A one-step dual modification strategy for enhancing sodium storage in O3-type NaNi1/3Fe1/3Mn1/3O2 cathodes

Abstract

O3-type sodium nickel–iron–manganese oxide (NaNi_1/3Fe_1/3Mn_1/3O₂) is recognized as a promising cathode material for sodium ion batteries (SIBs) due to its high capacity, low cost, and ease of synthesis. However, it suffers from structural instability, short cycling life, and environmental sensitivity caused by structural distortion and interfacial deterioration during cycling. Herein, a multifunctional composite coating and Zr doping are developed using an in situ one-step method. The multifunctional coating (MFC) layer can optimize the composition of grain boundaries to facilitate the rapid transfer of sodium ions and inhibit the interfacial erosion of the electrolyte and high-temperature side effects. In addition, the strong Zr–O bond stabilizes the internal crystal structure, suppressing undesirable phase transformations. Experimental tests demonstrate that the Zr-doped NFM material with the MFC layer demonstrates enhanced structural stability with a capacity retention of 80.02% after 300 cycles compared to 62.02% retention of the bare sample at 1C. Remarkably, at a high rate of 10C, it retains a specific discharge capacity of 102.1 mA h g⁻¹. When integrated into a full battery with a commercial hard carbon anode, it delivers an energy density of 346.38 W h kg⁻¹ (calculated based on cathode material mass), highlighting its substantial potential for practical deployment in SIBs.