Ni–Li anti-site defect induced intragranular cracking in Ni-rich layer-structured cathode

Abstract

High packing density of Ni-rich lithium transition metal oxide (LTMO) cathodes contribute to high energy density of lithium-ion batteries, however, resulting in severe intergranular and intragranular cracking issues. Most of previous works are focused on understanding the behaviors of intergranular cracks. However, the incubation mechanism of intragranular crack, especially at atomic scale, is still unclear though they are one of the main obstacles for practical application of Ni-rich LTMO cathode. Here, we reveal at atomic scale the intragranular cracking mechanism of LiNi 0.8 Mn 0.1 Co 0.1 O 2 cathode during cycling processes. Ni–Li anti-site defect enrichment region with lattice distortion has been identified as the nucleation site for intragranular crack in the primary particle. The growth of intragranular crack can be ascribed to the strain difference between layered phase and electrochemical inactive phase and the Columbic repulsion in cation-rich area, which originate from the Ni–Li anti-site defect in transformed structure. The golden strategy to acquire stable high-energy cathode lies in suppressing the migration of cations before cracks occur, providing new insights for the design of high-performance Ni-rich LTMO cathodes. We reveal at atomic scale the intragranular cracking mechanism of LiNi 0.8 Mn 0.1 Co 0.1 O 2 (NMC811) cathode during cycling processes. At atomic-scale, nucleation at Ni-Li anti-site defect enrichment region with lattice distortion has been firstly identified as the startup mechanism for intragranular crack in NMC811 cathode. The strain difference between layered phase and electrochemical inactive phase and the Columbic repulsion in the cation-rich area are considered as the two driving forces for the development of intragranular crack. Both of them originate from Ni-Li anti-site defect in transformed structure. • Ni-Li anti-site defect enrichment region has been identified as nucleation site for intragranular crack of NMC811. • The strain difference and the Columbic repulsion are considered as two driving forces for the growth of intragranular crack. • Suppress the migration of cations is a golden strategy to acquire high energy cathode with long cycle life.