| CPC H01M 10/484 (2013.01) [G01R 31/374 (2019.01); H01M 10/0585 (2013.01); H01M 10/48 (2013.01); H01M 50/569 (2021.01)] | 6 Claims |

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1. A method of measuring electrolyte concentration of a secondary battery, the method comprising:
manufacturing a measuring unit in which a first electrode plate, an insulating film and a second electrode plate are sequentially stacked;
connecting electric wires to one end of the first electrode plate and the second electrode plate;
inserting the measuring unit into a space between an electrode and a separator of a battery cell; and
drawing out the electric wire to an outside of the battery cell;
calculating a concentration of electrolyte ions contained in the insulating film by connecting a measuring device to the electric wire.
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