TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The step (c) is performed by using a spray granulation device having many spray nozzles, each of which has many sub-nozzles. The spray granulation device is set at: a flow rate of 0.3-1.5 l/minute; an air flow rate from 50-150 m3/minute; a nozzle pressure of 2-8 kg/cm2; and an outlet temperature of 90-120 degrees C. The step (d) is performed under nitrogen atmosphere at 650-850 degrees C for 3-10 hours. Preferred Components: Hot air introduced into the spray granulation device has a temperature of 180-240 degrees C. (I) has an olivine structure. The phosphate-containing precursor is at least one of phosphoric acid, diammonium phosphate or ammonium phosphate. The lithium-containing precursor is at least one of lithium carbonate, lithium hydroxide or lithium chloride. The metal source is at least one of iron, manganese or cobalt source. The iron source is at least one of iron(II) oxalate, iron nitrate, iron oxide, iron(III) phosphate, iron(III) sulfate or iron powders. The manganese source is at least one of manganese sulfate, manganese nitrate, manganese acetate, manganese carbonate, manganese chloride, manganese oxide, manganese dioxide or manganese trioxide.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The type of the spray nozzle is rotary type, pressure type and/or two-fluid type. The number of the spray nozzles in the spray granulation device is 8-16.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The carbon source is at least one of sugar, vitamin C, citric acid, polyethylene, polypropylene, benzene ring-containing polymer or linear hydrocarbon. EXAMPLE - Diammonium phosphate, lithium carbonate, iron(II) oxalate and manganese sulfate were mixed in a molar ratio of 1:0.5:0.5:0.5, following by adding 10 mole% vitamin C and grinding to form a mixture. The mixture was converted into a granular mixture by using a spray granulation device (at flow rate of 0.3 l/minute, the air flow rate is 120 m3/minute, and nozzle pressure is 8 kg/cm2). The temperature of hot air introduced into the spray granulation device is 230 degrees C, and the outlet temperature is 110 degrees C. The formed granular mixture was sintered at 650 degrees C under nitrogen atmosphere for 10 hours to obtain porous lithium-iron-manganese-phosphate containing particles (LiFe0.5Mn0.5PO4).