NOVELTY - An iron source solution and phosphorus source solution are mixed. Deionized water and a dispersant are dispersed. The mixed solution of phosphorus source and iron source, metal dopant compound solution, and alkaline solution are added, reacted, filtered, washed, and sintered to obtain a dopant-metal-ion-containing iron phosphate. A carbon source is added to a dispersant solution and stir-mixed with iron phosphate. The mixed material is spray-dried, sintered and cooled, to obtain a micro-nano lithium iron phosphate anode material doped with metal ion.    USE - Preparation of metal-ion-doped micro-nano lithium-iron phosphate anode material for lithium ion batteries used in solar energy applications, electric automobiles, and high-power applications.    ADVANTAGE - The method ensures accurate iron-phosphorus ratio by liquid-phase homogeneous reaction, improves conductivity and tap density of material, and enables uniform dispersion and spray drying. The obtained product has narrow grain size distribution, high tap density, and excellent fluidity. The method uses quick low-temperature heat-treatment process, is simple and economical, and enables large-scale production.    DETAILED DESCRIPTION - An iron source, a phosphorus source, and a dopant metal ion compound are weighed such that the molar ratio of iron and phosphorus is 1:1. The three components are dissolved in water separately, to obtain solutions. The iron source solution and phosphorus source solutions are mixed to obtain a mixed solution with a concentration of 0.75-2 mol/L. The doping amount of metal ion is 0.01-0.05 with respect to total amount of iron ions. The concentration of dopant metal compound solution is 0.1-1 mol/L. An alkaline solution with a concentration of 0.1-3 mol/L is prepared. Deionized water and a dispersant (0.1-0.5%) are stir-dispersed uniformly in a reactor at 200-2000 rpm for 0.5-4 hours. The mixed solution of phosphorus source and iron source, metal dopant compound solution, and alkaline solution are added to the reactor, stirred, mixed uniformly at 200-2000 rpm, and reacted for 0.5-4 hours at 15-80 degrees C. The feeding rate of phosphorus source solution and iron source solution is 2-15 ml/min, the feeding rate of dopant metal ion compound solution is 1-10 ml/minute, and the feeding rate of alkaline solution is such that the pH is adjusted to 1.5-6. The obtained product is filtered, washed thrice with deionized water and then once with ethanol at 80 degrees C, dried for 4-8 hours at 350-550 degrees C, and sintered for 4-8 hours to obtain a dopant-metal-ion-containing iron phosphate. A lithium source is weighed such that the molar ratio of lithium, iron and phosphorus is (1-1.05):(0.95-1):1. A carbon source (0.5-5%) is added to an aqueous solution containing a dispersant (0.1-0.5%), stir-mixed at 200-800 rpm for 0.25-2 hours with iron phosphate, and the solid content is adjusted to 10-50% using deionized water. The mixed material is added to a spray dryer, controlling the inlet temperature at 180-250 degrees C and outlet temperature at 90-120 degrees C. The dried material is sintered at 400-700 degrees C for 8-12 hours under protection of inert gas, and cooled to obtain a micro-nano lithium iron phosphate anode material doped with metal ion.