Method for manufacturing lithium-containing complex phosphate elliptical particles

A manufacturing method of a positive electrode active material comprising:

• a step of mixing a lithium compound, a phosphorus compound, and water to form a first mixed solution;
• a step of adjusting pH by adding a first aqueous solution to the first mixed solution to form a second mixed solution;
• a step of mixing an iron(II) compound with the second mixed solution to form a third mixed solution;
• and
• a step of heating the third mixed solution under a pressure higher than or equal to 0.1 MPa and lower than or equal to 2 MPa at a highest temperature higher than 150° C. and lower than or equal to 250° C. for less than 5 hours to form a fourth mixed solution,
• wherein the positive electrode active material comprises a secondary particle including a plurality of primary particles,
• wherein the plurality of primary particles comprises a first particle and a second particle,
• wherein the first aqueous solution is ammonium aqueous solution,
• wherein pH of the third mixed solution is more than or equal to 3.5 and less than or equal to 5.0,
• wherein each of the first particle and the second particle is a lithium-containing complex phosphate comprising one or more of iron, nickel, manganese, and cobalt,
• wherein each of the first particle and the second particle comprises a major diameter in a major axis and a minor diameter in a minor axis when observed with a microscope,
• wherein the major axes of the first particle and the second particle are substantially parallel to each other,
• wherein the major diameter of the first particle is two to six times larger than the minor diameter of the first particle and the minor diameter of the first particle is more than or equal to 20 nm and less than or equal to 130 nm, and
• wherein a median value of particle diameters of the plurality of particles obtained with use of laser diffraction and scattering method is more than or equal to 500 nm and less than or equal to 6 μm, and
• wherein a specific surface area is more than or equal to 18 m2/g and less than or equal to 50 m2/g.