Modifying surface chemistry and stress concentration to enable highly stable ultrahigh-Ni cathodes

The issues of surface degradation and internal cracking severely limit the commercialization of ultrahigh-Ni cathodes LiNi1-x-y-zCoxMnyAlzO2 (1-x-y-z ≥ 0.9) for long lifespan electric vehicles. Herein, a universal strategy with Li/Ni anti-site defect surface layer coupled with radially ordered morphology has been precisely implemented in the boron-niobium co-modified ultrahigh-Ni cathode LiNi0.9Co0.07Mn0.01Al0.02O2 (NCMA-BN), simultaneously dissipating stress accumulation and ameliorating interfacial/thermal stability. Density functional theory calculations and crucial experimental parameters reveal that Li/Ni anti-site defects driven by boron-niobium co-doping toughen the lattice oxygen framework and surface layered structure. The radially aligned primary particles of NCMA-BN are smaller and more densely packed, relieving bulk stress concentration and inter/intragranular cracking, as demonstrated by finite element analysis and postmortem electrode measurements. As a result of this multi-functional regulation strategy, the modified cathode exhibits remarkably improved capacity retention after 100 cycles at 1 C (89.4% vs. 70.7%) and after 300 cycles at 3 C (84.6% vs. 43.3%) compared to the pristine cathode. It is believed that these benefits are realized through the dual-modification of surface chemistry and bulk stress concentration, which provides a novel insight into the rational design of ultrahigh-Ni cathodes and their future commercialization.