Facile solvothermal synthesis of Na1.5□0.5Mn1.5Fe1.5(PO4)3: Electrochemical study as a dual electrode material for lithium-ion batteries

Na1.5□0.5Mn1.5Fe1.5(PO4)3 (where □ denotes vacancies) microrods were obtained through a solvothermal synthesis in ethylene glycol. The combination of the XRD, Mössbauer and magnetic analyses confirm that the sodium vacancies in the Na1.5□0.5Mn1.5Fe1.5(PO4)3 structure are linked to the oxidation of Mn and Fe transition metals. The electrochemical tests have shown that Na1.5□0.5Mn1.5Fe1.5(PO4)3 is a dual electrode material for Li-ion batteries. The electrochemical study in the potential range of 1.5-4.5 V indicate that such material can be used as 3 V cathode with specific capacities of 109, 97, and 80 mAh·g−1 at current densities of 5, 10, and 20 mA·g−1, respectively. When it is tested in the potential range of 0.03-3.0 V as negative electrode material, it delivers a reversible capacity of about 170 mAh·g−1 at 200 mA·g−1 current density during >100 cycles.