Manufacturing method for electrodes for secondary batteries

Abstract

A positive electrode (11), which is an example of this secondary battery electrode, includes: a positive electrode core material (20); an electrically conductive adhesive layer (22) disposed on the positive electrode core material (20); and a positive electrode mixture layer (24) disposed on the adhesive layer (22). The positive electrode core material (20) includes, at one end in a lateral direction of the positive electrode core material (20), an exposed portion (28) where the adhesive layer (22) and the positive electrode mixture layer (24) are not disposed. An insulating protection layer (26) that includes resin is disposed on the exposed portion (28) of the one end. A predetermined gap is provided between the protective layer (26) and an end surface of one end in the lateral direction of the adhesive layer (22).

Description

[Technical Field]

[0001] This disclosure relates to electrodes for secondary batteries, secondary batteries, and technologies for manufacturing electrodes for secondary batteries. [Background technology]

[0002] In a secondary battery having a wound electrode body in which a positive electrode and a negative electrode are wound around each other with a separator, known structures for the part that extracts current from within the battery include a lead-type current collection structure and a tabless structure (see, for example, Patent Documents 1 to 9). In a lead-type current collection structure, for example, multiple lead wires led out from the electrodes (positive electrode and negative electrode) or multiple current collector tabs protruding from the electrodes are welded to a current collector plate provided inside the battery for collecting current from the electrodes. In a tabless structure, for example, the current collector at the short-side end of the electrode is exposed, and the current collector plate provided inside the battery and the exposed portion of the current collector are welded together. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2009-43515 [Patent Document 2] Japanese Patent Publication No. 2002-352789 [Patent Document 3] Japanese Patent Publication No. 2006-172780 [Patent Document 4] Japanese Patent Publication No. 2008-108742 [Patent Document 5] Japanese Patent Publication No. 2007-227137 [Patent Document 6] Japanese Patent Publication No. 2006-32112 [Patent Document 7] Japanese Patent Publication No. 2001-93583 [Patent Document 8] Japanese Patent Publication No. 2006-260892 [Patent Document 9] Japanese Patent Publication No. 2010-118315 [Overview of the project]

Problems to be Solved by the Invention

[0004] By the way, in a lead type current collecting structure or a tabless current collecting structure, the metal bonding between the lead wire, the current collector tab or the exposed part and the current collecting plate is performed by fusion bonding processes such as resistance welding or laser welding. In these fusion bonding processes, when the metal of the lead wire or the current collector (current collector tab or exposed part) is melted, the air intervening between the metals of the lead wire or the current collector rapidly expands in volume due to the heat of the metal melting, or a low melting point foreign substance contained in the metal material of the lead wire or the current collector rapidly vaporizes due to the heat of the metal melting, causing the metal material to expand in volume. In some cases, events such as this occur. Due to the force caused by such volume expansion, the molten metal during welding scatters as fine metal powder, and so-called "spatter" occurs. If such spatter remains attached to the electrode, it can be a cause of internal short circuit. Also, in a wound electrode body, due to winding displacement of the electrode or separator, etc., the lead wire or current collector (current collector tab or exposed part) of one electrode may contact the other electrode that becomes the counter electrode, resulting in an internal short circuit.

[0005] Therefore, an object of the present disclosure is to provide an electrode for a secondary battery, a secondary battery, and a method for manufacturing an electrode for a secondary battery that can suppress the occurrence of an internal short circuit.

Means for Solving the Problems

[0006] An electrode for a secondary battery according to one aspect of the present disclosure is an electrode for a secondary battery including a core material, a conductive adhesive layer disposed on the core material, and a composite layer disposed on the adhesive layer, wherein the core material has an exposed part at one end in the short side direction of the core material where the adhesive layer and the composite layer are not disposed, and an insulating protective layer containing resin is disposed on the exposed part at the one end, and the protective layer is spaced apart from the end surface at one end in the short side direction of the adhesive layer by a predetermined distance.

[0007] A secondary battery according to one aspect of the present disclosure includes a wound electrode body in which a positive electrode and a negative electrode are wound with a separator interposed therebetween, and at least one of the positive electrode and the negative electrode is the above electrode for a secondary battery.

[0008] The method for manufacturing an electrode for a secondary battery according to one aspect of the present disclosure includes, when manufacturing the electrode for the secondary battery, an adhesive layer forming step of forming the adhesive layer on the core material except for the exposed portion by a wet process, a protective layer forming step of forming the protective layer on the exposed portion by a wet process, and a composite sheet forming step of producing a composite sheet by a dry process and attaching the produced composite sheet to the adhesive layer to form the composite layer.

Effect of the Invention

[0009] According to one aspect of the present disclosure, it is possible to suppress the occurrence of internal short circuits.

Brief Description of the Drawings

[0010] [Figure 1] It is a schematic cross-sectional view showing a main part of the secondary battery according to this embodiment. [Figure 2] It is a schematic plan view showing the positive electrode before winding. [Figure 3] It is a schematic cross-sectional view of the positive electrode taken along line A-A in FIG. 2. [Figure 4] It is a schematic plan view showing the negative electrode before winding. [Figure 5] It is a schematic cross-sectional view of the negative electrode taken along line A-A in FIG. 4. [Figure 6] It is a schematic cross-sectional view showing a modified example of the main part of the secondary battery according to this embodiment. [Figure 7] It is a schematic plan view showing the positive electrode before winding. [Figure 8] It is a schematic cross-sectional view of the positive electrode taken along line A-A in FIG. 7. [Figure 9] It is a schematic cross-sectional view showing a modified example of the positive electrode taken along line A-A in FIG. 7. [Figure 10] It is a schematic cross-sectional view showing a modified example of the positive electrode taken along line A-A in FIG. 7. [Figure 11] It is a schematic cross-sectional view showing a modified example of the positive electrode taken along line A-A in FIG. 7. [Figure 12] It is a schematic plan view showing a modified example of the positive electrode. [Figure 13] This is a schematic plan view showing a modified example of the positive electrode. [Figure 14] This is a schematic plan view showing a modified example of the positive electrode. [Modes for carrying out the invention]

[0011] In the embodiments described below, the secondary battery electrodes of this disclosure are applied to both the positive and negative electrodes; however, the secondary battery electrodes of this disclosure only need to be applied to at least one of the positive or negative electrodes. Note that the drawings referenced in the following descriptions of embodiments are schematic representations, and the dimensional ratios of the components depicted in the drawings may differ from those of the actual objects.

[0012] Figure 1 is a schematic cross-sectional view showing the main parts of a secondary battery according to this embodiment. The secondary battery 10 of this embodiment comprises a wound electrode body 14 in which a long positive electrode 11 and a long negative electrode 12 are wound around a separator 13, and a positive electrode current collector plate 16 and a negative electrode current collector plate 18 arranged above and below the electrode body 14, respectively. The secondary battery 10 of this embodiment also has an electrolyte, although it is not shown. The secondary battery 10 of this embodiment also has a battery case, although it is not shown, that houses the electrode body, current collector plates, electrolyte, etc. The battery case is composed of, for example, a bottomed cylindrical case body with an opening, and a sealing body that seals the opening of the case body via a gasket.

[0013] Figure 2 is a schematic plan view showing the positive electrode before winding. Note that the insulating protective layer, which will be described later, is not shown in Figure 2. Figure 3 is a schematic cross-sectional view of the positive electrode along line AA in Figure 2. The positive electrode 11 has a positive electrode core material 20, a conductive adhesive layer 22 disposed on the positive electrode core material 20, a positive electrode composite layer 24 disposed on the adhesive layer 22, and an insulating protective layer 26 containing resin. The adhesive layer is conductive in order to reduce interfacial resistance while ensuring the strength of the core material by reducing the amount of penetration of the active material into the core material. The protective layer is insulating in order to suppress internal short circuits. Note that in the electrode according to this disclosure, both the conductive adhesive layer and the insulating protective layer are disposed in contact with the same surface of the core material.

[0014] The positive electrode core material 20 has an exposed portion 28 at one end in the short direction of the positive electrode core material 20 where the adhesive layer 22 and the positive electrode composite layer 24 are not disposed. A protective layer 26 is disposed on the exposed portion 28. As shown in Figure 3, the protective layer 26 is disposed at a predetermined distance S from the end face of the adhesive layer 22 at one end in the short direction, and the positive electrode composite layer 24 is disposed on the distance S. However, the protective layer 26 shown in Figure 3 is thicker than the adhesive layer 22 and is in contact with the end face of the positive electrode composite layer 24 at one end in the short direction. Also, as shown in Figure 3, the protective layer 26 does not need to be disposed in a region of a predetermined width from the edge at one end in the short direction of the positive electrode core material 20. The adhesive layer 22, positive electrode composite layer 24, and protective layer 26 may be disposed on only one side of the positive electrode core material 20, but it is desirable that they be disposed on both sides of the positive electrode core material 20.

[0015] Figure 4 is a schematic plan view showing the negative electrode before winding. Note that the insulating protective layer is not shown in Figure 4. Figure 5 is a schematic cross-sectional view of the negative electrode along line AA in Figure 4. The negative electrode 12 has a negative electrode core material 30, a conductive adhesive layer 22 placed on the negative electrode core material 30, a negative electrode composite layer 32 placed on the adhesive layer 22, and an insulating protective layer 26 containing resin.

[0016] The negative electrode core material 30 has exposed portions 34a and 34b at one end and the other end in the short direction of the negative electrode core material 30, where the adhesive layer 22 and the negative electrode composite layer 32 are not disposed. An insulating protective layer 26 is disposed on the exposed portions 34a and 34b. As shown in Figure 5, the protective layer 26 disposed on the exposed portion 34a is positioned at a predetermined distance S from the end face of the adhesive layer 22 at one end in the short direction, with the negative electrode composite layer 32 disposed on the distance S. However, the protective layer 26 disposed on the exposed portion 34a as shown in Figure 5 is thicker than the adhesive layer 22 and is in contact with the end face of the negative electrode composite layer 32 at one end in the short direction. Also, for example, as shown in Figure 5, the protective layer 26 does not need to be disposed in a region of a predetermined width from the edge at one end in the short direction of the negative electrode core material 30.

[0017] Furthermore, as shown in Figure 5, the protective layer 26 placed on the exposed portion 34b is positioned at a predetermined distance S from the end face of the other end in the short direction of the adhesive layer 22, with the negative electrode composite layer 32 positioned on the distance S. However, the protective layer 26 placed on the exposed portion 34b shown in Figure 5 is thicker than the adhesive layer 22 and is in contact with the end face of the other end in the short direction of the negative electrode composite layer 32. Also, as shown in Figure 5, the end face of the other end of the negative electrode core material 30 may be covered with the protective layer 26. The adhesive layer 22, the negative electrode composite layer 32, and the protective layer 26 may be placed on only one side of the negative electrode core material 30, but it is desirable that they be placed on both sides of the negative electrode core material 30.

[0018] In the positive electrode 11 shown in Figures 2 and 3, the exposed portion 28 of the positive electrode core material 20 forms a protruding portion 36 that extends from one end in the short direction of the adhesive layer 22 and the positive electrode composite layer 24. When the positive electrode 11 is made into a wound electrode body 14, as shown in Figure 1, the protruding portion 36 protrudes from one end of the electrode body 14. The tip of the protruding portion 36 of the positive electrode 11 that protrudes from one end of the electrode body 14 is welded to the positive electrode current collector plate 16. In this embodiment, the tip of the protruding portion 36 to which the positive electrode current collector plate 16 is welded becomes the welding area, but it is preferable that the protective layer 26 is not placed in this welding area in order to ensure the bonding strength with the current collector. That is, as shown in Figure 3, it is preferable that the welding area is included in the region of the exposed portion 28 where the protective layer 26 is not placed.

[0019] Furthermore, in the negative electrode 12 shown in Figures 4 and 5, the exposed portion 34a of the negative electrode core material 30 forms a first protrusion 38 that protrudes from one end in the short direction of the adhesive layer 22 and the negative electrode composite layer 32. When the negative electrode 12 is made into a wound electrode body 14, as shown in Figure 1, the first protrusion 38 protrudes from the other end of the electrode body 14. The first protrusion 38 of the negative electrode 12 that protrudes from the other end of the electrode body 14 is welded to the negative electrode current collector plate 18. In this embodiment, the tip of the first protrusion 38 to which the negative electrode current collector plate 18 is welded becomes the welding area, and it is preferable that the protective layer 26 is not placed in this welding area in order to ensure the bonding strength with the current collector. That is, as shown in Figure 5, it is preferable that the welding area is included in the region of the exposed portion 34a where the protective layer 26 is not placed. Furthermore, in the negative electrode 12 shown in Figures 4 and 5, the exposed portion 34b of the negative electrode core material 30 forms a second protrusion 40 that protrudes from the other end in the short direction of the adhesive layer 22 and the negative electrode composite layer 32.

[0020] Since the positive electrode 11 is positioned opposite the negative electrode 12 via a separator 13 and wound around it, dust generated during welding is unlikely to adhere to the surface of the positive electrode composite layer 24 opposite the negative electrode 12 via the separator 13. The same applies to the negative electrode 12 side. Here, as shown in Figures 3 and 5, by placing a protective layer with a thickness approximately equal to the sum of the thickness of the adhesive layer and the composite layer on the exposed portion, the degree of unevenness between the surface of the composite layer and the surface of the protective layer can be suppressed, preventing dust from entering the recessed areas.

[0021] When the protective layer and adhesive layer are formed by a wet process without a gap S, a mixed region is formed where the components of the protective layer and the adhesive layer are mixed. This mixed region is inferior to the adhesive layer in terms of conductivity and inferior to the protective layer in terms of insulation. In contrast, the occurrence of this mixed region can be suppressed by providing a gap S between the protective layer and the adhesive layer. It is preferable that the gap S (the distance between the protective layer and the adhesive layer) be narrower than the width of the mixed region. The gap S can be determined by forming the mixed region in advance and measuring its size.

[0022] The composite layer placed on the gap S prevents dust from entering the gap S. In each drawing, the gap S is shown as a space enclosed by the core material, adhesive layer, protective layer, and composite layer, but the composite layer (composite sheet) may come into contact with the core material when the composite layer (composite sheet) on the core material is pressurized. The protective layer shown in Figures 3, 5, and later in Figures 8 and 10 has a thickness approximately equal to the sum of the thickness of the adhesive layer and the thickness of the composite layer. An electrode with such a thick protective layer can be manufactured by applying a paint for forming the adhesive layer and a paint for forming the protective layer onto the core material using a wet process, then forming the composite layer, and then applying another paint for forming the protective layer. In this manufacturing process, the protective layer is formed in two layers: a lower layer and an upper layer. It is preferable to provide the gap S when forming the adhesive layer and the protective layer (lower layer).

[0023] The electrode body 14, in which the positive electrode current collector plate 16 and the negative electrode current collector plate 18 are welded together, is housed in the case body along with the electrolyte. The negative electrode current collector plate 18 is connected to the inner bottom surface of the case body, for example, by welding. The positive electrode current collector plate 16 is connected to a sealing plate, for example, by welding.

[0024] As in this embodiment, the exposed portion 28 of the positive electrode core material 20 and the negative electrode 12, and the exposed portions (34a, 34b) of the negative electrode core material 30 and the positive electrode 11 are not only insulated by the separator 13 but also by the insulating protective layer 26. Therefore, even if dust generated by welding the protruding portion made of the exposed portion to the current collector adheres to the electrodes, the insulation between the exposed portion of one electrode and the other electrode can be ensured, thus suppressing internal short circuits. Furthermore, even if the separator comes out of the space between the protruding portion made of the exposed portion of one electrode and the other electrode due to, for example, misalignment of the electrodes or separator, the insulating protective layer ensures the insulation between both electrodes, thus suppressing internal short circuits.

[0025] Figure 6 is a schematic cross-sectional view showing a modified example of the main part of the secondary battery according to this embodiment. Figure 7 is a schematic plan view showing the positive electrode before winding. In Figure 7, the insulating protective layer is not shown. Figure 8 is a schematic cross-sectional view of the positive electrode along line AA in Figure 7. The positive electrode 11 constituting the wound electrode body 14 shown in Figure 6 has exposed portions 28a and 28b at one end and the other end in the short direction of the positive electrode core material 20, where the adhesive layer 22 and the positive electrode composite layer 24 are not disposed. In addition, an insulating protective layer 26 containing resin is disposed on the exposed portions 28a and 28b. Furthermore, as shown in Figure 8, the protective layer 26 disposed on the exposed portion 28a is disposed at a predetermined distance S from the end face of the adhesive layer 22 at one end in the short direction. However, the protective layer 26 disposed on the exposed portion 28a shown in Figure 8 is thicker than the thickness of the adhesive layer 22 and is in contact with the end face of the positive electrode composite layer 24 at one end in the short direction. Furthermore, as shown in Figure 8, the protective layer 26 does not need to be placed in a region of a predetermined width from the edge at one end of the positive electrode core material 20 in the short direction. Also, as shown in Figure 8, the protective layer 26 placed on the exposed portion 28b is placed with a predetermined gap S between it and the end face at the other end of the adhesive layer 22 in the short direction. However, the protective layer 26 placed on the exposed portion 28b shown in Figure 8 is thicker than the adhesive layer 22 and is in contact with the end face at the other end of the positive electrode composite layer 24 in the short direction. Also, as shown in Figure 8, the end face at the other end of the positive electrode core material 20 may be covered with the protective layer 26.

[0026] Since the positive electrode 11 is positioned opposite the negative electrode 12 via a separator 13 and wound around it, dust generated during welding is unlikely to adhere to the surface of the positive electrode composite layer 24 opposite the negative electrode 12 via the separator 13. Here, as shown in Figure 8, by placing a protective layer with a thickness approximately equal to the sum of the thickness of the adhesive layer and the composite layer on the exposed portion, the degree of unevenness between the surface of the composite layer and the surface of the protective layer can be suppressed, preventing dust from entering the recessed areas.

[0027] In the positive electrode 11 shown in Figures 7 and 8, the exposed portion 28 of the positive electrode core material 20 forms a first protrusion 36 that protrudes from one end in the short direction of the adhesive layer 22 and the positive electrode composite layer 24. When the positive electrode 11 is made into a wound electrode body 14, as shown in Figure 6, the first protrusion 36 protrudes from one end of the electrode body 14. The first protrusion 36 of the positive electrode 11 that protrudes from one end of the electrode body 14 is welded to the positive electrode current collector plate 16. Also, in the positive electrode 11 shown in Figures 7 and 8, the exposed portion 28 of the positive electrode core material 20 forms a second protrusion 37 that protrudes from the other end in the short direction of the adhesive layer 22 and the positive electrode composite layer 24.

[0028] The following describes variations of electrodes for a secondary battery, using the positive electrode 11 as an example. All of the following variations can be applied to the negative electrode 12.

[0029] Figure 9 is a schematic cross-sectional view showing a modified example of the positive electrode along line AA in Figure 7. The protective layer 26 positioned on the exposed portion 28a is preferably thicker than the adhesive layer 22 and in contact with the end face of one end of the positive electrode composite layer 24, as shown in Figure 8, in order to suppress internal short circuits in the battery. However, as shown in Figure 9, it may be equal to or less in thickness than the adhesive layer 22 and not in contact with the end face of one end of the positive electrode composite layer 24. Similarly, the protective layer 26 positioned on the exposed portion 28b is preferably thicker than the adhesive layer 22 and in contact with the end face of the other end of the positive electrode composite layer 24, as shown in Figure 8, in order to suppress internal short circuits in the battery. However, as shown in Figure 9, it may be equal to or less in thickness than the adhesive layer 22 and not in contact with the end face of the other end of the positive electrode composite layer 24. Although not shown in the diagram, the positive electrode composite layer 24 may be positioned to cover a portion of the outer surface of the protective layer 26.

[0030] Even with the positive electrode shown in Figure 9, the gap S suppresses the occurrence of mixed regions, and the composite layer placed on the gap S prevents dust from entering the gap S. Since a protective layer is placed on the exposed portion, internal short circuits can be suppressed.

[0031] Figure 10 is a schematic cross-sectional view showing a modified positive electrode along line AA in Figure 7. It is preferable that the protective layer 26 located on the exposed portion 28a is thicker than the total thickness of the adhesive layer 22 and the positive electrode composite layer 24, and covers a portion of the outer surface of the positive electrode composite layer 24, in order to suppress internal short circuits in the battery. Similarly, it is preferable that the protective layer 26 located on the exposed portion 28b is thicker than the total thickness of the adhesive layer 22 and the positive electrode composite layer 24, and covers a portion of the outer surface of the positive electrode composite layer 24, in order to suppress internal short circuits in the battery.

[0032] The significance of the configuration shown in Figure 10 lies in the fact that the corners of the end face of the positive electrode composite layer are covered with a protective layer. This suppresses the pressure on the separator caused by the corners of the end face of the positive electrode composite layer. Among the electrodes, for example, the negative electrode may expand and contract with charging and discharging, and the expansion of the electrode may cause localized pressure on the corners of the end face of the composite layer to be applied to the separator, potentially putting a load on the separator. In contrast, since the protective layer generally has a lower elastic modulus and is softer than the positive electrode composite layer, covering the end face of the positive electrode composite layer with the protective layer can reduce the load on the separator caused by the end face of the composite layer.

[0033] Figure 11 is a schematic cross-sectional view showing a modified example of the positive electrode along line AA in Figure 7. As shown in Figure 11, one end or part of the other end of the positive electrode composite layer 24 in the longitudinal direction may be embedded in the protective layer 26.

[0034] Figure 12 is a schematic plan view showing a modified example of the positive electrode. The positive electrode 11 in Figure 12 is in its pre-winding state, and the protective layer 26 is not shown. In the positive electrode 11 shown in Figure 12, the exposed portion 28 at one end of the positive electrode core material 20 in the short direction forms a protruding portion 36 that extends from one end of the adhesive layer 22 and the positive electrode composite layer 24 in the short direction, and multiple protruding portions 36 are formed intermittently in the longitudinal direction of the positive electrode core material 20. When the positive electrode 11 is made into a wound electrode body 14, multiple intermittently formed protruding portions 36 protrude from one end of the electrode body 14. The tips of the multiple protruding portions 36 that protrude from one end of the electrode body 14 are welded to the positive electrode current collector plate 16. Therefore, since the tips of the protruding portions to which the positive electrode current collector plate 16 is welded become the welding area, it is preferable to place the protective layer 26 on the protruding portions 36 (exposed portion 28) excluding the welding area in order to ensure the joint strength with the current collector.

[0035] Figure 13 is a schematic plan view showing a modified positive electrode. The positive electrode 11 in Figure 13 is in its pre-winding state, and the protective layer 26 is not shown. In the positive electrode 11 shown in Figure 13, the exposed portion 28 at one end of the positive electrode core material 20 in the short direction forms a protruding portion 36 that extends from one end of the adhesive layer 22 and the positive electrode composite layer 24 in the short direction. Multiple lead wires 46 are attached to the protruding portion 36 at predetermined intervals in the longitudinal direction of the positive electrode core material 20 by welding or the like. When the positive electrode 11 is made into a wound electrode body 14, multiple lead wires 46 protrude from one end of the electrode body 14. The tips of the multiple lead wires 46 protruding from one end of the electrode body 14 are welded to the positive electrode current collector plate 16. It is desirable that the protective layer 26 be coated not only on the exposed portion 28 but also on the lead wires 46. However, since the tip of the lead wire 46 to which the positive electrode current collector plate 16 is welded becomes the welding area, it is preferable that the protective layer 26 be coated on the lead wire 46 excluding the welding area in order to ensure the joint strength with the current collector. Instead of the protective layer 26, insulating tape can also be attached to the surface of the lead wire 46. It is also preferable to attach insulating tape to the welding area after welding.

[0036] Figure 14 is a schematic plan view showing a modified positive electrode. The positive electrode 11 in Figure 14 is in its pre-winding state, and the protective layer 26 is not shown. In the positive electrode 11 shown in Figure 14, the exposed portion 28 at one end of the positive electrode core material 20 in the short direction is intermittently formed in the longitudinal direction of the positive electrode core material 20, and forms a recess 48 that is recessed from one end of the adhesive layer 22 and the positive electrode composite layer 24 in the short direction. Multiple lead wires 46 are attached to the recess 48 by welding or the like. When the positive electrode 11 is made into a wound electrode body 14, multiple lead wires 46 protrude from one end of the electrode body 14. The tips of the multiple lead wires 46 protruding from one end of the electrode body 14 are welded to the positive electrode current collector plate 16. It is desirable that the protective layer 26 be coated not only on the exposed portion 28 but also on the lead wires 46. However, since the tip of the lead wire 46 to which the positive electrode current collector plate 16 is welded becomes the welding area, it is preferable that the protective layer 26 be coated on the lead wire 46 excluding the welding area in order to ensure the joint strength with the current collector. Instead of the protective layer 26, insulating tape can also be attached to the surface of the lead wire 46. It is also preferable to attach insulating tape to the welding area after welding.

[0037] The following describes the materials used for the positive electrode 11, negative electrode 12, separator 13, and electrolyte.

[0038] [Positive electrode] The positive electrode core material 20 can be a metal foil that is stable within the potential range of the positive electrode 11, such as aluminum or an aluminum alloy, or a film with the metal arranged on its surface.

[0039] The positive electrode composite layer 24 contains positive electrode active material particles, a binder, etc. Furthermore, the positive electrode composite layer 24 preferably contains a conductive material, as this can improve the conductivity of the layer.

[0040] Examples of positive electrode active material particles include lithium transition metal oxide particles containing transition metal elements such as Co, Mn, and Ni. Lithium transition metal oxide particles are, for example, Li x CoO2, Li x KiO2, Li x MnO2, Lix Co y Ni 1-y O2, Li x Co y M 1-y O z , Li x Ni 1-y M y O z , Li x Mn2O4, Li x Mn 2-y M y O4, LiMPO4, Li2MPO4F (M; at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3). These may be used alone or in combination of multiple kinds. In terms of achieving a higher capacity of the secondary battery 10, the cathode active material particles are Li x NiO2, Li x Co y Ni 1-y O2, Li x Ni 1-y M y O z (M; at least one of Na, Mg, Sc, Y, Mn, Fe, Co, Ni, Cu, Zn, Al, Cr, Pb, Sb, B, 0 < x ≤ 1.2, 0 < y ≤ 0.9, 2.0 ≤ z ≤ 2.3), etc. lithium nickel composite oxide particles are preferably included.

[0041] The conductive material includes, for example, carbon-based particles such as carbon black (CB), acetylene black (AB), ketjen black, graphite, etc. These may be used alone or in combination of two or more kinds.

[0042] Examples of binders include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, carboxymethylcellulose (CMC) or its salts (CMC-Na, CMC-K, CMC-NH4, etc., or partially neutralized salts), and polyethylene oxide (PEO). These may be used individually or in combination of two or more types.

[0043] When the positive electrode composite layer 24 is divided into three equal parts in the thickness direction, forming a first region, a second region, and a third region from the positive electrode core material 20 side, it is preferable that the binder content (a) in the first region, the binder content (b) in the second region, and the binder content (c) in the third region satisfy (ca) / (a+b+c)≦±10%. Satisfying this condition results in a state where the binder is uniformly present in the positive electrode composite layer 24. For example, the above condition can be satisfied by forming the positive electrode composite layer 24 by a dry process described later.

[0044] The adhesive layer 22 has the function of bonding the positive electrode core material 20 and the positive electrode composite layer 24. The adhesive layer 22 is conductive in order to ensure electrical conductivity between the core material and the composite layer. The adhesive layer 22 may also contain a binder and a conductive material. The volume resistivity of the adhesive layer 22 is 10 4 It is preferable that the density is Ωcm or less. The thickness of the adhesive layer 22 is, for example, 0.1 μm to 10 μm.

[0045] Examples of conductive materials included in the adhesive layer 22 include carbon black (CB), acetylene black (AB), Ketjenblack, and carbon-based particles such as graphite. The content of the conductive material in the adhesive layer 22 is preferably 50% to 95% by mass, more preferably 55% to 90% by mass, and particularly preferably 60% to 85% by mass. By making the content of the conductive material in the adhesive layer 22 relatively high in this way, the interfacial resistance can be reduced.

[0046] Examples of binders included in the adhesive layer 22 include fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, and polyolefin resins. The binder content in the adhesive layer 22 is preferably, for example, 20% by mass or more and 60% by mass or less.

[0047] The adhesive layer 22 preferably contains an insulating filler. The inclusion of an insulating filler in the adhesive layer 22 allows the insulating filler to act as a resistive component in the event of an internal short circuit caused by conductive foreign matter, thereby suppressing the increase in the short-circuit current between the positive and negative electrodes.

[0048] The protective layer 26 contains resin and is insulating. The volume resistivity of the protective layer 26 is, for example, 10, which is important for suppressing the occurrence of internal short circuits in the battery. 7 It is preferable that the density is Ω·cm or greater. Examples of resins used in the protective layer 26 include polyethylene, polypropylene, polyphenylene ether, polybenzimidazole, polyimide, polyetherimide, polyamideimide, polyphenylene sulfide, polyethersulfone, polysulfone, polyetherketone, polymethylpentene, aramid, polyvinylidene fluorolide, polyamide, polyethylene terephthalate, polybutylene terephthalate, polyarylate, polyacetal, and the like.

[0049] The protective layer 26 preferably contains an insulating filler. The insulating filler is, for example, 10 12The material is preferably an inorganic material having a resistivity of Ωcm or more, such as metal oxides, metal nitrides, and metal fluorides. Examples of metal oxides include aluminum oxide, titanium oxide, zirconium oxide, silicon oxide, manganese oxide, magnesium oxide, and nickel oxide. Examples of metal nitrides include boron nitride, aluminum nitride, magnesium nitride, and silicon nitride. Examples of metal fluorides include aluminum fluoride, lithium fluoride, sodium fluoride, magnesium fluoride, calcium fluoride, barium fluoride, aluminum hydroxide, and boehmite. The content of the insulating filler in the adhesive layer 22 is preferably in the range of 1% by mass or more and 10% by mass or less.

[0050] [Negative electrode] The negative electrode core material 30 can be a metal foil that is stable in the potential range of the negative electrode 12, such as copper, or a film with the metal arranged on its surface. The negative electrode composite layer 32 includes, for example, a negative electrode active material, a binder, etc.

[0051] Examples of negative electrode active materials include lithium alloys such as metallic lithium, lithium-aluminum alloy, lithium-lead alloy, lithium-silicon alloy, and lithium-tin alloy; carbon materials such as graphite, coke, and calcined organic materials; and metal oxides such as SnO2, SnO, and TiO2. These may be used individually or in combination of two or more.

[0052] Examples of binders included in the negative electrode composite layer 32 are, as in the case of the positive electrode 11, fluororesins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide resins, acrylic resins, polyolefin resins, carboxymethylcellulose (CMC) or its salts (CMC-Na, CMC-K, CMC-NH4, etc., or partially neutralized salts), polyethylene oxide (PEO), etc. These may be used individually or in combination of two or more types.

[0053] When the negative electrode composite layer 32 is divided into three equal parts in the thickness direction, forming a first region, a second region, and a third region from the negative electrode core material 30 side, it is preferable that the content of the binder in the first region (a), the content of the binder in the second region (b), and the content of the binder in the third region (c) satisfy (ca) / (a+b+c)≦±10%. Satisfying this condition results in a state where the binder is uniformly present in the negative electrode composite layer 32. For example, the above condition can be satisfied by forming the negative electrode composite layer 32 by a dry process described later.

[0054] The adhesive layer 22 and protective layer 26 on the negative electrode 12 side may be the same as those on the positive electrode 11 side.

[0055] [Separator] For the separator 13, for example, a porous sheet having ion permeability and insulating properties can be used. Specific examples of porous sheets include microporous thin films, woven fabrics, and nonwoven fabrics. Suitable materials for the separator 13 include olefin resins such as polyethylene and polypropylene, and cellulose. The separator 13 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. Alternatively, it may be a multilayer separator containing a polyethylene layer and a polypropylene layer, or a separator 13 with a material such as aramid resin or ceramic coated on its surface may be used.

[0056] [Electrolyte] The electrolyte comprises a solvent such as a non-aqueous solvent and an electrolyte salt dissolved in the solvent. The electrolyte is not limited to a liquid electrolyte (electrolyte solution) but may also be a solid electrolyte using a gel-like polymer or the like. Examples of non-aqueous solvents include esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixed solvents of two or more of these. The non-aqueous solvent may contain halogen-substituted solvents in which at least some of the hydrogen atoms in the solvent are replaced with halogen atoms such as fluorine.

[0057] Examples of the above esters include cyclic carbonate esters such as ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate; linear carbonate esters such as dimethyl carbonate (DMC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, and methyl isopropyl carbonate; cyclic carboxylic acid esters such as γ-butyrolactone and γ-valerolactone; and linear carboxylic acid esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), ethyl propionate, and γ-butyrolactone.

[0058] Examples of the above ethers include 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-butylene oxide, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, cyclic ethers such as crown ethers, 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methylphenyl ether Examples include chain ethers such as ethylphenyl ether, butylphenyl ether, pentylphenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether, o-dimethoxybenzene, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl.

[0059] As the halogen-substituted product, it is preferable to use fluorinated cyclic carbonate esters such as fluoroethylene carbonate (FEC), fluorinated linear carbonate esters, or fluorinated linear carboxylic acid esters such as methyl fluoropropionate (FMP).

[0060] The electrolyte salt is preferably a lithium salt. Examples of lithium salts include LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiCF3SO3, LiCF3CO2, Li(P(C2O4)F4), LiPF 6-x (C n F 2n+1 ) x (1 < x < 6, n is 1 or 2), LiB 10 Cl 10 、LiCl、LiBr、LiI、lithium chloroborane, lithium lower aliphatic carboxylate, borate salts such as Li2B4O7, Li(B(C2O4)F2), imide salts such as LiN(SO2CF3)2, LiN(C1F 2l+1 SO2)(C m F 2m+1 SO2){l, m are integers of 1 or more}, etc. The lithium salt may be used alone or in combination of plural kinds. Among these, from the viewpoints of ionic conductivity, electrochemical stability, etc., it is preferable to use LiPF6. The concentration of the lithium salt is preferably 0.8 to 1.8 mol per 1 L of the non-aqueous solvent.

[0061] Hereinafter, an example of the manufacturing method of the electrode for a secondary battery of this embodiment will be described. The manufacturing method of the electrode for a secondary battery of this embodiment is applicable to both the positive electrode and the negative electrode. When manufacturing the positive electrode, the composite material, active material, and core material described below are read as the positive electrode composite material, positive electrode active material, and positive electrode core material, and when manufacturing the negative electrode, the composite material, active material, and core material described below are read as the negative electrode composite material, negative electrode active material, and negative electrode core material.

[0062] The manufacturing method of the electrode for a secondary battery has an adhesive layer forming step, a protective layer forming step, and a composite material layer forming step.

[0063] (Adhesive layer forming step) In the adhesive layer formation process, an adhesive layer is formed on the core material, excluding the exposed areas, using a wet process. The wet process is a method that uses a paint containing a solvent. Specifically, a paint containing a binder, conductive material, insulating filler, solvent, etc., is applied to the core material, leaving the exposed areas uncovered, to form the adhesive layer. The solvent is not particularly limited, such as an organic solvent or aqueous solvent, but a solvent that dissolves the binder is preferred.

[0064] (Protective layer formation process) In the protective layer formation process, a protective layer is formed on the exposed portion of the core material by a wet process. Specifically, a coating containing resin, solvent, etc., is applied to the exposed portion of the core material to form the protective layer. The solvent is not particularly limited, such as an organic solvent or an aqueous solvent, but a solvent that dissolves resin is preferred. The protective layer formation process may be performed simultaneously with the adhesive layer formation process, or after the adhesive layer formation process and before the composite layer formation process. Alternatively, the protective layer formation process may be performed after the composite layer formation process.

[0065] Paint application can be performed using, for example, a slit die coater, reverse roll coater, lip coater, blade coater, knife coater, gravure coater, and dip coater.

[0066] (Mixture layer formation process) In the composite layer formation process, a composite sheet is prepared by a dry process, and the prepared composite sheet is attached to the adhesive layer to form the composite layer. A dry process is a process in which a composite sheet is prepared without the use of solvents. A method for preparing a composite sheet by a dry process includes, for example, a mixing step in which an active material, binder, conductive material, etc., are mixed to prepare electrode composite particles with a solid content of substantially 100%, a rolling step in which the electrode composite particles are rolled into a sheet to prepare a composite sheet, and a compression step in which the composite sheet is compressed to prepare a high-density composite sheet.

[0067] A fibrous binder is preferred. The fibrous binder is preferably PTFE particles belonging to a fine powder that can be fibrillated.

[0068] In the mixing step, the raw materials such as the active material, binder, and conductive material can be mixed using, for example, a conventionally known mechanical agitator. Suitable mixers include devices that can apply mechanical shear force, such as cutter mills, pin mills, bead mills, microparticle compounding devices (devices that generate shear force between a rotor with a special shape that rotates at high speed inside a tank and a collision plate), granulators, twin-screw extruders, and planetary mixers, with cutter mills, microparticle compounding devices, granulators, and twin-screw extruders being preferred.

[0069] The mixing step may include a step of mixing the active material and the conductive material to produce a coating active material, and a step of mixing the coating active material and a fibrous binder. As a method for mixing the active material and the conductive material, for example, a mechanofusion method may be used. The mechanofusion method is a dry processing method carried out in a mechanofusion reactor having a cylindrical chamber equipped with a compression device and rotating at high speed. Examples of mechanofusion reactors include the "Nobilta" (registered trademark) pulverizer or "Mechanofusion" (registered trademark) pulverizer manufactured by Hosokawa Micron Corporation (Japan), the "Hybridicer" (trademark) pulverizer manufactured by Nara Machinery Works Co., Ltd., "Balance Gran" manufactured by Freund Turbo K.K., and "COMPOSI" manufactured by Nippon Coke Industries Co., Ltd.

[0070] In the rolling step, for example, the electrode composite particles are rolled using two opposing rolls to form a sheet. The two rolls are positioned with a predetermined gap between them and rotate in the same direction. The electrode composite particles are fed into the gap between the two rolls and compressed and stretched into a sheet by the two rolls. The resulting composite sheet may be passed through the gap between the two rolls multiple times, or it may be stretched one or more times using other rolls with different roll diameters, peripheral speeds, gaps, etc. Alternatively, the rolls may be heated to hot-press the electrode composite particles.

[0071] In the compression step, for example, the asphalt sheet is compressed using two opposing rolls to produce a high-density asphalt sheet. The two rolls may, for example, have the same roll diameter, be positioned with a predetermined gap between them, and rotate in the same direction at the same peripheral speed. The two rolls may be subjected to a linear pressure of, for example, 1 t / cm to 3 t / cm. The two rolls may be subjected to a linear pressure of, for example, 0.1 t / cm to 3 t / cm. The temperature of the two rolls is not particularly limited and may be, for example, room temperature. The active material density of the high-density asphalt sheet is, for example, 3.0 g / cm³ for the positive electrode asphalt layer. 3 ~4.0g / cm 3 For the negative electrode composite layer, the concentration is 1.2 g / cm³. 3 ~2.0g / cm 3 Yes. The thickness of the composite sheet is, for example, 30 μm to 300 μm, preferably 50 μm to 200 μm.

[0072] The resulting composite sheet is then attached to an adhesive layer formed on a core material to form a composite layer. For example, the composite sheet and the adhesive layer of the core material are placed facing each other and fed into the gap between two opposing rolls, thereby attaching the composite sheet to the adhesive layer formed on the core material.

[0073] The composite layer may be formed by a wet process. For example, a coating containing an active material, a binder, a conductive material, and a solvent may be applied to the adhesive layer to form a coating film, and the coating film may be rolled to form the composite layer. However, the method of forming a composite sheet by a dry process and then bonding the composite sheet to the adhesive layer to produce electrodes for secondary batteries reduces the pressure on the core material compared to the method of forming a coating film on the adhesive layer and rolling it by a wet process, thus making the core material less susceptible to damage. [Explanation of Symbols]

[0074] 10 Secondary battery, 11 Positive electrode, 12 Negative electrode, 13 Separator, 14 Electrode body, 16 Positive electrode current collector plate, 18 Negative electrode current collector plate, 20 Positive electrode core material, 22 Adhesive layer, 24 Positive electrode composite layer, 26 Protective layer, 28, 28a, 28b, 34a, 34b Exposed parts, 30 Negative electrode core material, 32 Negative electrode composite layer, 36, 38 Protrusion or first protrusion, 37, 40 Second protrusion, 46 Lead wire, 48 Recess.

Claims

1. A secondary battery electrode comprising a core material, a conductive adhesive layer disposed on the core material, and a composite layer disposed on the adhesive layer, wherein the core material has an exposed portion at one end in the short direction of the core material where the adhesive layer and the composite layer are not disposed, and an insulating protective layer containing resin is disposed on the exposed portion at the one end, the protective layer is spaced at a predetermined distance from the end face at one end in the short direction of the adhesive layer, the protective layer is thicker than the total thickness of the adhesive layer and the composite layer, contacts the end face at one end in the short direction of the composite layer, and covers a part of the outer surface of the composite layer, An adhesive layer forming step, in which the adhesive layer is formed on the core material excluding the exposed portion by a wet process, A protective layer forming step, in which the protective layer is formed on the exposed portion by a wet process, A method for manufacturing an electrode for a secondary battery, comprising: a step of producing an asphalt mixture sheet by a dry process; and a step of forming an asphalt mixture layer by attaching the produced asphalt mixture sheet to the adhesive layer to form the asphalt mixture layer.

2. The method for manufacturing an electrode for a secondary battery according to claim 1, wherein the protective layer formation step is performed after the adhesive layer formation step and before the composite layer formation step, or simultaneously with the adhesive layer formation step.

3. The method for manufacturing an electrode for a secondary battery according to claim 1, wherein the protective layer formation step is performed after the composite layer formation step.

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