Activating Ferroelectric-Magnetic Synergistic Effects at Cathode-Electrolyte Interfaces Toward Superfast and Stable Sodium Storage

Layered oxides are promising cathode candidates for sodium-ion batteries due to their high energy density. However, the rate and cycling performances are hindered by severe interfacial side reactions and sluggish kinetics. Using NaNi_0.5Mn_0.5O₂ (NM) as a model material, ferroelectric-magnetic synergistic effects are activated at the NM-electrolyte interfaces via constructing a multiferroic layer on the NM surface, significantly realizing the superfast and stable sodium storage. First, the nucleation and growth of interfacial layers are regulated by ferroelectric-magnetic synergistic effects, resulting in the formation of a thin interfacial layer enriched with NaF. Second, a uniform sodium-ion distribution at the NM-electrolyte interfaces is established, boosting the charge transfer kinetics. Third, the distortion of NiO₆ local structure is reduced, minimizing the structural change and improving the cycling stability. As a result, superior cycling (82.1% retention after 1000 cycles) and rate capabilities (up to 50–100C) in half cells, as well as high energy densities (340.7 Wh kg⁻¹) and fast-charging properties (≈113 s per charge with ≈240.0 Wh kg⁻¹ input) in full cells, are achieved. This work presents a novel strategy for improving rate and cycling capabilities by harnessing ferroelectric-magnetic synergistic effects, offering a pathway for designing advanced electrodes in secondary batteries.