Ionic potential mediated compositional-structural dual gradient engineering in P2/O3 cathodes for high-energy sodium storage

doi:10.1016/j.jechem.2025.12.029

Ionic potential mediated compositional-structural dual gradient engineering in P2/O3 cathodes for high-energy sodium storage

2025-12-23

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DOI：10.1016/j.jechem.2025.12.029

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Sodium-ion batteries (SIBs) are regarded as a promising alternative to lithium-ion batteries for grid-scale energy storage owing to their low cost and sustainability; however, their competitiveness is still limited by relatively low energy density. Here, we report a scalable Mn-Fe-Ni layered oxide with a compositional-structural dual-gradient (DG) architecture synthesized via a three-step co-precipitation method. By exploiting the opposite roles of high-ionic-potential Mn and low-ionic-potential Fe in stabilizing the P2 and O3 frameworks, respectively, a pure compositional Mn/Fe gradient is translated into a structural P2/O3 gradient with precisely guided synthesis conditions. The Fe-deficient surface effectively suppressed Fe4+-induced side reactions, while the stable P2-type shell and the enlarged R value of the O3 core further enhanced cycling stability during structural evolution. The optimized cathode delivered an energy density of 478 Wh kg−1 at 4.2 V, with 82% capacity retention after 200 cycles in half cells and 91% retention after 1600 cycles in full cells. This study demonstrates a viable pathway for developing high-energy-density and long-lifetime cathodes for sodium-ion batteries.

Ionic potential mediated compositional-structural dual gradient engineering in P2/O3 cathodes for high-energy sodium storage

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