TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Method: The heating step is a heating process of the solid powder in nitrogen or argon gas. The providing step further comprises adding a carbohydrate or a polymer, which is heated at high temperature to supply a trace of carbon increasing electrical conductivity, and the carbohydrate or the polymer is 1-25 wt.%. Preferred Condition: The heating process is carried out at 400-1000degreesC for 1-15 hours. Preferred Component: The inorganic acids are hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, hypochlorous acid, and/or hydrofluoric acid. The lithium salt is lithium hydrate, lithium fluoride, lithium nitrate, lithium chloride, lithium bromide, lithium acetate, lithium oxide, lithium phosphate, lithium hydrophosphate, lithium dihydrophosphate, lithium ammonium phosphate, and/or lithium diammonium phosphate. The phosphate salt is diammonium hydrophosphate, ammonium dihydrophosphate, triammonium phosphate, phosphorus pentoxide, phosphoric acid, lithium hydrophosphate, lithium dihydrophosphate, lithium ammonium phosphate, and/or lithium diammonium phosphate. The vanadium salt is vanadium oxide (VO2), V2O3, V2O5, and/or ammonium VO3. Preferred Composition: The molar ratio of the iron power, the lithium salt, and the phosphate salt dissolved into the mixed acid solution is 0.9-1.2: 0.9-1.2: 0.9-1.2.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The organic acid is acetic acid, citric acid, oxalic acid, tartaric acid, propionic acid, and/or butyric acid. EXAMPLE - 800 g Olivine lithium-iron-phosphate (LiFePO4) and 200 g monoclinic lithium-vanadium-phosphate (Li3V2(PO4)3) and cathode material powders were mixed together. In the mixed powders, the molar ratio of LiFePO4 and Li3V2(PO4)3 was 5:0.5. After adding the mixed powders into the 3 wt.% polyethylene glycol (PEG) solution, the mixed solution was dried by the spray drying method to obtain composite cathode material precursor powders with even distribution of olivine LiFePO4 and monoclinic Li3V2(PO4)3. The powders obtained by the spray drying method were put into nitrogen gas and heated at 750degreesC for 1 hour, after which 1000 g LiFePO4/Li3V2(PO4)3 composite cathode material powders were obtained. The discharge capacity of the LiFePO4/Li3V2(PO4)3 composite cathode material powders was higher than the discharge capacity of pure olivine LiFePO4 and monoclinic Li3V2(PO4)3 cathode material powders.