Sodium-ion battery, iron-based multi-element positive electrode material and precursor thereof, and preparation method of precursor

The invention discloses a sodium ion battery, an iron-based multi-element positive electrode material and a precursor thereof, and a preparation method, and belongs to the technical field of batteries. The preparation method of the iron-based multi-element positive electrode material precursor comprises the following steps: reacting a base solution, a precipitant solution, a complexing agent solution and a metal salt aqueous solution, and stopping feeding when the material growth granularity reaches a preset value; the concentration of ammonia in the base solution is 1.5 g/L-16 g/L, and the pH value is 9.5-12; the pH value range of the system in the seed crystal synthesis process is controlled to be 9.5-12 by the precipitant solution, and the ammonia concentration of the system is controlled to be 0-16g/L by the complexing agent solution; the reaction temperature is 30-70 DEG C; by at least regulating and controlling key parameters, such as temperature, pH value and ammonia concentration, of the seed crystal