Trace high-entropy doping unlocks a high-energy, high-rate and stable Mn-based NASICON cathode for sodium-ion...

Na₃MnTi(PO₄)₃ (NMTP), a representative polyanionic compound, promises high capacity and high energy density for sodium storage. However, NMTP usually suffers from inferior cyclability and large Na⁺ diffusion energy barriers. Here, we introduce a trace high-entropy doping design on NMTP. By introducing a synergistic cocktail of five elements at low concentrations, NMTP achieves high capacity, high rate, and stable cycling simultaneously. Specifically, the resulting high-entropy Na_3.14MnTi_0.9(VFeAlCrCu)_0.02(PO₄)₃ (HE-Na_3.14MTP) delivers a capacity (167.2 mAh g^-1) near the theoretical capacity, an elevated energy density of 553 Wh kg^-1 at 0.1C, and retains 91% of its capacity after 900 cycles at a demanding 5C rate. This work tackles the capacity fading and Na⁺ diffusion barrier issues of NMTP through high-entropy design and this strategy might be applicable to other Mn-based electrode materials.