Abstract: A positive electrode active material is granular and comprises a compound represented by formula 1: (NaxAy)a?bM1[M2(CN)6]?, wherein A is selected from at least one of alkali metal elements and has an ionic radius greater than that of sodium, M1 and M2 are each independently selected from at least one of transition metal elements, 0<y?0.2, 0<x+y?2, 0???1, a+b=2, 0.85?a?0.98, (represents a vacancy, and b represents the number of vacancies; and when the positive electrode active material is dissolved, at a temperature of 20° C., into an aqueous solution having a concentration of 5 g/100 g water, a pH value of the aqueous solution is in a range of 7.6 to 8.5. The positive electrode active material has good cycling and rate performance, and a high specific capacity.

Abstract: The present application provides a positive electrode active material which may be in a particulate form and comprise a compound represented by Formula 1: NaxAyM1[M2(CN)6]?·zH2O??Formula 1 wherein, A is selected from at least one of an alkali metal element and an alkaline earth metal element, and the ionic radius of A is greater than the ionic radius of sodium; M1 and M2 are each independently selected from at least one of a transition metal element, 0<y?0.2, 0<x+y?2, 0<??1, and 0?z?10; and the particles of the positive electrode active material may have a gradient layer in which the content of the A element decreases from the particle surface to the particle interior.