Reactor for preparing precursor of lithium composite transition metal oxide and method for preparing precursor

A reactor for preparing a precursor of lithium composite transition metal oxide for lithium secondary batteries, the reactor having a closed structure comprising:

• a stationary hollow cylinder;
• a rotary cylinder having the same axis as the stationary hollow cylinder and an outer diameter smaller than an inner diameter of the stationary hollow cylinder;
• an electric motor to generate power, enabling rotation of the rotary cylinder;
• a rotation reaction area disposed between the stationary hollow cylinder and the rotary cylinder, wherein ring-shaped vortex pairs that are uniformly arranged in a rotation axis direction and rotate in opposite directions are formed in the rotation reaction area;
• and
• an inlet through which a reactant fluid is fed into the rotation reaction area and an outlet through which the reactant fluid is discharged from the rotation reaction area,
• wherein a ratio of a distance between the stationary hollow cylinder and the rotary cylinder to the outer diameter of the rotary cylinder is higher than 0.05 and lower than 0.4.