Electrochemical Activity of P2 Structured Na-M-O Cathode for Sodium Ion Batteries
The Na-M-O powders were synthesized by solid-state method. Stoichiometric mixture of Na2CO3 and precursor were mixed by ball-milling. Then the mixed powders were pelletized, and the pellets were calcined at high temperature. After calcination, heated pellets were quenched. All chemicals and products were handled in an Ar-filled gloved box to avoid air exposure. Phase identification of calcined products was done by X-ray diffraction (XRD) with Cu Kα radiation and the collected XRD data were analyzed by using the Rietveld refinement program, Fullprof. Electro-chemical test were carried out in a 2032 coin type sodium cell. Galvanostatic electrochemical charge and discharge tests in 0.5M NaPF6 EC:DEC solutions were carried out at room temperature. Also, the products were characterized by SEM, TEM and so on.
The XRD patterns of Na-M-O compounds were obtained without impurities peak, respectively. The produced materials showed P2 phase even if adding other transition metal elements. Electrochemical tests were observed in the potential domain between 2.0 and 4.5 V at 20 mA g-1 current density. Initial capacity of Na-M-O electrodes showed high capacity. And the capacity retention was significantly improved by adding other transition metal elements. Details will be discussed in the conference site.