Design of Na2WO4-infused grain boundary for O3-type Ni-rich layered cathodes in sodium–ion batteries

The expansion of the battery industry and the search for alternatives to lithium–ion batteries are driving research into high-performance cathode materials for sodium–ion batteries (SIBs). The O3-type Ni-rich cathodes with high capacity are promising for use in SIBs. However, the large size of Na+ ions and side reactions with electrolyte mean that they require assistance with sluggish kinetics. This work reveals a fruitful solution in the form of strengthening the grain boundaries of polycrystalline cathodes, which are vital sites of electrochemical reactions. The infusion of Na2WO4 during calcination enhances the performance of NaNi0.8Mn0.2O2, while also opening new possibilities for research into SIBs. This process facilitates Na+ ion diffusion during cycling and suppresses undesirable side reactions, thereby significantly increasing the reversible capacity of NaNi0.8Mn0.2O2. The exceptional rate capability of Na2WO4-infused NaNi0.8Mn0.2O2, even at high current densities and low operating temperatures, instills a sense of optimism regarding the potential of grain boundary modification to improve performance for SIBs. [Display omitted] •Grain boundary modification enhances the performance of Ni-rich cathodes for SIBs.•Na2WO4-infused samples are prepared by the molten salt-assisted coating method.•During cycling, Na2WO4 serves as an ion diffusion channel.•The introduction of Na2WO4 improves rate capability at high voltage.•Grain boundary modification suppresses the side reactions with the electrolyte.