An epitaxial coating with preferred orientation stabilizing High-Energy Ni-Rich NCA cathodes

Abstract

Surficial activity and stability of layered Ni-Rich cathodes are important and interactive electrochemical characteristics of lithium-ion batteries (LIBs), especially under aggressive working conditions (e.g., high cutoff voltages, or high charging/discharging rates, or a moist storage/assembling environment). Here, we construct metal–organic framework (MOF)-derived α-LiAlO2 epitaxial coatings (5 ∼ 10 nm) on LiNi0.80Co0.15Al0.05O2 (NCA) surface, in which α-LiAlO2 are realized by the controlled-pyrolysis of MOF and in-situ lithiation with surficial lithium impurities on NCA particles. The α-LiAlO2 epitaxial coatings share the same crystal structure and orientation with the NCA substrate, which enable the surface-engineered NCA cathodes to achieve enhanced chemical stability and Li+-migration kinetics (including the interface between NCA substrates and α-LiAlO2 layers). In detail, the epitaxial α-LiAlO2-coated NCA displays a high capacity of 178.3 mA h g−1 at 5C, a capacity retention of 70.1% after 200 cycles (vs. 42.2% of the pristine NCA, 3.0–4.5 V), and a much-improved chemical/electro- stabilities in the air-exposure testing. DFT calculation shows that the induced Fermi-level in spin-up channel supports the increased electrical conductivity of the α-LiAlO2 coated NCA materials. This work demonstrates a new idea for design of specific crystal orientations, which would be applied to fulfill efficient production, machining, and applications of functional electrode materials.