Synergistic structure of LiFeO2 and Fe2O3 layers with electrostatic shielding effect to suppress surface lattice oxygen release of Ni-rich cathode

The Ni-rich cathodes used for lithium-ion batteries (LIBs) suffer from severe surface side reactions, slow kinetics, and microcracks during long-term cycling. To address these problems, a dual-modified protective coating consisting of LiFeO&FeO layers (denoted as LFO) was fabricated on the surface of the cathode material LiNiCoMnO (NCM811) by capturing the lithium impurities in the electrolyte solution using an electric field. The LiFeO layer acts as an ionic conductor, accelerating interfacial Li transport, and exhibits a synergistic effect with the bulk material during the charging/discharging process. The FeO layer, which contains abundant oxygen vacancies, acts as an electrostatic shielding layer and effectively inhibits the outward migration of O (α < 2), thus improving the structural stability. Hence, the interface-protected NCM@LFO3 cathode showed excellent cycling stability (capacity retention of 82.4% after 600 cycles at 1 C) and even at a high cut-off voltage of 4.5 V (capacity retention of 88.9 % after 200 cycles at 1 C).