Secondary battery and method for manufacturing secondary battery

Abstract

To facilitate sticking of a laminate film to an electrode laminate.SOLUTION: The secondary battery according to the present disclosure includes a flat plate-shaped electrode laminate 11 in which a positive electrode and a negative electrode are alternately laminated in a state of being insulated from each other, a convex portion protruding from an outer peripheral surface of the electrode laminate 11, a structure covering a concave portion formed by the convex portion, and a laminate film 20 attached to the electrode laminate 11 so as to cover the structure. The structural body has an accommodating portion side 14d for accommodating the convex portion on a surface facing the convex portion, and has a flat surface on a surface different from the surface facing the convex portion. The laminate film 20 is attached to a flat surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a secondary battery and a method for manufacturing a secondary battery. [Background technology]

[0002] Patent Document 1 discloses a technique for laminating a laminate in which positive and negative current collector foils are alternately stacked while being insulated from each other. In Patent Document 1, a laminate film is positioned so that it contacts the edge of the laminate. With the inner layer of the laminate film heated, a pressure roller is used to press the outer layer toward the inner layer while moving the pressure roller, welding the laminate film to the edge of the laminate. This eliminates air pockets that may occur between the laminate and the laminate film during lamination. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-128896 Summary of the Invention [Problem to be solved by the invention]

[0004] Bipolar batteries are known that have bipolar electrodes in which electrode layers of different polarities are formed on both sides of a current collector. A bipolar battery includes an electrode stack in which multiple bipolar electrodes and multiple separators are alternately stacked. A liquid injection port is provided on the outer periphery of the electrode stack for injecting an electrolyte into the space formed between adjacent bipolar electrodes. Furthermore, a housing for a voltage detection terminal connected to the current collector of the bipolar electrode may be provided on the outer periphery of the electrode stack.

[0005] In this way, when unevenness is formed on the outer peripheral surface of the electrode laminate due to structures such as the liquid injection port and the voltage detection housing, there is a problem in that it is difficult to attach a laminate film to the outer peripheral surface of the electrode laminate, even if a pressure roller is used as in Patent Document 1.

[0006] The present disclosure has been made in consideration of such problems, and aims to provide a secondary battery and a method for manufacturing a secondary battery that can easily attach a laminate film to an electrode stack. [Means for solving the problem]

[0007] A secondary battery according to the present disclosure includes a flat electrode laminate in which positive electrodes and negative electrodes are alternately stacked while being insulated from each other, protrusions protruding from the outer peripheral surface of the electrode laminate, a structure covering recesses formed by the protrusions, and a laminate film attached to the electrode laminate so as to cover the structure.

[0008] The structure may have a housing portion that houses the convex portion on a surface facing the convex portion, and a flat surface on a surface different from the surface facing the convex portion, and the laminate film may be attached to the flat surface.

[0009] The structure may have an upper flat surface that is approximately flush with the upper surface of the electrode stack, and a lower flat surface that is approximately flush with the lower surface of the electrode stack, and the laminate film may be attached to the upper flat surface and the lower flat surface of the structure and to at least a portion of the upper surface and lower surface of the electrode stack.

[0010] The protrusion may include a liquid inlet and a housing for a voltage detection terminal, and the liquid inlet and the housing for a voltage detection terminal may be formed on the same surface of the electrode stack.

[0011] The method for manufacturing a secondary battery according to the present disclosure includes alternately stacking positive electrodes and negative electrodes while insulated from each other to form a flat electrode laminate, covering recesses formed by protrusions protruding from the outer peripheral surface of the electrode laminate with a structure, and attaching a laminate film to the electrode laminate so as to cover the structure. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to easily attach a laminate film to an electrode stack. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view of a secondary battery according to an embodiment; [Figure 2] FIG. 2 is a top view of the secondary battery according to the embodiment. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] 1A to 1C are diagrams illustrating a method for manufacturing a secondary battery according to an embodiment. [Figure 5] 1A to 1C are diagrams illustrating a method for manufacturing a secondary battery according to an embodiment. [Figure 6] 1A to 1C are diagrams illustrating a method for manufacturing a secondary battery according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. For clarity of explanation, the following description and drawings have been omitted and simplified as appropriate. In addition, the same elements in each drawing are designated by the same reference numerals, and duplicate explanations have been omitted as necessary.

[0015] The embodiments relate to a secondary battery (storage battery) mounted on a vehicle such as a hybrid vehicle that can run using the power of at least one of a motor and an engine, or an electric vehicle that runs using driving force obtained from electrical energy.

[0016] Fig. 1 is a perspective view of a secondary battery according to an embodiment. Fig. 2 is a top view of a secondary battery according to an embodiment. Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2. For ease of explanation, the cover material 14 and the laminate film 20 are omitted from Fig. 1.

[0017] 1 and 2, a secondary battery 10 includes an electrode stack 11, a liquid inlet 12, a housing 13 for a voltage detection terminal, a cover material 14, and a laminate film 20. The electrode stack 11 is a flat battery module in which positive electrodes and negative electrodes are alternately stacked while being insulated from each other. As shown in FIGS. 2 and 3, the electrode stack 11 includes multiple cells 1, a sealing member 4, and an external current collector plate 5.

[0018] The electrode stack 11 includes a plurality of cells 1 stacked on top of each other. Each cell 1 may include a pair of adjacent current collectors (not shown), and a positive electrode active material layer, a separator, and a negative electrode active material layer (none of which are shown) disposed between the pair of current collectors. The secondary battery 10 according to this embodiment may be a bipolar battery configured by stacking a plurality of cells 1. In a bipolar battery, bipolar electrodes (not shown) serve as both the positive and negative electrodes of adjacent cells 1, and the plurality of cells 1 are connected in series.

[0019] Although not shown in detail in FIG. 3 , the bipolar electrode may have a current collector, a positive electrode active material layer, and a negative electrode active material layer. The current collector is made of, for example, metal. The current collector is, for example, rectangular in top view. The positive electrode active material layer is provided on one surface of the current collector. The negative electrode active material layer is provided on the other surface of the current collector. The multiple bipolar electrodes are stacked such that the positive electrode active material layer of one bipolar electrode and the negative electrode active material layer of the bipolar electrode adjacent to that one bipolar electrode face each other.

[0020] The separator is disposed between the positive electrode active material layer and the negative electrode active material layer of the adjacent bipolar electrodes, and has the function of insulating the positive electrode active material layer and the negative electrode active material layer from direct contact while allowing ions to pass through.

[0021] The outer current collector of the outermost cell among the multiple cells is the outermost current collector. One outermost current collector is provided with only a positive electrode active material layer so as to face, via a separator, the negative electrode active material layer of the bipolar electrode adjacent to the one outermost current collector. The other outermost current collector is provided with only a negative electrode active material layer so as to face, via a separator, the positive electrode active material layer of the bipolar electrode adjacent to the other outermost current collector.

[0022] As shown in FIG. 2 , an external current collector 5 can be provided on the outside of each of the pair of outermost current collectors via a conductive adhesive. The secondary battery 10 has a structure in which current is extracted from the electrode stack 11 via the external current collector 5. The external current collector 5 is, for example, a metal sheet. As the external current collector 5, for example, a conductive metal such as stainless steel, iron, copper, aluminum, titanium, or nickel is used. The material of the external current collector 5 is not particularly limited, and a metal can be appropriately used depending on the purpose.

[0023] The sealing member 4 seals the internal space formed between adjacent current collectors. The sealing member 4 is made of an insulating material such as polyethylene, polystyrene, or acrylonitrile-styrene resin. The sealing member 4 holds the ends of the bipolar electrode, separator, and outermost current collector. In this embodiment, the internal space is filled with an electrolyte. The outermost surfaces in the stacking direction of the electrode stack 11 are referred to as the upper surface and lower surface, respectively. The four side surfaces connecting the upper surface and lower surface are referred to as the outer peripheral surfaces.

[0024] The liquid injection port 12 is used when injecting an electrolyte into an internal space formed between adjacent current collectors. The voltage detection terminal housing 13 holds a voltage detection terminal (not shown) electrically connected to the electrode stack 11. The voltage detection terminal housing 13 is made of an insulating material. The voltage detection terminal housing 13 is provided on the surface of the sealing member 4 opposite to the surface on which the electrode stack 11 is arranged.

[0025] The voltage detection terminal is electrically connected to the current collector. A plurality of voltage detection terminal housings 13 may be formed corresponding to the plurality of voltage detection terminals. As shown by the dashed lines in FIG. 1, the number of voltage detection terminal housings 13 may correspond to the number of cells 1, for example.

[0026] The liquid inlet 12 and the voltage detection terminal housing 13 protrude from the outer peripheral surface of the electrode stack 11. That is, the liquid inlet 12 and the voltage detection terminal housing 13 are convex portions protruding from the outer peripheral surface of the electrode stack 11. In the embodiment, the liquid inlet 12 and the voltage detection terminal housing 13 are formed on the same of the four side surfaces that constitute the outer peripheral surface of the electrode stack 11. Note that other components, such as an exhaust gas valve, may be formed as convex portions on the outer peripheral surface of the electrode stack 11.

[0027] The cover material 14 is a structure that covers the recesses formed by the protrusions. The cover material 14 is formed of a resin material such as PPS (polyphenylene sulfide) or PP (polypropylene). The cover material 14 has a housing portion 14d that houses the protrusions on the surface facing the protrusions. The housing portion 14d may have a shape that corresponds to the protrusions and recesses formed on the outer peripheral surface of the electrode stack 11. The cover material 14 can be formed by injection molding using a mold that has a shape that corresponds to the protrusions and recesses of the electrode stack 11, for example.

[0028] When the liquid inlet 12 and the voltage detection terminal housing 13 are formed on the same surface of the electrode stack 11, the liquid inlet 12 and the voltage detection terminal housing 13 can be covered simultaneously by a single cover material .

[0029] The cover material 14 also has a flat surface on a side different from the side facing the convex portion of the electrode stack 11. In the example shown in FIG. 3, the three sides of the cover material 14 other than the side facing the electrode stack 11 are flat. The three flat surfaces include an upper flat surface 14a, a lower flat surface 14b, and a middle flat surface 14c. The upper flat surface 14a is located on the upper surface side of the electrode stack 11. The lower flat surface 14b is located on the lower surface side of the electrode stack 11. The middle flat surface 14c is located on the side surface side of the electrode stack 11. The middle flat surface 14c connects the upper flat surface 14a and the lower flat surface 14b.

[0030] That is, the cover material 14 is a substantially rectangular box-shaped member having an open storage section 14d on the surface facing the electrode stack 11. The cover material 14 has substantially the same length as the surface of the electrode stack 11 on which the convex portions are formed. Therefore, the shape of the electrode stack 11 with the cover material 14 attached is a simple flat plate with no convex portions. A laminate film 20, which will be described later, is attached to the flat surface of the cover material 14.

[0031] The cover material 14 can function as a spacer that maintains residual space in order to suppress an increase in internal pressure due to gas generated from the electrode stack 11 during, for example, initial charging or high-temperature aging. The cover material 14 can also have the function of protecting each structure provided in the electrode stack 11, such as the liquid injection port 12 and the voltage detection terminal housing 13.

[0032] The cover material 14 may have an upper flat surface 14a that is substantially flush with the upper surface of the electrode laminate 11, and a lower flat surface 14b that is substantially flush with the lower surface of the electrode laminate 11. The laminate film 20 is attached to the middle flat surface 14c, the upper flat surface 14a and the lower flat surface 14b of the cover material 14, and at least a portion of the upper and lower surfaces of the electrode laminate 11. In other words, the laminate film 20 is arranged so as to wrap the side of the electrode laminate 11 on which the cover material 14 is arranged, together with the cover material 14.

[0033] 3, the upper surface of the sealing member 4 and the upper flat surface 14a are flush with each other. Also, the lower surface of the sealing member 4 and the lower flat surface 14b are flush with each other. As a result, there is no difference in level between the upper flat surface of the cover material 14 and the upper surface of the electrode stack 11, and between the lower flat surface of the cover material 14 and the lower surface of the electrode stack 11. This makes it easier to attach the laminate film 20 when it is attached across from the cover material 14 to the electrode stack 11.

[0034] The laminate film 20 is attached to the electrode stack 11 with the cover material 14 attached. The laminate film 20 is arranged so as to surround the periphery of the external current collector plate 5 in a top view. As shown in FIG. 2 , in this embodiment, four laminate films 20 are arranged along the four sides of the rectangular external current collector plate 5, respectively.

[0035] One of the four laminate films 20 is placed on the surface of the electrode stack 11 on which the cover material 14 is attached. This laminate film 20 has a width that is approximately the same as the length of the sides of the electrode stack 11 and the length of the cover material 14. This laminate film 20 has a length that extends from the middle flat surface 14c of the cover material 14, passing through the upper flat surface 14a to a portion of the upper surface of the electrode stack 11, and also passing through the lower flat surface 14b to a portion of the lower surface of the electrode stack 11.

[0036] The remaining three laminate films 20 are respectively placed on three surfaces of the electrode stack 11 that are not fitted with the cover material 14. Each laminate film 20 has a width that is approximately the same as the length of the side of the electrode stack 11 on which it is placed. Each laminate film 20 also has a length that extends from the side surface of the electrode stack 11 to a part of the upper surface and a part of the lower surface.

[0037] Adjacent laminate films 20 sandwiching a corner of the electrode laminate 11 may partially overlap each other and be welded to each other. Also, adjacent laminate films 20 sandwiching a corner of the electrode laminate 11 may be processed and arranged so that there is no gap between them.

[0038] The four laminate films 20 form holes when viewed from above. Similarly, the four laminate films 20 form holes when viewed from below. External current collecting plates 5 are arranged inside the upper and lower holes formed by the four laminate films 20, respectively.

[0039] In the embodiment, the laminate film 20 on the surface on which the cover material 14 is disposed is attached to the cover material 14 and the sealing member 4. A gap may be formed between the laminate film 20 and the external current collector plate 5. On the upper surface of the electrode stack 11, a moisture-impermeable resin is used around the external current collector plate 5, so the space between the external current collector plate 5 and the laminate film 20 may be exposed.

[0040] The laminate film 20 may be bonded to the cover material 14 and the sealing member 4, and may also be bonded to the external current collector plate 5 via an insulating sealant. That is, the laminate film 20 may cover the cover material 14 and the sealing member 4 and extend onto a part of the external current collector plate 5.

[0041] The laminate film 20 has the function of suppressing the permeation of gas and moisture into the internal space containing the electrolyte, which is formed between adjacent current collectors in the electrode laminate 11. The laminate film 20 is provided around the entire outer periphery of the electrode laminate 11, and can seal the electrode laminate 11 having the cover material 14 inside.

[0042] The four laminate films 20 have a structure in which the conductive intermediate layers 22 contained in the laminate films 20 do not come into contact with each other. In order to further improve the insulation and prevent short circuits due to contact between the intermediate layers 22 of the laminate films 20, the outer edges of the laminate films 20 may be subjected to a known insulation treatment (edge ​​insulation treatment).

[0043] A known laminate film can be used for the laminate film 20. For example, as shown in FIG. 3, a laminate film in which an inner layer 21, an intermediate layer 22, and an outer layer 23 are laminated is used. The inner layer 21 functions as a sealant layer used for bonding to other members. The inner layer 21 is made of a thermoplastic resin. Examples of thermoplastic resins include polyolefins such as polyethylene (PE) and polypropylene (PP), polyesters such as polyethylene terephthalate (PET), polystyrene, polyvinyl chloride, and polyamides such as nylon.

[0044] The intermediate layer 22 is disposed between the inner layer 21 and the outer layer 23. The intermediate layer 22 may be made of a metal foil such as aluminum, iron, or stainless steel. The intermediate layer 22 functions as a gas barrier layer. The outer layer 23 functions as a sealant layer and / or a protective layer. The outer layer 23 may be made of the same thermoplastic resin as the inner layer 21. The melting point of the inner layer 21 may be lower than the melting point of the outer layer 23. The three-layer laminate film described above is an example, and a laminate film having three or more layers may also be used.

[0045] Here, a method for manufacturing a secondary battery according to the embodiment will be described with reference to Figures 4 to 6. Figures 4 to 6 are diagrams for explaining the method for manufacturing a secondary battery according to the embodiment. Although not shown here, first, positive electrodes and negative electrodes are alternately stacked while being insulated from each other to form a flat electrode stack 11. A protrusion including a liquid injection port 12 and a voltage detection terminal housing 13 is formed on one side of the electrode stack 11.

[0046] 4, the laminate film 20 is positioned relative to the cover material 14. The laminate film 20 includes an upper portion 20a, a lower portion 20b, and an intermediate portion 20c between the upper portion 20a and the lower portion 20b. The laminate film 20 is positioned so that the upper portion 20a covers the upper flat surface 14a of the cover material 14 and the upper surface of the sealing member 4, and so that the lower portion 20b covers the lower flat surface 14b of the cover material 14 and the lower surface of the sealing member 4.

[0047] Then, the middle portion 20c of the laminate film 20 is welded to the middle flat surface 14c of the cover material 14 on the side opposite to the surface facing the electrode laminate 11. For example, the laminate film 20 can be welded to the cover material 14 by pressing the outer layer 23 toward the inner layer 21 while the middle portion 20c is heated by a heater (not shown). The middle layer 22 is heated so that its temperature is between the melting points of the inner layer 21 and the outer layer 23. By performing heating in this manner, the inner layer 21 can be welded to the electrode laminate 11 without the outer layer 23 melting.

[0048] A pressure roller may be used to weld the laminate film 20 and the cover material 14. The pressure roller and the cover material 14 may be moved relative to each other so that the pressure roller moves along the length of the cover material 14 while the pressure roller presses the outer layer 23 of the laminate film 20 toward the inner layer 21.

[0049] 5, the cover material 14 with the laminate film 20 attached is placed so as to cover the recesses formed by the protrusions of the electrode stack 11. As a result, the recesses and protrusions formed by the liquid inlet 12 and the voltage detection terminal housing 13 of the electrode stack 11 are covered by the cover material 14. The liquid inlet 12 and the voltage detection terminal housing 13 are housed in the housing portion 14d of the cover material 14. As a result, the outer shape of the electrode stack 11 with the cover material 14 attached becomes flat.

[0050] 5, the position of the laminate film 20 when the cover material 14 is attached to the electrode stack 11 is indicated by a broken line. The cover material 14 is attached to the electrode stack 11 with the laminate film 20 welded to the middle flat surface 14c and not welded to the upper flat surface 14a and the lower flat surface 14b.

[0051] Then, the upper portion 20a of the laminate film 20 is folded toward the upper flat surface 14a of the cover material 14, and the lower flat surface 14b is folded toward the lower flat surface 14b. Then, the upper portion 20a and the lower portion 20b are pressed against the electrode stack 11 with a predetermined pressure while being heated, thereby welding the laminate film 20 to the electrode stack 11. As a result, the laminate film 20 is attached to the electrode stack 11 so as to cover the cover material 14. As described above, the welding surface of the laminate film 20 becomes the flat surfaces of the cover material 14 (the upper flat surface 14a, the lower flat surface 14b, and the middle flat surface 14c), making the lamination process easier.

[0052] 6, laminate films 20 are attached to the three surfaces of the electrode laminate 11 that do not have the cover material 14 attached. Because no protrusions are formed on the surfaces of the electrode laminate 11 that do not have the cover material 14 attached, it is also possible to attach laminate films 20 to the top, bottom, and side surfaces of the electrode laminate 11 simultaneously, as in Patent Document 1, for example.

[0053] As an example, with the upper portion 20a, lower portion 20b, and middle portion 20c of the laminate film 20 heated by a heater, pressure rollers arranged on the upper, lower, and side surfaces of the electrode laminate 11 are used to pressurize the outer layer 23 toward the inner layer 21, while the pressure rollers are moved along the sides of the electrode laminate 11. This allows the laminate film 20 to be welded to the end of the electrode laminate 11 while pushing out any air between the laminate film 20 and the electrode laminate 11.

[0054] The laminating film 20 is attached to the three surfaces of the electrode laminate 11 on which the cover material 14 is not attached, for example, as follows. First, the laminating film 20 is welded to the surface of the electrode laminate 11 opposite to the surface on which the cover material 14 is not attached. Then, the laminating film 20 is welded to the remaining two surfaces connecting the surface of the electrode laminate 11 on which the cover material 14 is attached and the surface on the opposite side. At this time, the laminating film 20 on the other two surfaces can be welded so as to overlap part of the laminating film 20 on the two surfaces that have already been welded (the surface on which the cover material 14 is disposed and the surface opposite thereto). This ensures the airtightness of the electrode laminate 11.

[0055] As described above, according to the embodiment, even when unevenness is formed on the outer periphery of the electrode stack 11 by the liquid injection port 12, the voltage detection terminal housing 13, etc., the electrode stack 11 can be made flat by using the cover material 14. This allows the laminate film 20 to be easily attached to the entire outer periphery of the electrode stack 11 without any gaps, and the airtightness of the electrode stack 11 can be ensured.

[0056] In a comparative example in which the electrode laminate 11 is placed inside a bag-shaped exterior made of two laminate films bonded together, the laminate film had to be embossed to accommodate the electrode laminate. To achieve this, a high-strength embossing member was placed on the laminate film to form a recess for accommodating the electrode laminate. Furthermore, the bonded portion of the two laminate films had to be folded toward the electrode laminate, which resulted in a problem of reduced energy density.

[0057] In contrast, according to the embodiment, since the laminate film 20 is attached to the electrode stack 11, there is no need to use a high-strength member. This makes it possible to reduce costs. Furthermore, since embossing is not required, it is possible to reduce the manufacturing process and capital investment. Furthermore, since there is no excess laminate film attached, it is possible to suppress a decrease in the energy density of the secondary battery 10.

[0058] The present disclosure is not limited to the above-described embodiments, and can be modified as appropriate within the scope of the present disclosure.

[0059] In the embodiment, the secondary battery 10 is a bipolar battery, but is not limited thereto. For example, the secondary battery 10 may be a monopolar battery including an electrode laminate in which positive electrode current collector foils on which positive electrode active material layers are formed and negative electrode current collector foils on which negative electrode active material layers are formed are alternately stacked in an insulated state. An electrolyte may be filled between adjacent positive electrode current collector foils and negative electrode current collector foils. When a protrusion protruding from the outer peripheral surface of such an electrode laminate is formed, lamination can be easily performed by using the cover material 14 described above. [Explanation of symbols]

[0060] 1 cell 4 Sealing member 5 External current collector plate 10 Secondary battery 11 Electrode laminate 12 Filling port 13 Voltage detection terminal housing 14 Cover material 14a Upper flat surface 14b Lower flat surface 14c Intermediate flat surface 14d Storage section 20 Laminating film 20a Upper part 20b Lower part 20c middle part 21 Inner layer 22 Middle Class 23 Outer layer

Claims

1. a flat electrode stack in which positive electrodes and negative electrodes are alternately stacked while being insulated from each other; a protrusion protruding from the outer peripheral surface of the electrode stack; a structure covering the recess formed by the protrusion; a laminate film attached to the electrode stack so as to cover the structure; A secondary battery having

2. The structure is a housing portion that houses the protrusion on a surface facing the protrusion, a flat surface on a surface opposite to the convex portion; The laminate film is attached to the flat surface. The secondary battery according to claim 1 .

3. the structure has an upper flat surface that is substantially flush with the upper surface of the electrode stack, and a lower flat surface that is substantially flush with the lower surface of the electrode stack, the laminate film is attached to the upper flat surface and the lower flat surface of the structure and to at least a portion of the upper surface and the lower surface of the electrode stack; The secondary battery according to claim 2 .

4. the protrusion includes a liquid inlet and a housing for a voltage detection terminal, the liquid injection port and the voltage detection terminal housing are formed on the same surface of the electrode stack; The secondary battery according to claim 1 .

5. Positive electrodes and negative electrodes are alternately stacked in a mutually insulated state to form a flat electrode stack; a structure covering a recess formed by a protrusion protruding from the outer peripheral surface of the electrode laminate; A laminate film is attached to the electrode stack so as to cover the structure. A method for manufacturing a secondary battery.

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