Method for manufacturing gel polymer electrolyte secondary battery and gel polymer electrolyte secondary battery obtained thereby
The present disclosure relates to a method for manufacturing a secondary battery including a gel polymer electrolyte and a secondary battery obtained thereby. The method can inhibit thermal crosslinking of a gel polymer electrolyte during the wetting with an electrolyte, and facilitate thermal crosslinking after the wetting with an electrolyte is finished. In addition, the method can increase uniformity of thermal crosslinking by controlling the oxygen content in a cell.
1 . A method for manufacturing a lithium secondary battery, comprising:
inserting a stack cell comprising a separator interposed between a positive electrode and a negative electrode to a battery casing;
injecting a composition for a gel polymer electrolyte into the battery casing to which the stack cell is inserted;
sealing the battery casing under oxygen-containing atmosphere;
aging the battery casing after the sealing;
removing oxygen from the battery casing;
thermally curing the battery casing; and
degassing by pressurizing the battery casing to remove the gases remaining in the battery, wherein the removing oxygen is a step of pressurizing the battery casing, by pressurizing a region where the electrode assembly is positioned, oxygen present in the region wherein the electrode assembly is positioned is transferred to a region where the electrode assembly is not present.
2 . The method according to claim 1 , wherein the sealing is carried out at 130-150° C. for 1-10 seconds.
3 . The method according to claim 1 , wherein the aging is carried out at room temperature for 72 hours or less.
4 . The method according to claim 1 , wherein the removing oxygen comprises inserting the battery casing between a pair of jigs facing each other and applying pressure thereto.
5 . The method according to claim 4 , wherein the removing oxygen comprises pressurizing merely a predetermined portion in the battery casing.
6 . The method according to claim 1 wherein a portion of the battery casing where not pressurized is removed after the thermally curing the battery casing.
7 . The method according to claim 1 , wherein the removing oxygen is carried out under a pressure of 3-15 kgf/cm 2 .
8 . The method according to claim 7 , wherein the removing oxygen is carried out for 30 seconds to 10 minutes.
9 . The method according to claim 1 , wherein the thermally curing the battery casing is carried out at a temperature of 60-70° C.
10 . The method according to claim 9 , wherein the thermally curing the battery casing is carried out for 5-24 hours.
11 . The method according to claim 1 , wherein the composition for the gel polymer electrolyte comprises: a lithium salt; a non-aqueous organic solvent; a polymerization initiator; and at least one polymerizable compound selected from the group consisting of a polymerizable monomer, oligomer and copolymer.
12 . A lithium secondary battery obtained by the method according to claim 1 , comprising the stack cell provided with the gel polymer electrolyte layer between the positive electrode and the a negative electrode,
wherein the gel polymer electrolyte layer has a polymer matrix and is formed by thermal curing,
the gel polymer electrolyte layer has a crosslinking degree of 80% or more, and
the stiffness of the secondary battery is at least 10% higher than the stiffness of a secondary battery not subjected to the removing oxygen.
13 . The method according to claim 1 , wherein an oxygen included in oxygen-containing atmosphere inhibits a chain reaction of monomers of the gel polymer electrolyte through radical quenching.
14 . The method according to claim 1 , wherein the method further includes after the thermally curing the battery casing, degassing by pressurizing the battery casing under a pressure of −85 kPa to −95 kPa for 40-60 minutes to remove the gases remaining in the battery.