JP5397125B2 - Manufacturing method of secondary battery - Google Patents

Description

  The present invention relates to a method for manufacturing a secondary battery using a laminate film as an exterior body, and in particular, a secondary battery in which a seal portion is not peeled off by an electrolytic solution attached when discharging gas that is likely to be generated inside when charging. It relates to a manufacturing method.

  A secondary battery such as a lithium ion secondary battery using a laminate film as an outer package is formed by laminating a battery element having a laminate structure in which a positive electrode and a negative electrode sandwiched between insulating electrolyte layers are stacked. It is enclosed in a package formed of an exterior body made of a film. The electrolytic solution is injected into the package according to the following procedure.

  FIG. 1 is a partial plan view schematically showing a part of a conventional lithium ion secondary battery. As shown in FIG. 1 (a), a battery element (not shown) is sealed in the package 1, and the peripheral edge 3 of the outer package body of the package 1 is bonded by heat-sealing leaving the opening 2. The In FIG. 1, a hatched portion is shown as a heat-sealed portion.

  Next, as shown in FIG.1 (b), electrolyte solution is infused through the opening part 2 from the injection device 4 provided with the injection needle. After depressurizing the entire package 1, the battery element is precharged in a state where the pressure is returned to atmospheric pressure, and as shown in FIG. 1C, the opening 2 is adhered to complete the injection of the electrolyte. (See Patent Document 1).

  When pre-charging is performed, carbonate-based components may be decomposed to generate methane-based gases. When gas is generated, bubbles are generated in the electrolytic solution, and when the bubbles are ruptured in the vicinity of the opening 2, the electrolytic solution is still part of the package 1 forming the opening 2, that is, still thermally fused. There was a risk of sticking to parts that were not. Further, even when the electrolytic solution is poured, there is a possibility that the electrolytic solution adheres to a portion of the peripheral portion 3 of the outer package that has not been heat-sealed.

  When the electrolytic solution adheres to a portion of the package 1 that has not yet been heat-sealed, the adhesive force due to heat-sealing is reduced, and the seal tends to be incomplete. In addition, a chemical reaction occurs when the attached electrolytic solution comes into contact with moisture in the air, and a gas such as hydrogen fluoride is generated, which may damage the resin layer used for the seal portion of the outer package. . Therefore, for example, in Patent Document 2, the opening 2 is covered with a laminate film different from the outer package so that the above-described problem does not occur even when the electrolytic solution adheres.

Japanese Patent Laid-Open No. 2001-210372 JP 2000-223087 A

  However, the secondary battery manufacturing method disclosed in Patent Document 2 increases the length, thickness, and weight of the entire secondary battery by the amount of the laminate film that is separately heat-sealed. There was a problem in that the volumetric energy density of the material decreased.

  The present invention has been made in view of such circumstances, and the electrolytic solution adheres to the opening when the generated gas is discharged to the outside without increasing the length, thickness, and weight of the secondary battery. It aims at providing the manufacturing method of the secondary battery which does not.

  In order to achieve the above object, a method for manufacturing a secondary battery according to the first aspect of the present invention is a method for manufacturing a secondary battery in which battery elements are encapsulated by an outer package made of a laminate film that can be heat-sealed to each other. A step of applying a heat-resistant protective layer to the inner surface of at least one ventilation portion for discharging the gas generated inside the secondary battery to the outside of the exterior body, and in a state in which the battery element is accommodated, The step of heat-sealing the peripheral portion of the outer package, the step of precharging by connecting to an external power source, the portion to which the protective layer is applied is opened, and the gas generated by the precharging is The method includes a step of discharging from the ventilation portion to the outside, and a step of heat-sealing the ventilation portion by removing the protective layer.

  In the first invention, the battery element is encapsulated by an exterior body made of a laminate film that can be heat-sealed to each other. A heat-resistant protective layer is pasted on the inner surface of at least one ventilation portion that discharges gas generated inside the secondary battery to the outside of the exterior body. In a state in which the battery element is accommodated, the peripheral edge of the outer package is heat-sealed and connected to an external power source for preliminary charging. The part to which the protective layer is affixed is opened, and the gas generated by the preliminary charging is discharged from the ventilation part to the outside. Then, the protection layer is removed and the ventilation part is heat-sealed. As a result, even when the electrolyte adheres to the ventilation part due to splashing during electrolyte injection, bursting of bubbles generated by the generated gas, etc., the electrolyte only adheres to the surface of the protective layer. After the preliminary charging is completed, the protective layer is removed and heat fusion is performed, so that it is possible to perform heat fusion in a state where the attached electrolyte is also reliably removed. Therefore, it is possible to maintain high sealing performance without changing the structure of the secondary battery, and it is possible to avoid occurrence of peeling due to damage of the resin layer due to chemical reaction.

  In the method for manufacturing a secondary battery according to a second aspect of the present invention, in the first aspect of the invention, the ventilation portion protrudes from a region enclosing the battery element of the exterior body to a peripheral portion of the exterior body. A step of cutting the peripheral portion of the exterior body including a part of the ventilation portion after the preliminary charging, and a step of discharging gas from the ventilation portion cut and opened to the outside It is characterized by including.

  In the second invention, the ventilation portion is provided so as to protrude from the region enclosing the battery element of the outer package to the peripheral edge of the outer package. After the preliminary charging, the outer peripheral body is cut at the peripheral portion including a part of the ventilation portion to open the ventilation portion, and the gas is discharged to the outside from the opened ventilation portion. As a result, even when gas is generated in the case of pre-charging, the vent part can be opened and the gas discharged to the outside in a safe environment. Can do.

  The method for manufacturing a secondary battery according to a third aspect of the present invention is the method according to the first or second aspect, wherein the secondary battery has a substantially rectangular plate shape, and the ventilation portion is connected to an electrode of the battery element. It is characterized in that it is provided on another side different from the one side on which a certain current collecting terminal is provided.

  In the third invention, the secondary battery has a substantially square plate shape, and the ventilation portion is provided on another side different from the one side provided with the current collecting terminal connected to the electrode of the battery element. As a result, the vicinity of the current collecting terminal where the sealing performance tends to be low can be separated from the ventilation portion, and the sealing performance after heat-sealing can be kept high.

  With the above configuration, even when the electrolyte adheres to the ventilation part due to splashing at the time of injecting the electrolyte, rupture of bubbles caused by the generated gas, etc., the electrolyte only adheres to the surface of the protective layer. In addition, after the preliminary charging is completed, the protective layer is removed and heat fusion is performed, so that it is possible to perform heat fusion in a state where the attached electrolyte is also reliably removed. Therefore, it is possible to maintain high sealing performance without changing the structure of the secondary battery, and it is possible to avoid occurrence of peeling due to damage of the resin layer due to chemical reaction.

It is a fragmentary top view which shows typically a part of conventional lithium ion secondary battery. It is a top view which shows typically the structure of the lithium ion secondary battery which concerns on Embodiment 1 of this invention. It is sectional drawing in the III-III line | wire of FIG. 2 which shows typically an example of the laminated structure of a lithium ion secondary battery. It is a top view which shows typically the state which looked at the exterior body of the lithium ion secondary battery which concerns on Embodiment 1 of this invention from the inner surface. It is sectional drawing in the surface which carried out the heat sealing | fusion which shows typically the state which heat-sealed the peripheral part of the exterior body of the lithium ion secondary battery which concerns on Embodiment 1 of this invention. FIG. 3 is a cross-sectional view of the heat-sealed surface schematically showing a state in which one side of the peripheral portion of the exterior body of the lithium ion secondary battery according to Embodiment 1 of the present invention is cut along an AA line. It is sectional drawing in the surface which carried out the heat sealing | fusion which shows typically the state which carried out the heat sealing | fusion again of the peripheral part of the exterior body of the lithium ion secondary battery which concerns on Embodiment 1 of this invention. It is a top view which shows typically the state which looked at the exterior body of the lithium ion secondary battery which concerns on Embodiment 2 of this invention from the inner surface. It is sectional drawing in the surface thermally bonded which shows typically the state which heat-sealed the peripheral part of the exterior body of the lithium ion secondary battery which concerns on Embodiment 2 of this invention. It is sectional drawing in the surface which carried out the heat sealing | fusion which shows typically the state which carried out the heat sealing | fusion again of the peripheral part of the exterior body of the lithium ion secondary battery which concerns on Embodiment 2 of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, a laminated lithium ion secondary battery will be described as a secondary battery. However, the battery element is not particularly limited to this, and a lithium secondary battery, a polymer secondary battery is not limited thereto. Any secondary battery, such as a battery, that can generate gas during pre-charging may be used.

(Embodiment 1)
FIG. 2 is a plan view schematically showing the configuration of the lithium ion secondary battery according to Embodiment 1 of the present invention. 3 is a cross-sectional view taken along the line III-III in FIG. 2, schematically showing an example of a laminated structure of the lithium ion secondary battery.

  The battery element 9 of the lithium ion secondary battery according to Embodiment 1 of the present invention includes a positive electrode plate 21 in which positive electrode mixtures 212 and 212 are formed on a positive electrode current collector 211, and a negative electrode on a negative electrode current collector 221. A negative electrode plate 22 formed with a mixture 222, 222 and a separator 23 interposed therebetween are provided. Although not shown, an electrolytic solution is injected into the exterior body 19, and the positive electrode plate 21, the negative electrode plate 22, and the separator 23 are impregnated.

  Further, the battery element 9 is covered with an exterior body 19, and external lead terminals (tabs) 11 (external lead terminals 11a for positive electrodes, negative electrodes for negative electrodes) that charge and discharge electricity from the inside of the exterior body 19 to the outside. An external lead terminal 11b) is provided.

  The positive electrode plate 21 or the negative electrode plate 22 is formed by laminating the positive electrode active material or the negative electrode active material as the positive electrode mixture 212 or the negative electrode mixture 222 on both surfaces or one surface of the positive electrode current collector 211 or the negative electrode current collector 221, respectively. Is. For the positive electrode current collector 211 used for the positive electrode plate 21, a metal foil such as aluminum, stainless steel, or nickel can be used, and aluminum is particularly preferable. Moreover, metal foil, such as copper, stainless steel, nickel, can be used for the negative electrode collector 221 used for the negative electrode plate 22, and copper is particularly preferable.

Examples of the positive electrode active material used for the positive electrode mixture 212 include lithium cobaltate composite oxide (LCO), lithium manganate composite oxide (LMO), lithium nickelate composite oxide (LNO), and lithium-nickel-manganese-cobalt composite. An oxide (LNMCO), a lithium-manganese-nickel composite oxide (LMNO), a lithium-manganese-cobalt composite oxide (LMCO), a lithium-nickel-cobalt composite oxide (LNCO), or the like can be used. The positive electrode active material may be a mixture of the above materials. The positive electrode active material may be an olivine-based material such as LiFePO ₄ . As the negative electrode active material used for the negative electrode mixture 222, carbon materials such as graphite, hard carbon, and soft carbon, ceramics such as lithium titanate, and alloy materials such as Si and Sn can be used. The negative electrode active material may be a mixture of the above materials.

  The separator 23 is not particularly limited as long as it is a known material such as a polyolefin resin. In the present invention, the separator is not limited by its name, and instead of the separator, a solid electrolyte having a function (role) as a separator, a gel electrolyte, or the like may be used. A separator containing an inorganic material such as alumina or zirconia may also be used.

  In addition, as electrolyte solution, chain carbonates, such as cyclic carbonates, such as ethylene carbonate (EC) and propylene carbonate (PC), diethyl carbonate (DEC), and dimethyl carbonate (DMC), are used individually or in combination of 2 or more types. it can. Furthermore, chain ester systems such as methyl formate, ethyl formate, methyl acetate, and ethyl acetate, cyclic ester systems such as γ-butyrolactone, and cyclic sulfones such as sulfolane may be included.

  Various loads such as motors and electrical components (not shown) are connected to the positive external lead terminal 11a and the negative external lead terminal 11b, and the positive external lead terminal 11a and the negative external lead terminal 11b are connected to the positive external lead terminal 11b. A very large charge / discharge current flows. Therefore, the width and thickness of the external lead terminal 11a for the positive electrode and the external lead terminal 11b for the negative electrode are mainly determined by the current value during charging / discharging. In addition, the battery element 9 is sealed in the exterior body 19 under reduced pressure in order to prevent external impact and environmental degradation during use.

  From the viewpoint of weight reduction, the aluminum laminate film used as the outer package 19 is provided with a resin layer 19a serving as an outer surface layer on the outer side of a metal layer 19b serving as an intermediate layer of aluminum, stainless steel, nickel, copper, etc. It is a three-layer structure in which a resin layer 19c serving as an inner surface layer is laminated on the inner side. The resin layer 19a is preferably made of a synthetic resin having excellent chemical resistance and mechanical strength such as polyethylene, polypropylene, modified polyolefin, ionomer, amorphous polyolefin, polyethylene terephthalate, and polyamide. The resin layer 19c is preferably a chemical-resistant synthetic resin, and for example, polyethylene, polypropylene, modified polyolefin, ionomer, ethylene-vinyl acetate copolymer, or the like is preferably used. The battery element 9 is sealed (sealed) under reduced pressure in the exterior body 19 by joining a part or all of the periphery of the exterior body 19 by thermal fusion or the like, and the external lead terminal 11a for the positive electrode and the negative electrode The external lead terminal 11 b for use is taken out of the exterior body 19.

  FIG. 4 is a plan view schematically showing a state in which the exterior body 19 of the lithium ion secondary battery according to Embodiment 1 of the present invention is viewed from the inner surface (the surface on the resin layer 19c side). As shown in FIG. 4, a heat-resistant protective layer 31 is attached to a predetermined position on the surface of the resin layer 19c. The protective layer 31 is provided at a position to be a ventilation portion for degassing when the peripheral edge portion of the exterior body 19 is heat-sealed, and a tape made of a material that does not dissolve at the time of heat-sealing, such as a polyimide tape, is used. Affixed. Since the protective layer 31 is not affixed at a position in contact with the outer edge of the resin layer 19c, the peripheral edge of the exterior body 19 is reliably sealed at the time of heat sealing.

  FIG. 5 is a cross-sectional view of the heat-sealed surface schematically showing a state in which the peripheral edge portion of the exterior body 19 of the lithium ion secondary battery according to Embodiment 1 of the present invention is heat-sealed. In FIG. 5, the heat-sealed part is hatched.

  As shown in FIG. 5, the external lead terminals 11 and 11 are sandwiched between exterior bodies (laminate films) 19, and the peripheral portion 32 of the exterior body 19 is heat-sealed. The portion to which the protective layer 31 is affixed is not thermally fused and is connected to the package space 20 in which the battery element 9 is accommodated and the electrolyte is injected. Specifically, first, three sides to which the protective layer 31 is not attached are heat-sealed, and the battery element 9 is accommodated and connected to the external lead terminals 11 and 11 and an electrolyte is injected. Even when splashing occurs during electrolyte injection, the electrolyte adheres only to the surface of the protective layer 31. And the one side where the protective layer 31 is affixed is heat-sealed. In this state, the external lead terminals 11 and 11 are connected to an external power source to precharge the lithium ion secondary battery.

  Since the electrolytic solution uses a solution in which lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate / diethyl carbonate, etc., when the lithium ion secondary battery becomes high temperature in the precharge, etc. These components are decomposed and methane-based gas is likely to be generated. When methane-based gas is generated, bubbles are generated in the electrolytic solution, and the generated bubbles burst, so that the electrolytic solution adheres only to the surface of the protective layer 31.

  After the preliminary charging is completed, the exterior body 19 is cut along the AA line. The AA line is not limited to the vicinity of the end of the protective layer 31 as long as it is within the range including the protective layer 31. FIG. 6 is a heat-sealed surface schematically showing a state in which one side of the peripheral edge portion 32 of the exterior body 19 of the lithium ion secondary battery according to Embodiment 1 of the present invention is cut along an AA line. FIG.

  As shown in FIG. 6, one end of the protective layer 31 is exposed to the outside along the line AA. Therefore, the exterior body 19 is not heat-sealed only in the portion to which the protective layer 31 is attached, and functions as a ventilation portion that can discharge the gas generated inside to the outside.

  When the gas is discharged to the outside, the vaporized electrolyte may also be liquefied at the ventilation portion and adhere to the inner surface of the ventilation portion. However, in the first embodiment, since the ventilation portion is covered with the protective layer 31, the electrolytic solution adheres only to the surface of the protective layer 31.

  Further, when the electrolytic solution adheres to the inner surface of the ventilation portion, when moisture in the air chemically reacts with lithium hexafluorophosphate in the electrolytic solution, hydrogen fluoride is generated, and the outer package (laminate film) 19 There is also a risk of causing delamination between the inner metal layer 19b and the resin layer 19c. However, in the first embodiment, since the ventilation portion is covered with the protective layer 31, the electrolytic solution adheres only to the surface of the protective layer 31, and even when hydrogen fluoride is generated, the exterior body 19 does not cause the above failure.

  After sufficiently degassing, the protective layer 31 adhered to the ventilation portion is removed, and heat fusion is performed again. FIG. 7 is a cross-sectional view of the heat-sealed surface schematically showing a state in which the peripheral edge portion 32 of the exterior body 19 of the lithium ion secondary battery according to Embodiment 1 of the present invention is heat-sealed again. . As shown in FIG. 7, the portion 33 to which the protective layer 31 has been attached is also heat-sealed, whereby the electrolyte is completely sealed.

  As described above, according to the first embodiment, even when the electrolytic solution adheres to the inner surface of the ventilation portion due to splashing at the time of injecting the electrolytic solution, rupture of bubbles generated by the generated gas, or the like, Only the surface of the protective layer 31 adheres, and after the preliminary charging is completed, the protective layer 31 is removed and heat fusion is performed again, so that the attached electrolytic solution is also reliably removed and heat fusion is performed. be able to. Therefore, it is possible to maintain high sealing performance without changing the structure of the lithium ion secondary battery, and it is possible to avoid occurrence of peeling due to damage of the resin layer due to chemical reaction.

(Embodiment 2)
Since the configuration of the lithium ion secondary battery according to the second embodiment of the present invention is the same as that of the first embodiment, detailed description thereof is omitted by attaching the same reference numerals. In the second embodiment, the position where the protective layer 31 is pasted is different from the first embodiment.

  FIG. 8 is a plan view schematically showing the exterior body 19 of the lithium ion secondary battery according to Embodiment 2 of the present invention as viewed from the inner surface (surface on the resin layer 19c side). As shown in FIG. 8, a heat-resistant protective layer 31 is affixed so as to be in contact with the outer edge of the exterior body 19 at a predetermined position on the surface on the resin layer 19 c side. The protective layer 31 is provided at a position to be a ventilation portion for degassing when the peripheral edge portion of the exterior body 19 is heat-sealed, and a tape made of a material that does not dissolve at the time of heat-sealing, such as a polyimide tape, is used. Affixed. Unlike Embodiment 1, since the protective layer 31 is affixed at a position where it contacts the outer edge of the resin layer 19c, the electrolytic solution is injected from the portion where the protective layer 31 is affixed even after heat sealing. The gas generated during the preliminary charging can be discharged to the outside.

  FIG. 9 is a cross-sectional view of the heat-sealed surface schematically showing a state in which the peripheral edge portion 32 of the outer package 19 of the lithium ion secondary battery according to Embodiment 2 of the present invention is heat-sealed. In FIG. 9, the heat-sealed part is hatched.

  As shown in FIG. 9, the external lead terminals 11, 11 are sandwiched between exterior bodies (laminate films) 19, and the peripheral portion 32 of the exterior body 19 is heat-sealed. The portion to which the protective layer 31 is affixed is not thermally fused and is connected to the package space 20 in which the battery element 9 is accommodated and the electrolyte is injected. Even when splashing occurs during electrolyte injection, the electrolyte adheres only to the surface of the protective layer 31. And the one side where the protective layer 31 is affixed is heat-sealed. In this state, the external lead terminals 11 and 11 are connected to an external power source to precharge the lithium ion secondary battery.

  Since the electrolytic solution uses a solution in which lithium hexafluorophosphate is dissolved in a mixed solvent of ethylene carbonate / diethyl carbonate, etc., when the lithium ion secondary battery becomes high temperature in the precharge, etc. These components are decomposed and methane-based gas is likely to be generated. When methane-based gas is generated, bubbles are generated in the electrolytic solution, and the generated bubbles burst, so that the electrolytic solution adheres only to the surface of the protective layer 31.

  Unlike Embodiment 1, the outer layer 19 is not heat-sealed at the portion where the protective layer 31 is attached, and when the gas is generated inside during the preliminary charging, the generated gas is discharged to the outside. Can act as a ventilation part. When the gas is discharged to the outside, the vaporized electrolyte may also be liquefied at the ventilation portion and adhere to the inner surface of the ventilation portion. However, in the second embodiment, since the ventilation portion is covered with the protective layer 31, the electrolytic solution adheres only to the surface of the protective layer 31.

  Further, when the electrolytic solution adheres to the inner surface of the ventilation portion, when moisture in the air chemically reacts with lithium hexafluorophosphate in the electrolytic solution, hydrogen fluoride is generated, and the outer package (laminate film) 19 There is also a risk of causing delamination between the inner metal layer 19b and the resin layer 19c. However, in the second embodiment, since the ventilation portion is covered with the protective layer 31, the electrolytic solution adheres only to the surface of the protective layer 31, and even when hydrogen fluoride is generated, the exterior body 19 does not cause the above failure.

  After sufficiently degassing, the protective layer 31 adhered to the ventilation portion is removed, and heat fusion is performed again. FIG. 10 is a cross-sectional view of the heat-sealed surface schematically showing a state in which the peripheral edge portion 32 of the exterior body 19 of the lithium ion secondary battery according to Embodiment 2 of the present invention is heat-sealed again. . As shown in FIG. 10, the portion 33 to which the protective layer 31 has been attached is also heat-sealed, so that the electrolytic solution is completely sealed.

  As described above, according to the second embodiment, even when the electrolytic solution adheres to the inner surface of the ventilation portion due to splashing at the time of injecting the electrolytic solution, rupture of bubbles generated by the generated gas, or the like, Only the surface of the protective layer 31 adheres, and after the preliminary charging is completed, the protective layer 31 is removed and heat fusion is performed again, so that the attached electrolytic solution is also reliably removed and heat fusion is performed. be able to. Therefore, it is possible to maintain high sealing performance without changing the structure of the lithium ion secondary battery, and it is possible to avoid occurrence of peeling due to damage of the resin layer due to chemical reaction.

  Moreover, since the size of the exterior body 19 can be made as small as possible, the laminate film can be saved, and the manufacturing cost can be reduced.

  In addition, the present invention is not limited to the above-described embodiments, and it goes without saying that various modifications and substitutions are possible within the scope of the gist of the present invention. Moreover, it is not limited to a lithium ion secondary battery, The same effect can be expected if it is a stacked secondary battery having the same or similar structure that can be charged and discharged.

DESCRIPTION OF SYMBOLS 9 Battery element 11 External lead terminal 11a External lead terminal for positive electrodes 11b External lead terminal for negative electrodes 19 Exterior body 31 Protective layer 32 Peripheral portion

Claims (3)

In the manufacturing method of the secondary battery in which the battery element is encapsulated with an exterior body made of a laminate film that can be heat-sealed with each other,
A step of applying a heat-resistant protective layer to the inner surface of at least one ventilation portion for discharging the gas generated inside the secondary battery to the outside of the outer body;
In a state in which the battery element is accommodated, the step of heat-sealing the peripheral edge of the exterior body;
Connecting to an external power supply and pre-charging,
Unpacking the part to which the protective layer is applied, and discharging the gas generated by the preliminary charging to the outside from the ventilation part;
And a step of heat-sealing the ventilation portion by removing the protective layer. The ventilation portion is provided so as to protrude from a region enclosing the battery element of the exterior body to a peripheral portion of the exterior body,
Cutting the peripheral portion of the exterior body including a part of the ventilation portion after the preliminary charging; and
The method for producing a secondary battery according to claim 1, further comprising a step of discharging gas to the outside from the vent portion cut and opened. The secondary battery has a substantially square plate shape,
3. The secondary battery according to claim 1, wherein the ventilation portion is provided on another side different from the one side provided with a current collecting terminal connected to an electrode of the battery element. 4. Production method.

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