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METHOD AND DEVICE FOR CLASSIFYING UNIT CELLS HAVING UNIFORM OPERATIONAL CHARACTERISTICS USED IN STORAGE BATTERY BY USING SCREENING TECHNOLOGY TO IMPROVE QUALITY AND SAFETY OF BATTERY
METHOD AND DEVICE FOR CLASSIFYING UNIT CELLS HAVING UNIFORM OPERATIONAL CHARACTERISTICS USED IN STORAGE BATTERY BY USING SCREENING TECHNOLOGY TO IMPROVE QUALITY AND SAFETY OF BATTERY
PURPOSE: Provided is a method for classifying a plurality of unit cells constituting a storage battery into a group of unit cells having uniform operational characteristics so as to improve capacity, cycle characteristics and overcharge/overdischarge safety of a storage battery. CONSTITUTION: The method comprises the steps of: (a) subjecting at least one unit cell constituting a storage battery to repeated cycles in which the unit cells are high-rate discharged and charged again to a fully charged voltage, and measuring a change in voltages of the unit cells while the unit cells are discharged to a standard discharge voltage to obtain first information about a change in voltages; (b) causing the unit cells to be in an open hold state at a second temperature under the standard fully charged voltage and measuring impedance values of the unit cells to obtain first information about impedance, causing the unit cells to be in the standard discharge voltage state, and measuring impedance values of the unit cells again to obtain second information about impedance; (c) subjecting the unit cells to a third temperature, measuring a change in voltages while the unit cells are discharged to obtain second information about a change in voltages, and measuring a change in voltages while the unit cells are charged again to obtain third information about a change in voltages; and (d) classifying the unit cells into groups each having similar characteristics based on the first, the second and the third information about a change in voltages as well as the first and the second information about a change in impedance values.
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