Boosting the electrochemical performance and moisture stability of O3-type NaNi1/3Fe1/3Mn1/3O2 cathodes using novel Na2MoO4 coatings prepared via a polyvinylpyrrolidone-anchored complex coating process

O3-type layered oxides are considered highly promising cathode materials for sodium-ion batteries owing to their notable specific capacities, high theoretical energy densities, and low costs. However, the applications of O3-type layered oxides are limited owing to their structural degradation during charge-discharge cycles and poor moisture stability, which negatively affect their performance and durability. Notably, surface modifications of these materials play a crucial role in mitigating these challenges by providing a protective layer safeguarding the cathode material. In this study, Na2MoO4 (NMO) was successfully coated onto the surface of Na(Ni1/3Fe1/3Mn1/3)O-2 (NFM) using a polyvinylpyrrolidone (PVP)-assisted wet chemical method. Despite their low costs and good electrical conductivities, Mo-based coatings are yet to be explored as potential coating materials for O3-type layered oxide cathodes. Here, the main PVP chain facilitates the formation of a uniform NMO coating layer by effectively anchoring Mo6+ ions onto the surface of the (Ni1/3Fe1/3Mn1/3)C2O4<middle dot>xH(2)O ((NFM)C2O4) precursor. The presence of the NMO nanocoating layer on the NFM surface was confirmed via various characterization techniques. The NMO-coated NFM exhibited notable improvements in electrochemical performance compared to pristine NFM. In addition, the NMO-coated NFM exhibited superior moisture stability. This study presents an effective strategy to simultaneously improve the electrochemical performance and moisture stability of O3-type layered cathodes for sodium-ion batteries.