Strain Engineering of Ni-Rich Cathode Enables Exceptional Cyclability in Pouch-Type Full Cells.

Abstract

Ni-rich layered oxides are at the forefront of the development of high-energy Li-ion batteries, yet the extensive applications are retarded by the deteriorative capacity and thermal instability. Herein, an in situ co-precipitation strategy is implemented to achieve the novel super-dispersed Nb-doped Ni-rich cathode that consists of the elongated and radially aligned primary particles with increased oxygen stable {001} planes. The unique microstructure homogenizes the intragranular and intergranular strain distribution and stabilizes the spherical secondary particles, effectively inhibiting microcrack formation and propagation and surface degradation. The super-dispersed Nb doping prevents the Li/Ni disordering and lattice oxygen escape, thereby further strengthening the crystal structure and thermal stability. Accordingly, this cathode delivers a high reversible capacity of 229.0 mAh g^-1 at 0.1 C with much better retention at 55 °C and 5 C after 100 cycles than the conventional Nb-doped Ni-rich cathodes. In a pouch-type full cell, it exhibits exceptionally long life with a capacity retention of 91.9% at 1 C after 500 cycles and 80.5% at 5 C after 2000 cycles within 3.0-4.2 V, greatly prolonging the service period to cater to the lightweight and intelligence of electric vehicles.