Mn-Doped\nNa<sub>4</sub>Fe<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub>P<sub>2</sub>O<sub>7</sub> as a Low-Cost and High-Performance\nCathode Material for Sodium-Ion Batteries

Na₄Fe₃(PO₄)₂P₂O₇ (NFPP) is considered to be an ideal cathode\nmaterial\nfor sodium-ion batteries due to its high theoretical capacity, stable\nstructure, small volume change, low cost, and nontoxicity. However,\nthe inherent low electronic conductivity of polyanionic materials\nlimits the application of this material. In this work, we improved\nthe electronic conductivity and structural stability of the material\nthrough a dual modification synergistic strategy of manganese ion\ndoping and surface carbon coating and prepared Na₄Fe_2.9Mn_0.1(PO₄)₂P₂O₇@C (0.1 Mn-NFPP@C) composites by a simple mechanical-assisted\nchemical synthesis method. It can release 119.6 mAh g^–1 at 0.1C. The capacity retention rate is 97.4% after 100 cycles at\n1C and 84.8% after 3000 cycles at 10C. Many tests and calculations\nin this work also show that 0.1 Mn-NFPP@C modified by Mn²⁺ doping and carbon coating has higher electronic conductivity and\nelectrochemical kinetics and thus exhibits better electrochemical\nperformance.