Calcium-induced pinning effect for high-performance Co-free Ni-rich NMA layered cathode

Abstract

Further commercialization of Co-free Ni-rich layered cathodes for state-of-the-art lithium-ion batteries (LIBs) is severely hindered by their underachieved structural ordering and charging/discharging capability. Herein, supported by density functional theory calculations, a high-performance Co-free Ni-rich Ca-pillared LiNi0.845Mn0.10Al0.05Ca0.005O2 (Ca-NMA) cathode that couples robust layered structure with fast Li+ kinetics is structurally designed by activating the pinning effect with Ca2+ doping. Notably, the suppressed Li/Ni mixing and expanded lattice c-axis are simultaneously achieved by the introduction of low-valence Ca2+ with a large radius (1.00 Å), as confirmed by X-ray diffraction (XRD), synergistically leading to the enhanced Li+ transport capability. More greatly, transitional-metal (TM) slab sliding during deep charging is effectively inhibited owing to the pinning of Ca at TM layer, which significantly alleviates the H2-H3 phase transitions revealed by in-situ XRD, enabling the inhibited kinetics hinderance at high voltages (≥ 4.2 V) coupled with the eliminated particle cracking during prolonged cycling. Consequently, the as-designed Ca-NMA cathode exhibits much-enhanced cyclability (94.9% capacity retention after 200 cycles) and rate capability (73.4% capacity retention at 10 C over 0.1 C) than those of LiNi0.85Mn0.10Al0.05O2 and LiNi0.85Co0.10Mn0.05O2 analogues. This work provides a prospective strategy to design low-cost and high-performance Co-free Ni-rich cathodes for next-generation advanced LIBs.