Method for manufacturing positive electrode plate for non-aqueous electrolyte secondary battery and method for manufacturing non-aqueous electrolyte secondary battery

Abstract

In a positive electrode plate, for a nonaqueous electrolyte secondary battery, according to the present invention, a protective layer is formed in a region, of an exposed core part, adjacent to a positive electrode active material layer. A method, for producing a positive electrode plate, according to the present invention comprises: a coating and drying step for drying a positive electrode active material layer and a protective layer after applying the protective layer so as to form a raised part from a portion, further inward in the widthwise direction than an exposed core-part side end, to the center in the widthwise direction, said applying involving applying the positive electrode active material layer and the protective layer onto a positive electrode core; and a compression step for compressing the protective layer and the positive electrode material layer so as to press the positive electrode active material layer and the raised part formed by the coating and drying step.

Description

[Technical field]

[0001] The present disclosure relates to a method for manufacturing a positive electrode plate for a nonaqueous electrolyte secondary battery and a method for manufacturing a nonaqueous electrolyte secondary battery. [Background technology]

[0002] In recent years, non-aqueous electrolyte secondary batteries, such as lithium ion batteries, have been widely used as secondary batteries that achieve high output and high energy density. The non-aqueous electrolyte secondary battery has an electrode assembly in which a positive electrode plate and a negative electrode plate are stacked with a separator interposed therebetween.

[0003] Patent Document 1 describes that a positive electrode plate of a non-aqueous electrolyte secondary battery includes a metal foil, and an active material layer and an insulating layer formed on the surface of the metal foil, the portion along the edge of the metal foil is an active material non-forming portion, the insulating layer is formed on the active material non-forming portion, and the thickness of the insulating layer gradually decreases from a position adjacent to the active material layer toward the core exposed portion. Also, the end of the insulating layer on the core exposed portion side has an arc-shaped cross section that gradually approaches the surface of the core exposed portion.

[0004] Patent Document 2 describes that, in a positive electrode plate of a secondary battery, after the coating and drying process of the insulator and before the press processing of the insulator, the insulator applied to the core is made to have the same thickness as or thicker than the dried positive electrode mixture layer. Then, the positive electrode mixture layer and the insulator are hot-pressed by pressing. At this time, the thickness of the insulator is gradually reduced toward the end of the core exposed portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2017-188371 A [Patent Document 2] Patent No. 6336821 Summary of the Invention

[0006] In a positive electrode plate for a secondary battery, a protective layer may be formed on at least one surface of the positive electrode core in an area adjacent to the positive electrode active material layer. The protective layer is, for example, a porous layer. On the other hand, in order to increase the capacity and output of a secondary battery, it is necessary to increase the packing density of the positive electrode active material layer. With this increase in packing density, the part of the positive electrode core where the positive electrode active material layer is provided is pushed in the plate thickness direction and stretched. At this time, the core exposed part of the positive electrode core where the positive electrode active material layer is not provided is not pushed in the plate thickness direction, so that the stretch is small. As a result, a difference in stretch occurs between the part of the positive electrode core where the positive electrode active material layer is provided and the positive electrode core exposed part. For this reason, when the positive electrode active material layer is compressed, wrinkles may occur in the positive electrode core exposed part, or when a wound electrode body is produced by stacking a positive electrode plate, a negative electrode plate, and a separator, a problem of a winding deviation of the positive electrode plate may occur during the winding process of the electrode body.

[0007] A positive electrode plate for a non-aqueous electrolyte secondary battery according to one embodiment of the present disclosure Manufacturing method a method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery having a main body portion in which a positive electrode active material layer is formed on a positive electrode core, and a core exposed portion in which the positive electrode core is exposed without the positive electrode active material layer formed thereon, the positive electrode plate for a non-aqueous electrolyte secondary battery having a protective layer formed in an area of ​​the core exposed portion adjacent to the positive electrode active material layer, the positive electrode active material layer and the protective layer being applied onto the positive electrode core, the protective layer being applied to form a raised portion from a portion inward in the width direction from a side end of the core exposed portion to a leap portion in the width direction to the center, and the method includes a coating and drying step in which the positive electrode active material layer and the protective layer are dried, and a compression step in which the protective layer and the positive electrode active material layer are compressed so as to press against the raised portion formed by the coating and drying step and the positive electrode active material layer.

[0008] A method for producing a nonaqueous electrolyte secondary battery according to one embodiment of the present disclosure includes the steps of: Manufacturing method The method includes an electrode assembly preparation step of preparing an electrode assembly including a positive electrode plate for a non-aqueous electrolyte secondary battery manufactured by the above-mentioned method, a negative electrode plate, and a separator, and an arrangement step of arranging the electrode assembly and the non-aqueous electrolyte in an exterior body.

[0009] According to the positive electrode plate for a nonaqueous electrolyte secondary battery and the manufacturing method for a nonaqueous electrolyte secondary battery of one aspect of the present disclosure, it is possible to prevent the occurrence of wrinkles in the positive electrode plate, and also to prevent misalignment of the positive electrode plate when forming a wound electrode assembly. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of a nonaqueous electrolyte secondary battery according to an example of the embodiment. [Diagram 2] FIG. 2 is a perspective view showing an unfolded winding end of a wound electrode body that constitutes the nonaqueous electrolyte secondary battery of FIG. [Diagram 3] FIG. 3 is a flowchart illustrating a method for manufacturing a nonaqueous electrolyte secondary battery according to an example of the embodiment. [Figure 4] FIG. 4 is a flowchart showing a method for manufacturing a positive electrode plate for a nonaqueous electrolyte secondary battery according to an example of the embodiment. [Diagram 5] FIG. 5 is a development view of a portion in the longitudinal direction of a positive electrode plate before cutting that forms the positive electrode plate for a nonaqueous electrolyte secondary battery constituting the electrode body of FIG. [Figure 6] FIG. 6 is a cross-sectional view taken along line AA of FIG. [Figure 7] FIG. 7(a) is an enlarged view of the upper half of FIG. 6, showing the state of a pre-cut positive electrode plate after coating and drying and before the compression process in one example of an embodiment, and FIG. 7(b) is an enlarged view of the upper half of FIG. 6, showing the state of a pre-cut positive electrode plate after coating and drying and after the compression process in one example of an embodiment. [Figure 8] FIG. 8 is a schematic diagram of a press used in the compression step in one embodiment. [Figure 9] FIG. 9 is a front view of a roller constituting the press machine of FIG. [Figure 10] FIG. 10(a) is an enlarged view of the upper half of FIG. 6, showing the state of the pre-cut positive electrode plate after coating and drying and before the compression process in the manufacturing method of Comparative Example 1, and FIG. 10(b) is an enlarged view of the upper half of FIG. 6, showing the state of the pre-cut positive electrode plate after coating and drying and after the compression process in the manufacturing method of Comparative Example 1. [Figure 11]FIG. 11(a) is an enlarged view of the upper half of FIG. 6, showing the state of the pre-cut positive electrode plate after coating and drying and before the compression process in the manufacturing method of Comparative Example 2, and FIG. 11(b) is an enlarged view of the upper half of FIG. 6, showing the state of the pre-cut positive electrode plate after coating and drying and after the compression process in the manufacturing method of Comparative Example 2. [Figure 12] FIG. 12(a) is an enlarged view of the upper half of FIG. 6, showing the state of the pre-cut positive electrode plate after coating and drying and before the compression process in the manufacturing method of Comparative Example 3, and FIG. 12(b) is an enlarged view of the upper half of FIG. 6, showing the state of the pre-cut positive electrode plate after coating and drying and after the compression process in the manufacturing method of Comparative Example 3. [Figure 13A] FIG. 13A is a schematic diagram showing a positive electrode plate manufactured by the manufacturing method according to the embodiment in a state after a cutting step. [Figure 13B] FIG. 13B is a schematic diagram showing the positive electrode plate manufactured by the manufacturing method of Comparative Example 1 in a state after a cutting step. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present inventors have conducted intensive studies to solve the above-mentioned problems, and have found that a method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery having a main body portion in which a positive electrode active material layer is formed on a positive electrode core and a core exposed portion in which the positive electrode core is exposed without the positive electrode active material layer formed on the positive electrode core, the positive electrode plate for a non-aqueous electrolyte secondary battery has a protective layer formed in a region of the core exposed portion adjacent to the positive electrode active material layer, the positive electrode active material layer and the protective layer are applied onto the positive electrode core, and the protective layer is applied to form a raised portion between a portion inside the side end of the core exposed portion in the width direction and the center in the width direction, and then the positive electrode active material layer and the protective layer are dried in a coating and drying process, and the protective layer and the positive electrode active material layer are compressed so as to press the raised portion formed by the coating and drying process against the positive electrode active material layer, thereby preventing the occurrence of wrinkles in the positive electrode plate and preventing the positive electrode plate from being misaligned when forming a wound electrode body. This will be described in detail below.

[0012] An example of an embodiment of the present disclosure will be described in detail below. In the following description, specific shapes, materials, directions, values, etc. are examples for facilitating understanding of the present disclosure, and can be appropriately changed according to the application, purpose, specifications, etc. Below, a prismatic battery in which a wound electrode body is housed in an exterior body that is a prismatic metal case will be described.

[0013] (Structure of secondary battery) First, the configuration of a nonaqueous electrolyte secondary battery 10 manufactured by the manufacturing method of the embodiment will be described with reference to Figures 1 and 2. Figure 1 is a cross-sectional view of the nonaqueous electrolyte secondary battery 10, and Figure 2 is a perspective view showing an unfolded end of a wound electrode body 20 constituting the nonaqueous electrolyte secondary battery 10. Hereinafter, the nonaqueous electrolyte secondary battery 10 will be referred to as a secondary battery 10.

[0014] The secondary battery 10 includes an exterior body 12 serving as a case, and a wound electrode body 20 disposed inside the exterior body 12. A nonaqueous electrolyte solution equivalent to a nonaqueous electrolyte is stored inside the exterior body 12. The nonaqueous electrolyte solution is, for example, an electrolyte solution containing a lithium salt, and has lithium ion conductivity.

[0015] 2, the electrode body 20 has a winding structure in which the winding axis O extends in the longitudinal direction of the secondary battery 10, and is flattened in that the positive electrode plate 22 and the negative electrode plate 26 are wound with separators 30, 31 interposed therebetween. The electrode body 20 is wound in a stacked state in which, for example, the long positive electrode plate 22, the long separator 30, the long negative electrode plate 26, and the long separator 31 are arranged on the outermost periphery.

[0016] As shown in FIG. 1, the metallic exterior body 12 is box-shaped with an opening at the top end, and the secondary battery 10 includes a sealing plate 14 that closes the opening. The exterior body 12 and the sealing plate 14 can be made of aluminum or an aluminum alloy. A positive electrode terminal 15 protrudes from one longitudinal end (left end in FIG. 1) on the sealing plate 14, and a negative electrode terminal 16 protrudes from the other longitudinal end (right end in FIG. 1). The positive electrode terminal 15 and the negative electrode terminal 16 are fixed and attached to the sealing plate 14 via a resin gasket while being inserted into two through holes formed in the sealing plate 14, respectively. The winding axis of the electrode body 20 is parallel to the longitudinal direction of the sealing plate 14 (left-right direction in FIG. 1). An insulating sheet folded into a box shape may be provided inside the exterior body 12 to insulate the electrode body 20 from the exterior body 12.

[0017] (Positive plate) The positive electrode plate 22 has a positive electrode core 23 and a positive electrode active material layer 24 formed on both sides of the positive electrode core 23 and containing a positive electrode active material. For the positive electrode core 23, a foil of a metal stable in the potential range of the positive electrode, such as aluminum or an aluminum alloy, or a film with the metal disposed on the surface layer can be used. For the positive electrode active material, a lithium transition metal oxide capable of inserting and detaching lithium ions can be used. In addition to the positive electrode active material, the positive electrode active material layer 24 preferably contains a binder and a conductive material. The positive electrode plate 22 has a main body portion 22a in which the positive electrode active material layer 24 is formed on the positive electrode core 23, and a positive electrode core exposed portion 22b in which the positive electrode active material layer is not formed on the positive electrode core 23 and the positive electrode core 23 is exposed. The positive electrode core exposed portion 22b is formed at one end in the width direction of the positive electrode plate 22 before it is wound. Furthermore, the positive electrode plate 22 has a protective layer 25 formed along the longitudinal direction in a region of the positive electrode core exposed portion 22b adjacent to the positive electrode active material layer 24. In FIG. 2, the protective layer 25 is shown as a sandy portion. The protective layer 25 is, for example, a porous layer, and has a smaller thickness than the positive electrode active material layer 24. As a result, the protective layer 25 is positive electrodeAn air passage is formed between the separators 30 and 31 by a step formed between the core exposed portion 22b and the positive electrode active material layer 24. For this reason, the gas generated in the positive electrode active material layer 24 during overcharge is made to easily flow outside the electrode body 20 through the inside of the protective layer 25, so that the pressure-sensitive current cutoff mechanism provided in the secondary battery 10 can be quickly and surely activated before the internal pressure of the battery rises significantly, thereby improving the safety during overcharge.

[0018] Examples of the positive electrode active material include lithium transition metal oxides containing transition metal elements such as Co, Mn, and Ni. The lithium transition metal oxide is, for example, Li x CoO2, Li x NiO2, Li x MnO2, Li x 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 positive electrode active material preferably contains lithium nickel composite oxides such as 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.

[0019] Examples of the conductive material used in the positive electrode active material layer 24 include carbon particles such as carbon black (CB), acetylene black (AB), ketjen black, carbon nanotubes (CNT), and graphite. These may be used alone or in combination of two or more. Carbon black is preferably used as the conductive material used in the positive electrode active material layer 24.

[0020] Examples of the binder used in the positive electrode active material layer 24 include fluorine-based resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyimide-based resins, acrylic-based resins, and polyolefin-based resins. These may be used alone or in combination of two or more. As the conductive material used in the positive electrode active material layer 24, polyvinylidene fluoride is preferably used.

[0021] The protective layer 25 preferably contains an inorganic oxide and a binder. Examples of the inorganic oxide used in the protective layer 25 include alumina, titania, zirconia, and silica. Examples of the binder used in the protective layer 25 include resins such as polyvinylidene fluoride (PVDF). The protective layer 25 may contain a conductive material, such as a carbon material. In addition, the porosity of the protective layer 25 is preferably greater than the porosity of the positive electrode active material layer 24.

[0022] The positive electrode plate 22 can be manufactured by applying a positive electrode active material layer slurry containing a positive electrode active material, a binder, a dispersion medium, etc., and a protective layer slurry onto a positive electrode core 23, drying the coating to remove the dispersion medium, and then compressing the coating to form a positive electrode active material layer 24 and a protective layer 25 on both sides of the positive electrode core 23.

[0023] (Negative plate) The negative electrode plate 26 has a negative electrode core 27 and a negative electrode active material layer 28 formed on both sides of the negative electrode core 27 and containing a negative electrode active material. For the negative electrode core 27, a foil of a metal stable in the potential range of the negative electrode, such as copper or a copper alloy, or a film with the metal disposed on the surface layer can be used. For the negative electrode active material, a carbon material capable of inserting and detaching lithium ions, a silicon compound, or the like can be used. In addition to the negative electrode active material, the negative electrode active material layer 28 preferably contains a binder. The negative electrode plate 26 has a main body portion 26a in which the negative electrode active material layer 28 is formed on the negative electrode core 27, and a negative electrode core exposed portion 26b in which the negative electrode active material layer is not formed on the negative electrode core 27 and the negative electrode core 27 is exposed. The negative electrode core exposed portion 26b is formed at one end in the width direction of the negative electrode plate 26 before it is wound.

[0024] The negative electrode active material is not particularly limited as long as it can reversibly absorb and release lithium ions, and examples of the negative electrode active material include carbon materials such as natural graphite and artificial graphite, metals that can be alloyed with lithium, such as silicon (Si) and tin (Sn), or alloys and composite oxides containing metal elements such as Si and Sn. Carbon materials are preferred as the negative electrode active material, and natural graphite is more preferred. The negative electrode active material may be used alone or in combination of two or more types.

[0025] The negative electrode plate 26 can be manufactured by applying a negative electrode active material layer slurry containing a negative electrode active material, a binder, a dispersion medium, etc. onto a negative electrode core 27, drying the coating to remove the dispersion medium, and then compressing the coating to form a negative electrode active material layer 28 on both sides of the negative electrode core 27.

[0026] 1, in the electrode body 20, a wound positive electrode core exposed portion 22b is disposed at one end (left end in FIG. 1) of the winding axis direction (left-right direction in FIG. 1) in which the winding axis extends. A wound negative electrode core exposed portion 26b is disposed at the other end (right end in FIG. 1) of the electrode body 20 in the winding axis direction.

[0027] (Separator) In a wound state, the separator 30 is disposed between the positive electrode plate 22 and the negative electrode plate 26, and electrically separates the positive electrode plate 22 from the negative electrode plate 26. The separator 31 disposed on the outermost periphery prevents a short circuit between the negative electrode plate 26, which is the outermost electrode, and external members.

[0028] Each separator 30, 31 is made of a porous sheet having ion permeability and insulation properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. The separators 30, 31 are preferably made of an olefin resin such as polyethylene or polypropylene, or cellulose. The separators 30, 31 may be a laminate having a cellulose fiber layer and a thermoplastic resin fiber layer such as an olefin resin. The separators 30, 31 may be a multilayer separator including a polyethylene layer and a polypropylene layer, or may have a material such as an aramid resin or ceramic applied to the surface of the separators 30, 31. For example, each separator 30, 31 may be a three-layer separator of a polyethylene layer / polypropylene layer / polyethylene layer.

[0029] In addition, in the electrode body 20, an insulating tape 60 (Figure 1) is attached to one side surface in the thickness direction of the electrode body 20 so as to fix the end portion of the separator 31 arranged on the outermost circumference to the outer periphery of the electrode body 20.

[0030] Furthermore, the positive electrode current collector 47 is electrically connected to the wound positive electrode core exposed portion 22b. As a result, the positive electrode current collector 47 is electrically connected to the positive electrode plate 22. The positive electrode current collector 47 is integrally connected to a positive electrode receiving member 48 arranged on the opposite side in the thickness direction of the electrode body 20 (the front side of the paper surface of FIG. 1) with the positive electrode core exposed portion 22b sandwiched therebetween. The positive electrode current collector 47 is electrically connected to the lower end of a positive electrode terminal 15 which vertically penetrates a first insulating member 61 arranged on the inner surface of the sealing plate 14.

[0031] The negative electrode current collector 50 is electrically connected to the wound negative electrode core exposed portion 26b. This electrically connects the negative electrode current collector 50 to the negative electrode plate 26. The negative electrode current collector 50 is integrally connected to a negative electrode receiving member 58 arranged on the opposite side in the thickness direction of the electrode body 20 (the front side of the paper surface of FIG. 1) with the negative electrode core exposed portion 26b sandwiched therebetween. The negative electrode current collector 50 is electrically connected to the lower end of the negative electrode terminal 16 which vertically penetrates a second insulating member 62 arranged on the inner surface of the sealing plate 14.

[0032] The opening of exterior body 12 is closed by welding sealing plate 14 to the open end.

[0033] (Method of manufacturing positive electrode plate and secondary battery) Next, a method for manufacturing the secondary battery 10, particularly the positive electrode plate 22, will be described with reference to FIGS. 3 to 9. FIG. 3 is a flow chart showing a method for manufacturing the secondary battery 10 according to an embodiment. The method for manufacturing the secondary battery 10 includes a positive electrode plate fabrication step S1, a negative electrode plate fabrication step S2, a winding step S3, and an arrangement step S4. The positive electrode plate fabrication step S1 fabricates the positive electrode plate 22. The negative electrode plate fabrication step S2 fabricates the negative electrode plate 26. The winding step S3 fabricates the electrode body 20 by winding the positive electrode plate 22, the negative electrode plate 26, and the separators 30 and 31 in a stacked state. The positive electrode plate fabrication step S1, the negative electrode plate fabrication step S2, and the winding step S3 constitute an electrode body fabrication step. The arrangement step S4 arranges the electrode body 20 and the non-aqueous electrolyte in the exterior body 12, and welds the sealing plate 14 to the open end of the exterior body 12. The order of the positive electrode plate preparation step S1 and the negative electrode plate preparation step S2 may be reversed, or they may be performed simultaneously. Next, the positive electrode plate preparation step S1 will be described in detail.

[0034] (Positive electrode plate manufacturing process) FIG. 4 is a flow chart showing a manufacturing method of the positive electrode plate 22 according to an embodiment. The manufacturing method of the positive electrode plate 22 includes a coating and drying step S1a, a compression step S1b, and a cutting step S1c. The manufacturing method of this embodiment is a method for simultaneously manufacturing two positive electrode plates 22, and first, a pre-cut positive electrode plate 32 (FIGS. 5 and 6) having a width equal to the combined width of the two positive electrode plates 22 is manufactured. FIG. 5 is a development view of a part of the pre-cut positive electrode plate 32 in the longitudinal direction. FIG. 6 is a cross-sectional view taken along the line AA in FIG. 5. As shown in FIGS. 5 and 6, the coating and drying step S1a and the compression step S1b shown in FIG. 4 are performed in a state in which the positive electrode core exposed portion 32b is disposed on each of both ends of the main body portion 32a forming the pre-cut positive electrode plate 32. In the coating and drying step S1a, a positive electrode active material layer 34 and a protective layer 25 are applied onto the positive electrode core 33.

[0035] 7(a) is an enlarged view of the upper half of FIG. 6 showing the state of the pre-cut positive electrode plate 32 after the coating and drying process and before the compression process in one embodiment, and FIG. 7(b) is an enlarged view of the upper half of FIG. 6 showing the state of the pre-cut positive electrode plate 32 after the coating and drying process and after the compression process in one embodiment. In the coating of the positive electrode active material layer 34 and the protective layer 25, as shown in FIG. 7(a), a protuberance 25a is formed in the protective layer 25, which extends in the longitudinal direction (front and back direction of the paper in FIG. 7) from a portion located inward in the width direction (left and right direction in FIG. 7) from the side end P of the core exposed portion to the center A1 in the width direction. At this time, the outer end of the protuberance 25a in the width direction is located inward in the width direction from the side end P of the core exposed portion. The outer surface in the thickness direction from this outer end in the width direction to the side end P of the exposed portion of the core may be closer to the positive electrode core 33 than the outer surface in the thickness direction on the inner side in the width direction of the protective layer 25, or may be a flat surface at the same thickness direction position as the outer surface in the thickness direction on the inner side in the width direction. And For example, LiNi 0.35 Co 0.35 Mn 0.30 The lithium-containing metal composite oxide represented by O2, carbon black as a conductive material, and polyvinylidene fluoride (P VDF) is mixed to prepare a positive electrode active material layer slurry. Furthermore, a protective layer slurry containing an inorganic oxide and a binder is prepared to form the protective layer 25. The positive electrode active material layer slurry and the protective layer slurry are applied to both sides of the positive electrode core 33 by a die coater. Applying the positive electrode active material layer slurry and the protective layer slurry corresponds to applying the positive electrode active material layer and the protective layer. For example, a protective layer supply port is provided on the upper part of the die head of the die coater, and the positive electrode active material layer slurry supplied from the positive electrode active material layer supply unit and the protective layer slurry supplied from the protective layer supply port are guided to the discharge port of the die head, and the positive electrode active material layer slurry and the protective layer slurry are discharged to different positions in the width direction of the positive electrode core 33 by a shim plate provided at the discharge port. Then, the positive electrode active material layer slurry is applied to the center of the positive electrode core 33 in the width direction, and the protective layer slurry is applied to both ends of the region in the width direction where the positive electrode active material layer slurry is applied. Furthermore, the protective layer 25 is made thinner than the positive electrode active material layer 34, and each of the protective layers 25 has a raised portion 25a formed between the portion inside the core exposed portion side end P in the width direction and the width direction center A1. For example, a first opening for discharging the positive electrode active material layer slurry and two second openings for discharging the protective layer slurry are formed on the shim plate so that the opening end side of the discharge port opens, and one or both of the shape of the second openings and the discharge flow rate of each slurry are changed. In this way, a pre-cut positive electrode plate before the drying process in which a raised portion of the protective layer slurry is formed at a predetermined position is formed. Thereafter, the pre-cut positive electrode plate before the cutting process is formed by drying the pre-cut positive electrode plate with a dryer.

[0036] FIG. 8 is a schematic diagram of a press machine 40 used in the compression step S1b (FIG. 4) in one example of the embodiment. FIG. 9 is a front view of a compression roller 41 constituting the press machine 40. The press machine 40 of FIG. 8 and FIG. 9 is used in the compression step S1b. The press machine 40 includes a pair of opposing compression rollers 41. As shown in FIG. 9, each of the pair of compression rollers 41 includes an intermediate pressing portion 42 that compresses the positive electrode active material layer 34 (FIGS. 5 to 7), and two end pressing portions 43 that are provided on both ends of the intermediate pressing portion 42 and have a larger diameter than the intermediate pressing portion 42. The end pressing portions 43 are used to compress the protective layer 25. The pair of compression rollers 41 are rotatably arranged in a state facing each other. In the compression step S1b, the pre-cut positive electrode plate 32 before the compression step after drying is passed between the pair of compression rollers 41 to compress the pre-cut positive electrode plate 32. At this time, in the pre-cut positive electrode plate 32, each protective layer 25 and each positive electrode active material layer 34 are compressed so as to press the raised portion 25a formed by the coating and drying process and the positive electrode active material layer 34. As a result, as shown in FIG. 7(b), the pre-cut positive electrode plate 32 is manufactured, which has a main body portion 32a in which the positive electrode active material layer 34 is formed on the positive electrode core 33, and a positive electrode core exposed portion 32b in which the positive electrode core 33 is exposed without the positive electrode active material layer formed on the positive electrode core 33. In this pre-cut positive electrode plate 32, the protective layer 25 is formed in an area of ​​the positive electrode core exposed portion 32b adjacent to the positive electrode active material layer 34. In the pre-cut positive electrode plate 32 of FIG. 7(b), the raised portion 25a (FIG. 7(a)) of the protective layer 25 is compressed, and the outer surface in the thickness direction is approximately flat. At this time, the thickness of the protective layer 25 is smaller than the thickness of the positive electrode active material layer 34. Since the pre-cut positive electrode plate 32 is manufactured as described above, the occurrence of wrinkles in the positive electrode plate 22 can be prevented, as described later, and misalignment of the positive electrode plate 22 during the formation of the wound electrode body 20 can be prevented.

[0037] In the cutting step S1c (FIG. 4), after the compressing step S1b, the main body portion 32a is cut at the widthwise center A2 (FIG. 7(b)) along the longitudinal direction (the front-to-back direction of the paper surface of FIG. 7(b)) to form two positive electrode plates 22 (FIG. 2). For example, the cutting step S1c is performed using a slitting machine. The slitting machine has two cylindrical rollers with blades formed on the outer circumferential surfaces thereof rotatably arranged opposite to each other, and the pre-cut positive electrode plate 32 is cut at the widthwise center A2 by passing the pre-cut positive electrode plate 32 between the two bladed rollers to produce two positive electrode plates 22.

[0038] In the winding step, the positive electrode plate 22, the negative electrode plate 26, and the separators 30 and 31 manufactured as described above are stacked and wound to form a wound electrode body 20 (FIG. 2). After that, through an arrangement step S4 (FIG. 3), the secondary battery 10 is manufactured.

[0039] (effect) According to the above-mentioned manufacturing method of the positive electrode plate 22 and the secondary battery 10, when the positive electrode active material layer 34 and the protective layer 25 are applied onto the positive electrode core 33, the protruding portion 25a is formed in the protective layer 25 between the portion inside in the width direction from the side end P of the core exposed portion to the width direction center A1, and then the positive electrode active material layer 34 and the protective layer 25 are dried. After application and drying, the protective layer 25 and the positive electrode active material layer 34 are compressed so as to press the protruding portion 25a and the positive electrode active material layer 34. As a result, when the positive electrode active material layer 34 is compressed, the protruding portion 25a of the protective layer 25 is compressed, so that not only the portion of the positive electrode core 33 where the positive electrode active material layer 34 is provided but also the portion where the protruding portion 25a is provided is pressed and stretched in the plate thickness direction. This reduces the difference in elongation between the portion of the positive electrode core 23, 33 where the positive electrode active material layer 24, 34 is provided and the positive electrode core exposed portion 22b, 32b, and thus suppresses curvature of the positive electrode plate 22. This suppresses the occurrence of wrinkles in the positive electrode core exposed portion 22b, 32b when the positive electrode active material layer 24, 34 is compressed, and also suppresses the occurrence of misalignment of the positive electrode plate 22 during the winding process of the electrode body 20. Furthermore, since the raised portion 25a of the protective layer 25 is located between the portion located inward in the width direction from the core exposed portion side end P to the width direction center A1, by compressing the protective layer 25 so as to press this position, it is possible to suppress the occurrence of waving, which is a corrugated uneven deformation portion, in the protective layer 25-forming portion of the positive electrode core 23.

[0040] Hereinafter, the manufacturing method of the positive electrode plate 22 of the present disclosure will be further described with reference to examples, and the manufacturing methods of the positive electrode plates of Comparative Examples 1 to 3 will be described.

[0041] <Example> [Preparation of positive electrode plate] As the positive electrode active material, LiNi 0.35 Co 0.35 Mn 0.30 The lithium-containing metal composite oxide represented by O2, carbon black as a conductive material, and polyvinylidene fluoride (P VDF) was mixed in a solid content mass ratio of 96:3:1 and kneaded to prepare a positive electrode active material layer slurry. In addition, a protective layer slurry containing an inorganic oxide and a binder was prepared to form a protective layer 25. The positive electrode active material layer slurry and the protective layer slurry were applied to both sides of a positive electrode core 33 made of an aluminum foil having a thickness of 15 μm, and the coating film was dried, and then the coating film was compressed using a compression roller to prepare a pre-cut positive electrode plate 32. Thereafter, the pre-cut positive electrode plate 32 was cut at the center in the width direction to a predetermined electrode size, and a positive electrode plate 22 in which a positive electrode active material layer 24 was formed on both sides of the positive electrode core 33 was prepared. In the pre-cut positive electrode plate 32, the width W1 (FIG. 5) of the positive electrode active material layer 24 was 179 mm, the width W2 (FIG. 5) of the protective layer 25 was 7.0 mm, and the width W3 (FIG. 5) of the positive electrode core exposed portion 32b including the protective layer 25 formation portion was 15 mm. The thickness D1 of one side of the positive electrode active material layer 34 after compression treatment was: 25μm 7, a raised portion 25a was formed in each of the protective layers 25 in the longitudinal direction (extending in the front-to-back direction of the paper in FIG. 7) between a portion located inward in the width direction from the side end P of the core exposed portion to the center A1 in the width direction by applying the protective layer 25. After the application of the protective layer 25 and before the compression treatment, the distance L1 (FIG. 7(a)) of the raised portion 25a from the side end P of the core exposed portion was 2 to 3 mm, and the maximum thickness D2 (FIG. 7(a)) of the protective layer 25 on one side before the compression treatment, that is, the thickness of the protective layer to the top of the raised portion in the embodiment, was 20 μm. Furthermore, the thickness D3 (FIG. 7(b)) of the protective layer 25 on one side after the compression treatment was 15 μm.

[0042] Table 1 shows the width W2, distance L1, and thicknesses D2, D3 of the protective layer 25 of the positive electrode plate 22 or the pre-cut positive electrode plate 32 in the manufacturing methods of the example and comparative examples 1 to 3 described later. Table 1 also shows the amount of warping (curving) at the width center of the positive electrode plate 22 in the manufacturing methods of the example and comparative examples 1 to 3, that is, the thickness direction distance from the thickness direction center at the longitudinal center position to the thickness direction center at one longitudinal end, and the presence or absence of waviness (protective layer waviness) in the portion of the positive electrode core 23 where the protective layer 25 is formed.

[0043] [Table 1]

[0044] <Comparative Example 1> FIG. 10(a) is an enlarged view of the upper half of FIG. 6 showing the state of the pre-cut positive electrode plate 63 before the compression process in the manufacturing method of Comparative Example 1, and FIG. 10(b) is an enlarged view of the upper half of FIG. 6 showing the state of the pre-cut positive electrode plate 63 after the compression process in the manufacturing method of Comparative Example 1. In Comparative Example 1, as shown in FIG. 10(a), when the positive electrode active material layer 34 and the protective layer 25 are applied to the pre-cut positive electrode plate 63, a protruding portion is not formed in the protective layer 25, and the outer surface in the thickness direction of the protective layer 25 is made to be a substantially flat surface. Then, in the compression process, only the portion where the positive electrode active material layer 34 is provided is compressed by a compression roller to obtain the pre-cut positive electrode plate 63 after the compression process as shown in FIG. 10(b). Furthermore, in Comparative Example 1, the maximum thickness D2 of the protective layer 25 on one side before the compression process was set to 15 μm. The positive electrode plate was produced with the other configurations being the same as those of the embodiment.

[0045] <Comparative Example 2> FIG. 11(a) is an enlarged view of the upper half of FIG. 6 showing the state of the pre-cut positive electrode plate 64 before the compression step in the manufacturing method of Comparative Example 2, and FIG. 11(b) is an enlarged view of the upper half of FIG. 6 showing the state of the pre-cut positive electrode plate 64 after the compression step in the manufacturing method of Comparative Example 2. In Comparative Example 2, as shown in FIG. 11(a), when the positive electrode active material layer 34 and the protective layer 25 are applied to the pre-cut positive electrode plate 64, a protruding portion 25b extending continuously from the core exposed portion side end P in the longitudinal direction (the front and back direction of the paper surface of FIG. 11) was formed in the protective layer 25 near the core exposed portion side end P. Then, in the compression step, the protective layer 25 and the positive electrode active material layer 34 were compressed by a compression roller so as to press the protruding portion 25b and the positive electrode active material layer 34, thereby obtaining the pre-cut positive electrode plate 64 after the compression step as shown in FIG. 11(b). In Comparative Example 2, the distance L1 from the end P of the core exposed portion of the protruding portion 25b after application of the protective layer 25 and before compression treatment was set to 0 to 1 mm. Furthermore, the thickness D3 of the protective layer 25 on one side after compression treatment was set to 14 μm. A positive electrode plate was produced with the other configurations being the same as those of the Example.

[0046] <Comparative Example 3> 12(a) is an enlarged view of the upper half of FIG. 6 showing the state of the pre-cut positive electrode plate 65 before the compression step in the manufacturing method of Comparative Example 3, and FIG. 12(b) is an enlarged view of the upper half of FIG. 6 showing the state of the pre-cut positive electrode plate 65 after the compression step in the manufacturing method of Comparative Example 3. In Comparative Example 3, as shown in FIG. 12(a), when the positive electrode active material layer 34 and the protective layer 25 are applied to the pre-cut positive electrode plate 65, a protruding portion 25c extending continuously from the positive electrode active material layer side end Q in the longitudinal direction (the front and back direction of the paper surface of FIG. 12) was formed in the protective layer 25 near the positive electrode active material layer side end Q. Then, in the compression step, the protective layer 25 and the positive electrode active material layer 34 were compressed by a compression roller so as to press the protruding portion 25c and the positive electrode active material layer 34, thereby obtaining the pre-cut positive electrode plate 65 after the compression step as shown in FIG. 12(b). In Comparative Example 3, the distance L1 from the end P of the core exposed portion of the protruding portion 25c after application of the protective layer 25 and before compression treatment was set to 6 to 7 mm. Furthermore, the thickness D3 of the protective layer 25 on one side after compression treatment was set to 14 μm. A positive electrode plate was produced with the other configurations being the same as those of the Examples.

[0047] [Evaluation method and results] The amount of warping (curving) of a certain length of positive electrode plate manufactured by the four manufacturing methods of the above Example and Comparative Examples 1 to 3, and the presence or absence of waviness in the protective layer 25 were evaluated. From the evaluation results shown in Table 1, in the Example, the amount of warping was small at 9 mm. Also, in the Example, waviness was not observed in the portion of the positive electrode core 33 where the protective layer 25 was formed. It can be seen that such small warping and no waviness can make it difficult for the positive electrode plate to become misaligned when forming a wound electrode body.

[0048] On the other hand, in Comparative Example 1, the amount of warpage was large, at 16 mm, as shown in Table 1. The reason for this is thought to be that in Comparative Example 1, no raised portion is formed in protective layer 25, and protective layer 25 is not compressed, so that the difference in elongation becomes large between the portion of positive electrode core 33 on which positive electrode active material layer 34 is provided and the portion on which protective layer 25 is provided. On the other hand, in Comparative Example 1, protective layer 25 is not compressed, so as shown in Table 1, no waviness was observed in the portion of positive electrode core 33 on which protective layer 25 is formed.

[0049] FIG. 13A is a schematic diagram showing the positive electrode plate 22 manufactured by the manufacturing method of the embodiment in a state after the cutting process. FIG. 13B is a schematic diagram showing the positive electrode plate 46 manufactured by the manufacturing method of Comparative Example 1 in a state after the cutting process. As shown in FIG. 13A, in the manufacturing method of the embodiment, the difference in elongation due to the compression process between the part where the positive electrode active material layer 24 is provided and the part where the protective layer 25 is provided in the positive electrode plate 22 can be reduced, so that the difference in length in the longitudinal direction (left and right direction in FIG. 13A) at both ends in the width direction (up and down direction in FIG. 13A) of the positive electrode plate 22 can be reduced. As a result, the shape of the positive electrode plate 22 when viewed from one end side in the thickness direction (front side of the paper surface in FIG. 13A) can be made into a long rectangular shape with high shape accuracy. Therefore, it was found that it is possible to prevent the winding deviation of the positive electrode plate 22 when forming a wound electrode body 20 including the positive electrode plate 22.

[0050] On the other hand, as shown in FIG. 13B, in the manufacturing method of Comparative Example 1, the difference in elongation caused by the compression process between the part where the positive electrode active material layer 24 is provided and the part where the protective layer 25 is provided in the positive electrode plate 46 becomes large, and the part where the positive electrode active material layer 24 is provided becomes larger in elongation than the part where the protective layer 25 is provided. As a result, the difference in length in the longitudinal direction (left and right direction in FIG. 13B) at both ends in the width direction (up and down direction in FIG. 13B) of the positive electrode plate 46 becomes large, and the shape of the positive electrode plate 46 when viewed from one end side in the thickness direction is deformed so that it is bent from a long rectangular shape to a substantially arc shape with the positive electrode active material layer 24 side on the inside. In FIG. 13B, the bending of the positive electrode plate 46 is exaggerated. As a result of the deformation of the positive electrode plate 46 as described above, when forming a wound electrode body 20 including the positive electrode plate 46, the winding misalignment of the positive electrode plate 46 is easily generated.

[0051] Furthermore, in Comparative Example 2, the raised portion 25b of the protective layer 25 is compressed, so that the difference in elongation between the portion of the positive electrode core 33 where the positive electrode active material layer 34 is provided and the portion of the positive electrode core 33 where the protective layer 25 is provided is reduced, and the amount of warping was reduced to 9 mm as shown in Table 1. Meanwhile, in Comparative Example 2, waviness occurred near the core exposed portion side end P of the protective layer 25-forming portion of the positive electrode core 33. The reason for this is considered to be that the raised portion 25b of the protective layer 25 is continuous with the core exposed portion side end P of the protective layer 25, so that the positive electrode core 33 is pressed near the core exposed portion side end P of the protective layer 25-forming portion in the compression process. More specifically, since there is a large difference between the thickness of protective layer 25 including raised portion 25b near end P of the core exposed portion and the thickness of positive electrode core 33, it is believed that the vicinity of end P of protective layer 25 near the core exposed portion in positive electrode core 33 is pressed, increasing the difference in elongation on both sides of the boundary at end P of the core exposed portion of positive electrode core 33. It is believed that this has caused waving near end P of the core exposed portion of positive electrode core 33.

[0052] In Comparative Example 3, the raised portion 25c of the protective layer 25 is compressed in the same manner as in Comparative Example 2, but unlike Comparative Example 2, the raised portion 25c is adjacent to the positive electrode active material layer 34. As a result, in Comparative Example 3, the difference in elongation between the portion of the positive electrode core 33 where the positive electrode active material layer 34 is provided and the portion of the protective layer 25 where the portion away from the positive electrode active material layer 34 to the outside in the width direction is disposed increases, and as a result, the amount of warping increases to 14 mm as shown in Table 1. Furthermore, in Comparative Example 3, waving occurs near the boundary between the portion of the positive electrode core 33 where the protective layer 25 is formed and the portion where the positive electrode active material layer 34 is formed. The reason for this is considered to be that the raised portion 25c of the protective layer 25 is continuous from the positive electrode active material layer side end Q, and in the compression process, the positive electrode core 33 is pressed at two positions, the portion where the positive electrode active material layer 34 is provided and the portion where the raised portion 25c is provided. More specifically, since there is a large difference between the thickness of protective layer 25 including raised portion 25c at end Q of the positive electrode active material layer side and the thickness of positive electrode active material layer 34, it is considered that the vicinity of end Q of protective layer 25 of positive electrode core 33 and the portion where positive electrode active material layer 34 is formed are pressed, resulting in a large difference in elongation on both sides of the boundary between protective layer 25 and positive electrode active material layer 34 of positive electrode core 33. It is considered that this has caused waviness to occur near the boundary.

[0053] In the above embodiment, the positive electrode plate 22 has the positive electrode active material layer 24 formed on both sides of the positive electrode core 23. However, the positive electrode plate manufactured by the manufacturing method disclosed herein is not limited to this configuration, and the positive electrode plate may have a configuration in which the positive electrode active material layer is formed on only one side of the positive electrode core. [Explanation of symbols]

[0054] 10 Nonaqueous electrolyte secondary battery (secondary battery) 12 Exterior body 14 Sealing plate 15 Positive terminal 16 Negative terminal 20 Electrode body 22 Positive electrode plate 22a Main body 22b Positive electrode core exposed part 23 Positive electrode core 24 Cathode active material layer 25 Protective layer 25a~25c Raised section 26 Negative plate 26a Main body 26b Negative electrode core exposed part 27 Negative electrode core 28 Negative electrode active material layer 30,31 Separator 32 Positive electrode plate before cutting 32a Main body 32b Positive electrode core exposed part 33 Positive electrode core 34 Cathode active material layer 40 Press Machine 41 Compression Roller 42 Intermediate pressing part 43 End pressing part 46 Positive plate 47 Positive electrode current collector 48 Positive electrode support member 50 Negative electrode current collector 58 Negative electrode receiving member 60 Electrical Tape 61 First insulating member 62 Second insulating member 63~65 Positive plate before cutting

Claims

1. A method for manufacturing a positive electrode plate for a non-aqueous electrolyte secondary battery, the positive electrode plate having a main body portion in which a positive electrode active material layer is formed on a positive electrode core, and a core exposed portion in which the positive electrode core is exposed without the positive electrode active material layer formed on the positive electrode core, comprising: In the positive electrode plate for a nonaqueous electrolyte secondary battery, a protective layer is formed in a region of the substrate exposed portion adjacent to the positive electrode active material layer, a coating and drying step of coating the positive electrode active material layer and the protective layer on the positive electrode core, the protective layer forming a raised portion between a portion inside the side end of the core exposed portion in the width direction and a center in the width direction, and then drying the positive electrode active material layer and the protective layer; a compression step of compressing the protective layer and the positive electrode active material layer so as to press the protruding portion formed in the coating and drying step and the positive electrode active material layer. A method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery.

2. The method for producing a positive electrode plate for a nonaqueous electrolyte secondary battery according to claim 1, the coating and drying step and the compressing step are performed in a state where the core exposed portion is disposed on each of both ends of the main body portion, The method further includes a cutting step of cutting the body portion at a center in a width direction thereof after the compressing step to form two positive electrode plates for the nonaqueous electrolyte secondary battery. A method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery.

3. The method for producing a positive electrode plate for a nonaqueous electrolyte secondary battery according to claim 1 or 2, The protective layer has a thickness smaller than that of the positive electrode active material layer. A method for producing a positive electrode plate for a non-aqueous electrolyte secondary battery.

4. an electrode assembly preparation step of preparing an electrode assembly including the positive electrode plate for a non-aqueous electrolyte secondary battery produced by the production method according to any one of claims 1 to 3, a negative electrode plate, and a separator; and arranging the electrode assembly and the non-aqueous electrolyte inside an exterior body. A method for manufacturing a non-aqueous electrolyte secondary battery.

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