Na3MnPO4CO3 as cathode for aqueous sodium ion batteries: Synthesis and electrochemical characterization

Abstract A low temperature ionothermal method making use of deep eutectic mixtures (DES) as solvent medium is reported for the synthesis of sedorenkite type Na3MnPO4CO3. The synthesized material is electrochemically characterized as a cathode material for aqueous sodium ion batteries. The physical characterization of the synthesized material is done by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and thermo-gravimetric analysis (TGA). The SEM and XRD data of the sample shows that the particle size is altering between 20 and 25 nm. Further, the electrochemical properties of the material are studied using cyclic voltammetry and galvanostatic charge-discharge techniques. The CV profiles of Na3MnPO4CO3 in 5 M NaNO3 recorded at different scan rates show that the material undergoes reversible sodium ion insertion/de-insertion with a resistive behavior. Thus, the reaction is found to be diffusion controlled. The cell, NaTi2(PO4)3/5 M NaNO3/Na3MnPO4CO3 delivers a discharge capacity of 68 mA h g−1 at C/5 rate and retains a discharge capacity of 65.13 mA h g−1 up to 50 cycles with good rate capability.