JP6818237B2 - How to manufacture a secondary battery - Google Patents

Description

The present invention relates to a method for manufacturing a secondary battery. More specifically, the present invention relates to a method of manufacturing a secondary battery by joining an electrode body and a current collector plate.

In recent years, secondary batteries such as lithium ion secondary batteries and nickel-metal hydride batteries have become increasingly important as power sources for vehicles, personal computers and mobile terminals. In particular, a lithium ion secondary battery that is lightweight and has a high energy density is preferably used as a high output power source for mounting on a vehicle.

The above-mentioned secondary battery generally includes an electrode body having a sheet-shaped positive electrode and a negative electrode, an electrode terminal connected to an external device, and a current collector plate connecting the electrode body and the electrode terminal. ing.
Each of the positive and negative electrodes constituting the electrode body is formed by applying a mixture layer to the surface of a metal foil having a thickness of about several μm, and the exposed portion where the metal foil is exposed is one end. It is provided in. Then, the electrode body of the secondary battery is manufactured by laminating (or winding) the positive electrode and the negative electrode via a separator. A power generation region in which a mixture layer is laminated is formed in the central portion in the width direction of the electrode body thus produced. Further, a positive electrode connection region in which an exposed portion of the positive electrode (exposed portion of the positive electrode) is overlapped is formed at one end in the width direction, and an exposed portion of the negative electrode (exposed portion of the negative electrode) is overlapped at the other end. A negative electrode connection region is formed. Then, in a general secondary battery, a current collector plate is bonded to each of the positive electrode connection region and the negative electrode connection region, and the electrode body and the electrode terminal are electrically connected via the current collector plate.

Welding using a high-energy ray such as a laser or an electron beam is performed for joining the electrode body and the current collector plate described above, but such welding may cause various problems.
For example, it is necessary to increase the laser output in order to reliably weld each connection region and the current collector plate, but when a high-power laser is applied to a metal member, high-temperature molten metal called sputtering is generated. If the spatter scatters and enters the power generation region of the electrode body, an internal short circuit may occur.
Further, if the output of the laser is set too high, the laser may reach the power generation region through the member to be joined (metal foil or current collector plate). In such a case, the mixture layer constituting the power generation region may be damaged by heat and the battery performance may be significantly deteriorated.

Various techniques have been conventionally proposed in order to prevent the above-mentioned various problems related to welding. For example, in Patent Document 1, a current collector plate in which a protrusion is formed on a surface opposite to an electrode group (electrode body) is used. The protrusion of the current collector plate is formed so as to exist on a line segment connecting the end of the electrode plate (exposed portion of the electrode), the welded point of the current collector plate, and the separator at the shortest distance. There is. According to the technique of Patent Document 1, even if spatter occurs during laser irradiation, the scattering of the spatter can be blocked by the protrusion of the current collector plate, so that the spatter invades the power generation region. Can be suppressed. Further, even if the laser penetrates the member to be joined, the laser can be blocked by the protrusion, so that it is possible to prevent the penetrating laser from damaging the power generation region of the electrode body.

Japanese Unexamined Patent Publication No. 2013-51057

However, it cannot be said that the technique described in Patent Document 1 described above can reliably prevent all the problems that may occur due to laser welding, and there is room for improvement.

For example, the method described in Patent Document 1 is a technique for suppressing spatter scattering, not a technique for preventing spatter generation itself. Therefore, when a large amount of sputtering is generated and diffused as in the case where a positive metal foil made of aluminum having high thermal conductivity is irradiated with a high-power laser, there is a high possibility that the sputtering will invade the power generation region.
Further, in the method described in Patent Document 1, since welding is performed by a laser, it is difficult to completely prevent the laser from reaching the power generation region and damaging the mixture layer. For example, in the technique of Patent Document 1, there is a possibility that a laser enters a gap between a plurality of metal foils forming a connection region and reaches a power generation region.

Further, in the conventional method, after laser welding, the metal foil constituting the connection region may be broken, which may cause a joint failure. Specifically, the metal foil is a very thin metal member having a thickness of about several μm, and has a smaller heat capacity than the current collector plate. Therefore, when the metal foil and the current collector plate are welded by a laser, the metal foil may solidify and shrink at the joint interface (melting interface) between the metal foil and the current collector plate and break. In the method described in Patent Document 1, breakage of the metal leaf due to the above-mentioned solidification shrinkage is not taken into consideration, and it is difficult to prevent such a problem.

The present invention has been made in view of the above points, and its main purpose is to surely prevent various problems that may occur in the bonding between the electrode body and the current collector plate, and to make a high quality secondary battery efficient. An object of the present invention is to provide a method for manufacturing a secondary battery that can be manufactured well.

In order to realize the above object, the present invention provides a method for manufacturing a secondary battery having the following configuration (hereinafter, also simply referred to as “manufacturing method”).

The method for manufacturing a secondary battery disclosed here is an electrode body in which a sheet-shaped positive electrode and a negative electrode are stacked, an electrode terminal connected to an external device, and a current collector plate connecting the electrode body and the electrode terminal. It is a method of manufacturing a secondary battery equipped with.
The positive electrode of the secondary battery obtained by such a manufacturing method is a sheet-shaped positive electrode in which a positive electrode mixture layer is provided on the surface of a positive electrode metal foil made of aluminum, and the positive electrode metal foil is exposed at one end in the width direction. A positive electrode exposed portion is formed. Further, a positive electrode connection region in which a positive electrode exposed portion is overlapped is formed at one end in the width direction of the electrode body of the secondary battery.
Then, in the manufacturing method disclosed here, the positive electrode connection region of the electrode body is sandwiched between the current collector plates, and a pyrolysis resin having a sublimation temperature of 250 ° C. to 500 ° C. is applied to at least one of the positive electrode connection region and the current collector plate. The resin application step is provided, and the pyrolysis resin is irradiated with a laser, and when the pyrolysis resin begins to sublimate, the current collector plate and the positive electrode connection region are pressed and pressure-welded.

As a result of conducting various studies in order to solve the various problems described above, the present inventor has come to the conclusion that "pressure welding" is used for joining the electrode body and the current collector plate instead of the conventional laser welding. It was.
The above-mentioned "pressure welding" is to heat the members to be joined in close contact with each other and pressurize the members to be joined at the timing when the temperature is raised to a temperature at which the plastic deformation becomes large (plastic deformation temperature). It is a joining method that fuses while deforming.
Since the heating temperature in such pressure welding is sufficient to be such that the plastic deformation becomes large, it is not necessary to irradiate the bonding target with a high-power laser as required for laser welding. Therefore, it is possible to reliably prevent the occurrence of spatter and penetration of the object to be joined. Further, in such pressure welding, since the positive electrode metal foil and the current collector plate are joined by plastic deformation, it is possible to preferably prevent the molten positive electrode metal foil from breaking due to solidification shrinkage.

However, in order to suitably join metal members by pressure welding, it is necessary to precisely adjust the timing at which pressurization is started. Specifically, if pressurization is started when the positive electrode metal leaf or the current collector plate is not sufficiently heated, the positive electrode metal leaf or the current collector plate cannot be sufficiently plastically deformed, and a joint failure may occur. There is. On the other hand, if the positive electrode metal leaf or the current collector plate is heated too much, the positive electrode metal leaf may melt and break due to solidification shrinkage.

In view of this point, the present inventor has studied a method capable of starting pressurization at an appropriate temperature when pressure welding the positive electrode connection region of the electrode body and the current collector plate.
As a result, it is thought that a pyrolysis resin that sublimates when heated to a desired temperature is applied to the positive metal foil (and / or the current collector plate), and pressurization is started at the timing when the pyrolysis resin sublimates. I arrived. Specifically, a heat-decomposable resin that sublimates at a temperature higher than the plastic deformation temperature of the positive metal foil and lower than the melting point of the positive metal foil is applied to the positive metal foil (and / or the current collector plate). It was considered that if the pressurization was started when the thermally decomposable resin began to sublimate, the positive electrode connection region and the current collector plate could be suitably plastically deformed without being melted.

The manufacturing method disclosed here is based on the above findings, and when a secondary battery using a positive electrode metal foil made of aluminum (melting point: 660.3 ° C.) is manufactured, the sublimation temperature is high. A pyrolysis resin at 250 ° C. to 500 ° C. is applied to the positive electrode connection region (and / or the current collector plate), and when the pyrolysis resin sublimates, the current collector plate and the positive electrode connection region are pressurized.
As a result, each of the current collector plate and the positive electrode connection region can be joined by pressure welding without using laser welding, so that various problems such as short circuit due to spatter, damage to the power generation region, and breakage of the metal foil occur. It can be reliably prevented. Therefore, according to the manufacturing method disclosed here, a high-quality secondary battery can be efficiently manufactured.

It is a perspective view which shows typically the secondary battery obtained by the manufacturing method of the secondary battery which concerns on one Embodiment of this invention. It is explanatory drawing which shows typically each member which comprises the electrode body of the secondary battery shown in FIG. It is a perspective view which shows typically the structure of the electrode body of the secondary battery shown in FIG. It is a side view which shows the internal structure of the secondary battery shown in FIG. It is sectional drawing explaining the manufacturing method of the secondary battery which concerns on one Embodiment of this invention. It is sectional drawing explaining the manufacturing method of the secondary battery which concerns on one Embodiment of this invention. It is sectional drawing explaining the manufacturing method of the secondary battery which concerns on one Embodiment of this invention. It is sectional drawing explaining the manufacturing method of the secondary battery which concerns on one Embodiment of this invention. It is sectional drawing explaining the manufacturing method of the secondary battery which concerns on one Embodiment of this invention. It is a graph showing the relationship between the temperature and mechanical properties of aluminum, and the vertical axis shows "tensile strength (N / mm ² )", "proof stress (N / mm ² )" and "elongation (%)". The horizontal axis indicates "temperature (° C)". It is a graph showing the relationship between the temperature of aluminum and mechanical properties. The vertical axis shows "tensile strength (N)" and "temperature (° C.)", and the horizontal axis shows "displacement amount (mm)". Shown. It is sectional drawing which shows typically the current collector plate used in the manufacturing method of the secondary battery which concerns on other embodiment of this invention.

Hereinafter, a lithium ion secondary battery will be described as an example of the secondary battery according to the embodiment of the present invention. The secondary battery disclosed here is not limited to the lithium ion secondary battery, and can be applied to various secondary batteries (for example, a nickel hydrogen battery).

Further, in the following drawings, members / parts having the same action are described with the same reference numerals. The dimensional relationships (length, width, thickness, etc.) in each figure do not reflect the actual dimensional relationships. In addition, matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention (for example, the composition and manufacturing method of the electrolytic solution) are designed by those skilled in the art based on the prior art in the art. It can be grasped as a matter.

1. 1. Structure of the secondary battery First, the secondary battery obtained by the manufacturing method according to the present embodiment will be described. FIG. 1 is a perspective view schematically showing a secondary battery obtained by the manufacturing method according to the present embodiment. Further, FIG. 2 is an explanatory view schematically showing each member constituting the electrode body of the secondary battery shown in FIG. 1, and FIG. 3 schematically shows the configuration of the electrode body of the secondary battery shown in FIG. It is a perspective view. Further, FIG. 4 is a side view showing the internal structure of the secondary battery shown in FIG. In each figure of the present specification, reference numeral X indicates "battery width direction", Y indicates "battery thickness direction", and Z indicates "battery height direction".

(1) Case The secondary battery 100 shown in FIG. 1 includes a flat square case 50. The case 50 is composed of a flat square case body 52 having an open upper surface and a plate-shaped lid 54 that closes the opening on the upper surface of the case body 52. The case body 52 and the lid 54 are preferably made mainly of a lightweight metal material having good thermal conductivity, and examples of such metal material include aluminum.
Further, in the secondary battery 100, electrode terminals 60 and 62 are provided on the lid 54 forming the upper surface of the case 50. The electrode terminals 60 and 62 are formed so as to project outside the case 50, and are connected to other external devices such as a battery and a vehicle motor.

(2) Electrode body The electrode body is housed inside the case 50 together with the electrolytic solution (not shown). As shown in FIGS. 2 and 3, in the present embodiment, a laminated electrode body in which a plurality of sheet-shaped positive electrode 10 and negative electrode 20 are stacked via a separator 40 is used as the electrode body 80.

(A) Positive electrode The positive electrode 10 is formed by applying the positive electrode mixture layer 14 to the surface (both sides) of the positive electrode metal foil 12. Then, at one end of the positive electrode 10 in the width direction X, a positive electrode exposed portion 16 is formed in which the positive electrode metal foil 12 is exposed without the positive electrode mixture layer 14 being applied. Further, in the present embodiment, the positive electrode metal leaf 12 made of aluminum is used, and the thickness of the positive electrode metal leaf 12 is 5 μm to 20 μm. The positive electrode mixture layer 14 contains a positive electrode active material (lithium transition metal composite oxide or the like) as a main component, and also contains additives such as a conductive agent and a binder. As each material contained in the positive electrode mixture layer 14, the same materials as those used in a general lithium ion secondary battery can be used without limitation, and the present invention is not characterized. Detailed description will be omitted.

(B) Negative electrode On the other hand, the negative electrode 20 is formed by applying the negative electrode mixture layer 24 to the surface (both sides) of the negative electrode metal foil 22. Then, at one end of the negative electrode 20 in the width direction X, a negative electrode exposed portion 26 is formed in which the negative electrode metal foil 22 is exposed without the negative electrode mixture layer 24 being applied. For the negative electrode metal foil 22, for example, a copper foil having a thickness of 5 μm to 20 μm can be used. Further, the negative electrode mixture layer 24 contains a negative electrode active material (graphite or the like) as a main component and an additive such as a binder. As for the negative electrode mixture layer 24, the same as that used in a general lithium ion secondary battery can be used without limitation as in the case of the positive electrode mixture layer 14, and thus a detailed description thereof will be given here. Is omitted.

(C) Separator The separator 40 is arranged so as to be interposed between the positive electrode 10 and the negative electrode 20. Specific examples of the separator 40 include a single-layer structure sheet material made of a porous polyolefin resin, a laminated structure sheet material in which a plurality of types of resin sheets are laminated, and the like.

(D) Laminated Structure As described above, the electrode body 80 is formed by stacking a plurality of positive electrode 10 and negative electrode 20 via a separator 40. As shown in FIGS. 2 and 3, the positive electrode mixture layer 14 and the negative electrode mixture layer 24 are laminated so as to face each other at the central portion of the electrode body 80 in the width direction X, and are mainly used for charging and discharging. A power generation region 80a is formed. Further, at one end of the electrode body 80 in the width direction X, a positive electrode connecting region 80b in which a plurality of exposed positive electrode portions 16 (positive electrode metal foil 12) of the positive electrode 10 are stacked is formed. A negative electrode connection region 80c in which a plurality of exposed negative electrode portions 26 (negative electrode metal foil 22) of the negative electrode 20 are stacked is formed at the other end of the electrode body 80.

(4) Current collector plate The electrode body 80 described above is electrically connected to the electrode terminal 60 via the current collector plate. Specifically, as shown in FIG. 4, the electrode body 80 is bonded to the current collector plate 30 in the positive electrode connection region 80b, and the current collector plate 30 is bonded to the electrode terminal 60.
The current collector plate 30 is a comb-shaped member including a plurality of holding members 32 extending in the height direction Z, and slits are formed between the holding members 32. The upper end of the positive electrode exposed portion 16 (positive electrode metal foil 12) constituting the positive electrode connection region 80b is inserted into each of the plurality of slits of the current collector plate 30, and the upper end portion of the positive electrode exposed portion 16 is sandwiched. It is sandwiched between the members 32. Then, in the present embodiment, the positive electrode exposed portion 16 constituting the positive electrode connection region 80b is in pressure contact with the holding member 32 of the current collector plate 30.
Further, the current collector plate 30 is preferably made of aluminum. By configuring the current collector plate 30 with the same metal material as the positive electrode metal foil 12 in this way, the positive electrode metal foil 12 constituting the positive electrode connection region 80b and the current collector plate 30 can be more easily pressed against each other. ..
Although a specific description is omitted, the secondary battery 100 is provided with a connection structure similar to that on the positive electrode side on the negative electrode side. That is, the negative electrode connection region 80c (see FIG. 3) of the electrode body 80 of the secondary battery 100 is joined to a current collector plate (not shown), and the electrode terminal 62 (see FIG. 1) is connected via the current collector plate. ) Is connected.

2. 2. Method for Manufacturing a Secondary Battery Next, a method for manufacturing a secondary battery according to the present embodiment for manufacturing the above-mentioned secondary battery 100 will be described with reference to FIGS. 5A to 5E. 5A to 5E are cross-sectional views illustrating a method of manufacturing a secondary battery according to the present embodiment. 5A to 5E are views for explaining each step of the manufacturing method according to the present embodiment in the region near the current collector plate 30 in the cross section seen from the direction of VV in FIG. ..

(1) Electrode body preparation step In the manufacturing method according to the present embodiment, first, the electrode body 80 as shown in FIG. 3 is prepared. In this step, the electrode body 80 prepared in advance may be prepared, or the electrode body 80 may be newly manufactured according to a known method. When the electrode body 80 is newly produced, as shown in FIG. 2, the positive electrode 10 and the negative electrode 20 are stacked so that the positive electrode mixture layer 14 and the negative electrode mixture layer 24 face each other via the separator 40. At this time, the positive electrode 10 and the negative electrode 20 are stacked so that the positive electrode exposed portion 16 protrudes from one end in the width direction X and the negative electrode exposed portion 26 protrudes from the other end. As a result, as shown in FIG. 3, an electrode body in which a power generation region 80a is formed in the central portion in the width direction X, a positive electrode connection region 80b is formed at one end, and a negative electrode connection region 80c is formed at the other end. The laminated electrode body) 80 can be manufactured.

Further, as shown in FIG. 5A, in the manufacturing method according to the present embodiment, a plurality of positive electrode exposed portions 16 (positive electrode metal foil) constituting the positive electrode connecting region 80b so that the positive electrode connecting region 80b becomes a convex bundle. Bend each of 12). By forming the convex positive electrode connection region 80b in this way, the positive electrode connection region 80b can be easily inserted into the slit of the current collector plate 30 in the resin applying step described later. In this case, since the current collector plate 30 is joined to the convexly molded portion of the positive electrode connection region 80b, the surface area of the convexly molded portion is from the viewpoint of securing a suitable bonding area. the preferably in the range of ^{1 mm} 2 to 10 mm ² (for example, 5 mm ^2).

(2) Resin Applying Step Next, in the manufacturing method according to the present embodiment, the resin applying step is carried out. As shown in FIG. 5B, in this step, first, the positive electrode connection region 80b of the electrode body 80 is sandwiched between the current collector plates 30. Specifically, a current collector plate 30 provided with a plurality of sandwiching members 32 as shown in FIG. 4 is used, and a positive electrode exposed portion 16 (positive electrode) forming a positive electrode connection region 80b is formed in a slit between the sandwiching members 32. The upper end of the metal foil 12) is inserted.

Then, as shown in FIG. 5C, in this step, the pyrolysis resin P is applied so as to cover both the positive electrode connection region 80b of the electrode body 80 and the sandwiching member 32 of the current collector plate 30.
Here, the "pyrolytic resin P" in the present specification is a temperature at which the sublimation temperature is higher than the plastic deformation temperature of the aluminum constituting the positive electrode metal foil 12 and lower than the melting point of the aluminum. Refers to a polymer material.
More specifically, as the "pyrolytic resin P" in the present embodiment, a polymer material having a sublimation temperature of 250 ° C. to 500 ° C. (for example, acrylic resin) is used. As shown in FIG. 6, in the aluminum material represented by JIS standard A1100, "elongation" greatly increases at 250 ° C., and "tensile strength" and "proof stress" decrease significantly (in other words, 250). It becomes easy to plastically deform at the boundary of ℃). Therefore, by using the pyrolysis resin P having a sublimation temperature of 250 ° C. or higher, pressure welding can be started at a timing such that each member to be joined is preferably plastically deformed in the pressure welding step described later.
On the other hand, as shown in FIG. 7, there is no big difference in the "displacement amount" of aluminum between the case where aluminum is heated to near the melting point (660.3 ° C.) and the case where aluminum is heated to about 500 ° C. If a polymer material that sublimates at such a high temperature is used, the positive electrode metal leaf 12 and the current collector plate 30 will melt when the polymer material sublimates, and the positive metal leaf 12 will break due to solidification shrinkage. Is more likely to occur. In consideration of this, a resin having a sublimation temperature of 500 ° C. or lower is used as the pyrolysis resin P.

(5) Pressure welding process As shown in FIG. 5D, in this process, first, the pyrolysis resin P is irradiated with the laser L. As the laser L at this time, a CO ₂ laser, a YAG laser, a fiber laser, a semiconductor laser, or the like is preferably used. If the output of the laser L is too low, the time required for the pyrolysis resin P to sublimate becomes long, which may reduce the production efficiency. On the other hand, if the output is too high, the pyrolysis resin P may be instantly sublimated and the positive electrode metal leaf 12 and the current collector plate 30 may be directly irradiated with the high output laser. Considering this, it is preferable to set the output of the laser L in the range of 0.5 kW to 3.0 kW. Further, considering the heating efficiency of the pyrolysis resin P, the diameter φ of the laser spot is preferably 0.02 mm to 1 mm.

Then, in this step, as shown in FIG. 5E, when the heated pyrolysis resin P begins to sublimate, the laser irradiation is stopped and the current collector plate 30 and the positive electrode connection region 80b are pressurized. Specifically, the current collector plate 30 and the positive electrode connection region 80b are pressurized with a predetermined pressure N so that the positive electrode connection region 80b is sandwiched between the sandwiching members 32 of the current collector plate 30. At this time, in the manufacturing method according to the present embodiment, the positive electrode connection region 80b and the current collector plate 30 are heated at a temperature (250 ° C to 500 ° C) higher than the plastic deformation temperature of aluminum and lower than the melting point. Therefore, when pressed at a predetermined pressure N, they are fused while being plastically deformed to each other. The pressure N at this time is preferably set to 100N to 1500N (for example, 1000N). As a result, the positive electrode connection region 80b and the current collector plate 30 can be suitably plastically deformed.

In the manufacturing method according to the present embodiment, the electrode body 80 and the current collector plate 30 are joined by pressure welding by plastic deformation instead of conventional laser welding. In the manufacturing method according to the present embodiment using such pressure welding, it is not necessary to use a high-power laser, so that spatter is generated by irradiating the positive electrode metal foil 12 made of aluminum with the high-power laser, and the high-power laser is generated. It is possible to preferably prevent the power generation region 80a of the electrode body 80 from being damaged by penetrating the member to be joined.
Further, in the manufacturing method according to the present embodiment, the current collector plate 30 and the positive electrode connection region 80b are not directly irradiated with the laser L, but the members to be joined are heated via the pyrolysis resin P. Therefore, it is possible to reliably prevent the laser L from entering the gap between the positive electrode metal foils 12 and damaging the power generation region 80a.
Further, in the manufacturing method according to the present embodiment, since the positive electrode metal foil 12 and the current collector plate 30 are joined without being melted, the positive electrode metal foil 12 is surely solidified and shrunk at the melting interface to break. Can be prevented.
Further, in the production method according to the present embodiment, the pyrolysis resin P having a sublimation temperature of 250 ° C. to 500 ° C. is applied, and the pressurization is started when the pyrolysis resin P is sublimated. As a result, it is possible to easily grasp whether or not the current collector plate 30 and the positive electrode connection region 80b have been heated to an appropriate temperature, and pressurization can be started at an appropriate timing. Therefore, the electrode body 80 and the current collector plate can be started. It is possible to press contact with 30 more reliably.

As described above, according to the method for manufacturing a secondary battery according to the present embodiment, each of the current collector plate 30 and the positive electrode connection region 80b can be joined by pressure welding without using laser welding, and thus by sputtering. It is possible to reliably prevent the occurrence of various problems such as a short circuit, damage to the power generation region 80a, and breakage of the positive electrode metal foil 12. Therefore, according to the manufacturing method disclosed here, a high-quality secondary battery can be efficiently manufactured.

3. 3. Other Aspects Although one embodiment of the method for manufacturing a secondary battery disclosed herein has been described above, the present invention is not limited to the above-described embodiment, and various modifications can be made.
For example, as shown in FIGS. 5B and 5C, in the resin application step of the above-described embodiment, the positive electrode connection region 80b of the electrode body 80 is sandwiched between the sandwiching members 32 of the current collector plate 30, and then the pyrolysis resin P is applied. ing. However, the order in the resin application step is not particularly limited, and the positive electrode connection region 80b may be sandwiched between the current collector plates 30 after the pyrolysis resin P is applied to the positive electrode connection region 80b of the electrode body 80. Even in this case, the electrode body 80 and the current collector plate 30 can be preferably plastically deformed and pressure-welded in the pressure welding step.

Further, in the above-described embodiment, the pyrolysis resin P is applied so as to cover both the positive electrode connection region 80b of the electrode body 80 and the sandwiching member 32 of the current collector plate 30. However, the pyrolysis resin P may be applied to either the positive electrode connection region 80b or the current collector plate 30. Even in this case, the electrode body 80 and the current collector plate 30 can be preferably plastically deformed and pressure-welded in the pressure welding step.

Further, in the above-described embodiment, as shown in FIGS. 2 and 3, a laminated electrode body in which a plurality of positive electrodes 10 and 20 are laminated is used. However, the electrode body may be formed by stacking the positive electrode and the negative electrode, and is not limited to the laminated electrode body in which the positive electrode and the negative electrode are stacked. Another example of such an electrode body is a wound electrode body formed by winding a long sheet-shaped positive electrode and a negative electrode. In such a wound electrode body, a power generation region in which a positive electrode mixture layer and a negative electrode mixture layer are wound is formed in a central portion in the width direction, and a connection region (positive electrode) in which exposed portions of positive and negative electrodes are wound is formed. Connection area and negative electrode connection area) are formed at both ends in the width direction. Then, the manufacturing method disclosed here is applied when joining the positive electrode connection region in which the above-mentioned positive electrode exposed portion is wound to the current collector plate.

Further, in the manufacturing method according to the above-described embodiment, the bonding on the positive electrode side of the electrode body (the bonding between the positive electrode connection region and the current collector plate) is pressure-welded using a pyrolysis resin. However, pressure welding using a pyrolysis resin can be used not only for bonding on the positive electrode side but also for bonding on the negative electrode side (bonding between the negative electrode connection region and the current collector plate).

Further, in the above-described embodiment, a slit substantially perpendicular to the thickness direction Y is formed between the sandwiching members 32 of the current collector plate 30 (see FIG. 5B). However, the shape of the current collector plate is not limited to this, and various changes can be made. For example, as shown in FIG. 8, a current collector plate 30a in which slits inclined at a predetermined inclination angle θ with respect to the thickness direction Y are formed between the holding members 32a can also be used. By using such a current collector plate 30a, it is possible to prevent the laser light from leaking to the back side of the current collector plate 30a. It is more preferable that the current collector plate 30a is formed so as to satisfy the following formula (1) when the thickness of the holding member 32a is A and the width of the slit is B. As a result, it is possible to more preferably prevent the electrode body and the separator from being damaged by the leaked laser beam.
B ≤ A / tan θ (1)

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

10 Positive electrode 12 Positive electrode metal foil 14 Positive electrode mixture layer 16 Positive electrode exposed part 20 Negative electrode 22 Negative electrode metal foil 24 Negative electrode mixture layer 26 Negative electrode exposed part 30, 30a Current collector plate 32, 32a Holding member 40 Separator 50 Case 52 Case body 54 Lid Body 60, 62 Electrode terminal 80 Electrode body (laminated electrode body)
80a Power generation area 80b Positive electrode connection area 80c Negative electrode connection area 100 Secondary battery A Thickness of holding member B Slit width L Laser N Pressure P Thermal decomposition resin X (Battery) Width direction Y (Battery) Thickness direction Z (Battery) ) Height direction φ Laser spot diameter θ Tilt angle

Claims (1)

A method for manufacturing a secondary battery including an electrode body in which a sheet-shaped positive electrode and a negative electrode are stacked, an electrode terminal connected to an external device, and a current collector plate connecting the electrode body and the electrode terminal. And
The positive electrode is a sheet-shaped positive electrode in which a positive electrode mixture layer is provided on the surface of a positive electrode metal foil made of aluminum, and a positive electrode exposed portion in which the positive electrode metal foil is exposed is formed at one end in the width direction.
A positive electrode connection region on which the positive electrode exposed portion is overlapped is formed at one end in the width direction of the electrode body.
A resin applying step of sandwiching the positive electrode connection region of the electrode body with the current collector plate and applying a pyrolysis resin having a sublimation temperature of 250 ° C. to 500 ° C. to at least one of the positive electrode connection region and the current collector plate.
Manufacture of a secondary battery including a pressure welding step of irradiating the pyrolysis resin with a laser and pressurizing and pressure-welding the current collector plate and the positive electrode connection region when the pyrolysis resin begins to sublimate. Method.

Images