Secondary battery and method for manufacturing the same
The present invention relates to a secondary battery, in which a sealing property is improved, and a method for manufacturing the same. The secondary battery includes: a can member having an opening; a top cap assembly sealing the opening; a gasket insulating the opening from the top cap assembly; and a hot melt applied to a surface of the gasket, wherein the hot melt has fluidity and viscosity at a predetermined temperature or more and is hardened at a temperature less than the predetermined temperature.
1. A method for manufacturing a secondary battery, the method comprising:
a preparation step of preparing a can member, a top cap assembly, and a gasket;
a coating step of applying a hot melt that is dissolved in an organic solvent to the gasket;
a drying step of drying the gasket to evaporate the organic solvent after the coating step;
an assembly step of assembling the can member and the top cap assembly with the gasket after the drying step to manufacture the secondary battery, the hot melt being applied to an entire first surface of the gasket coupling to the can member and an entire second surface of the gasket coupling to the top cap assembly; and
an activation step of activating the secondary battery,
wherein the activation step comprises changing a phase of the hot melt by changing a temperature of the secondary battery, such that the gasket is airtightly adhered to the can member and the top cap assembly by the hot melt that is changed in phase,
wherein during the activation step, the hot melt transitions between a softened viscous state at a first temperature equal to or greater than a predetermined temperature and a hardened state at a second temperature less than the predetermined temperature, the predetermined temperature being a glass transition temperature of the hot melt,
wherein the hot melt is permeated into a groove extending into the can member,
wherein the hot melt comprises a thermoplastic resin, a tackifier, and a coupling agent, the coupling agent being bound to an oxide of the can member via oxide binding on an inner surface of a metal material of the can member,
wherein the thermoplastic resin comprises a polyester-based resin, the tackifier comprises at least one or more of a phenol-based resin, a carbon-based resin, and a rosin-based resin, and the coupling agent comprises one or more of aminosilane and vinylsilane,
wherein the activation step comprises:
a room-temperature aging process of aging the secondary battery at a room temperature;
a high-temperature aging process of aging the secondary battery at the first temperature that is higher than the room temperature; and
a charging/discharging process of charging and discharging the secondary battery at the second temperature that is lower than the first temperature, after the high-temperature aging process, and
wherein the hot melt permeates into the groove extending into the can member during the high-temperature aging process without a separate step for melting the hot melt.
2. The method of claim 1 , wherein
the predetermined temperature is 60° C.
3. The method of claim 2 , wherein the hot melt is in a hardened state during the room-temperature aging process, the hot melt is changed in phase to a viscous state in which the hot melt has fluidity and viscosity during the high-temperature aging process, and the hot melt is again changed in phase to the hardened state at the room temperature.
4. The method of claim 1 , wherein the organic solvent comprises at least one or more of toluene, xylene, and methyl ethyl ketone.