JP2021192339A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

To provide a non-aqueous electrolyte secondary battery in a state where an electrode body is more stably held by a battery case via an insulator film.SOLUTION: A non-aqueous electrolyte secondary battery comprises a battery case 40, an electrode body (a wound electrode body 10 in Fig. 3), a non-aqueous electrolyte 20 and an insulator film 30. The insulator film 30 is disposed between the battery case 40 and the electrode body (the wound electrode body 10). When a sum of surface roughness Ra(A2) [μm] of an inner surface of the battery case 40 and surface roughness Ra(A2) [μm] of a surface of the insulator film 30 opposed to the inner surface of the battery case 40 is defined as Ra(A) and a sum of surface roughness Ra(B1) [μm] of an outer surface of the electrode body (the wound electrode body 10) and Ra(A1) [μm] is defined as Ra(B), the condition: 0.749≤Ra(A)/Ra(B)≤1.022 is satisfied.SELECTED DRAWING: Figure 3

Description

The present invention relates to a non-aqueous electrolyte secondary battery. More specifically, the present invention relates to a non-aqueous electrolyte secondary battery including a battery case, a non-aqueous electrolyte solution housed in the battery case, and an electrode body housed in the battery case via an insulating film.

Since secondary batteries such as lithium-ion secondary batteries are lightweight and can obtain high energy density, they are portable power sources such as personal computers and mobile terminals, or EVs (electric vehicles), HVs (hybrid vehicles), and PHVs (plug-in hybrids). It is widely used as a power source for driving vehicles such as automobiles. As an example of a secondary battery, a battery in which an electrode body is housed in a metal battery case via an insulating film is known. By interposing an insulating film between the battery case and the electrode body, the electrode body can be held in the battery case in a state where the electrical connection between the battery case and the electrode body is isolated.

For example, in Patent Document 1, the three-dimensional average surface roughness of the surface of the insulating film facing the inner surface of the battery case is made larger than the three-dimensional average surface roughness of the surface of the insulating film facing the electrode body side. A battery having a configuration in which the three-dimensional average surface roughness on both sides of the insulating film exceeds a certain value is disclosed. With this configuration, the coefficient of static friction between the battery case and the insulating film is improved, so that the electrode body can be held in the battery case with a smaller restraining load (external pressure pressed in the thickness direction of the electrode body).

Japanese Unexamined Patent Publication No. 2016-189303

By the way, in order for the electrode body to be held in the battery case via the insulating film, it is important that the battery case and the insulating film and the electrode body and the insulating film are in close contact with each other. If the insulating film does not adhere to the electrode body and the battery case, the electrode body may be misaligned in the battery case and the current collecting terminal may be exposed.

An object of the present invention is to provide a non-aqueous electrolyte secondary battery in a state where the electrode body is more stably held in a battery case via an insulating film.

The non-aqueous electrolyte secondary battery disclosed herein is a non-aqueous electrolyte secondary battery including a battery case, an electrode body housed in the battery case, a non-aqueous electrolyte solution, and an insulating film. The insulating film is arranged between the battery case and the electrode body, and faces the surface roughness Ra (A1) [μm] of the inner surface of the battery case and the inner surface of the battery case of the insulating film. The sum of the surface roughness Ra (A2) [μm] is Ra (A), and the sum of the surface roughness Ra (B1) [μm] of the outer surface of the electrode body and the Ra (A1) [μm]. Is Ra (B), the non-aqueous electrolyte secondary battery satisfies the condition: 0.749 ≦ Ra (A) / Ra (B) ≦ 1.022.
According to the study of the present inventor, by adjusting the surface roughness of the inner surface of the battery case, the surface roughness of the insulating film, and the surface roughness of the outer surface of the electrode body, the surface roughness between the battery case and the insulating film or the electrode body and the insulating film can be adjusted. It was found that one of the spaces could be prevented from slipping. Specifically, the battery case so that the quotient obtained by dividing the Ra (A) by the Ra (B) satisfies the condition of 0.749 ≦ Ra (A) / Ra (B) ≦ 1.022. The surface roughness of the inner surface, the surface roughness of the surface of the insulating film facing the inner surface of the battery case, and the surface roughness of the outer surface of the electrode body were adjusted.

According to such a configuration, it is possible to prevent slipping between the battery case and the insulating film, or between the electrode body and the insulating film. Therefore, since the electrode body is more stably held in the battery case, the position of the electrode body does not shift, and it is possible to prevent the current collecting terminal from being exposed.

It is sectional drawing which shows typically the internal structure of the secondary battery 1 which concerns on one Embodiment. It is a schematic diagram which shows the structure of the winding electrode body 10 of the secondary battery 1 which concerns on one Embodiment. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. It is a schematic diagram which shows the static friction coefficient measuring method.

Hereinafter, one of the typical embodiments in the present disclosure will be described in detail with reference to the drawings. Matters other than those specifically mentioned in the present specification and necessary for implementation are grasped as design matters of those skilled in the art based on the prior art in the art. The batteries disclosed herein can be implemented on the basis of what is disclosed herein and common general knowledge in the art.

As used herein, the term "battery" refers to a general storage device capable of extracting electrical energy, and is a concept including a primary battery and a secondary battery. "Secondary battery" refers to a general storage device that can be charged and discharged repeatedly, and includes so-called storage batteries (that is, chemical batteries) such as lithium ion secondary batteries, nickel hydrogen batteries, and nickel cadmium batteries, as well as electric double layer capacitors and the like. Includes capacitors (ie, physical batteries). Hereinafter, a flat-angle lithium-ion secondary battery, which is a type of secondary battery, will be described in detail by way of example. However, the secondary battery according to the present disclosure is not intended to be limited to those described in the following embodiments.

Further, in the present specification, the "surface roughness Ra" is a so-called "arithmetic mean roughness", which is a parameter in the height direction. For the surface roughness Ra, only the reference length L is extracted from the roughness curve in the direction of the average line, the x-axis is taken in the direction of the average line of the extracted portion, and the y-axis is taken in the direction perpendicular to the x-axis. When expressed by f (x), it means the value obtained by the following equation (1) expressed in micrometer (μm).

The secondary battery 1 shown in FIG. 1 includes a wound electrode body 10, a non-aqueous electrolytic solution 20, an insulating film 30, and a battery case 40. The battery case 40 houses the wound electrode body 10, the non-aqueous electrolytic solution 20, and the insulating film 30 in a sealed state inside. The shape of the battery case 40 in this embodiment is a flat square shape. However, the shape of the battery case 40 may be a box shape other than a square shape (for example, a bottomed cylindrical box shape). The battery case 40 includes a bottomed box-shaped case body 42 having an opening at one end, and a plate-shaped lid 44 that closes the opening of the case body. The lid 44 has a safety valve 46 that releases the internal pressure when the internal pressure inside the battery case 40 rises above a predetermined level, and a supply port for supplying the non-aqueous electrolytic solution 20 to the inside of the battery case 40. A liquid injection port (not shown) is provided. Further, the lid 44 is provided with a positive electrode current collecting terminal 52 and a negative electrode current collecting terminal 54 for external connection. As the material of the battery case 40, for example, a lightweight metal material having good thermal conductivity such as aluminum, stainless steel, and nickel-plated steel is used. However, it is also possible to change the configuration of the battery case. For example, a flexible laminate may be used as the battery case.

As shown in FIG. 2, the wound electrode body 10 of the present embodiment has a long positive electrode (positive electrode sheet) 60, a long separator 80, a long negative electrode (negative electrode sheet) 70, and a long shape. The separators 80 are stacked in the same order in the length direction, and are wound in the longitudinal direction of the long positive electrode and negative electrode. Specifically, in the positive electrode 60, the positive electrode active material layer 64 is formed along the longitudinal direction on one side or both sides of the long positive electrode current collector 62. In the negative electrode 70, the negative electrode active material layer 74 is formed along the longitudinal direction on one side or both sides of the long negative electrode current collector 72. The positive electrode active material layer non-formed portion 66 and the negative electrode active material layer non-formed portion 76 are located at both ends of the wound electrode body 10 in the direction of the winding axis WL (the sheet width direction orthogonal to the longitudinal direction). do. The positive electrode active material layer non-forming portion 66 of the positive electrode 60 and the negative electrode active material layer non-forming portion 76 of the negative electrode 70 are overlapped so as to protrude from each other in the width direction of the separator. The positive electrode active material layer non-forming portion 66 is a portion where the positive electrode current collector 62 is exposed without forming the positive electrode active material layer 64. The positive electrode active material layer non-forming portion 66 is bonded to a positive electrode internal terminal 52a (see FIG. 1) and electrically bonded to a positive electrode current collecting terminal 52 (see FIG. 1). Further, the negative electrode active material layer non-forming portion 76 is a portion where the negative electrode current collector 72 is exposed without forming the negative electrode active material layer 74. The negative electrode active material layer non-forming portion 76 is bonded to the negative electrode internal terminal 54a (see FIG. 1) and electrically connected to the negative electrode current collecting terminal 54 (see FIG. 1).

As the materials and members constituting the positive and negative electrodes of the wound electrode body 10, the same materials and members as those used for conventional general secondary batteries can be used without limitation. For example, as the positive electrode current collector 62, those used as the positive electrode current collector of this type of secondary battery can be used without particular limitation. Typically, a metal positive electrode current collector having good conductivity is preferred. For example, a metal material such as aluminum, nickel, titanium, or stainless steel can be adopted as the positive electrode current collector 62. Examples of the positive electrode active material of the positive electrode active material layer 64 include lithium composite metal oxides such as a layered structure and a spinel structure (for example, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , LiFeO). ₂ , LiMn ₂ O ₄ , LiNi _0.5 Mn _1.5 O ₄ , LiCrMnO ₄ , LiFePO _4, etc.). In the positive electrode active material layer 64, the positive electrode active material and a material (conductive material, binder, etc.) used as needed are dispersed in an appropriate solvent (for example, N-methyl-2-pyrrolidone: NMP) to form a paste (paste). Alternatively, it can be formed by preparing a composition (in the form of a slurry), applying an appropriate amount of the composition to the surface of the positive electrode current collector 62, and drying the composition.

As the negative electrode current collector 72, those used as the negative electrode current collector of this type of secondary battery can be used without particular limitation. Typically, a metal negative electrode current collector having good conductivity is preferable, and for example, copper (for example, copper foil) or an alloy mainly composed of copper can be used. Examples of the negative electrode active material of the negative electrode active material layer 64 include a particle-like (or spherical or scaly) carbon material containing a graphite structure (layered structure) at least in part, and a lithium transition metal composite oxide (for example, Li _4). Lithium-titanium composite oxides such as Ti ₅ O ₁₂ ), lithium transition metal composite nitrides and the like. In the negative electrode active material layer 74, a negative electrode active material and a material (binder or the like) used as needed are dispersed in an appropriate solvent (for example, ion-exchanged water) to prepare a paste-like (or slurry-like) composition. , An appropriate amount of the composition can be applied to the surface of the negative electrode current collector 72 and dried.

As the separator 80, a separator made of a conventionally known porous sheet can be used without particular limitation. For example, a porous sheet (film, non-woven fabric, etc.) made of a polyolefin resin such as polyethylene (PE) and polypropylene (PP) can be mentioned. The porous sheet may have a single-layer structure or a plurality of structures having two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). Further, the porous sheet may be configured to have a heat-resistant layer (Heat Resistant Layer: HRL) made of heat-resistant particles having heat resistance and insulating properties on one or both sides of the porous sheet. This heat-resistant layer can be, for example, a layer containing an inorganic filler and a binder (also referred to as a filler layer). As the inorganic filler, for example, alumina, boehmite, silica and the like can be preferably adopted.

The non-aqueous electrolyte solution 20 housed in the battery case 40 together with the wound electrode body 10 typically contains a supporting salt in a suitable non-aqueous solvent, and the conventionally known non-aqueous electrolytic solution is not particularly limited. Can be adopted. For example, as the non-aqueous solvent, ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and the like can be used. Further, as the supporting salt, for example, a lithium salt (for example, LiBOB, LiPF _6, etc.) can be preferably used.

As shown in FIG. 1, an insulating film 30 that separates the wound electrode body 10 and the battery case 40 is arranged between the wound electrode body 10 and the inner surface of the battery case 40. With such an insulating film 30, it is possible to prevent direct contact between the wound electrode body 10 which is a power generation element and the battery case 40, and to secure electrical insulation between the wound electrode body 10 and the battery case 40.
The material of the insulating film 30 is composed of a material that can function as an insulating member. Flexible materials are typically preferred, and examples thereof include various thermoplastic resins, typically polyolefin resin materials such as polypropylene (PP) and polyethylene (PE). Among them, polypropylene can be particularly preferably used.

The average thickness of the insulating film 30 may be about 100 μm, but can be appropriately changed according to the configuration conditions of the secondary battery 1 and the like. For example, the average thickness of the insulating film 30 is preferably 20 μm or more and 200 μm or less.
Further, the insulating film 30 may have a single-layer structure or a laminated structure having two or more layers.

The insulating film 30 may be formed in a bag shape surrounding the wound electrode body 10. For example, the insulating film 30 has a bottomed bag shape with an opening on the upper end side, and the wound electrode body 10 can be accommodated inside the insulating film 30 through such an opening.

FIG. 3 is a vertical cross-sectional view schematically showing a vertical cross-sectional structure along lines III-III in FIG. 1. As shown in FIG. 3, the insulating film 30 is attached (that is, in close contact with) to the inner wall of the battery case 40 and held. Typically, the wide, narrow, and bottom surfaces of the bag-shaped insulating film 30 are held in close contact with the wide, narrow, and bottom surfaces of the inner wall of the battery case 40, respectively. ..

Surface roughness Ra (A1) of the inner surface of the battery case 40 (the surface on the side where the wound electrode body 40 is housed and in contact with the insulating film 30), the surface of the insulating film 30 facing the inner surface of the battery case 40. Surface roughness Ra (A2), surface roughness Ra (B2) of the surface of the insulating film 30 facing the outer surface of the wound electrode body 10, and the outer surface of the wound electrode body 10 (the surface in contact with the insulating film 30). The surface roughness Ra (B1) is measured by a surface roughness measuring instrument. As the surface roughness measuring device, either a contact type measuring device or a non-contact type measuring device can be used. Specifically, as the contact type measuring instrument, a stylus type measuring instrument, an atomic force microscope (AFM), or the like can be used. Further, as the non-contact measuring instrument, a laser microscope, a white interferometer, or the like can be used.

The surface roughness Ra (A1) of the inner surface of the battery case 40 is preferably in the range of 0.2 μm to 0.5 μm.
Further, the surface roughness Ra (B1) of the outer surface (the surface in contact with the insulating film 30) of the wound electrode body 10 is preferably in the range of 0.02 μm to 0.3 μm. Further, the outer surface of the wound electrode body 10 is preferably made of a separator 80, and the outer surface is not particularly limited as long as it is a material constituting the separator 80. For example, a heat-resistant layer made of polypropylene (PP), polyethylene (PE), and heat-resistant particles having heat resistance and insulating properties can be suitably used as the material for the outer surface.

Further, the surface roughness Ra (A2) of the surface of the insulating film 30 facing the inner surface of the battery case 40 is preferably 0.02 μm to 0.2 μm. Further, the surface roughness Ra (A2) is more preferably in the range of 0.030 μm to 0.033 μm, or 0.12 μm to 0.19 μm.
Further, the surface roughness Ra (A2) of the surface of the insulating film 30 facing the inner surface of the battery case 40 and the surface roughness Ra (B2) of the surface of the insulating film 30 facing the outer surface of the wound electrode body 10 are different. May be. For example, when the insulating film 30 has a laminated structure of two or more layers, the surface of the insulating film 30 having the Ra (A2) and the surface having the Ra (B2) can be made of different materials, so that the insulating film 30 can be made of different materials. Ra (A2) and Ra (B2) may be different.

The sum Ra (A) of the surface roughness Ra (A1) of the inner surface of the battery case 40 and the surface roughness Ra (A2) of the surface of the insulating film 30 facing the inner surface of the battery case 40, and the Ra (A1) above. The sum Ra (B) with the surface roughness Ra (B1) of the outer surface of the wound electrode body 10 is preferably 0.673 μm or less.

The surface roughness of the inner surface of the battery case 40, the surface of the insulating film 30 facing the inner surface of the battery case 40, the surface of the insulating film 30 facing the outer surface of the wound electrode body 10 and the outer surface of the wound electrode body 10 are physical. Surface roughness can be adjusted by specific processing. For example, the surface roughness can be adjusted by laser irradiation, sputtering, ion printing, or the like.

It is preferable that the secondary battery 1 is used by applying a restraining pressure from the outer surface of the battery case 40 in the thickness direction of the wound electrode body 10. With such a configuration, the frictional force between the battery case 40 and the insulating film 30 and between the wound electrode body 10 and the insulating film 30 increases, and the wound electrode body 10 can be more stably held in the battery case 40. .. Therefore, even if an impact is applied to the secondary battery 1 from the outside, the possibility that the wound electrode body 10 is displaced in the battery case 40 can be reduced.

Although the secondary battery 1 provided with the wound electrode body 10 has been described as one embodiment, the electrode body is not intended to be limited to the wound electrode body, and the electrode body has a sheet-shaped positive electrode body and a sheet-shaped electrode body. The negative electrode body may be an electrode body in which negative electrodes are alternately laminated via a separator.

Hereinafter, examples relating to the present invention will be described, but the present invention is not intended to be limited to those shown in such examples.

<Example>
[Surface roughness measurement]
The surface roughness Ra (A1) of the inner surface of the battery case and the surface roughness Ra (A2) of the surface of the insulating film facing the inner surface of the battery case were measured by a stylus type SE500A (manufactured by Kosaka Laboratory Co., Ltd.). Specifically, the inner surface of the battery case and the surface of the insulating film facing the inner surface of the battery case are measured differently under the conditions of a stylus tip radius of 5 μm, a feed speed of 0.5 mm / s, and a measurement length of 4 mm. The measurement was performed three times at the position, and the average was calculated.
Further, the surface roughness Ra (B1) of the separator constituting the outer surface of the electrode body was measured with a laser microscope LEXT OLS4000 (manufactured by Olympus Corporation). Specifically, a part of the separator was cut out, Pt coated, and then the surface roughness (B1) was measured using a lens having a magnification of 50.

Examples 1 to 16 of Table 1 show an electrode body having a battery case measuring Ra (A1), an insulating film measuring Ra (A2), and a separator measuring Ra (B1) on the outer surface. Combined with. Further, Ra (A) which is the sum of Ra (A1) and Ra (A2), Ra (B) which is the sum of Ra (A1) and Ra (B1), and Ra (A). Is divided by Ra (B) above, and the quotient is shown in Table 1.

As described in one embodiment described above, a wound electrode body was prepared by stacking and winding the positive electrode on which the positive electrode active material layer was formed, the separator, the negative electrode on which the negative electrode active material layer was formed, and the separator in this order. Further, a positive electrode current collector terminal and a negative electrode current collector terminal were joined to the positive electrode active material layer non-formed portion and the negative electrode active material layer non-formed portion of the wound electrode body, respectively.

A non-aqueous electrolytic solution was applied to the surface of the insulating film facing the inner surface of the battery case and the outer surface of the wound electrode body having a separator on the outer surface, and used for the following measurement of the coefficient of static friction. The operations after the application of the non-aqueous electrolytic solution were performed in the glove box in an argon atmosphere.

[Measurement of coefficient of static friction]
As shown in FIG. 4, the insulating film 30 and the wound electrode body 10 were inserted into the battery case 40, and the insulating film 30 was arranged between the battery case 40 and the wound electrode body 10. At this time, the positive electrode current collecting terminal 52 and the negative electrode current collecting terminal 54 joined to the wound electrode body 10 were housed so as to face the opening side of the battery case 40. Then, the battery case 40 is fixed to the restraint jig 90 so that the pair of wide surfaces of the battery case 40 and the pair of comb teeth 92 are in contact with each other, and the restraint load is applied between one of the comb teeth 92 and the restraint jig 90. A load cell 94 for measurement was arranged.
Next, a pre-restraint load of 10000 N was applied for 10 seconds from the wide surface direction of the battery case 40. Then, the restraining load is set to 200N, which is the lower limit holding load value generally required for holding the electrode body, and the current collecting terminals (positive electrode current collecting terminal 52 and negative electrode current collecting terminal 54) bonded to the wound electrode body 10 are set. ), The force gauge 96 was pulled up toward the opening of the battery case 40 so as to be perpendicular to the restraint load direction. As a result, the peak load value (sliding load value) was obtained, and the coefficient of static friction was obtained by the following equation (2), which is shown in Table 1.
Coefficient of static friction = (sliding load value) ÷ 200N ÷ 2 ... (2)

When the current collector terminal is pulled up, slippage may occur between the battery case 40 and the insulating film 30, or between the wound electrode body 10 and the insulating film 30. In such a case, the sliding load value cannot be accurately obtained and the coefficient of static friction cannot be calculated. Therefore, it is indicated by a hyphen (−) in the column of the coefficient of static friction in Table 1.

As shown in Table 1, Examples 1 to 8 satisfying the conditions: 0.749 ≤ Ra (A) / Ra (B) ≤ 1.022 are between the battery case 40 and the insulating film 30, or the wound electrode body 10. The coefficient of static friction could be obtained without slipping on either side of the insulating films 30. On the other hand, in Examples 9 to 16 which do not satisfy the above conditions, slippage occurs between the battery case 40 and the insulating film 30, or between the wound electrode body 10 and the insulating film 30, and the coefficient of static friction cannot be obtained. rice field.

Although the detailed description has been given with reference to specific embodiments, these are merely examples and do not limit the scope of the claims. The techniques described in the claims include various modifications and modifications of the above-described embodiments.

1 Secondary battery 10 Winding electrode body 20 Non-aqueous electrolyte 30 Insulation film 40 Battery case 42 Case body 44 Lid body 46 Safety valve 52 Positive electrode current collecting terminal 52a Positive electrode internal terminal 54 Negative electrode current collecting terminal 54a Negative electrode internal terminal 60 Positive electrode 62 Positive electrode Collector 64 Positive electrode active material layer 66 Positive electrode active material layer Non-formed part 70 Negative electrode 72 Negative electrode current collector 74 Negative electrode active material layer 76 Negative electrode active material layer Non-formed part 80 Separator 90 Restraint jig 92 Comb tooth 94 For restraint load measurement Load cell 96 force gauge

Claims (1)

With a battery case,
The electrode body, the non-aqueous electrolyte solution, and the insulating film housed in the battery case,
A non-aqueous electrolyte secondary battery equipped with
The insulating film is arranged between the battery case and the electrode body.
Ra (A) is the sum of the surface roughness Ra (A1) [μm] of the inner surface of the battery case and the surface roughness Ra (A2) [μm] of the surface of the insulating film facing the inner surface of the battery case. ,
When the sum of the surface roughness Ra (B1) [μm] of the outer surface of the electrode body and the Ra (A1) [μm] is Ra (B),
Conditions: 0.749 ≤ Ra (A) / Ra (B) ≤ 1.022
A non-aqueous electrolyte secondary battery.

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