 3.0-4.3 V in a 1.5-Ah pouch cell. This work offers a universal strategy to achieve isotropic strain distribution for conveniently enhancing the durability of Ni-rich cathodes.