Secondary batteries

Abstract

To provide a secondary battery capable of suppressing deposition of a metallic foreign matter.SOLUTION: A secondary battery 1 including an electrode body 30 including stacked electrodes includes a film 10 arranged on an outer surface of the secondary battery 1 in a thickness direction and a pressing portion that presses on a portion of the outer surface. The secondary battery 1 is arranged adjacent to a pressing member 2 having at least one protruding portion 20 that presses the secondary battery 1 from the thickness direction. The pressing portion is located at least in a portion of a non-opposing position, not opposing the protruding portion 20 of the pressing member 2.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a secondary battery. [Background technology]

[0002] Currently, secondary batteries such as lithium-ion batteries are used in electric vehicles, hybrid vehicles, plug-in hybrid vehicles, etc. For example, Patent Document 1 discloses a secondary battery that includes four insulating plates disposed between an electrode group and a case. The purpose of this secondary battery is to insulate the electrode group from the case with the insulating plates and to maintain the shape of the electrode group. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-54567 Summary of the Invention [Problem to be solved by the invention]

[0004] When manufacturing a secondary battery pack by arranging multiple secondary batteries, a spacer with a protrusion may be placed between two adjacent secondary batteries. When the secondary battery expands due to charging and discharging, the protrusions of the spacer apply pressure to the secondary battery. Therefore, pressure is directly applied to the part of the spacer facing the protrusion, and not to the part not facing the protrusion.

[0005] In the portions facing the protrusions of the spacer, the distance between the electrodes stacked in the secondary battery is small. On the other hand, in the portions not facing the protrusions, the distance between the electrodes of the secondary battery is large. Therefore, in the portions not facing the protrusions, gas generated by the charge and discharge of the secondary battery is likely to accumulate inside the electrode body, making it easier for metallic foreign matter such as lithium to precipitate. Figure 16 shows the results of lithium precipitation in a wound electrode body. As shown in Figure 16, lithium precipitated in positions where the distance between the electrodes of the wound electrode body was large. Lithium was particularly precipitated in the flat portion near the center of the wound electrode body.

[0006] However, the secondary battery disclosed in Patent Document 1 is intended to insulate the electrode group and the case while maintaining the shape of the electrode group, and therefore has the problem of being unable to suppress the deposition of metallic foreign matter caused by external forces applied to the outer surface of the secondary battery.

[0007] The present invention has been made to solve such problems, and has an object to provide a secondary battery capable of suppressing the deposition of metallic foreign matter. [Means for solving the problem]

[0008] A secondary battery including an electrode assembly including stacked electrodes according to one aspect of the present invention comprises: a film disposed on an outer surface of the secondary battery in a thickness direction; a pressing portion that presses a part of the outer surface, The secondary battery is disposed adjacent to a pressing member having at least one protrusion that presses the secondary battery in a thickness direction, The pressing portion is present at least in a portion of the pressure member at a non-opposing position that does not face the protrusion.

[0009] the film is configured to have a thick portion corresponding to the pressed portion and having a thickness greater than that of other portions of the film in the thickness direction; The thickened portion of the film is formed at least in part at the non-opposing position.

[0010] The thick portion of the film is formed so as to face the center of the electrode body.

[0011] The thick portion of the film can be formed so as to extend in the width direction of the secondary battery.

[0012] The thick portion of the film can be formed so as to face the flat portion of the electrode body including the wound electrodes.

[0013] The thick portion of the film can be formed so as to extend in the height direction of the secondary battery.

[0014] The thickness of the thick portion is preferably configured so that the distance between the electrodes at the center of the electrode body is equal to or less than the distance between the electrodes at portions other than the center of the electrode body.

[0015] When the pressing portion is present only at the non-opposing position, it is preferable that the thickness of the thick portion is configured so that the distance between the electrodes at the non-opposing position is equal to or less than the distance between the electrodes at the opposing position opposite the protrusion of the pressure member.

[0016] The film thickness may be formed by stacking one or more films.

[0017] The pressing portion is formed by a pressing member separate from the film, The pressing members may be disposed on at least one of the upper and lower surfaces of the film at least in part at non-opposing positions.

[0018] The protrusion of the pressure member has an elongated shape, the pressure member has a plurality of inter-projection regions defined by elongated projections; The pressure member may be configured so that the inter-projection area facing the center of the electrode body is larger than the other inter-projection areas.

[0019] The pressure member may be configured so that the density of the protrusions at a position facing the center of the secondary battery is smaller than the density of the protrusions at positions other than the facing position. [Effects of the Invention]

[0020] According to the present invention, a secondary battery capable of suppressing deposition of metallic foreign matter can be provided. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a diagram showing a secondary battery according to a first embodiment of the present invention. [Figure 2] 1 is a front view showing an example of a spacer according to a first embodiment of the present invention. [Figure 3] 1 is a diagram showing an example of an electrode assembly according to a first embodiment of the present invention. [Figure 4] FIG. 1 is a development view showing an example of a film according to a first embodiment of the present invention. [Figure 5] FIG. 3 is a development view showing another example of the film according to the first embodiment of the present invention. [Figure 6] 1 is a front view showing a film in a folded state according to a first embodiment of the present invention. [Figure 7] 1 is a side view showing a film in a folded state according to a first embodiment of the present invention. [Figure 8] FIG. 4 is a development view showing an example of a film according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a development view showing another example of the film according to the second embodiment of the present invention. [Figure 10] FIG. 10 is a front view showing a film in a folded state according to a second embodiment of the present invention. [Figure 11] FIG. 10 is a side view showing a film in a folded state according to a second embodiment of the present invention. [Figure 12] FIG. 10 is a developed view showing a film according to a third embodiment of the present invention. [Figure 13] FIG. 10 is a front view showing a film in a folded state according to a third embodiment of the present invention. [Figure 14] FIG. 10 is a developed view showing a film according to a fourth embodiment of the present invention. [Figure 15]FIG. 10 is a front view showing a film and a pressing member in a folded state according to a fourth embodiment of the present invention. [Figure 16] FIG. 10 is a diagram showing the results of lithium deposition in a wound electrode body. DETAILED DESCRIPTION OF THE INVENTION

[0022] First Embodiment Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a secondary battery 1 according to a first embodiment of the present invention. The secondary battery 1 includes a film 10 disposed on its outer surface. It is preferable that the film 10 be insulating. Details of the film 10 will be described later.

[0023] When a secondary battery pack is manufactured using multiple secondary batteries 1, the multiple secondary batteries 1 are arranged in the thickness direction as shown in Fig. 1. Between adjacent secondary batteries 1, spacers 2 are placed adjacent to the secondary batteries 1. The spacers 2 correspond to pressure members that apply pressure to the secondary batteries 1 in the thickness direction.

[0024] 2 is a front view showing an example of the spacer 2 according to the first embodiment. As shown in FIG. 2, the spacer 2 has at least one protrusion 20. This protrusion 20 applies pressure to the secondary battery 1. The protrusion 20 can be provided on both sides of the spacer 2.

[0025] As shown in Fig. 2, the protrusions 20 can be elongated. The spacer 2 has a plurality of inter-protrusion regions defined by the elongated protrusions 20. The spacer 2 is configured so that the inter-protrusion region 21 facing the center of the electrode body of the secondary battery 1 is larger than the other inter-protrusion regions. In other words, the spacer 2 is configured so that the density of the protrusions 20 at the position facing the center of the electrode body of the secondary battery 1 is smaller than the density of the protrusions 20 at positions other than that position.

[0026] The protrusions 20 have the function of allowing the cooling fluid to pass along the outer side surface of the secondary battery 1. In the case of the spacer 2 shown in Fig. 2, the cooling fluid flows in from below the spacer 2 and is discharged outward in the width direction of the spacer 2 along the protrusions 20. This cools the secondary battery 1.

[0027] 3 is a diagram showing an example of an electrode assembly 30 included in the secondary battery 1 according to the first embodiment. In this embodiment, the electrode assembly 30 is formed by stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator, and then flattening the stack. Therefore, curved portions 31 are formed at the top and bottom of the electrode assembly 30, and a flat portion 32 is formed in the center of the electrode assembly 30.

[0028] FIG. 4 is a development view showing an example of the film 10 according to the first embodiment. After being placed on the outer surface of the secondary battery 1, the film 10 is folded along the dashed lines in FIG. 4 so as to encase the secondary battery 1. The film 10 is configured to have a thick portion that is thicker than other portions of the film 10 in the thickness direction of the secondary battery 1. For example, as shown in FIG. 4, the thick portion of the film 10 can be formed by stacking a single film 10. Alternatively, the thick portion can be formed by stacking individual films 10 as shown in FIG. 5.

[0029] The thick portion presses at least a portion of the outer surface of the secondary battery 1 in the thickness direction. The thick portion corresponds to a pressing portion. The thick portion can be fixed with tape, adhesive, or the like. Although two films 10 are shown in FIG. 5, the thick portion may be formed by stacking three or more films 10.

[0030] In the first embodiment, the thick portion can be formed by doubling the film 10. The thick portion of the film 10 is formed in at least a part of a position that does not face the protrusion 20 of the spacer 2 (hereinafter referred to as the "non-facing position"). In addition, the thick portion of the film 10 is preferably formed so as to face the center of the electrode body 30 in the secondary battery 1.

[0031] The thickness of the thick portion is preferably configured so that the distance between the electrodes at the center of the electrode body 30 is equal to or less than the distance between the electrodes at portions other than the center of the electrode body 30.

[0032] Fig. 6 is a front view showing the film 10 in a folded state according to the first embodiment. Fig. 7 is a side view showing the film 10 in a folded state according to the first embodiment. In the first embodiment, the thick portion of the film 10 extends in the width direction of the secondary battery 1 and is formed so as to face the flat portion 32 of the electrode body 30.

[0033] In the above-described embodiment, the film 10 is arranged to wrap the secondary battery 1. The secondary battery 1 is arranged adjacent to a spacer 2 having at least one protrusion 20 that applies pressure to the secondary battery 1 in the thickness direction. The film 10 is configured to have a thick portion that is thicker in the thickness direction than other portions of the film 10. The thick portion of the film 10 is formed in at least a portion of a non-facing position that does not face the protrusion 20 of the spacer 2.

[0034] In this way, by forming the thick portion of the film 10 at the non-opposing position, the thick portion presses the electrode body 30 at the non-opposing position. Therefore, the distance between the electrodes at the non-opposing position can be made equal to or less than the distance between the electrodes at the opposing position. As a result, gas generated by charging and discharging can be prevented from accumulating in the electrode body 30, and the deposition of metallic foreign matter can be suppressed.

[0035] Furthermore, the thick portion of the film 10 is formed so as to face the central portion of the electrode assembly 30. Gas generated by charging and discharging is less likely to be discharged from the central portion of the electrode assembly 30, which is formed by stacking electrodes, compared to the outer portions of the electrode assembly 30 in the width direction. In the above-described embodiment, the thick portion of the film 10 is formed so as to face the central portion of the electrode assembly 30, and therefore the thick portion of the film 10 presses against the central portion of the electrode assembly 30. Therefore, the distance between the electrodes in the central portion of the electrode assembly 30 can be made equal to or less than the distance between the electrodes in portions other than the central portion of the electrode assembly 30. As a result, gas generated by charging and discharging can be prevented from accumulating in the central portion of the electrode assembly 30, and the deposition of metallic foreign matter can be suppressed.

[0036] <Second embodiment> Fig. 8 is a developed view showing an example of film 10 according to a second embodiment of the present invention. Fig. 9 is a developed view showing another example of film 10 according to the second embodiment. Fig. 10 is a front view showing film 10 according to the second embodiment in a folded state. Fig. 11 is a side view showing film 10 according to the second embodiment in a folded state. In the second embodiment, film 10 is formed so that the thick portion of film 10 extends in the height direction of secondary battery 1.

[0037] The thick portion of the film 10 is formed so as to face the central portion of the electrode assembly 30. The thick portion of the film 10 can also be formed by overlapping one film 10 as shown in FIG. 8. The thick portion can also be formed by overlapping individual films 10 as shown in FIG. 9. The thickness of the thick portion is preferably configured so that the distance between the electrodes at the central portion of the electrode assembly 30 is equal to or less than the distance between the electrodes at portions other than the central portion of the electrode assembly 30. The thick portion may also be formed by overlapping three or more films 10. Other features are the same as those of the first embodiment.

[0038] <Third embodiment> Fig. 12 is a developed view showing a film 10 according to a third embodiment of the present invention. Fig. 13 is a front view showing the film 10 according to the third embodiment in a folded state. The film 10 according to the third embodiment is a modified version of the film 10 according to the second embodiment. Only the differences from the second embodiment will be described below.

[0039] In the third embodiment, as shown in Figures 12 and 13, the film 10 has a thick portion formed only at the non-opposing position. Therefore, the films 10 do not overlap at the opposing position, but overlap only at the non-opposing position. As a result, only the electrode body 30 at the non-opposing position is pressed by the thick portion. The thickness of the thick portion is preferably configured so that the distance between the electrodes at the non-opposing position is equal to or less than the distance between the electrodes of the electrode body 30 at the position opposing the protrusion 20 of the spacer 2 (hereinafter referred to as the "opposing position"). Note that in the example shown in Figures 12 and 13, the thick portion of the film 10 extends in the height direction of the secondary battery 1, but in other embodiments, the thick portion may extend in the width direction of the secondary battery 1.

[0040] <Fourth embodiment> Fig. 14 is a developed view showing a film 10 according to a fourth embodiment of the present invention. Fig. 15 is a front view showing the film 10 and pressing member 40 in a folded state according to the fourth embodiment. The film 10 according to the fourth embodiment is a modified version of the film 10 according to the second embodiment. Only the differences from the second embodiment will be described below.

[0041] In the fourth embodiment, a pressing member 40 is disposed without providing a thick portion of the film 10. The pressing member 40 is a member separate from the film 10, and may be, for example, a tape or an insulating plate. The pressing member 40 corresponds to a pressing portion. The pressing member 40 is disposed on at least one of the upper and lower surfaces of the film 10 in at least a portion of a non-opposing position.

[0042] The present invention is not limited to the above-described embodiment, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the above-described embodiment, the thick portion is formed by doubling the film 10, but in other embodiments, the thick portion may be formed by doubling the film 10.

[0043] In another embodiment, the thick portion may be formed by adjusting the thickness of the film 10 without overlapping the film 10 .

[0044] Furthermore, in other embodiments, a non-wound electrode assembly 30 may be formed by stacking multiple positive electrode sheets, multiple negative electrode sheets, and multiple separators. [Explanation of symbols]

[0045] 1 Secondary battery 10 Film 2 spacers 20 Protrusion 21 Interprotrusion area 30 Electrode body 31 Curved section 32 Flat area 40 Pressing member

Claims

1. A secondary battery including an electrode assembly including stacked electrodes, a film disposed on an outer surface of the secondary battery in a thickness direction; a pressure member having at least one protrusion that applies pressure to the secondary battery in the thickness direction is disposed adjacent to the secondary battery; the film has a thick portion formed to face a central portion of the electrode body and pressing a part of the outer surface, the thick portion is disposed at least at a non-opposing position that does not face the protrusion of the pressing member. Secondary battery.

2. 2. The secondary battery according to claim 1, wherein the thickness of the thick portion is configured so that the distance between the electrodes at the center of the electrode body is equal to or less than the distance between the electrodes at portions other than the center of the electrode body.

3. The thick portion is formed only at the non-opposing position, 2. The secondary battery according to claim 1, wherein the thickness of the thick portion is configured so that the distance between the electrodes at the non-facing position is equal to or less than the distance between the electrodes at the facing position facing the protrusion of the pressing member.

4. 4. The secondary battery according to claim 1, wherein the thick portion of the film is formed by stacking one or more of the films.

5. the pressure member includes a plurality of elongated protrusions, 5. The secondary battery according to claim 1, wherein at least some of the plurality of elongated protrusions extend downward in the center of the electrode body and extend in the width direction at the width direction ends of the secondary battery.

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