The separator and the nonaqueous electrolyte secondary battery having the same

Abstract

The present application provides a separator having excellent antistatic properties, gas release properties during winding, and impregnation properties of a nonaqueous electrolyte solution during formation of an electrode body. The separator disclosed herein has a base material layer made of a porous resin and a ceramic layer containing 85% by mass or more of first inorganic particles on at least one surface thereof. The main surface of the separator has a long side. The separator further has an adhesive layer provided on at least one of the main surfaces thereof at a predetermined pitch to form a stripe pattern. The adhesive layer contains an adhesive resin and second inorganic particles. The content of the second inorganic particles in the adhesive layer is 3% to 65% by mass. The angle of the long side of the main surface of the separator with respect to the adhesive layer is 20° to 70°.

Description

Technical Field

[0001] This invention relates to a separator. It also relates to a non-aqueous electrolyte secondary battery having the separator. Background Technology

[0002] In recent years, non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries have been used as portable power sources for personal computers, mobile terminals, etc., and as power sources for vehicle drives such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs).

[0003] In non-aqueous electrolyte secondary batteries, a separator is used to insulate the positive and negative electrodes. As such a separator, a separator consisting of a porous resin substrate and a ceramic layer containing inorganic particles is known. Furthermore, to improve the adhesion between the electrode and the separator, a technique for depositing an adhesive resin on the surface of the separator is known (see, for example, Patent Document 1).

[0004] Patent Document 1: Japanese Patent No. 5572101 Specification Summary of the Invention

[0005] However, the inventors conducted in-depth research and found that when an adhesive resin is applied to the surface of the separator, the adhesive resin becomes charged. This causes the separators to stick together during manufacturing, making it impossible to unwrap the core and resulting in defects caused by discharge. Furthermore, it was found that this hinders gas (air) release during the winding of the separator, making smooth winding difficult and reducing the operability of the wound body. Moreover, it was discovered that when the separator is bonded to the electrode to form the electrode body, the reduced porosity of the separator, rather than a decrease in the impregnation of the aqueous electrolyte, adversely affects the battery's resistive characteristics.

[0006] Therefore, the object of the present invention is to provide an insulating material with excellent antistatic properties, gas release properties during winding, and impregnation properties of non-aqueous electrolyte when forming an electrode body.

[0007] The spacer disclosed herein comprises a porous resin substrate layer and a ceramic layer containing at least 85% by mass of a first inorganic particle on at least one surface. The main surface of the spacer has a long side. The spacer further comprises an adhesive layer formed by stripes at predetermined intervals on at least one of the main surfaces. The adhesive layer contains an adhesive resin and a second inorganic particle. The content of the second inorganic particle in the adhesive layer is 3% to 65% by mass. The angle between the adhesive layer and the long side of the main surface of the spacer is 20° to 70°.

[0008] Based on this configuration, an insulating material with excellent antistatic properties, gas release during winding, and impregnation of non-aqueous electrolyte during electrode formation can be provided.

[0009] In a preferred embodiment of the separator disclosed herein, the angle between the adhesive layer and the long side of the main surface of the separator is 45° to 60°. This configuration provides a separator with higher impregnation properties for non-aqueous electrolytes.

[0010] In a preferred embodiment of the separator disclosed herein, the adhesive resin is polyvinylidene fluoride (PVDF). With this configuration, the adhesion between the separator and the electrode becomes particularly high, and the adhesive resin can also be prevented from adversely affecting the battery characteristics.

[0011] In a preferred embodiment of the separator disclosed herein, the second inorganic particles contained in the adhesive layer are particles of alumina, boehmite, magnesium oxide, or barium sulfate. This configuration prevents the second inorganic particles from adversely affecting battery characteristics; these particles are inexpensive and cost-effective.

[0012] In a preferred embodiment of the separator disclosed herein, the width of the adhesive layer is 0.5 mm to 4 mm, and the coverage ratio of the main surface of the separator caused by the adhesive layer is 50% to 90%. With this configuration, a separator with particularly high impregnation properties for non-aqueous electrolytes can be provided.

[0013] On the other hand, the non-aqueous electrolyte secondary battery disclosed herein includes an electrode body comprising a positive electrode, a negative electrode, and a separator insulating them, as well as a non-aqueous electrolyte. The aforementioned separator is the one described above. With this configuration, a non-aqueous electrolyte secondary battery with excellent production efficiency can be provided. Attached Figure Description

[0014] Figure 1 This is a schematic diagram (top view) viewed from a direction perpendicular to the main surface of the separator according to one embodiment of the present invention.

[0015] Figure 2 This is a partial cross-sectional view schematically illustrating an embodiment of the isolation member of the present invention.

[0016] Figure 3 yes Figure 1 A magnified view of the area near the long side.

[0017] Figure 4 This is a schematic cross-sectional view illustrating the internal structure of a lithium-ion secondary battery having an separator according to one embodiment of the present invention.

[0018] Figure 5 It means Figure 4 An exploded view of the structure of the wound electrode body of a lithium-ion secondary battery. Detailed Implementation

[0019] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that matters not mentioned in this specification but necessary for implementing the present invention can be considered as design considerations for those skilled in the art based on prior art. The present invention can be implemented based on the disclosures in this specification and common technical knowledge in the field. Furthermore, in the following drawings, components and parts that perform the same function are labeled with the same symbols. Also, the dimensional relationships (length, width, thickness, etc.) in the drawings do not necessarily reflect actual dimensional relationships.

[0020] It should be noted that in this manual, "secondary battery" refers to an energy storage device capable of repeated charging and discharging, encompassing both storage batteries and energy storage components such as double-layer capacitors. Furthermore, in this manual, "lithium-ion secondary battery" refers to a secondary battery that utilizes lithium ions as charge carriers, achieving charging and discharging through the movement of lithium ions' charge between the positive and negative electrodes.

[0021] The isolation element of this embodiment, which will be used as an example of the isolation element disclosed herein, is illustrated in [example of example]. Figures 1-3 . Figure 1 This is a schematic diagram (top view) viewed from a direction perpendicular to the main surface of the isolation member in this embodiment. Figure 2 This is a partial cross-sectional view of the isolation component in this embodiment. Figure 3 yes Figure 1 A magnified view of the area near the long side.

[0022] like Figure 2 As shown, the isolation member 70 of this embodiment includes a substrate layer 72 made of porous resin and a ceramic layer 74 containing first inorganic particles. Figure 1 In the diagram, the MD direction indicated by the arrow is the length direction of the spacer 70, as shown below. Figure 1 As shown, the main surface of the spacer 70 has a long side parallel to the MD direction. In the example shown, the spacer 70 is elongated for easy continuous manufacturing. However, the spacer 70 may not be elongated as long as its main surface has a long side.

[0023] The porous resin constituting the substrate layer 72 can be a known porous resin used in separators of non-aqueous electrolyte secondary batteries. Examples of resins include polyolefins, polyesters, cellulose, and polyamides. Among these, polyolefins are preferred from the perspective of imparting a so-called cutting function to the separator 70. Examples of suitable polyolefins include polyethylene (PE) and polypropylene (PP).

[0024] The substrate layer 72 can be a single-layer structure or a multi-layer structure with two or more layers (for example, a three-layer structure with PP layers stacked on both sides of the PE layer).

[0025] The thickness of the substrate layer 72 is not particularly limited as long as it can insulate the positive and negative electrodes. For example, it is 8μm to 40μm, preferably 10μm to 25μm, and more preferably 10μm to 14μm.

[0026] The porosity of the substrate layer 72 is not particularly limited and can be the same as that of known substrate layers for separators in non-aqueous electrolyte secondary batteries. The porosity of the substrate layer 72 is, for example, 20% to 70%, preferably 30% to 60%, and more preferably 40% to 50%. It should be noted that the porosity of the substrate layer 72 can be determined by mercury porosimetry.

[0027] The permeability of the substrate layer 72 is not particularly limited and can be the same as that of known substrate layers for separators in non-aqueous electrolyte secondary batteries. The permeability of the substrate layer 72, for example, is 50 seconds / 100 mL to 600 seconds / 100 mL in Glyph values, preferably 150 seconds / 100 mL to 300 seconds / 100 mL. It should be noted that the Glyph value of the substrate layer 72 can be determined by the method specified in JIS P8117 (2009).

[0028] The type of the first inorganic particles contained in the ceramic layer 74 is not particularly limited. Examples of the first inorganic particles include particles of oxide ceramics such as alumina (Al2O3), silicon dioxide (SiO2), titanium dioxide (TiO2), zirconium oxide (ZrO2), magnesium oxide (MgO), cerium oxide (CeO2), and zinc oxide (ZnO); particles of nitride ceramics such as silicon nitride, titanium nitride, and boron nitride; particles of metal hydroxides such as calcium hydroxide, magnesium hydroxide, and aluminum hydroxide; particles of clay minerals such as mica, talc, boehmite, zeolite, apatite, and kaolin; particles of sulfates such as barium sulfate and strontium sulfate; and glass fibers. Among these, particles of alumina and boehmite are preferred. Alumina and boehmite have high melting points and excellent heat resistance. In addition, alumina and boehmite have high Mohs hardness, and excellent mechanical strength and durability. Furthermore, alumina and boehmite are relatively inexpensive, thus reducing raw material costs.

[0029] The shape of the first inorganic particle is not particularly limited and can be spherical or non-spherical. The average particle size (D50) of the first inorganic particle is not particularly limited, but is, for example, 0.1 μm to 5 μm, preferably 0.3 μm to 3 μm, and more preferably 0.5 μm to 1.5 μm. It should be noted that in this specification, the average particle size (D50) refers to the median particle size (D50), which is the particle size corresponding to 50% of the cumulative frequency from the smallest particle side in a volume-based particle size distribution based on laser diffraction and scattering. Therefore, the average particle size (D50) can be determined using a known laser diffraction and scattering particle size distribution measuring device, etc.

[0030] The ceramic layer 74 may contain components other than the first inorganic particles; examples include binders and thickeners. Examples of binders include fluorinated polymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVDF); acrylic binders; rubber-based binders such as styrene-butadiene rubber (SBR); and polyolefin binders. Examples of thickeners include carboxymethyl cellulose (CMC) and methyl cellulose (MC).

[0031] The content of the first inorganic particles in the ceramic layer 74 is 85% by mass or more. By having the content of the first inorganic particles at 85% by mass or more, the ceramic layer 74 can be endowed with high strength and heat resistance. The content of the first inorganic particles in the ceramic layer 74 is preferably 90% to 97% by mass, more preferably 92% to 97% by mass.

[0032] The binder content in the ceramic layer 74 is 15% by mass or less, preferably 3% to 10% by mass, and more preferably 3% to 8% by mass.

[0033] The thickness of the ceramic layer 74 is not particularly limited, for example, it is 0.3μm to 6.0μm, preferably 0.5μm to 4.5μm, and more preferably 1.0μm to 2.0μm.

[0034] The porosity of the ceramic layer 74 is not particularly limited and can be the same as that of the known ceramic layer 74 in the separator of a non-aqueous electrolyte secondary battery. The porosity of the ceramic layer 74 is, for example, 30% to 90%, preferably 40% to 80%, and more preferably 50% to 70%. It should be noted that the porosity of the ceramic layer 74 can be determined by mercury porosimetry.

[0035] It should be noted that in the example shown, the spacer 70 has a ceramic layer 74 on only one main surface of the substrate layer 72. However, the spacer 70 may have ceramic layers 74 on both main surfaces of the substrate layer 72.

[0036] The separator 70 in this embodiment further includes an adhesive layer 76. Therefore, the separator 70 has a configuration in which the adhesive layer 76 is applied to the laminate of the substrate layer 72 and the ceramic layer 74.

[0037] In the example shown, the spacer 70 has a main surface on the side of the substrate layer 72 and a main surface on the side of the ceramic layer 74. An adhesive layer 76 is disposed on at least one main surface of the spacer 70. Figure 2 In the example shown, the spacer 70 has an adhesive layer 76 on both main surfaces (i.e., the main surface on the substrate layer 72 side and the main surface on the ceramic layer 74 side). However, the spacer 70 may have an adhesive layer 76 only on the main surface on the substrate layer 72 side, or it may have an adhesive layer 76 only on the main surface on the ceramic layer 74 side.

[0038] In this embodiment, the adhesive layer 76 is arranged at a predetermined interval to form a striped pattern. Therefore, as shown in the figure, the adhesive layer 76 is formed as a protrusion extending in one direction. Consequently, areas with the adhesive layer 76 and areas without the adhesive layer 76 are alternately formed on the main surface of the spacer 70 on which the adhesive layer 76 is provided. It should be noted that, due to manufacturing limitations, a slight amount of adhesive component may adhere to areas without the adhesive layer 76 (for example, the coverage rate of the adhesive layer 76 components in areas without the adhesive layer 76 is 5% or less, preferably 1% or less).

[0039] In this embodiment, the stripe pattern caused by the adhesive layer 76 is formed as an inclined stripe pattern. Furthermore, the angle between the adhesive layer 76 and the long side of the main surface of the spacer 70 (i.e., Figure 3 The angle θ shown is 20° to 70°. Therefore, the adhesive layer 76 is relative to the length direction of the spacer 70. Figure 1 The direction of the arrow MD is inclined within the range of 20° to 70°. It should be noted that the angle between the adhesive layer 76 and the long side of the main surface of the spacer 70 can be acute or obtuse; in this specification, the acute angle is used.

[0040] By utilizing the adhesive layer 76 formed with such an inclined stripe pattern, both the adhesion between the spacer 70 and the electrode and the impregnation of the non-aqueous electrolyte are excellent. That is, by forming the adhesive layer 76 with a stripe pattern, a flow path for the non-aqueous electrolyte is formed between adjacent adhesive layers 76, allowing the non-aqueous electrolyte to easily penetrate into the interior of the spacer 70 in the region between adjacent adhesive layers 76 (i.e., the region on the main surface of the spacer 70 without adhesive layers 76). Furthermore, the moderately inclined stripe pattern caused by the adhesive layer 76 facilitates the impregnation of the non-aqueous electrolyte within the spacer.

[0041] Therefore, if the angle θ between the adhesive layer 76 and the long side of the main surface of the separator 70 deviates from the range of 20° to 70°, the impregnation of the non-aqueous electrolyte is insufficient. From the viewpoint of higher impregnation of the non-aqueous electrolyte, this angle θ is preferably 30° to 65°, and more preferably 45° to 60°.

[0042] When a separator 70 with high impregnation of non-aqueous electrolyte is used in a non-aqueous electrolyte secondary battery, the battery resistance can be reduced.

[0043] Furthermore, when such a separator 70 with high impregnation of non-aqueous electrolyte is used in a non-aqueous electrolyte secondary battery, the time required to impregnate the electrode body containing the separator 70 with the non-aqueous electrolyte during its manufacturing can be shortened, thereby improving the production efficiency of the non-aqueous electrolyte secondary battery.

[0044] Furthermore, during repeated charge-discharge cycles of a non-aqueous electrolyte secondary battery, although non-aqueous electrolyte is discharged from the electrode body due to the expansion of the active material used in the electrodes, the discharged non-aqueous electrolyte easily returns to the electrode body. Therefore, the increase in resistance of the non-aqueous electrolyte secondary battery during repeated charge-discharge cycles can be suppressed.

[0045] Here, in the substrate layer 72 and ceramic layer 74 of the separator 70, the ceramic layer 74 has high permeability to the non-aqueous electrolyte. Therefore, when the adhesive layer 76 is provided on the main surface of the substrate layer 72, which has low permeability to the non-aqueous electrolyte, the effect of improving the impregnation of the non-aqueous electrolyte based on the adhesive layer 76 can be further enhanced.

[0046] Furthermore, since the adhesive layer 76 is continuously formed in one direction, the adhesion to the electrode is improved compared to the prior art where the adhesive layer is arranged in a dotted pattern.

[0047] The coverage ratio of the main surface of the separator 70 to which the adhesive layer 76 is formed (in other words, the coating area of ​​the adhesive layer 76 on the main surface of the separator 70) is not particularly limited. From the viewpoint of higher adhesion, this coverage ratio is preferably 50% or more, more preferably 60% or more. On the other hand, from the viewpoint of particularly high non-aqueous electrolyte impregnation and particularly low battery resistance, this coverage ratio is preferably 90% or less, more preferably 80% or less.

[0048] The width of adhesive layer 76 (i.e., the dimension of adhesive layer 76 in the direction perpendicular to the elongation direction); Figure 3 The dimension W shown is not particularly limited, for example, it is 0.5mm to 4mm, preferably 3mm to 4mm.

[0049] The distance between the adhesive layers 76 (i.e., the width of the gap between the adhesive layers 76); Figure 3 The dimension P shown is not particularly limited, for example, it is 0.5mm to 4mm, preferably 0.5mm to 2mm.

[0050] The thickness of the adhesive layer 76 (i.e., the dimension of the spacer 70 in the direction perpendicular to the main surface) is not particularly limited, for example, it is 0.5μm to 4.5μm, preferably 0.5μm to 2.5μm, and more preferably 1.0μm to 2.0μm.

[0051] From the viewpoint of further improving the impregnation of non-aqueous electrolyte by arranging areas that are easily penetrated by non-aqueous electrolyte at specified intervals, the width of adhesive layer 76 is 0.5 mm to 4 mm, and the coverage ratio of adhesive layer 76 on the main surface of the separator is preferably 50% to 90%.

[0052] It should be explained that Figure 2In the example shown, the adhesive layer 76 has a rectangular cross-section. The rectangular cross-section of the adhesive layer 76 facilitates a large bonding area with the electrode. However, the cross-sectional shape of the adhesive layer 76 is not limited as long as it can bond the electrode to the spacer 70.

[0053] The adhesive layer 76 contains adhesive resin and a second type of inorganic particles. Because the adhesive layer 76 contains these second inorganic particles, it is less prone to becoming charged. Furthermore, by forming the adhesive layer 76 into a striped pattern, its antistatic properties are exceptionally high. Therefore, problems such as unintentional adhesion between spacers caused by the charging of the adhesive layer 76 during the manufacturing of spacers, poor core extraction, and defects caused by discharge can be eliminated.

[0054] Furthermore, by containing second inorganic particles and forming them in a striped pattern, the adhesive force of the adhesive layer 76 is optimized. Additionally, the second inorganic particles impart an uneven surface to the adhesive layer 76. This facilitates gas (air) release during the winding of the spacer 70. In other words, the spacer 70 is endowed with high gas release properties. Therefore, winding the spacer 70 becomes easier, and the operability of the wound spacer 70 is also improved.

[0055] The type of adhesive resin is not particularly limited as long as it can bond the electrode and the separator 70. Examples of adhesive resins include polyvinylidene fluoride (PVDF); diene rubbers such as styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), and acrylonitrile-butadiene-styrene rubber (NSBR); (meth)acrylic resins such as polyacrylic acid, butyl acrylate-ethylhexyl acrylate copolymer, and methyl methacrylate-ethylhexyl acrylate copolymer; cellulose derivatives such as carboxymethyl cellulose and hydroxyalkyl cellulose; polyacrylonitrile; polyvinyl chloride; polyvinyl alcohol; polyvinyl butyral; and polyvinylpyrrolidone. The adhesive layer 76 may contain one of these adhesive resins alone or two or more. Among these, polyvinylidene fluoride is preferred from the viewpoint of high adhesion between the separator and the electrode and preventing adverse effects on battery characteristics.

[0056] The adhesive resin content in the adhesive layer 76 is 35% by mass or more, preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more. On the other hand, the adhesive resin content is 97% by mass or less, preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0057] The same inorganic particles as those exemplified as the first inorganic particles can be used as the second inorganic particle. Preferably, the second inorganic particle is composed of alumina, boehmite, magnesium oxide, or barium sulfate particles. Using these particles prevents the second inorganic particle from adversely affecting battery characteristics; furthermore, these particles are inexpensive and cost-effective. Alumina and boehmite particles are more preferred as the second inorganic particle. The first inorganic particles contained in the ceramic layer 74 and the second inorganic particles contained in the adhesive layer 76 can be the same or different.

[0058] The average particle size (D50) of the second inorganic particles is not particularly limited, but is, for example, 0.1 μm to 5 μm, preferably 0.3 μm to 3 μm, and more preferably 0.5 μm to 1.5 μm.

[0059] Here, from the viewpoint of fully utilizing the effects brought about by the second inorganic particles, the content of the second inorganic particles in the adhesive layer 76 is 3% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 20% by mass or more. On the other hand, the adhesive layer 76 needs to have adhesiveness sufficient to function as an adhesive layer; therefore, the content of the second inorganic particles in the adhesive layer 76 is 65% by mass or less, preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0060] The adhesive layer 76 possesses sufficient adhesiveness to function as an adhesive layer, thus bonding the electrode and the separator with sufficient strength, thereby firmly fixing the electrode to the separator. This allows for a constant maintenance of the distance between the electrode plates (i.e., the distance between the positive and negative electrodes). As a result, in non-aqueous electrolyte secondary batteries, the deposition of metallic lithium and the retention of gas caused by uneven distance between the electrode plates can be suppressed. Furthermore, by bonding the electrode and the separator with sufficient strength, misalignment of the separator and electrode during electrode body manufacturing is less likely to occur, improving the production speed of the electrode body, the yield of the electrode body, and the insertion into the battery casing. From the viewpoint of maintaining a more constant distance between the electrode plates, the adhesive layer 76 is preferably provided on the two main surfaces of the separator 70.

[0061] The adhesive layer 76 may contain only adhesive resin and second inorganic particles, or it may further contain other components (in other words, other components). Examples of other components include additives such as defoamers, surfactants, wetting agents, pH adjusters, etc.

[0062] In the example shown, the spacer 70 has only three layers: a substrate layer 72, a ceramic layer 74, and an adhesive layer 76. However, the spacer 70 may also have layers other than the substrate layer 72, the ceramic layer 74, and the adhesive layer 76, without significantly hindering the effects of the present invention.

[0063] The separator 70 can be manufactured according to known methods. For example, a porous resin substrate is prepared as the substrate layer 72. The porous resin substrate is preferably a strip-shaped substrate. A ceramic layer forming slurry containing first inorganic particles is coated onto the porous resin substrate and dried to obtain a laminate with a ceramic layer 74 formed thereon.

[0064] Next, a coating liquid containing an adhesive resin, a second inorganic particle, and a solvent is prepared and applied to the laminate. At this time, the coating liquid is applied to the laminate at a predetermined interval to form a striped pattern. Furthermore, the coating is applied at an angle of 20° to 70° relative to the length direction, along the long side of the main surface of the laminate. Such coating can be performed, for example, using a roll coating machine equipped with a gravure roller having grooves inclined relative to the direction of rotation.

[0065] By drying the applied coating liquid, an adhesive layer 76 is formed, thereby obtaining the separator 70.

[0066] It should be noted that the separator 70 of this embodiment can be used in non-aqueous electrolyte secondary batteries according to known methods. Therefore, the separator 70 of this embodiment is typically a separator for non-aqueous electrolyte secondary batteries, and preferably a separator for lithium-ion secondary batteries.

[0067] Therefore, from another perspective, the non-aqueous electrolyte secondary battery disclosed herein comprises: an electrode body including a positive electrode, a negative electrode, and a separator insulating them, as well as a non-aqueous electrolyte. The separator is the one described above.

[0068] As an example of the non-aqueous electrolyte secondary battery disclosed herein, a general description of a lithium-ion secondary battery equipped with the aforementioned separator will be provided below with reference to the accompanying drawings. The lithium-ion secondary battery described below is merely illustrative and does not impose any limitations on the non-aqueous electrolyte secondary batteries disclosed herein.

[0069] Figure 4 The lithium-ion secondary battery 100 shown is a sealed battery constructed by housing a flat, square battery casing (i.e., an outer container) 30 containing a flat, wound electrode 20 and a non-aqueous electrolyte 80. The battery casing 30 is provided with a positive terminal 42 and a negative terminal 44 for external connection, as well as a thin-walled safety valve 36 configured to release internal pressure if the internal pressure of the battery casing 30 rises above a predetermined level. Additionally, the battery casing 30 is provided with an injection port (not shown) for injecting the non-aqueous electrolyte 80. The positive terminal 42 is electrically connected to a positive current collector 42a. The negative terminal 44 is electrically connected to a negative current collector 44a. The battery casing 30 is made of a lightweight and thermally conductive metal material, such as aluminum.

[0070] like Figure 4 and Figure 5 As shown, the wound electrode body 20 has a positive electrode sheet 50 and a negative electrode sheet 60, which are formed by two elongated insulating sheets 70 overlapping and wound along the length direction. The positive electrode sheet 50 has a positive active material layer 54 formed on one or both (here, both) sides of the elongated positive current collector 52 along the length direction. The negative electrode sheet 60 has a negative active material layer 64 formed on one or both (here, both) sides of the elongated negative current collector 62 along the length direction. The non-formed portions 52a of the positive active material layer (i.e., the portions where the positive current collector 52 is exposed without the formation of the positive active material layer 54) and the non-formed portions 62a of the negative active material layer (i.e., the portions where the negative current collector 62 is exposed without the formation of the negative active material layer 64) are formed to extend outward from both ends in the winding axis direction (i.e., the sheet width direction orthogonal to the aforementioned length direction) of the wound electrode body 20. A positive electrode current collector 42a and a negative electrode current collector 44a are respectively bonded to the non-forming portion 52a of the positive electrode active material layer and the non-forming portion 62a of the negative electrode active material layer.

[0071] As the positive current collector 52 constituting the positive electrode sheet 50, a known positive current collector used in lithium-ion secondary batteries can be used. Examples of such current collectors include sheets or foils made of metals with good conductivity (e.g., aluminum, nickel, titanium, stainless steel, etc.). Aluminum foil is preferred as the positive current collector 52.

[0072] The size of the positive current collector 52 is not particularly limited, and can be determined appropriately according to the battery design. When aluminum foil is used as the positive current collector 52, its thickness is not particularly limited, for example, it is 5μm to 35μm, preferably 7μm to 20μm.

[0073] The positive electrode active material layer 54 contains a positive electrode active material. As the positive electrode active material, known positive electrode active materials used in lithium-ion secondary batteries can be used. Specifically, for example, lithium composite oxides, lithium transition metal phosphate compounds, etc., can be used as the positive electrode active material. The crystal structure of the positive electrode active material is not particularly limited and can be a layered structure, a spinel structure, an olivine structure, etc.

[0074] As a lithium composite oxide, a lithium transition metal composite oxide containing at least one of Ni, Co, and Mn as a transition metal element is preferred. Specific examples include lithium nickel-based composite oxides, lithium cobalt-based composite oxides, lithium manganese-based composite oxides, lithium nickel manganese-based composite oxides, lithium nickel cobalt manganese-based composite oxides, lithium nickel cobalt aluminum-based composite oxides, and lithium iron nickel manganese-based composite oxides. These positive electrode active materials can be used alone or in combination of two or more. As a positive electrode active material, a lithium nickel cobalt manganese-based composite oxide is preferred.

[0075] It should be noted that in this specification, "lithium-nickel-cobalt-manganese composite oxides" refers not only to oxides with Li, Ni, Co, Mn, and O as constituent elements, but also to oxides containing one or more additive elements other than these. Examples of such additive elements include transition metals and typical metallic elements such as Mg, Ca, Al, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W, Na, Fe, Zn, and Sn. Additionally, additive elements can be half-metals such as B, C, Si, and P, and non-metals such as S, F, Cl, Br, and I. This also applies to the aforementioned lithium-nickel composite oxides, lithium-cobalt composite oxides, lithium-manganese composite oxides, lithium-nickel-manganese composite oxides, lithium-nickel-cobalt-aluminum composite oxides, and lithium-iron-nickel-manganese composite oxides.

[0076] The average particle size (median particle size: D50) of the positive electrode active material is not particularly limited, for example, it is 0.05 μm to 25 μm, preferably 1 μm to 20 μm, and more preferably 3 μm to 15 μm.

[0077] The positive electrode active material layer 54 may also contain components other than the positive electrode active material, such as lithium triphosphate, conductive materials, binders, etc. As a conductive material, carbon black such as acetylene black (AB) or other carbon materials (e.g., graphite) are preferably used. As a binder, polyvinylidene fluoride (PVDF) is an example that can be used.

[0078] The content of the positive electrode active material in the positive electrode active material layer 54 (i.e., the content of the positive electrode active material relative to the total mass of the positive electrode active material layer 54) is not particularly limited, but is preferably 70% by mass or more, more preferably 80% by mass to 97% by mass, and even more preferably 85% by mass to 96% by mass. The content of trilithium phosphate in the positive electrode active material layer 54 is not particularly limited, but is preferably 1% by mass to 15% by mass, more preferably 2% by mass to 12% by mass. The content of conductive material in the positive electrode active material layer 54 is not particularly limited, but is preferably 1% by mass to 15% by mass, more preferably 3% by mass to 13% by mass. The content of binder in the positive electrode active material layer 54 is not particularly limited, but is preferably 1% by mass to 15% by mass, more preferably 1.5% by mass to 10% by mass.

[0079] The thickness of the positive electrode active material layer 54 is not particularly limited, for example, it is 10μm to 300μm, preferably 20μm to 200μm.

[0080] As the negative electrode current collector 62 constituting the negative electrode sheet 60, a known negative electrode current collector used in lithium-ion secondary batteries can be used. Examples of such current collectors include sheets or foils made of metals with good conductivity (e.g., copper, nickel, titanium, stainless steel, etc.). Copper foil is preferred as the negative electrode current collector 62.

[0081] The size of the negative electrode current collector 62 is not particularly limited, and can be appropriately determined according to the battery design. When copper foil is used as the negative electrode current collector 62, its thickness is not particularly limited, for example, it is 5μm to 35μm, preferably 7μm to 20μm.

[0082] The negative electrode active material layer 64 contains a negative electrode active material. This negative electrode active material can be, for example, carbon materials such as graphite, hard carbon, or soft carbon. The graphite can be natural graphite, artificial graphite, or graphite coated with an amorphous carbon material (amorphous carbon-coated graphite).

[0083] The average particle size (median particle size: D50) of the negative electrode active material is not particularly limited, but is, for example, 0.1 μm to 50 μm, preferably 1 μm to 25 μm, and more preferably 5 μm to 20 μm. It should be noted that the average particle size (D50) of the negative electrode active material can be determined, for example, by laser diffraction scattering.

[0084] The negative electrode active material layer 64 may contain components other than the active material, such as binders and thickeners. Examples of binders include styrene-butadiene rubber (SBR) and polyvinylidene fluoride (PVDF). Examples of thickeners include carboxymethyl cellulose (CMC).

[0085] The content of the negative electrode active material in the negative electrode active material layer is preferably 90% by mass or more, more preferably 95% by mass to 99% by mass. The content of the binder in the negative electrode active material layer is preferably 0.1% by mass to 8% by mass, more preferably 0.5% by mass to 3% by mass. The content of the thickener in the negative electrode active material layer is preferably 0.3% by mass to 3% by mass, more preferably 0.5% by mass to 2% by mass.

[0086] The thickness of the negative electrode active material layer 64 is not particularly limited, for example, it is 10μm to 300μm, preferably 20μm to 200μm.

[0087] The separator 70 uses the above-described separator, that is, a separator in which an adhesive layer 76 containing a predetermined amount of second inorganic particles is formed on at least one main surface of the laminate of substrate layer 72 and ceramic layer 74 in an oblique stripe pattern at a predetermined angle.

[0088] Non-aqueous electrolytes typically contain a non-aqueous solvent and a supporting salt (electrolyte salt). As the non-aqueous solvent, various organic solvents used in common lithium-ion secondary battery electrolytes, such as carbonates, ethers, esters, nitriles, sulfones, and lactones, can be used without particular limitation. Specific examples include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), ethylene monofluorocarbonate (MFEC), ethylene difluorocarbonate (DFEC), difluoromethyl difluoromethyl carbonate (F-DMC), and dimethyl trifluorocarbonate (TFDMC). Such non-aqueous solvents can be used alone or in appropriate combinations of two or more.

[0089] As the supporting salt, lithium salts such as LiPF6, LiBF4, and lithium bis(fluorosulfonyl)imide (LiFSI) (preferably LiPF6) can be used. The concentration of the supporting salt is preferably 0.7 mol / L to 1.3 mol / L.

[0090] It should be noted that the non-aqueous electrolyte 80 may contain components other than those mentioned above, as long as it does not significantly impair the effect of the present invention. For example, film-forming agents such as oxalate complexes; gas generating agents such as biphenyl (BP) and cyclohexylbenzene (CHB); and various additives such as thickeners.

[0091] It should be explained that Figure 4 The amount of non-aqueous electrolyte 80 injected into the battery casing 30 is not strictly indicated.

[0092] The lithium-ion secondary battery 100 constructed as described above exhibits excellent impregnation of the non-aqueous electrolyte into the electrode body (especially the separator) during manufacturing, resulting in excellent production efficiency. Furthermore, in the lithium-ion secondary battery 100, the separator 70 and the electrodes are bonded with sufficient strength, thereby suppressing lamination misalignment during the manufacturing of the electrode body 20, which also contributes to excellent production efficiency. Additionally, the lithium-ion secondary battery 100 has low initial resistance, and the increase in resistance during repeated charge-discharge cycles is suppressed. Moreover, the lithium-ion secondary battery 100 exhibits high uniformity in the distance between the electrode plates, thus providing excellent resistance to lithium metal deposition.

[0093] The lithium-ion secondary battery 100 can be used for a variety of applications. Specific applications include portable power supplies for personal computers, portable electronic devices, mobile terminals, etc.; vehicle power supplies for electric vehicles (BEVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc.; and batteries for small energy storage devices, etc., with vehicle power supplies being the preferred option. The lithium-ion secondary battery 100 can also be used in the form of a battery pack typically consisting of multiple batteries connected in series and / or in parallel.

[0094] It should be noted that, as an example, a square lithium-ion secondary battery 100 having a flat, wound electrode body 20 has been described. However, the non-aqueous electrolyte secondary battery disclosed herein can also be configured as a lithium-ion secondary battery having a stacked electrode body (i.e., an electrode body in which multiple positive electrodes and multiple negative electrodes are alternately stacked). The stacked electrode body can include multiple separators, each with a separator between the positive and negative electrodes, or it can alternately stack the positive and negative electrodes while folding back a separator.

[0095] Furthermore, the non-aqueous electrolyte secondary battery disclosed herein can also be configured as a coin-type lithium-ion secondary battery, a button-type lithium-ion secondary battery, a cylindrical lithium-ion secondary battery, or a laminated shell type lithium-ion secondary battery. Additionally, the non-aqueous electrolyte secondary battery disclosed herein can also be configured as a non-aqueous electrolyte secondary battery other than a lithium-ion secondary battery using known methods.

[0096] The following describes test examples related to the present invention, but it is not intended to limit the present invention to the contents shown in these embodiments.

[0097] <Fabrication of the isolation component in the experimental example>

[0098] As a substrate, a long strip of porous polyethylene (PE) membrane is prepared to be manufactured by a wet process. The PE membrane has a thickness of 12 μm and a porosity of 45%.

[0099] A slurry containing alumina particles with an average particle size (D50) of 0.9 μm and a binder is prepared. This slurry is applied to both sides of the substrate and dried to obtain a laminate with a ceramic layer formed on the substrate. At this point, the amount of alumina particles relative to the total solids content of the slurry is 90% by mass or more. It should be noted that the thickness of the formed ceramic layer is 1.5 μm per side.

[0100] A coating solution containing polyvinylidene fluoride (PVDF), alumina particles with an average particle size (D50) of 0.9 μm, and N-methyl-2-pyrrolidone (NMP) was prepared. The amount of alumina particles relative to the total solids content of the coating solution was as shown in Table 1 (it should be noted that, with 0% by mass of inorganic particles, the coating solution contained only PVDF and NMP). In Test Examples 1-6, the coating solution was applied to both sides of the aforementioned laminate in a striped pattern. In these examples, the coating area of ​​the pattern was uniformly 80%, and the stripe width (width of the adhesive layer) was 4 mm. Furthermore, the stripe angle (°) (i.e., the angle of the adhesive layer relative to the long side of the main surface of the spacer) in each example was as shown in Table 1.

[0101] On the other hand, in Test Examples 7 and 8, the coating liquid was applied to both sides of the aforementioned laminate. The applied coating liquid was dried, thereby forming an adhesive layer.

[0102] It should be noted that in each test example, the surface coverage ratio of the adhesive layer (i.e., the ratio of the area of ​​the adhesive layer forming portion to the area of ​​the main surface of the spacer) is consistent with the coating area ratio of the coating liquid. In each test example, the thickness of the adhesive layer formed is 1.0 μm per single side. The spacers of each test example were obtained in this manner.

[0103] <Evaluation of the fabrication of lithium-ion secondary batteries>

[0104] LiNi will be used as the positive electrode active material 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (LNCM), acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder were mixed with N-methylpyrrolidone (NMP) at a mass ratio of LNCM:AB:PVdF = 87:10:3 to prepare a slurry for forming the positive electrode active material layer. This slurry was coated onto aluminum foil and dried to form the positive electrode active material layer. The resulting sheet was pressed and then cut into pieces with a width of 50 mm and a length of 230 mm to obtain the positive electrode sheet. It should be noted that a non-positive electrode active material layer portion is provided at the longitudinal end of the positive electrode sheet.

[0105] A slurry for forming the negative electrode active material layer was prepared by mixing graphite (C) as the negative electrode active material, styrene-butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener with deionized water at a mass ratio of C:SBR:CMC = 98:1:1. This slurry was coated onto copper foil and dried to form the negative electrode active material layer. The resulting sheet was pressed and then cut into sections with a width of 52 mm and a length of 330 mm to obtain the negative electrode sheet. It should be noted that a non-formed portion of the negative electrode active material layer is provided at the longitudinal end of the negative electrode sheet.

[0106] In the non-positive electrode active material layer of the positive electrode sheet, aluminum leads are installed by ultrasonic welding in a manner that protrudes into the width direction of the positive electrode sheet. In the non-negative electrode active material layer of the negative electrode sheet, nickel leads are installed by ultrasonic welding in a manner that protrudes into the width direction of the negative electrode sheet. The separators for each test example are cut to a dimension of 54 mm wide × 400 mm long. It should be noted that the stripe angle of the separator is the same before and after cutting.

[0107] The positive electrode, negative electrode, and two separators from each test example are overlapped. The resulting laminate is wound and pressed under a specified pressure to create a flat wound electrode body. At this point, the leads of both the positive and negative electrodes protrude from the wound electrode body in the same direction. It should be noted that the external dimensions of the wound electrode body are 41 mm × 54 mm.

[0108] An outer casing made of aluminum laminate was prepared. The obtained wound electrode body was housed in the outer casing made of aluminum laminate. After injecting the non-aqueous electrolyte into the outer casing, the outer casing was hermetically sealed. It should be noted that the non-aqueous electrolyte was a solution prepared by dissolving LiPF6 at a concentration of 1.1 mol / L in a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 3:4:3. The lithium-ion secondary batteries for evaluation of each test example were obtained in this manner.

[0109] <Characteristic Evaluation>

[0110] [Gas Emission Assessment]

[0111] For each test example, spacers were fabricated with a width of 3000 mm. These spacers were then wound onto an 8-inch core material using a winding machine at a tension of 150 gf. Here, since the gas (i.e., air) was not released during winding, it remained as air bubbles between the spacer layers, causing unevenness in the spacer layers. The appearance of the wound spacers was visually observed to investigate whether any unevenness was caused by the residual air bubbles. The results are shown in Table 1.

[0112] [Evaluation of electrical charge]

[0113] The spacers for each test example were placed on a metal plate, and a 63 mm square weight with a load of 1.98 N was placed on top. Using a tensile testing machine equipped with a load sensor, one end of the spacer was stretched horizontally at a speed of 1 mm / s. The average frictional force was measured when the spacer had moved 50 mm at a constant speed. The average frictional force was divided by 1.98 N to calculate the coefficient of kinetic friction. The results are shown in Table 1. It should be noted that the higher the electrical charge of the adhesive layer of the spacer, the higher the coefficient of kinetic friction.

[0114] [Immersion time for non-aqueous electrolytes]

[0115] Each evaluation lithium-ion secondary battery, injected with a non-aqueous electrolyte, was stored at 25°C. Every hour, each evaluation lithium-ion secondary battery was disassembled, and the area of ​​the portion of the separator not impregnated with the non-aqueous electrolyte was calculated. The time to completion of the non-aqueous electrolyte impregnation into the separator was determined based on the relationship between time and area. The results are shown in Table 1.

[0116] [Determination of adhesive strength of the separator]

[0117] The separators for each test example were clamped together with the positive and negative electrodes prepared above. They were then clamped together with a porous polyethylene film, and then with a Teflon sheet (registered trademark). The resulting laminate was pressed at 25°C under a pressure of 60 kN for 10 seconds. The pressed product was cut into strips of 20 mm × 120 mm to prepare test specimens. For separators with a striped adhesive layer, the length direction of the test specimen was parallel to the direction of the stripes (i.e., the elongation direction of the adhesive layer).

[0118] The test specimen was secured to the horizontal movable worktable of the tensile testing machine using double-sided tape. Only the isolator of the test specimen was lifted upwards at a speed of 200 mm / min at a 90° angle (i.e., vertically) using a push-pull force gauge. The movable worktable and the push-pull force gauge were moved synchronously. The load at which the isolator peeled off from the electrode was measured and taken as the adhesive force of the isolator. The results are shown in Table 1.

[0119] [Battery resistance]

[0120] Each evaluation lithium-ion secondary battery was placed in a 25°C atmosphere and charged to 50% SOC. Each evaluation lithium-ion secondary battery was then discharged for 10 seconds at a current ranging from 0.2C to 4.0C. The voltage values ​​after 10 seconds of discharge relative to each current value were plotted, and the IV resistance was determined from the slope of the straight line obtained by approximation. The results are shown in Table 1.

[0121] [Table 1]

[0122]

[0123] In Examples 1-6, the adhesive layer was applied to the main surface of the separator in a stripe pattern with a stripe angle of 20° to 70°. In Examples 7 and 8, the adhesive layer was applied to the entire main surface of the separator. Based on these comparisons, it can be seen that by applying the adhesive layer to the main surface of the separator in a stripe pattern with a stripe angle of 20° to 70°, the separator's impregnation with non-aqueous electrolytes is increased, thereby reducing battery resistance.

[0124] Furthermore, a comparison of Test Examples 2 with Test Examples 3-5, and a comparison of Test Examples 7 with Test Example 8, shows that by including inorganic particles in the adhesive layer, the gas release properties of the spacer are increased, and the spacer is less prone to becoming charged. Additionally, a comparison of Test Examples 4 with Test Example 8 shows that when the adhesive layer has a striped pattern, the spacer is particularly difficult to charge. On the other hand, the results of Test Example 5 show that if the content of inorganic particles in the adhesive layer is too high, sufficient adhesiveness as an adhesive layer will not be exhibited.

[0125] Based on the above results, it can be seen that by containing 3% to 65% inorganic particles in the adhesive layer and maintaining an angle of 20° to 70° between the adhesive layer and the long side of the main surface of the separator, high antistatic properties, high gas release during winding, and high impregnation of the non-aqueous electrolyte during electrode formation can be achieved. Therefore, the separator disclosed herein exhibits excellent antistatic properties, gas release during winding, and non-aqueous electrolyte impregnation during electrode formation.

[0126] The specific examples of the present invention have been described above in detail, but they are merely illustrative and not intended to limit the scope of the claims. The technology described in the claims includes various modifications and alterations to the specific examples described above.

Claims

1. A non-aqueous electrolyte secondary battery, comprising: An electrode body comprising a positive electrode, a negative electrode, and an insulating element that insulates them, and Non-aqueous electrolyte; The non-aqueous electrolyte secondary battery is used as a power source for vehicle propulsion. The electrode body is a wound electrode body. The separator comprises a porous resin substrate layer and a ceramic layer containing more than 85% by mass of a first inorganic particle on at least one surface thereon. The spacer is elongated. The main surface of the spacer has a pair of long sides. The spacer further comprises an adhesive layer formed by stripes on at least one of its main surfaces at predetermined intervals. The adhesive layer has a portion that forms a protrusion extending in one direction from one long side to the other long side of the main surface of the spacer. The adhesive layer contains adhesive resin and a second type of inorganic particles. The content of the second inorganic particles in the adhesive layer is 3% to 65% by mass. The angle between the adhesive layer and the long side of the main surface of the spacer is 20° to 70°. The width of the adhesive layer is 0.5mm to 4mm, and The coverage ratio of the main surface of the spacer caused by the adhesive layer is 50% to 90%.

2. The non-aqueous electrolyte secondary battery according to claim 1, wherein, The angle between the adhesive layer and the long side of the main surface of the separator is 45° to 60°.

3. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein, The adhesive resin is polyvinylidene fluoride.

4. The non-aqueous electrolyte secondary battery according to any one of claims 1 to 3, wherein, The second inorganic particles contained in the adhesive layer are particles of aluminum oxide, boehmite, magnesium oxide, or barium sulfate.

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