TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The solvent is an organic or inorganic solvent capable of dissolving the lithium salt, which is lithium bromide or lithium chloride. The concentration ratio (Na/Li) of Na+ in the reaction precursor to Li+ in the electrode material is 2-20, preferably 2-8. The electrode material for battery has a laminate crystal structure, a spinel crystal structure or an olivine crystal structure. Preferred Process: The temperature for the microwave heating treatment is 60-200 degrees C. The time duration for the microwave heating treatment is 3-240 minutes. The microwave frequency for the microwave heating treatment is 300 MHz to 300 GHz. The microwave power for the microwave heating treatment is 1-500 (preferably 100) W. The process for preparing the reaction precursor comprises a sol-gel process or a solid-state sintering process. EXAMPLE - A sodium salt, a nickel salt, and a manganese salt were weighed according to a proper molar ratio and deionized water was added to get a saturated ion solution. A saturated solution of citric acid was formulated. Then the saturated solution of citric acid was slowly dropped into the saturated ion solution and the pH value of the mixed solution was adjusted to 7-12 by aqueous ammonia, and the mixed solution was heated to 80 degrees C, to remove the excess moisture to form a high-viscosity gel. Then the gel was moved into an oven and dried for 10-12 hours to get a powder compound. Then the powder compound was calcined at different temperatures with an appropriate heating/cooling rate, to get a crystalline powder of sodium nickel manganese oxide compound of formula (NaNi(0.5)Mn(0.5)O2) (A). Then the crystalline powder of (A) was dispersed in n-hexanol and a solution of lithium bromide (2-10 doses) was added to it, to get a mixed solution. Then a microwave heating treatment was performed on the mixed solution at a heating temperature of 60-200 degrees C for 3-240 minutes, so that lithium ion are ion exchanged with sodium ion to give lithium nickel manganese oxide compound of formula (LiNi(0.5)Mn(0.5)O2).