METHOD OF TESTING LITHIUM-ION SECONDARY BATTERY, AND METHOD OF PRODUCING LITHIUM-ION SECONDARY BATTERY USING THE SAME

Provide is a method of testing a lithium-ion secondary battery which enables whether the battery is good or bad to be determined with high accuracy in a short time even when lithium iron phosphate is used as a cathode active material. The method of testing a lithium-ion secondary battery including a cathode containing lithium iron phosphate as a cathode active material, an anode containing a carbon material as an anode active material, and an electrolyte layer arranged between the cathode and the anode includes: adjusting a charging rate of the lithium-ion secondary battery to be in a plateau region and to be in the range from 25 to 35% or 70 to 90%; setting voltage of a test power supply to a voltage equal to or higher than voltage of the lithium-ion secondary battery; building a circuit by connecting the lithium-ion secondary battery and the test power supply; measuring a leakage current that flows through the circuit until the increase of the leakage current converges; and determining whether the lithium-ion secondary battery is good or bad based on the leakage current after the leakage current has converged.