Lithium-ion secondary battery and method for manufacturing the same

Abstract

The present invention aims to provide a lithium ion secondary battery which ensures the replaceability of electrolyte in the vicinity of an active material and which is excellent in output and responsiveness. The lithium ion secondary battery includes an electrode having a negative electrode foil, a negative electrode mixture layer (32a) provided on a surface of the negative electrode foil, and an insulating layer (31) containing ceramic particles (31p) provided on a surface of the negative electrode mixture layer (32a), and is characterized in that a plurality of voids (30) (pools) having a diameter of 2.5 μm or more are provided on the surface of the negative electrode mixture layer (32a) facing the boundary of the insulating layer (31) and the negative electrode mixture layer (32a).

Description

Technical Field

[0001] This invention relates to a lithium-ion secondary battery and its manufacturing method. Background Technology

[0002] Lithium-ion secondary batteries, used in applications such as automotive, are formed by stacking or winding a positive electrode, a negative electrode, and a thin-film separator between the positive and negative electrodes. The positive and negative electrodes are manufactured by coating both sides of electrode foil with an adhesive layer, followed by drying and stamping. The separator is a porous film made by stretching a sheet of resin. The positive and negative electrodes function to charge and discharge, while the separator provides electrical insulation between the positive and negative electrodes.

[0003] As mentioned above, the diaphragm is a porous membrane made of resin. Therefore, if an internal short circuit occurs due to foreign objects, external punctures, etc., it will generate heat, melt the diaphragm, expand the area of ​​the internal short circuit, and generate heat again. Therefore, it is not preferred.

[0004] Therefore, in order to prevent the expansion of the internal short-circuit area even if the diaphragm melts and disappears, an insulating layer composed of inorganic fillers was formed on the compound layer of the positive or negative electrode (Patent Document 1). The insulating layer is composed of inorganic fillers, so it will not melt due to heat. Even if the diaphragm melts due to heat, the insulating layer can be used to prevent the expansion of the internal short-circuit area of ​​the positive or negative electrode.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 5112853 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] The insulating layer formed on the electrolyte layer blocks the path for the electrolyte to move to the electrolyte layer (deteriorating fluid permeability). The responsiveness of a battery is determined by the amount of Li ions entering and leaving the positive or negative electrode active materials. However, if the fluid permeability of the electrolyte deteriorates as described above, the displacement properties of the electrolyte near the positive or negative electrode active materials (the exchange between the electrolyte after the reaction and the electrolyte before the reaction) deteriorate. Consequently, the Li ion concentration does not remain constant, and the amount of Li ions entering and leaving decreases. As a result, the battery's responsiveness deteriorates, leading to problems such as increased resistance (indicating battery performance) and decreased output.

[0010] Therefore, the object of the present invention is to provide a lithium-ion secondary battery that ensures excellent displacement, output and responsiveness of the electrolyte near the active material, and a method for manufacturing the same.

[0011] Technical means for solving the problem

[0012] The inventors have discovered a lithium-ion secondary battery with an insulating layer on an insulating layer, comprising an electrode by providing a pore at the interface between the insulating layer and the insulating layer. This electrode comprises: an electrode foil; an insulating layer formed by drying an insulating layer slurry containing a first solvent, disposed on the surface of the electrode foil; and an insulating layer formed by drying an insulating layer slurry dispersing ceramic particles to a second solvent, disposed on the surface of the insulating layer. The lithium-ion secondary battery is characterized in that the insulating layer has a plurality of particulate materials, the particulate materials being one or more selected from active material particles, conductive materials, and binders, disposed on the surface of the insulating layer and the insulating layer. In the region of the insulating layer bordering the plurality of particulate materials, on the surface of the mixture layer facing the boundary between the insulating layer and the mixture layer, a plurality of pores formed by the plurality of particulate materials and the insulating layer are provided. The diameter of the pores is 2.5 μm or more. The opening width of the pores on the surface of the mixture layer is greater than or equal to the particle size of the ceramic particles. A plurality of ceramic particles are formed adjacent to the pores. The ceramic particles are bonded to each other and form bridges on the surface of the mixture layer. The ceramic particles will not fall into the pores. The boiling point of the second solvent is below the boiling point of the first solvent.

[0013] This specification contains the disclosure of Japanese Patent Application No. 2018-116217, which forms the basis of the priority claim of this application.

[0014] The effects of the invention

[0015] According to the present invention, even if an insulating layer is formed on the compound layer, the pores (liquid pools) provided on the surface of the compound layer act as buffers to store fresh (pre-reaction) electrolyte, thereby maintaining a constant Li ion concentration in the electrolyte near the active material. As a result, a lithium-ion secondary battery with excellent output and responsiveness can be provided. Furthermore, the issues, structures, and effects other than those described above will become clear from the following description of the embodiments. Attached Figure Description

[0016] Figure 1 This is a perspective view of a square secondary battery according to one embodiment of the present invention.

[0017] Figure 2 This is an exploded 3D view of a square secondary battery.

[0018] Figure 3 A perspective view of the unfolded winding assembly of a battery can housing a square secondary battery.

[0019] Figure 4 This is a cross-sectional view of the winding along the short-length width.

[0020] Figure 5 This is a cross-sectional view near the surface of the negative electrode binder layer.

[0021] Figure 6 A diagram illustrating the fabrication process of the negative electrode.

[0022] Figure 7 This diagram illustrates the application and drying processes of the negative electrode paste and the insulating paste.

[0023] Figure 8 This diagram illustrates the drying process following the application of the negative electrode paste and the insulating paste.

[0024] Figure 9 for Figure 7 A magnified view of the die head and the rear roller.

[0025] Figure 10 This is the unfolded diagram of the mold head.

[0026] Figure 11 Scanning electron microscope (SEM) images of the cross-sections of the negative electrode mixture layer and the insulating layer formed according to the manufacturing method of this embodiment.

[0027] Figure 12 Scanning electron microscope (SEM) images of the cross sections of the negative electrode mixture layer and the insulating layer formed by a method other than the manufacturing method of this embodiment. Detailed Implementation

[0028] Hereinafter, embodiments of the lithium-ion secondary battery of the present invention will be described with reference to the accompanying drawings.

[0029] Figure 1 This is a perspective view of a square secondary battery 100, which is one embodiment of the lithium-ion secondary battery of the present invention. Figure 2 This is an exploded perspective view showing the structure of the square secondary battery 100. Additionally, Figure 3 This is a perspective view of the winding assembly 3 of the battery can 1 housing the square secondary battery 100. Furthermore, in this embodiment, the case where an additive layer and an insulating layer are provided on the negative electrode foil, which serves as the electrode foil, will be described. However, this is not a limitation; the additive layer and the insulating layer can be provided on the positive electrode foil, or the additive layer and the insulating layer can be provided on both the negative electrode foil and the positive electrode foil respectively.

[0030] like Figure 1As shown, the square secondary battery 100 includes a battery container consisting of a battery canister 1 and a battery cover 6. The battery canister 1 and the battery cover 6 are made of aluminum or aluminum alloy, etc. In this embodiment, the battery canister 1 is formed into a flat rectangular box shape with one end open by deep drawing. The battery canister 1 has a rectangular flat bottom surface 1d, a pair of wide side surfaces 1b respectively disposed on a pair of long sides of the bottom surface 1d, and a pair of narrow side surfaces 1c respectively disposed on a pair of short sides of the bottom surface 1d.

[0031] The battery cover 6 is a rectangular flat plate, laser-welded to block the opening of the battery can 1. In other words, the battery cover 6 seals the opening of the battery can 1. The battery cover 6 is equipped with the positive electrode 34 and the negative electrode 32 of the winding assembly 3 (see reference). Figure 3 The positive external terminal 14 and the negative external terminal 12 are electrically connected. In addition, a positive-side external insulator 24 and a negative-side external insulator 22 for preventing short circuits are respectively provided between the positive external terminal 14 and the battery cover 6, and between the negative external terminal 12 and the battery cover 6.

[0032] A flat bus welding part 142 is provided on the positive external terminal 14, and a flat bus welding part 152 is provided on the negative external terminal 12. During the manufacture of the battery pack, the bus is brought into contact with the bus welding parts 142 and 152 and welded, thereby connecting the bus to the positive external terminal 14 and the bus to the negative external terminal 12 respectively.

[0033] In addition, the battery cover 6 is provided with a gas vent valve 10. The gas vent valve 10 is formed by partially thinning the battery cover 6 using a stamping process. Alternatively, a thin-walled component can be installed in the opening of the battery cover 6 by laser welding or the like, using the thin-walled portion as a gas vent valve. When the square secondary battery 100 generates gas due to overcharging or other abnormalities, and the pressure inside the battery container rises to a specified pressure, the gas vent valve 10 ruptures, releasing the gas from the inside, thereby reducing the pressure inside the battery container.

[0034] like Figure 2 As shown, a winding assembly 3 (see reference) is housed in the battery canister 1 and held in the cover assembly 107. Figure 3 ). and the positive electrode 34 of the winding assembly 3 (reference) Figure 3 The positive current collector 180 is connected to the winding assembly 3, and the negative electrode 32 is connected to the winding assembly 3 (see reference). Figure 3The negative current collector 190 and the winding assembly 3, which are joined together, are housed in the battery can 1 under the cover of the insulating housing 108. The insulating housing 108 is made of an insulating resin such as polypropylene, and the battery can 1 is electrically insulated from the winding assembly 3. Furthermore, the cover assembly 107 referred to herein is an assembly that integrally assembles the winding assembly 3, the positive current collector 180, the positive external terminal 14, the negative current collector 190, the negative external terminal 12, and the battery cover 6.

[0035] The positive external terminal 14 is connected to the positive electrode 34 of the winding assembly 3 via the positive current collector 180 (reference). Figure 3 Electrical connection, the negative external terminal 12 is connected to the negative electrode 32 of the winding assembly 3 via the negative current collector 190 (reference). Figure 3 Electrical connection. Therefore, power is supplied to an external machine via the positive external terminal 14 and the negative external terminal 12, or external generated power is supplied to the winding assembly 3 via the positive external terminal 14 and the negative external terminal 12 for charging.

[0036] The positive current collector 180 has a seat portion 181 connected to the positive external terminal 14, a mating plane portion 183 connected to the positive electrode 34, and a plane portion 182 disposed between the seat portion 181 and the mating plane portion 183.

[0037] Similar to the positive current collector 180, the negative current collector 190 also has a structure having a seat surface 191 connected to the negative external terminal 12, a mating plane portion 193 connected to the negative electrode 32, and a plane portion 192 disposed between the seat surface 191 and the mating plane portion 193.

[0038] In addition, such as Figure 2 As shown, the battery cover 6 has a liquid injection hole 9 for injecting electrolyte into the battery container. The liquid injection hole 9 is sealed by a liquid injection plug 11 after the electrolyte is injected. For example, a non-aqueous electrolyte containing lithium salts such as lithium hexafluorophosphate (LiPF6) dissolved in an organic solvent such as ethylene carbonate can be used. The composition of the electrolyte is not particularly limited.

[0039] refer to Figure 3 The winding group 3 will be explained. Figure 3 The perspective view of the winding assembly 3 shows the state in which the winding assembly 3 is unfolded at the end of winding. The winding assembly 3, which is a power generation element, is formed into a stacked structure by winding the long, ruler-shaped positive electrode 34 and negative electrode 32 in a flat shape around the winding center axis W with the diaphragms 33 and 35 in between.

[0040] The positive electrode 34 has a positive electrode agent layer 34a formed by coating and drying a positive electrode agent layer slurry on both sides of the positive electrode foil, which serves as a positive electrode current collector, and a positive electrode foil exposed portion 34b that is not coated with the positive electrode agent layer slurry is provided at one end of the positive electrode foil in the width direction.

[0041] The negative electrode 32 has a negative electrode paste layer 32a formed by coating and drying a negative electrode paste layer on both sides of the negative electrode foil, which serves as the negative electrode current collector. A negative electrode foil exposed portion 32b, which is not coated with the negative electrode paste layer, is provided at one end of the negative electrode foil in the width direction. Furthermore, an insulating layer 31 containing ceramic particles is provided on the negative electrode paste layer 32a and a portion of the negative electrode foil exposed portion 32b.

[0042] The positive electrode foil exposed portion 34b and the negative electrode foil exposed portion 32b are areas where the metal surface of the electrode foil is exposed, and are respectively arranged in the direction of the winding center axis W. Figure 3 The width direction) is wound in a way that positions one side and the other side.

[0043] Figure 4 The diagram schematically shows a cross-section in the short-length direction of the winding assembly 3, which consists of a stacked positive electrode 34, a separator 33, and a negative electrode 32. Regarding the positive electrode 34, a positive electrode flux layer 34a is formed on both sides of the positive electrode foil, and a positive electrode foil exposed portion 34b is present at one end. Regarding the negative electrode 32, a negative electrode flux layer 32a is formed on both sides of the negative electrode foil, and a negative electrode foil exposed portion 32b is present at one end. An insulating layer 31 is formed covering a portion of the negative electrode flux layer 32a and the negative electrode foil exposed portion 32b. The separator 33 is located between the positive electrode 34 and the negative electrode 32.

[0044] Figure 5 The cross-section near the surface of the negative electrode mixture layer 32a is schematically shown. The negative electrode mixture layer 32a is composed of negative electrode active material particles 32p, and, although not shown, particulate matter selected from conductive materials and binders, etc., laminated together. The insulating layer 31 is composed of laminated ceramic particles 31p. The thickness of the insulating layer 31 is preferably in the range of 1 μm or more and 10 μm or less, but is not limited thereto. Here, a plurality of pores 30 are provided on the surface of the negative electrode mixture layer 32a facing the boundary between the negative electrode mixture layer 32a and the insulating layer 31. Specifically, the plurality of pores 30 are formed in such a way that they are surrounded by a plurality of particulate matter such as the negative electrode active material particles 32p and the insulating layer 31. Figure 5 (The slanted part).

[0045] The pores 30 function as a reservoir for the electrolyte, maintaining a constant Li-ion concentration near the negative electrode active material particles 32p, thus improving the output and responsiveness of the lithium-ion secondary battery. In this embodiment, to achieve the improved output and responsiveness, multiple pores with a diameter of 2.5 μm or more are provided. Here, pore 30 refers to a void formed on the surface of the negative electrode compound layer 32a that opens toward the interface between the negative electrode compound layer 32a and the insulating layer 31 in a cross-sectional scanning electron microscope (SEM) image of the laminate of the negative electrode compound layer 32a and the insulating layer 31. Furthermore, the diameter of pore 30 refers to the diameter of the circle circumscribed by pore 30 in the cross-sectional SEM image. Moreover, "providing multiple pores with a diameter of 2.5 μm or more" means that multiple pores with a diameter of 2.5 μm or more exist along a straight line of 100 μm length along the interface between the negative electrode compound layer 32a and the insulating layer 31 in the cross-sectional SEM image.

[0046] Furthermore, the diameter of the pore 30 is preferably 0.5 times or more the thickness of the insulating layer 31. This allows the pore 30 to hold a large amount of electrolyte exceeding the amount held in the insulating layer 31, maximizing the buffering function based on the pore 30. Here, the diameter of the pore 30 compared to the thickness of the insulating layer 31 refers to the average diameter of multiple pores 30 with a diameter of 2.5 μm or more existing along a straight line with a length of 100 μm along the interface between the negative electrode mixture layer 32a and the insulating layer 31 in a scanning electron microscope (SEM) image of the cross-section of the laminate of the negative electrode mixture layer 32a and the insulating layer 31.

[0047] Furthermore, the opening width of the pores 30 on the surface of the negative electrode mixture layer 32a is preferably greater than or equal to the particle size of the ceramic particles 31p. The ceramic particles 31p bond together to form bridges on the negative electrode mixture layer 32a, and pores 30 are formed adjacent to these bridges. Therefore, the opening width of the pores 30 is greater than or equal to the particle size of the ceramic particles 31p, thereby forming pores 30 of sufficient size. Furthermore, the particle size of the ceramic particles referred to here means the median diameter value in the particle size distribution (volume standard) obtained by measuring using a laser diffraction particle size distribution measuring device. Additionally, the opening width of the pores 30 refers to the average width of all pores 30 with a diameter of 2.5 μm or more that open towards the interface, as seen in a scanning electron microscope (SEM) image of the cross-section of the laminate of the negative electrode mixture layer 32a and the insulating layer 31.

[0048] Next, the manufacturing method of the lithium-ion secondary battery according to this embodiment will be described. Figure 6 This describes the manufacturing process of the negative electrode 32.

[0049] Regarding the negative electrode binder slurry, for example, 10 parts by weight of polyvinylidene fluoride (hereinafter referred to as PVDF) as a binder can be added to 100 parts by weight of amorphous carbon powder, which is used as the negative electrode active material, and N-methyl-2-pyrrolidone (hereinafter referred to as NMP) can be added as a first solvent and then mixed to prepare the negative electrode binder slurry. Furthermore, while the above describes the use of amorphous carbon as the negative electrode active material, it is not limited to this. It can also be natural graphite capable of lithium ion insertion and detachment, various artificial graphite materials, carbon materials such as coke, compounds of Si, Sn, etc. (e.g., SiO, TiSi2, etc.), or composite materials thereof. Regarding the particle shape, it can be flake-like, spherical, fibrous, blocky, etc., and is not particularly limited. In addition, when various types of graphite are specifically used as the negative electrode active material, in addition to NMP, water or a mixture of water and NMP can be selected as the first solvent, which can reduce the environmental impact. As an aqueous negative electrode binder slurry, an example is a negative electrode binder slurry in which 1 part by weight of styrene-butadiene rubber (hereinafter, SBR) as a binder and 1 part by weight of sodium carboxymethyl cellulose (hereinafter, CMC) as a tackifier are added to 100 parts by weight of natural graphite powder.

[0050] Regarding the insulating layer paste, for example, SBR with 3 parts by weight of binder added to 100 parts by weight of alumina as ceramic particles is used as a second solvent, and the second solvent is a solvent having a boiling point lower than that of the first solvent. Preferably, the boiling point of the second solvent is lower than that of the first solvent, for example, preferably 10°C or more lower than that of the first solvent. Boiling point is related to vapor pressure, therefore, as will be explained later, the drying actions of the first solvent and the second solvent are different, which easily leads to the formation of pores on the surface of the negative electrode binder layer. Specifically, examples of the second solvent include alcohol solvents, ketone solvents, or mixtures thereof, or mixtures thereof with water, or water. Examples of alcohol solvents include methanol, ethanol, isopropanol, etc., and examples of ketone solvents include acetone, methyl ethyl ketone, etc.

[0051] A second solvent can be used for mixing to prepare the insulating layer slurry. Furthermore, while alumina (Al2O3) was shown as the ceramic particles described above, it is not a limitation. For example, one or more ceramic particles selected from silica, zirconium oxide (ZrO2), magnesium oxide (MgO), lithium carbonate, and boehmite (Al2O3·H2O) can be used. Regarding the particle shape, it can be plate-like, flake-like, spherical, fibrous, blocky, etc., and is not particularly limited. Especially when the ceramic particles are plate-like, bridges are formed on the surface of the mixture layer when the ceramic particles are bonded together to form the insulating layer, preventing the ceramic particles from falling into pores and allowing pores of sufficient size to be formed, which is preferred. Furthermore, here, plate-like refers to ceramic particles having a thickness of 0.5 μm to 2 μm and a major diameter of 1 μm to 5 μm or more of the total material.

[0052] Furthermore, if the particle size of the ceramic particles is too small, they can easily fall into the pores on the surface of the negative electrode binder layer due to capillary action, sometimes making it difficult to form pores of an appropriate size. Conversely, if the particle size is too large, capillary action will not cause them to fall into the pores, but this may sometimes impair their function as an insulating layer. Therefore, these factors are taken into consideration when setting the particle size appropriately. For example, the particle size of the ceramic particles is preferably in the range of 0.5 μm or more and 3.0 μm or less. In addition, here, particle size refers to the median diameter value in the particle size distribution (volume standard) obtained by measuring using a laser diffraction particle size distribution measuring device.

[0053] The above describes the case of adding 3 parts by weight of SBR as a binder. However, binders generally do not hinder ion movement that occurs during the positive and negative electrode reactions, so a smaller amount is preferred and not particularly limited in terms of the amount added. Figure 6 The manufacturing process shown involves coating and drying the negative electrode paste and insulating paste onto a negative electrode foil such as copper foil to form a negative electrode paste layer 32a and an insulating layer 31, thereby fabricating the negative electrode 32.

[0054] Next, based on Figure 7 The coating and drying processes for the negative electrode slurry and the insulating slurry are described. Figure 7 The coating dryer 38 shown includes a die head 40 for applying various slurries, a rear roller 46, and a drying oven 41 for evaporating and drying the solvent in the coating film. Additionally, a conveyor roller 43 is provided for sequentially feeding negative electrode foils 45, such as copper foil, into the coating and drying sections of the coating dryer 38. An unwinding roller 42 and a rewinding roller 44 are provided for unwinding and rewinding the negative electrode foils 45. The negative electrode foils 45, such as copper foil, are fed from the unwinding roller 42 along the conveyor roller 43.

[0055] A negative electrode slurry with a thickness of 50 μm to 200 μm is coated on the negative electrode foil 45, and an insulating slurry with a thickness of 2 μm to 20 μm is coated on top of it. Then, it is conveyed to a drying oven 41, where circulating hot air at 60 to 100°C evaporates and dries the solvent components in the negative electrode slurry and insulating slurry, thereby forming the negative electrode slurry layer 32a and the insulating layer 31. The film thickness after drying is reduced to approximately half. After drying, it is wound into a roll shape together with the copper foil 45 using a take-up roller 44. The wound roll is then conveyed again from the unwind roller 42, and the same process is repeated on the back side to form the negative electrode 32.

[0056] Here, based on Figure 8 The drying process following the application of the negative electrode binder layer slurry and the insulating layer slurry is explained. Immediately after application (before drying), a first solvent 28 and a second solvent 29 are present in the applied negative electrode binder layer slurry and insulating layer slurry, respectively. In each dispersed solvent, particulate matter such as negative electrode active material particles 32p and ceramic particles 31p are dispersedly present. When drying begins, firstly, the second solvent 29 in the outermost insulating layer slurry, which has a low boiling point and therefore a low vapor pressure associated with the boiling point, evaporates. Due to the evaporation of the second solvent 29, the ceramic particles 31p are fixed together by the binder. Then, as drying progresses, the first solvent 28 in the negative electrode binder layer slurry evaporates. At this time, the ceramic particles 31p form bridges on the outermost surface of the negative electrode binder layer by bonding these particles together, so that the ceramic particles 31p do not fall into the gaps between the particulate matter such as negative electrode active material particles 32p. As a result, as... Figure 8 As shown (after drying), pores 30 are formed between the negative electrode active material particles 32p on the outermost surface of the negative electrode mixture layer.

[0057] based on Figure 9 The process of applying the negative electrode paste and the insulating paste onto the negative electrode foil is described. Figure 9 In the middle, Figure 7 The die head 40 and the rear roller 46 are schematically enlarged. The die head 40 consists of an exit block 47, a three-dimensional gasket 48, and an inlet block 49, and has an insulating layer slurry manifold 50 and a negative electrode mixture layer slurry manifold 51 inside. The two types of slurries are simultaneously discharged vertically from each manifold toward the negative electrode foil 45, thereby achieving simultaneous coating of the two layers.

[0058] Figure 10This is an unfolded view of the die head 40. A three-dimensional gasket 48 is sandwiched between the outlet block 47 and the inlet block 49, and grooves 52, serving as flow paths for the slurry, are formed on both sides of the three-dimensional gasket 48. In this way, the die head 40 has flow paths capable of applying both negative electrode binder slurry and insulating layer slurry, simultaneously discharging these slurries, thereby simultaneously forming a negative electrode binder layer 32a and an insulating layer 31 on the negative electrode foil 45.

[0059] Furthermore, the viscosity of the negative electrode mixture slurry and the insulating layer slurry during application is not particularly limited. However, regarding the insulating layer slurry, if the viscosity is too low, the insulating layer slurry will easily fill the gaps between the 32p particles of the negative electrode active material, making it difficult to form pores. Therefore, a certain viscosity is preferred. Specifically, the viscosity at 25°C is preferably 300 mPa·s or higher, and more preferably 500 mPa·s or higher.

[0060] After coating and drying, a roll forming press is used for stamping. Specifically, a roller heated to 60–120°C is used to clamp the laminate containing the negative electrode compound layer and the insulating layer on the negative electrode foil, and pressure is applied to perform the stamping process. After stamping, a longitudinal shearing process is performed to achieve a specified width, thereby obtaining... Figure 3 The negative electrode 32 is shown.

[0061] Figure 11 Scanning electron microscope (SEM) images showing cross-sections of the negative electrode binder layer and the insulating layer formed according to the manufacturing method of this embodiment. Figure 11 In this study, the insulating layer 31 has a thickness of 4 μm, and it was confirmed that multiple pores 30 with a diameter of 2.5 μm are formed on the surface of the negative electrode mixture layer 32a facing the boundary between the insulating layer 31 and the negative electrode mixture layer 32a. In contrast, Figure 12 This indicates a cross-section showing the formation of an insulating layer 31 after the negative electrode adhesive layer slurry is applied and dried to form the negative electrode adhesive layer 32a. Figure 12 In the negative electrode mixture layer 32a, ceramic particles forming the insulating slurry 31 penetrate into the spaces between the negative electrode active material particles due to capillary action, resulting in ceramic particles clogging the gaps between the negative electrode active material particles. Furthermore, Figure 11 as well as Figure 12 The lateral distance is 200μm.

[0062] Regarding the positive electrode 34, for example, 10 parts by weight of flake graphite as a conductive material and 10 parts by weight of PVDF as a binder are added to 100 parts by weight of lithium manganese oxide (chemical formula LiMn2O4) as the positive electrode active material. NMP is added as a dispersing solvent, and the mixture is kneaded to prepare a positive electrode paste. This paste is then coated and dried such that the weld portion (exposed positive electrode foil portion 34b) remains on both sides of the aluminum foil (positive electrode foil). Afterwards, a positive electrode paste with a thickness of 100 μm to 200 μm (excluding the aluminum foil) can be obtained by stamping and slitting processes, similar to those used for the negative electrode. Figure 3 The positive electrode 34 is shown.

[0063] Furthermore, while the above description focused on the use of lithium manganese oxide as the positive electrode active material, other lithium manganese oxides with a spinel crystal structure, lithium manganese composite oxides formed by replacing or doping a portion of them with metal elements, lithium cobalt oxides or lithium titanate with a layered crystal structure, or lithium metal composite oxides formed by replacing or doping a portion of them with metal elements can also be used.

[0064] In addition, in this embodiment, PVDF is used as the binder for the binder layer in the positive electrode 34 and the negative electrode 32, but polytetrafluoroethylene (PTFE), polyethylene, polystyrene, polybutadiene, butyl rubber, nitrile rubber, styrene-butadiene rubber, polysulfide rubber, nitrocellulose, cyanoethyl cellulose, various latexes, acrylonitrile, vinyl fluoride, vinylidene fluoride, fluorinated propylene, chlorofluorobutylene, acrylic resins and other polymers and mixtures thereof can also be used.

[0065] One end of the two ends of the winding assembly 3 in the width direction, i.e., the direction of the winding center axis W orthogonal to the winding direction, serves as the stacked portion of the positive electrode 34, and the other end serves as the stacked portion of the negative electrode 32. The stacked portion of the positive electrode 34 at one end is formed by stacking the exposed portion 34b of the positive electrode foil where the positive electrode binder layer 34a is not formed. The stacked portion of the negative electrode 32 at the other end is formed by stacking the exposed portion 32b of the negative electrode foil where the insulating layer 32a is not formed. The stacked portions of the positive electrode foil exposed portion 34b and the negative electrode foil exposed portion 32b can be pre-flattened and connected to the positive current collector 180 and the negative current collector 190 respectively by ultrasonic bonding. The resulting cap assembly 107 is then housed in the battery canister 1 to manufacture a lithium-ion secondary battery.

[0066] According to the manufacturing method of this embodiment, an electrode structure with pores (liquid pools) at the interface between the insulating layer and the compound layer can be obtained, which can provide a lithium-ion secondary battery with excellent output and responsiveness.

[0067] The embodiments of the present invention have been described in detail above, but the specific structure is not limited to these embodiments. Even if there are design changes that do not depart from the spirit of the present invention, they are also included in the present invention.

[0068] Symbol Explanation

[0069] 1 Battery can

[0070] 1b Wide side view

[0071] 1c Narrow Side

[0072] 1d bottom

[0073] 3 winding groups

[0074] 6. Battery cover

[0075] 9 Injection Holes

[0076] 10 Gas discharge valve

[0077] 11 Liquid injection plug

[0078] 12 Negative External Terminal

[0079] 14 Positive external terminal

[0080] 22 External insulator on the negative side

[0081] 24 Positive side external insulator

[0082] 28 First Solvent

[0083] 29 Second Solvent

[0084] 30 empty holes

[0085] 31 Insulation layer

[0086] 31p ceramic particles

[0087] 32 Negative electrode

[0088] 32a Negative Electrode Mixture Layer

[0089] 32b Exposed part of negative electrode foil

[0090] 32p negative electrode active material particles

[0091] 33 Diaphragm

[0092] 34 Positive electrode

[0093] 34a Positive electrode mixture layer

[0094] 34b Positive electrode foil exposed portion

[0095] 35 Diaphragm

[0096] 38 Coating Dryer

[0097] 40 mold heads

[0098] 41 Drying Oven

[0099] 42 Unwinding Roller

[0100] 43 Conveyor Rollers

[0101] 44. Take-up roller

[0102] 45 Negative electrode foil

[0103] 46 Rear Roller

[0104] 47 Side Block

[0105] 48 Three-dimensional gaskets

[0106] 49. Side Block

[0107] 50 Insulation Paste Manifold

[0108] 51 Negative electrode mixture slurry manifold

[0109] 52 slots

[0110] 100 square secondary battery

[0111] 107 Cover Assembly

[0112] 108 Insulating Box

[0113] 142 Bus soldering section

[0114] 152 Bus soldering section

[0115] 180 Positive current collector

[0116] 181 seats

[0117] 182 Planar section

[0118] 183 Joint plane portion

[0119] 190 Negative current collector

[0120] 191 facial

[0121] 192 Planar section

[0122] 193 Joint plane portion

[0123] All publications, patents and patent applications cited in this specification are incorporated herein by reference.

Claims

1. A lithium-ion secondary battery, comprising an electrode having: Electrode foil; A mixture layer, formed by drying a mixture slurry containing a first solvent, is disposed on the surface of the electrode foil; and An insulating layer, formed by drying an insulating slurry in which ceramic particles are dispersed into a second solvent, is disposed on the surface of the mixture layer. The lithium-ion secondary battery is characterized by the following: The mixture layer contains multiple particle-like substances. The particulate material is selected from one or more of the following: active material particles, conductive materials, and binders. In the region on the side of the plurality of particulate materials extending from the boundary between the compound layer and the insulating layer, on the surface of the compound layer facing the boundary between the insulating layer and the compound layer, a plurality of pores formed by the plurality of particulate materials and the insulating layer are provided. The diameter of the pores is 2.5 μm or more, and the opening width of the pores on the surface of the mixture layer is greater than or equal to the particle size of the ceramic particles. Multiple ceramic particles are formed adjacent to the pores, and these ceramic particles are bonded together to form bridges on the surface of the mixture layer, preventing the ceramic particles from falling into the pores. The boiling point of the second solvent is below that of the first solvent.

2. The lithium-ion secondary battery according to claim 1, characterized in that, The thickness of the insulating layer is greater than 1 μm and less than 10 μm.

3. The lithium-ion secondary battery according to claim 1, characterized in that, The diameter of the pore is at least 0.5 times the thickness of the insulating layer.

4. The lithium-ion secondary battery according to claim 1, characterized in that, The ceramic particles have a particle size of 0.5 μm or more and 3.0 μm or less.

5. The lithium-ion secondary battery according to claim 1, characterized in that, The ceramic particles are selected from one or more of alumina, boehmite, magnesium oxide, and zirconium oxide.

6. The lithium-ion secondary battery according to claim 1, characterized in that, The ceramic particles are plate-shaped particles.

7. A method for manufacturing a lithium-ion secondary battery, which is the method for manufacturing a lithium-ion secondary battery according to claim 1, characterized in that it comprises: In the simultaneous coating process, a mixture layer slurry containing a first solvent and an insulating layer slurry dispersing ceramic particles into a second solvent are simultaneously coated onto the electrode foil; and The drying process dries the applied mixture layer slurry and the insulating layer slurry to form the mixture layer and the insulating layer, thereby fabricating the electrode. The boiling point of the second solvent is below that of the first solvent.

8. The method for manufacturing a lithium-ion secondary battery according to claim 7, characterized in that, The first solvent is water and / or N-methyl-2-pyrrolidone. The second solvent is an alcohol solvent, a ketone solvent, or a mixture thereof, or a mixture thereof with water, or water.

9. The method for manufacturing a lithium-ion secondary battery according to claim 7, characterized in that, The viscosity of the insulating slurry at 25°C is above 300 mPa·s.

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