The evolution of structure–property relationship of P2-type Na 0.67 Ni 0.33 Mn 0.67 O 2 by vanadium substitution and organic electrolyte combinations for sodium-ion batteries

Solid-state synthesis of novel electrode materials of P2-type layered oxides Na 0.67 Ni 0.33-x V x Mn 0.67 O 2 (where x = 0, 0.05, and 0.11) for the application as cathode materials in rechargeable non-aqueous sodium-ion batteries is reported. Na 0.67 Ni 0.22 V 0.11 Mn 0.67 O 2 electrode delivers significantly improved capacity retention than the pristine P2-Na 0.67 Ni 0.33 Mn 0.67 O 2 when cycled between 1.5 and 4.3 V. The effect of organic ester electrolytes with 1.0 M NaClO 4 shows diverse effects in the cathode material. The best capacity retention for V-substituted electrodes is observed in ethylene carbonate (EC): propylene carbonate (PC): dimethyl carbonate (DMC) (0.45: 0.45: 0.1) with 1.0 M NaClO 4 salt at a C-rate of 0.2C among four different ester electrolytes investigated [PC, EC: PC (1: 1), EC: DEC (1: 1), and EC: PC: DMC (0.45: 0.45: 0.1)]. Graphical Abstract