JP6519129B2 - Method of manufacturing power storage device - Google Patents

Description

This invention relates to a method for producing a charge reservoir.

  In recent years, lithium ion secondary batteries have been adopted not only as power supplies for electronic devices, but also as power supplies for hybrid vehicles and electric vehicles. Usually, an electrode assembly as a power generation element is accommodated in a battery case of a lithium ion secondary battery, and the electrode assembly is a positive electrode obtained by applying a positive electrode active material to metal foil, and a negative electrode active material to metal foil. It has a coated negative electrode, and a separator interposed between the positive electrode and the negative electrode. As an electrode assembly, for example, a wound electrode assembly and a stacked electrode assembly exist. The wound type electrode body is formed by winding an electrode sheet in which a separator is interposed between a long positive electrode and a negative electrode. On the other hand, the stacked electrode assembly has a structure in which a large number of positive electrodes, negative electrodes and separators are alternately stacked.

  By the way, when inserting an electrode assembly into a battery case, it is necessary to provide a clearance between the battery case and the electrode assembly. If there is no clearance between the battery case and the electrode assembly, the electrode assembly is likely to interfere with and damage the open end of the battery case. Therefore, a part of the battery case is elastically deformed by using a suction device, and a gap corresponding to the stacking direction in the battery case is increased to avoid damage to the electrode assembly when the electrode assembly is inserted into the battery case Techniques are known (see, for example, Patent Document 1).

JP 2012-138211 A

  However, in the case where a part of the battery case is elastically deformed using a suction device as in Patent Document 1, a suction device which elastically deforms the battery case is required. In addition, a pressing device is required to eliminate the clearance between the housed electrode assembly and the battery case. Therefore, in the case of this type of power storage device, suction and pressing of the battery case are required in the production process, and there is a problem that the production process becomes large and complicated.

The present invention has been made in view of the above problems, an object of the present invention, in addition to be able to accommodate the battery case without damaging the electrode assembly, which can simplify the production process to provide a method of manufacturing a charge reservoir.

In order to solve the above-described problems, the present invention provides a layered electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked or wound while maintaining insulation, and a battery case for accommodating the electrode assembly. And the battery case includes a bottomed cylindrical case main body having a rectangular opening, and a lid joined to an opening end formed on the opening side of the case main body, The case main body is in contact with the end face in the stacking direction of the electrode assembly, and a pair of first side walls disposed opposite to each other so as to connect the first side wall. A method of manufacturing a power storage device comprising: two side walls; and a bottom wall provided at an end opposite to the opening side end, wherein the case main body is the bottom without the electrode assembly being accommodated. Of the pair of first side walls from the wall side toward the opening side The gap between the pair of first side walls is set constant by clamping the case main body in the stacking direction of the electrode assembly while holding the electrode assembly. And a step of joining the lid to the case body by welding at the time of pressing the case body .

In the present invention, since the case body is formed to increase the distance between the pair of first side walls from the bottom wall side toward the opening side, a sufficient clearance between the electrode assembly and the case body on the opening side is secured. can do. Therefore, the electrode assembly can be easily accommodated in the case body, and can be accommodated in the battery case without damaging the electrode assembly . Then, by pressing the case main body housing the electrode assembly in the stacking direction of the electrode assembly, the case main body is elastically deformed, the clearance between the electrode assembly and the case main body is eliminated, and the distance between the pair of first side walls is It is set constant. The production process can be simplified as compared with the prior art because the case body containing the electrode assembly is clamped using the case body having a sufficient clearance with the electrode assembly on the opening side. In addition, since the case body is clamped in the stacking direction of the electrode assembly, no gap is formed between the electrodes in the electrode assembly, and lithium deposition during initial charge due to the gap between the electrodes is prevented. It can be prevented .

Further, in the above method of manufacturing a power storage device, the electrode assembly may be accommodated in the case main body before the pressure is applied, with the lid attached .

In the method of manufacturing the above SL of the power storage device, the lid is provided with a contact portion abutting on the opening side end portion, and a step portion formed to extend from the abutment portion, the the step portion may be configured to be the inner wall abutting the first side wall in pressed pressure time of the case body.

According to the present invention, in addition which can be inserted into the battery case without damaging the electrode assembly, it is possible to provide a manufacturing method of a charge reservoir that can simplify the production process.

FIG. 1 is an exploded perspective view of a secondary battery according to an embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a secondary battery according to an embodiment of the present invention. FIG. 5 is an exploded perspective view of a portion of the electrode assembly. It is an arrow line view of the AA in FIG. It is an explanatory view explaining a part of manufacturing process of a rechargeable battery. It is a longitudinal cross-sectional view which shows the secondary battery before pinching after accommodation of an electrode assembly. It is a perspective view which shows a part of opening side of the battery case after pinching.

Hereinafter, a power storage device according to an embodiment of the present invention will be described with reference to the drawings.
In the present embodiment, a secondary battery as a power storage device is illustrated, and the secondary battery of the present embodiment is specifically a lithium ion secondary battery.

  As shown in FIGS. 1 and 2, the secondary battery 10 of the present embodiment is a square secondary battery. An electrode assembly 12 is accommodated in the battery case 11 of the secondary battery 10. The longitudinal direction of the battery case 11 shown in FIG. 1 is shown as the left and right direction, the height direction of the battery case 11 is shown as the vertical direction, and the short direction of the battery case 11 is shown as the front and rear direction. The height direction of the battery case 11 coincides with the housing direction of the electrode assembly 12. The electrode assembly 12 is a power generation element that produces a battery function (such as charge and discharge).

  As shown in FIG. 3, the electrode assembly 12 includes a sheet-like positive electrode 13 and a sheet-like negative electrode 14. The positive electrode 13 has a rectangular positive electrode body 15 and a strip-like positive electrode current collector 16 formed at the edge of the positive electrode body 15. The positive electrode body 15 has a positive electrode metal foil 17 and a positive electrode active material layer 18 formed of a positive electrode active material coated on both sides of the positive electrode metal foil 17. The positive electrode current collector 16 is formed of the positive electrode metal foil 17, and the positive electrode current collector 16 is not coated with the positive electrode active material. In addition, the positive electrode metal foil 17 of this embodiment is an aluminum foil.

  The negative electrode 14 has a rectangular negative electrode main body 19 and a strip-like negative electrode current collector 20 formed at the edge of the negative electrode main body 19. The negative electrode main body 19 has a negative electrode metal foil 21 and a negative electrode active material layer 22 formed of a negative electrode active material coated on both sides of the negative electrode metal foil 21. The negative electrode current collector 20 is formed of the negative electrode metal foil 21, and the negative electrode current collector 20 is not coated with the negative electrode active material. In addition, the negative electrode metal foil 21 of this embodiment is a copper foil. The left, right, upper and lower dimensions of the negative electrode body 19 are set to be slightly larger than that of the positive electrode body 15.

  The electrode assembly 12 has a layered structure in which a plurality of positive electrodes 13 and a plurality of negative electrodes 14 are alternately stacked while maintaining an insulating state, with a separator 23 interposed between the positive electrode 13 and the negative electrode 14. That is, the electrode assembly 12 of the present embodiment is a stacked electrode assembly in which the plurality of positive electrodes 13 and the plurality of negative electrodes 14 are alternately stacked while maintaining the insulating state. The separator 23 is set to substantially the same size as the negative electrode main body 19. The electrode assembly 12 is configured, for example, by laminating a plurality of positive electrodes 13 and a plurality of negative electrodes 14 as shown in FIGS. 3 and 4. And in this embodiment, the end face of the both sides of the lamination direction of the electrode assembly 12 is comprised by the negative electrode 14.

  The respective positive electrode current collectors 16 are arranged in a row along the stacking direction of the electrode assembly 12. The respective negative electrode current collectors 20 are arranged in a row along the stacking direction, similarly to the positive electrode current collector 16, so as not to overlap with the positive electrode current collector 16. In the present embodiment, the positive electrode current collectors 16 are set to the same size as one another, and the negative electrode current collectors 20 are also set to the same size as one another. Each positive electrode current collector 16 is collected on the front side of the electrode assembly 12 to form a positive electrode current collection group 25. Similar to the positive electrode current collector 16, each negative electrode current collector plate 28 is collected on the front side of the electrode assembly 12 to form a negative electrode current collection group 26.

  The positive electrode current collector plate 27 is joined to the positive electrode current collector group 25, and the negative electrode current collector plate 28 is joined to the negative electrode current collector group 26. As shown in FIG. 2, the positive electrode current collector plate 27 is provided with a positive electrode terminal 30 electrically connected via the overcurrent protection circuit 29. In addition, the negative electrode current collector plate 28 is provided with a negative electrode terminal 31 electrically connected via the overcurrent protection circuit 29.

  Next, the battery case 11 will be described. As shown in FIGS. 1 and 2, the battery case 11 includes a bottomed cylindrical case main body 35 and a rectangular flat lid 37 closing the opening 36 of the case main body 35. The case body 35 and the lid 37 are formed of a metal material (for example, aluminum). The lid 37 is fixed to the case main body 35 by laser welding. As shown in FIG. 2, on the inner surface of the case main body 35, an insulating sheet 38 as an insulating member for insulating the electrode assembly 12 accommodated in the battery case 11 is attached. Further, on the inner side surface of the lid 37, an insulating sheet 39 as an insulating member for insulating the electrode assembly 12 accommodated in the battery case 11 is attached.

  As shown in FIG. 1, the case body 35 includes a cylindrical wall 40 having a rectangular cross section, and a bottom wall 41 formed to close the end of the case body 35 opposite to the opening 36. The cylindrical wall 40 includes a pair of first side walls 42 disposed opposite to each other, and a pair of second side walls 43 orthogonal to the pair of first side walls 42 and disposed parallel to each other. The first side wall 42 of the present embodiment has the largest area in the battery case 11. The opening 36 of the cylindrical wall 40 is rectangular, and an opening side end 44 is formed on the opening 36 side of the cylindrical wall 40. The opening side end 44 is a portion to be joined with the lid 37 and has an end face parallel to the bottom wall 41.

  The case body 35 of this embodiment is clamped in the stacking direction of the electrode assembly 12 after the electrode assembly 12 is accommodated. Therefore, the case main body 35 before pinching and the case main body 35 after pinching have different shapes depending on the presence or absence of deformation due to pinching. In the present embodiment, when the case main body 35 before pinching and the case main body 35 after pinching are distinguished, the case main body 35A before pinching and the case main body 35B after pinching will be described.

As shown in FIGS. 5 and 6, in this embodiment, the distance G1 between the pair of first side walls 42 in the opening 36 and the distance G2 between the pair of first side walls 42 on the bottom wall 41 side, and the distance G1 is the distance G2 It is set larger. Then, the pressure front case body 35A is formed to increase the distance between the pair of first side walls 42 as it goes from the bottom wall 41 side to the opening 36 side. That is, the pair of first side walls 42 are not parallel to each other, but are inclined with respect to the direction orthogonal to the bottom wall 41. As shown in FIG. 5, when the virtual center line S is set in a direction passing through the center of the bottom wall 41 and orthogonal to the bottom wall 41, the pair of first side walls 42 are in line symmetry with each other about the virtual center line S. It is formed. The virtual center line S coincides with the center in the stacking direction of the electrode assembly 12 in a state in which the electrode assembly 12 is accommodated in the pressure case body 35A. Since the gap G1 is set larger than the gap G2, the edge on the opening 36 side of the second side wall 43 is larger than the edge on the bottom wall 41 side, and the shape of the second side wall 43 is trapezoidal.

  Since the gap G1 is set larger than the gap G2, the area of the opening 36 is set larger than the area on the inner wall side of the bottom wall 41. The distance G1 between the pair of first side walls 42 on the side of the opening 36 is set larger than the thickness T of the electrode assembly 12 in the stacking direction, and the distance G2 between the pair of first side walls 42 of the bottom wall 41 is the electrode assembly It is set equal to the thickness T in the stacking direction of twelve. Therefore, a clearance between the electrode assembly 12 and the first side wall 42 exists in the pre-clamping case main body 35A, and when the electrode assembly 12 is accommodated in the pre-clamping case main body 35A, the electrode assembly 12 is formed. Is less likely to interfere with the open end 44 of the front case body 35A. For this reason, the pinching front case main body 35A is structured to be easily accommodated without damaging the electrode assembly 12. In addition, since the distance G2 between the pair of first side walls 42 of the bottom wall 41 is set equal to the thickness T in the stacking direction of the electrode assembly 12, the pre-holding case main body 35A is the bottom of the electrode assembly 12. The end of the wall 41 side can be easily positioned in the stacking direction. 5 and 6, the inclination of the first side wall 42 is exaggerated and illustrated, but the inclination of the first side wall 42 is an inclination such that the inclination can not actually be confirmed visually.

After housing the electrode assembly 12, the pre-clamping case body 35 </ b> A is clamped by the pressing device W in the stacking direction of the electrode assembly 12. The pressing device W shown in FIG. 5 is provided with a pair of pressing molds M for pressing the pair of first side walls 42 in the stacking direction. When the pre-clamping case main body 35A in which the electrode assembly 12 is accommodated is clamped by the pressing device W in the stacking direction of the electrode assembly 12, elastic deformation occurs in the pre-clamping case main body 35A. A rear case main body 35B is formed. As shown in FIG. 4 and FIG. 5, the inclination of the pair of first side walls 42 is respectively eliminated by the elastic deformation at the time of pressing, and the pair of first side walls 42 become parallel to each other. For this reason, the clearance between the electrode assembly 12 and the first side wall 42, which is present in the pre-clamping case body 35A, disappears in the clumping post-case body 35B. Since the pair of first side walls 42 are parallel to each other by the clamping pressure, as shown in FIG. 7, the edge of the second side wall 43 at the opening side end 44 is outside with respect to the outer surface of the second side wall 43 To bow. For this reason, in the post-pressing case body 35B, the length in the left-right direction on the opening 36 side is larger than that of the front-pressing case body 35A. In the post-pressing case body 35B, the curvature of the second side wall 43 decreases toward the bottom wall 41, and almost no curvature occurs near the bottom wall 41.

  In the present embodiment, the lid 37 is joined to the post-pressing case main body 35B by laser welding using a laser welder (not shown) at the time of pressing by the pressing device W. The lid 37 is formed to fit the shape of the opening 36 side of the case main body 35B after the pressing. A pair of through holes 45 is formed in the lid 37. The positive electrode terminal 30 is inserted into one of the through holes 45, and the negative electrode terminal 31 is inserted into the other through hole 45. The insulating ring 50 is attached to the positive electrode terminal 30 and the negative electrode terminal 31, and the insulating ring 50 insulates the lid 37 from the positive electrode terminal 30 and the negative electrode terminal 31. As shown in FIGS. 4 and 6, the lid 37 of the present embodiment is formed extending from the contact portion 46 that contacts the opening side end 44 of the case main body 35 and the contact portion 46, and A step portion 47 is in contact with the inner wall of the first side wall 42. As shown in FIG. 6, the length X in the stacking direction of the step portion 47 in the lid 37 is set to be the same as the gap G2. Therefore, when the pressing device W squeezes from the state of the pre-clamping case main body 35A shown in FIG. 6, as shown in FIG. At the time of deformation, the opening 36 side of the first side wall 42 is positioned by the step portion 47.

Next, accommodation of the electrode assembly 12 of the secondary battery 10 according to the present embodiment in the battery case 11 will be described. The electrode assembly 12 assembled in advance and the pre-pressing case main body 35A are prepared. As shown in FIGS. 5 and 6, the electrode assembly 12 is in a state in which the lid 37 and the insulating ring 50 are attached. As shown in FIG. 5, by inserting the electrode assembly 12 from the opening 36 side of the pre-pressing case main body 35A, the electrode assembly 12 is accommodated in the pre-pressing case main body 35A. At this time, since there is a clearance between the electrode assembly 12 and the first side wall 42 in the pre-clamping case body 35A, the electrode assembly 12 can be easily accommodated, and the electrode assembly 12 is made of the crush-preceding case body 35A. The possibility of colliding with the open end 44 is small and hardly present. In the case body 35A, the distance between the pair of first side walls 42 decreases from the opening 36 toward the bottom wall 41. In the bottom wall 41, there is no clearance between the electrode assembly 12 and the first side wall 42. . For this reason, as shown in FIG. 6, in the bottom wall 41, the end on the bottom wall 41 side of the electrode assembly 12 is positioned in the stacking direction.

  After the electrode assembly 12 is accommodated in the pre-clamping case body 35A, the crush-preceding case main body 35A is clamped by the pressing device W in the stacking direction of the electrode assembly 12 as shown in FIG. The clamping pressure of the front case body 35A is performed by a pressing mold M that presses the pair of first side walls 42. When the pressing die M squeezes the pressing front case main body 35A, elastic deformation occurs in the pressing front case main body 35A, and the opening 36 side of the first side wall 42 abuts on the step portion 47, and The opening 36 side of the side wall 42 is positioned by the stepped portion 47. At this time, the pinching front case body 35A becomes a pinching rear case body 35B by elastic deformation. For this reason, the pair of first side walls 42 become parallel to each other by elastic deformation at the time of pinching, and the clearance between the electrode assembly 12 and the first side wall 42 disappears in the pinched case main body 35B. Further, at the time of the pressing, as shown in FIG. 7, the edge of the second side wall 43 at the opening side end 44 curves outward with respect to the outer side surface of the second side wall 43. In the post-pressing case body 35B, the curvature of the second side wall 43 decreases toward the bottom wall 41, and almost no curvature occurs near the bottom wall 41. The second side walls 43 are disposed to face each other so as to connect the pair of first side walls 42 after sandwiching pressure, but are not orthogonal to the pair of first side walls 42 and are not parallel to each other.

  Next, while the pressing mold M holds the post-nampling case main body 35B in a compressed state, the lid 37 and the post-naking post-case main body 35B are joined by laser welding. The contact portion 46 and the opening side end 44 of the lid 37 melt when receiving the laser light and solidify by cooling, the lid 37 is joined to the opening side end 44 of the case body 35 B after clamping. . When the laser welding is completed, the case body 35B after clamping, to which the lid 37 is joined, is released from the pressing device W. The post-pressing case main body 35B to which the lid 37 is joined, that is, the battery case 11 in which the electrode assembly 12 is accommodated is transferred to the next process such as pouring of the electrolytic solution.

The manufacturing method of the battery case 11 and the secondary battery 10 of the present embodiment exhibits the following effects.
(1) The pressing front case body 35A is formed so as to increase the distance between the pair of first side walls 42 from the bottom wall 41 to the opening 36, and thus the electrode assembly 12 on the opening 36 side It is possible to secure sufficient clearance with the case main body 35A. Therefore, the electrode assembly 12 can be easily accommodated in the pre-pressing case main body 35A, and can be accommodated in the battery case 11 without damaging the electrode assembly 12. Then, the pre-clamping case main body 35A in which the electrode assembly 12 is accommodated is elastically deformed by squeezing the electrode assembly 12 in the stacking direction, so that the clearance between the electrode assembly 12 and the clumped case main body 35B is eliminated. The distance between the first side walls 42 of the frame is set to be constant. The production process is simplified compared to the prior art because the clamping pre-case body 35A containing the electrode assembly 12 is clamped using the clamping pre-case body 35A with sufficient clearance from the electrode assembly 12 on the opening 36 side. Can be Further, since the pre-clamping case body 35A is clamped in the stacking direction of the electrode assembly 12, no gap is formed between the electrodes in the electrode assembly 12, and an initial stage caused by the gap between the electrodes is caused. Lithium deposition during charging can be prevented.

(2) Clamping Force The elastic deformation of the pinching front case main body 35A tends to be line symmetrical with each other at the center in the stacking direction of the electrode assembly 12 even if the pinching front body 35A is pinched. For this reason, it is possible to suppress the deviation of the pressure resistance strength in the post-pressing case body 35B.

(3) To hold the lid 37 to the post case main body 35B by welding when the front case main body 35A is pressed, the distance between the pair of first side walls 42 set by elastic deformation is kept constant. Can. In addition, even if the cover 37 is released from the clamping pressure after joining, the shape of the case body 35 can maintain the shape of the post-clamping case body 35B without returning to the shape before the clamping. For this reason, no clearance occurs between the electrode assembly 12 and the post-pressing case body 35B.

(4) The lid 37 is formed in accordance with the shape on the opening 36 side of the case main body 35B after pinching, and the shape of the pinched case main body 35B elastically deformed by joining the lid 37 can be maintained. . Further, since the step portion 47 is formed in the lid 37, the end in the opening 36 side of the first side wall 42 can be positioned in the stacking direction at the time of elastic deformation. As a result, the pair of first side walls 42 can be made parallel to each other in the post-pressing case body 35B.

In addition, the technical thought which can be derived from said embodiment is shown below.
A method of manufacturing a power storage device, comprising: storing a layered electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked or wound while maintaining insulation;
The battery case includes a bottomed cylindrical case body having an opening, and a lid joined to an opening side end portion formed on the opening side of the case body,
The case main body has a cylindrical wall having a rectangular cross section including the opening side end, and a bottom wall provided at an end of the cylindrical wall opposite to the opening side end,
The cylindrical walls are disposed to face each other so as to connect the pair of first side walls formed to increase the distance from the bottom wall side toward the opening side and the pair of first side walls. A pair of second side walls,
After the electrode assembly is accommodated in the case body, the case body is clamped in the stacking direction of the electrode assembly,
A method of manufacturing a power storage device, wherein an interval between the pair of first side walls is set to be constant by elastically deforming the case main body by a clamping pressure.
According to the method of manufacturing the power storage device, the same operation and effect as the operation and effect (1) of the above embodiment can be obtained.

  The present invention is not limited to the above embodiment, and various modifications can be made within the scope of the invention. For example, the following modifications may be made.

In the above embodiment, the pair of first side walls are not parallel to each other, but are inclined with respect to the direction orthogonal to the bottom wall, and are formed in line symmetry with each other about the virtual center line. It is not limited to symmetry. For example, one first side wall of the pair of first side walls may be provided in a direction perpendicular to the bottom wall, and the other first side wall may be provided inclined with respect to the direction perpendicular to the bottom wall. Alternatively, the first side walls may be formed such that the slopes of the pair of first side walls are different from each other. Also in this case, the pressing front case body is formed to increase the distance between the pair of first side walls as it goes from the bottom wall side to the opening side.
In the above embodiment, a lithium secondary battery has been illustrated as an example of the power storage device. The power storage device may be applied to primary batteries as well as secondary batteries other than lithium secondary batteries.
In the above embodiment, a laminated electrode assembly was described as an example of the electrode assembly, but the electrode assembly may be a flat wound electrode assembly.

DESCRIPTION OF SYMBOLS 10 secondary battery 11 battery case 12 electrode assembly 13 positive electrode 14 negative electrode 23 separator 30 positive electrode terminal 31 negative electrode terminal 35 case main body 35A front holding case main body 35B rear holding pressure case main body 36 opening 37 lid 42 first side wall 43 second Side wall 46 contact portion 47 step portion G1, G2 interval X length T thickness S virtual center line M pressing type W pressing device

Claims (3)

A layered electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked or wound while maintaining insulation;
A battery case for housing the electrode assembly;
The battery case includes a bottomed cylindrical case main body having a rectangular opening, and a lid joined to an opening side end formed on the opening side of the case main body,
The case main body is in contact with the end face in the stacking direction of the electrode assembly, and is disposed so as to connect the pair of first side walls disposed opposite to each other with the first side wall. A method of manufacturing a power storage device, comprising: a second side wall; and a bottom wall provided at an end opposite to the opening side end,
The case body is formed to increase the distance between the pair of first side walls from the bottom wall side toward the opening side in a state in which the electrode assembly is not accommodated .
Setting a constant distance between the pair of first side walls by sandwiching the case body in the stacking direction of the electrode assembly while the electrode assembly is accommodated;
And a step of joining the lid to the case body by welding at the time of pressing the case body. The method for manufacturing a power storage device according to claim 1, wherein the electrode assembly is accommodated in the case main body before being pressed, with the lid attached. The lid is an abutting portion that abuts on the open end.
And a step portion formed extending from the contact portion,
The method according to claim 1, wherein the step portion abuts against the inner wall of the first side wall when the case main body is pressed.

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