Secondary battery and manufacturing method

Abstract

To provide a secondary battery in which a short circuit in a gap between a cathode plate and an anode with a separator interposed therebetween can be prevented and a decrease in impregnation properties of an electrolytic solution into a wound electrode body can be suppressed.SOLUTION: A secondary battery according to an embodiment includes: a wound electrode body in which a cathode plate where a cathode active material layer is formed except for cathode current collector foil exposed portions extending along one long side of a band-shaped cathode current collector foil and an anode plate where an anode active material layer 41 is formed except for anode current collector foil exposed portions extending along one long side of a band-shaped anode current collector foil are wound around via a band-shaped separator; a battery case that houses the wound electrode body and an electrolytic solution; a cathode current collector terminal that is electrically connected to a cathode current collector foil portion where the cathode current collector foil exposed portions are collected; an anode current collector terminal electrically connected to an anode current collector foil portion where the anode current collector foil exposed portions are collected; and insulating layers formed in at least one of a region of the cathode current collector foil exposed portions except for the cathode current collector foil portion and a region of the anode current collector foil exposed portions except for the anode current collector foil portion.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a secondary battery including a wound electrode body in which a positive electrode plate and a negative electrode plate are wound via a separator. The positive electrode plate protrudes from the separator on the first side in the winding axis direction, and a positive electrode current collector is joined to this part. The outermost periphery of the negative electrode plate is wound on the outer peripheral side of the outermost periphery of the positive electrode plate. The portion of the separator wound on the outer peripheral side of the outermost periphery of the negative electrode plate extends to the first side and is stopped at the part where the positive electrode current collector and the positive electrode plate are joined. Thereby, entry of foreign matter into the gap between the outermost positive electrode plate and the negative electrode plate is reduced.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Patent Document 1, by extending the outermost separator and joining the separator to the positive electrode current collector together with the positive electrode plate, a short circuit in the gap between the outermost positive electrode plate and the negative electrode plate can be prevented. However, in Patent Document 1, the impregnation property of the wound electrode body when injecting the electrolytic solution is not considered, and there is a risk that the impregnation property of the electrolytic solution may decrease.

[0005] The present invention has been made in view of such problems, and an object of the present invention is to provide a secondary battery that can prevent a short circuit in the gap between the positive electrode plate and the negative electrode plate with a separator interposed therebetween and suppress a decrease in the impregnation property of the electrolytic solution into the wound electrode body.

Means for Solving the Problems

[0006] A secondary battery according to one embodiment comprises a wound electrode body formed by winding a positive electrode plate having a positive electrode active material layer formed on all sides except for the exposed positive electrode current collector portion along one long side of a strip-shaped positive electrode current collector foil, and a negative electrode plate having a negative electrode active material layer 41 formed on all sides except for the exposed negative electrode portion along one long side of a strip-shaped negative electrode current collector foil, with a strip-shaped separator in between; a battery case housing the wound electrode body and an electrolyte; a positive electrode current collector terminal electrically connected to a positive electrode foil section that bundles the exposed positive electrode current collector foil portions; a negative electrode current collector terminal electrically connected to a negative electrode foil section that bundles the exposed negative electrode current collector foil portions; and an insulating layer formed in at least one of the region of the exposed positive electrode current collector foil excluding the positive electrode foil section, and the region of the exposed negative electrode current collector foil excluding the negative electrode foil section. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent short circuits in the gap between the positive electrode plate and the negative electrode plate with a separator in between, and to suppress a decrease in the impregnation of the electrolyte into the wound electrode body. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the external dimensions of a secondary battery according to an embodiment. [Figure 2] Figure 1 is a diagram illustrating the internal structure of a secondary battery. [Figure 3] This is an exploded view illustrating the structure of a wound electrode body. [Figure 4] This is a side view of the wound electrode body. [Figure 5] This is an enlarged view of a portion of the cross-section of the wound electrode body at the cutting line V in Figure 4. [Figure 6] This is an enlarged view of a portion of the cross-section of the wound electrode body at the cutting line VI in Figure 4. [Modes for carrying out the invention]

[0009] Embodiments of the present invention will be described below with reference to the drawings. Note that the following embodiments are not intended to limit the technology disclosed herein. For clarity of explanation, the following descriptions and drawings have been omitted and simplified as appropriate. The dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect actual dimensional relationships. Furthermore, the same elements are denoted by the same reference numerals in each drawing, and redundant explanations are omitted where necessary.

[0010] The embodiments relate to a secondary battery used, for example, as a power source for electric vehicles. In this specification, "secondary battery" refers to a general energy storage device that can be repeatedly charged and discharged, and includes energy storage elements such as so-called storage batteries and electric double-layer capacitors. Here, the embodiments will be described in detail using a flat rectangular lithium-ion secondary battery as an example. A "lithium secondary battery" refers to a secondary battery that uses lithium ions as a charge carrier and achieves charging and discharging by the movement of charge associated with lithium ions between the positive and negative electrodes.

[0011] Figure 1 shows the external shape of a secondary battery 10 according to an embodiment. Figure 2 is a diagram illustrating the internal structure of the secondary battery 10 shown in Figure 1. As shown in Figures 1 and 2, the secondary battery 10 has a structure in which a wound electrode body 20 and an electrolyte (not shown) are housed in a battery case 11. W in the figures indicates the width direction of the battery case 11. H in the figures indicates the height direction of the battery case 11. The direction perpendicular to the width direction W and the height direction H is defined as the thickness direction D of the battery case 11. Note that these directions do not limit the installation configuration of the secondary battery 10.

[0012] The battery case 11 is a rectangular container with an external shape that is roughly a rectangular parallelepiped and has an internal space. For the battery case 11, a lightweight metal material with good thermal conductivity, such as aluminum or stainless steel (SUS), is used. The battery case 11 includes a main body 12 having an opening that opens upwards, and a lid 13 that closes the opening. The main body 12 has a roughly rectangular bottom surface, a pair of wide surfaces, and a narrow surface positioned between the pair of wide surfaces. In Figure 1, the pair of wide surfaces extend upwards from the front and rear ends of the bottom surface, respectively. The pair of narrow surfaces extend upwards from the left and right ends of the bottom surface, respectively. The periphery of the opening in the main body 12 and the outer edge of the lid 13 are laser-welded, sealing the battery case 11.

[0013] The lid 13 of the battery case 11 is provided with a positive external terminal 14 and a negative external terminal 15. The lid 13 also has an electrolyte injection port (not shown) for injecting electrolyte. The injection port may be provided, for example, between the positive external terminal 14 and the negative external terminal 15 of the lid 13. As shown in Figure 2, a portion of the positive external terminal 14 and the negative external terminal 15 are connected to the positive current collector terminal 16 and the negative current collector terminal 17, respectively, inside the battery case 11.

[0014] The wound electrode body 20 is housed in a space enclosed by the main body 12 and the cover 13. Figure 3 is an exploded view illustrating the configuration of the wound electrode body 20. Figure 4 is a side view of the wound electrode body 20. In Figure 4, the side of the wound electrode body 20 to which the positive electrode current collector terminal 16 is connected, as indicated by the dashed line in Figure 3, is shown.

[0015] As shown in Figure 3, the wound electrode body 20 includes a strip-shaped first separator 1, a second separator 2, a positive electrode plate 3, and a negative electrode plate 4. The length direction of the first separator 1, the second separator 2, the positive electrode plate 3, and the negative electrode plate 4 is the long side direction, and the width direction is the short side direction. The first separator 1, the positive electrode plate 3, the second separator 2, and the negative electrode plate 4 are stacked in order with their long sides aligned, and wound around a winding axis X. In this embodiment, the direction of the winding axis X of the wound electrode body 20 coincides with the width direction W of the secondary battery 10. As shown in Figure 4, the cross-section of the wound electrode body 20 is oval-shaped.

[0016] The positive electrode plate 3 includes a positive current collector foil 30 and a positive electrode active material layer 31. The positive current collector foil 30 is a support member for the positive electrode active material layer 31 and a conductive member for extracting charges from the positive electrode active material layer 31. A positive current collector foil exposed portion 32 is provided in a region along one long side of the strip-shaped positive current collector foil 30. The positive electrode active material layer 31 is formed in a region excluding the positive current collector foil exposed portion 32 on the positive current collector foil 30. The positive electrode active material layer 31 is formed in a strip shape along the other long side of the positive current collector foil 30. The positive electrode active material layer 31 can be formed on one side or both sides of the positive current collector foil 30. Here, it is assumed that the positive electrode active material layer 31 is formed on both sides of the positive current collector foil 30. That is, the positive electrode plate 3 is long, and in the width direction, the wide positive electrode active material layer 31 and the narrow positive current collector foil exposed portion 32 are arranged side by side.

[0017] Although not shown in FIG. 3, the negative electrode plate 4 includes a negative current collector foil 40 and a negative electrode active material layer 41 (see FIG. 5). The negative current collector foil 40 is a support member for the negative electrode active material layer 41 and a conductive member for extracting charges from the negative electrode active material layer 41. A negative current collector foil exposed portion is provided in a region along one long side of the strip-shaped negative current collector foil 40. The negative electrode active material layer 41 is formed in a region excluding the negative current collector foil exposed portion on the negative current collector foil 40. The negative electrode active material layer 41 is formed in a strip shape along the other long side of the negative current collector foil 40. The negative electrode active material layer 41 can be formed on one side or both sides of the negative current collector foil 40. Here, it is assumed that the negative electrode active material layer 41 is formed on both sides of the negative current collector foil 40. That is, the negative electrode plate 4 is long, and in the width direction, the wide negative electrode active material layer 41 and the narrow negative current collector foil exposed portion are arranged side by side.

[0018] As the members and materials constituting the secondary battery 10, those similar to those used in widely known lithium-ion secondary batteries are used and are not particularly limited. An example of the members and materials constituting the secondary battery 10 is shown below.

[0019] As the positive current collector foil 30 constituting the positive electrode plate 3, for example, aluminum foil (including aluminum alloy) etc. can be mentioned. Examples of the positive electrode active material contained in the positive electrode active material layer 31 include lithium transition metal oxides (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi 0.5 Mn 1.5 O4 etc.), lithium transition metal phosphate compounds (e.g., LiFePO4 etc.) etc. The positive electrode active material layer 31 may contain components other than the active material, for example, a conductive material, a binder etc. As the conductive material, for example, carbon black such as acetylene black (AB) and other carbon materials (e.g., graphite etc.) can be used. As the binder, for example, polyvinylidene fluoride (PVdF) etc. can be used.

[0020] As the negative current collector foil 40 constituting the negative electrode plate 4, for example, copper foil etc. can be mentioned. As the negative electrode active material contained in the negative electrode active material layer 41, for example, carbon materials such as graphite, hard carbon, soft carbon etc. can be used. When graphite is used as the negative electrode active material, the negative electrode active material may be natural graphite or artificial graphite, and may be coated with an amorphous carbon material. The negative electrode active material layer 41 may contain components other than the active material, for example, a binder, a thickener etc. As the binder, for example, styrene butadiene rubber (SBR) etc. can be used. As the thickener, for example, carboxymethyl cellulose (CMC) etc. can be used.

[0021] The first separator 1 and the second separator 2 insulate the positive electrode plate 3 and the negative electrode plate 4, and provide a movement path for charge carriers between the positive electrode active material layer 31 and the negative electrode active material layer 41. As the first separator 1 and the second separator 2, porous sheets (films) made of polyolefins such as polyethylene (PE), polypropylene (PP) etc. can be used. Such porous sheets may have a single-layer structure, or may have a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat-resistant layer (HRL) may be provided on the surfaces of the first separator 1 and the second separator 2.

[0022] The electrolyte typically comprises a non-aqueous solvent and a supporting salt. As the non-aqueous solvent, known solvents used in lithium-ion secondary battery electrolytes can be used. Examples of non-aqueous solvents include carbonates, ethers, esters, nitriles, sulfones, and lactones. Examples of carbonates include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC). Such non-aqueous solvents can be used individually or in combination of two or more.

[0023] Lithium salts such as LiPF6, LiBF4, and LiClO4 (preferably LiPF6) are preferably used as supporting salts. The electrolyte may contain other components. Examples of other components include gas generating agents such as biphenyl (BP) and cyclohexylbenzene (CHB), film-forming agents, dispersants, and thickeners.

[0024] In the central part of the wound electrode body 20 in the winding axis X direction, the positive electrode active material layer 31 and the negative electrode active material layer 41 are laminated together to form a core where the charge and discharge reaction takes place. In addition, in the wound electrode body 20, at one end in the winding axis X direction (the left end in Figure 3), there is a positive electrode current collector foil laminated portion 33 in which the exposed portion of the positive electrode current collector foil 32 extends beyond the negative electrode plate 4. In addition, in the wound electrode body 20, at the other end in the winding axis X direction (not shown, but the right end in Figure 3), there is a negative electrode current collector foil laminated portion in which the exposed portion of the negative electrode current collector foil extends beyond the positive electrode plate 3.

[0025] As shown in Figure 4, the central part of the positive electrode current collector foil laminated portion 33 in the height direction H is where the exposed portions 32 of the positive electrode current collector foil are grouped together (hereinafter referred to as "foil collection"), forming a positive electrode foil collection portion 34. Figure 5 is an enlarged view of a part of the cross-section of the wound electrode body at the cutting line V in Figure 4. In Figure 5, the vicinity of the positive electrode foil collection portion 34 at the cutting line V is shown as viewed from above (white arrow side). As shown in Figure 4, the positive electrode current collector terminal 16 is electrically connected to the positive electrode foil collection portion 34 by ultrasonic welding or the like. As shown in Figure 5, in the positive electrode foil collection portion 34, the adjacent positive electrode current collector foils 30 are collected, so no foreign matter enters between the positive electrode plate 3 and the negative electrode plate 4.

[0026] Similarly, in the central part of the negative electrode current collector foil laminate in the height direction H, the exposed portions of the negative electrode current collector foil are grouped together to form a negative electrode foil collection section. The negative electrode current collector terminal 17 is electrically connected to the negative electrode foil collection section. In the negative electrode foil collection section, adjacent negative electrode current collector foils are collected, so no foreign matter enters between the positive electrode plate 3 and the negative electrode plate 4.

[0027] An insulating layer 35 is formed in at least one of the regions of the exposed positive electrode current collector foil portion 32 excluding the positive electrode current collector portion 34, and the regions of the exposed negative electrode current collector foil portion excluding the negative electrode current collector portion. Preferably, the insulating layer 35 is formed in both the region of the exposed positive electrode current collector foil portion 32 excluding the positive electrode current collector portion 34, and the region of the exposed negative electrode current collector foil portion excluding the negative electrode current collector portion.

[0028] The insulating layer 35 formed on the exposed positive electrode current collector foil portion 32 will be described in detail below. Note that an insulating layer 35 is also formed on the exposed negative electrode current collector foil portion in the same way as on the exposed positive electrode current collector foil portion 32, so the description will be omitted. The insulating layer 35 is, for example, a cured liquid insulating paste. The insulating paste may include, for example, an insulating inorganic substance, an insulating paste solvent, and a resin component. The inorganic substance may be at least one of powdered alumina, boehmite, or titania. An NMP solution, which is an example of an organic solvent, is used as the insulating paste solvent. The resin component functions as a binder in the insulating layer 35. The resin component may be at least one selected from the group consisting of PVDF, PVA, and acrylic, which are polymer materials soluble in NMP. It is preferable that the insulating layer 35 has flexibility when collecting the exposed positive electrode current collector foil portion 32.

[0029] As shown in Figure 3, the insulating layer 35 is formed at predetermined intervals along the long side direction of the positive electrode current collector foil exposed portion 32. The "predetermined intervals" at which the insulating layer 35 is formed are preferably pitches that, when the positive electrode plate 3 is wound, cover the entire area of ​​the positive electrode current collector foil exposed portion 32 excluding the positive electrode foil portion 34. Furthermore, the insulating layer 35 is formed on both sides of the positive electrode current collector foil exposed portion 32. As a result, when the positive electrode plate 3 is wound to form the wound electrode body 20, the positive electrode current collector foil 30 is exposed only at the positive electrode foil portion 34.

[0030] Figure 6 is an enlarged view of a portion of the cross-section of the wound electrode body at the cutting line VI in Figure 4. In Figure 6, the vicinity of the positive electrode current collector foil laminated portion 33 at the cutting line VI is shown as viewed from above (white arrow side). As shown in Figure 6, in the positive electrode current collector foil laminated portion 33, insulating layers 35 are formed on both sides of the exposed portion 32 of the positive electrode current collector foil.

[0031] It is generally known that metallic foreign matter, such as welding spatter, is generated during battery manufacturing and can enter the secondary battery 10 through the liquid injection port. Once inside the secondary battery 10, this metallic foreign matter can cause a short circuit by creating electrical conductivity between the battery case 11 and the wound electrode body 20, or between the positive and negative electrodes within the wound electrode body 20.

[0032] Normally, during electrolyte impregnation, the electrolyte penetrates from the regions of the positive electrode current collector foil laminated sections 33 above and below the positive electrode foil collection section 34 to the center of the wound electrode body 20. If a metallic foreign object that has entered the secondary battery 10 through the electrolyte injection port causes a short circuit between the positive and negative electrodes in the wound electrode body 20, it is conceivable that the metallic foreign object would travel along the flow of electrolyte penetrating the wound electrode body 20. One way to prevent a short circuit via this route is to prevent the metallic foreign object from entering between the positive and negative electrodes.

[0033] In Patent Document 1, the outermost separator is extended and joined to the positive electrode current collector together with the positive electrode plate to suppress the intrusion of metallic foreign matter. However, being covered by the separator may reduce the impregnation of the electrolyte.

[0034] In contrast, in this embodiment, an insulating layer 35 is formed in the region of the positive electrode current collector foil exposed portion 32, excluding the positive electrode foil collection portion 34. Therefore, even if metallic foreign matter F enters the gap between the positive electrode plate 3 and the negative electrode plate 4 of the wound electrode body 20 when the electrolyte is injected, the occurrence of a short circuit can be suppressed. Also, as shown in Figure 6, in the positive electrode current collector foil laminated portion 33, the positive electrode plate 3 and the separator are not joined as in Patent Document 1, so when foil is collected, a gap is created in the positive electrode current collector foil laminated portion 33 other than the positive electrode foil collection portion 34. Therefore, it is possible to impregnate the wound electrode body 20 with electrolyte without changing the electrolyte injection conditions.

[0035] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. [Explanation of symbols]

[0036] 1. First separator 2. Second separator 3 Positive plate 4 Negative plate 10 Secondary battery 11 Battery case 12 Main unit 13 Lid 14 Positive external terminal 15 Negative external terminal 16 Positive current collection terminal 17 Negative current collection terminal 20 Wound electrode body 30 Positive electrode current collector foil 31 Positive electrode active material layer 32 Exposed portion of the positive electrode current collector foil 33. Laminated section of positive electrode current collector foil 34 Positive electrode foil collection section 35 Insulating layer 40 Negative electrode current collector foil 41 Negative electrode active material layer X Winding axis

Claims

1. A wound electrode body is formed by winding a positive electrode plate, in which a positive electrode active material layer is formed except for the exposed portion of the positive electrode current collector foil along one long side of a strip-shaped positive electrode current collector foil, and a negative electrode plate, in which a negative electrode active material layer is formed except for the exposed portion of the negative electrode current collector foil along one long side of a strip-shaped negative electrode current collector foil, with a strip-shaped separator in between. A battery case containing the aforementioned wound electrode body and electrolyte, A positive electrode current collector terminal electrically connected to the positive electrode current collector portion which comprises the exposed portion of the positive electrode current collector foil, A negative electrode current collector terminal electrically connected to the negative electrode foil portion which comprises the exposed portion of the negative electrode current collector foil, An insulating layer is formed in at least one of the regions of the exposed positive electrode current collector foil excluding the positive electrode current collector portion, and the regions of the exposed negative electrode current collector foil excluding the negative electrode current collector portion, and is flexible when collecting foil. Equipped with, When the positive electrode plate and the negative electrode plate are wound, the insulating layer is formed over the entire area of ​​at least one of the regions of the exposed positive electrode foil excluding the positive electrode foil portion and the region of the exposed negative electrode foil excluding the negative electrode foil portion, such that the insulating layer is formed at predetermined intervals along the long side direction of the positive electrode foil or the negative electrode foil. A secondary battery equipped with these features.

2. The insulating layer is formed in both the region of the exposed positive electrode current collector foil excluding the positive electrode current collector foil portion and the region of the exposed negative electrode current collector foil excluding the negative electrode current collector foil portion. The secondary battery according to claim 1.

3. The separator includes a first separator and a second separator. The first separator, the positive electrode plate, the second separator, and the negative electrode plate are stacked in order with their long sides aligned, and are wound around a winding axis set along the short side. The secondary battery according to claim 1.

4. The aforementioned battery case is a rectangular case having a roughly rectangular parallelepiped shape. The wound electrode body has an external shape of a flattened rectangular parallelepiped, At one end in the winding axis direction, the exposed portion of the positive electrode current collector foil is arranged in a stacked manner, extending beyond the negative electrode plate. At the other end in the winding axis direction, the exposed portion of the negative electrode current collector foil is arranged in a stacked manner, extending beyond the positive electrode plate. The wound electrode body is housed in the battery case such that the winding axis extends in the width direction of the battery case. The secondary battery according to claim 3.

5. A wound electrode body is formed by winding a positive electrode plate, in which a positive electrode active material layer is formed except for the exposed portion of the positive electrode current collector foil along one long side of a strip-shaped positive electrode current collector foil, and a negative electrode plate, in which a negative electrode active material layer is formed except for the exposed portion of the negative electrode current collector foil along one long side of a strip-shaped negative electrode current collector foil, with a strip-shaped separator in between. A battery case containing the aforementioned wound electrode body and electrolyte, A positive electrode current collector terminal electrically connected to the positive electrode current collector portion which comprises the exposed portion of the positive electrode current collector foil, A negative electrode current collector terminal electrically connected to the negative electrode foil portion which comprises the exposed portion of the negative electrode current collector foil, A method for manufacturing a secondary battery comprising: A step of forming a flexible insulating layer at predetermined intervals along the long side direction of the positive electrode current collector foil or the negative electrode current collector foil, such that when the positive electrode foil and the negative electrode foil are wound, the insulating layer is formed over the entire area of ​​at least one of the regions of the exposed positive electrode current collector foil excluding the positive electrode current collector portion and the region of the exposed negative electrode current collector foil excluding the negative electrode current collector portion. After the insulating layer is formed, the process involves winding the positive electrode plate and the negative electrode plate, A manufacturing method that includes [details omitted].

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