JP7373120B2 - Non-aqueous electrolyte secondary battery - Google Patents

Description

The present invention relates to a non-aqueous electrolyte secondary battery. Specifically, the present invention relates to a nonaqueous electrolyte secondary battery that includes a flat wound electrode body, a nonaqueous electrolyte, and a battery case that houses the wound electrode body.

Non-aqueous electrolyte secondary batteries such as lithium-ion secondary batteries (also referred to as lithium-ion batteries) are lighter and have higher energy density than existing batteries, so they can be used as high-output power supplies for vehicles, computers, and It is preferably used as a power source for mobile terminals. In particular, lithium-ion secondary batteries, which are lightweight and provide high energy density, are preferably used as high-output power sources for driving vehicles such as electric vehicles (EVs), hybrid vehicles (HVs), and plug-in hybrid vehicles (PHVs). There is.

This type of secondary battery has, for example, a structure in which an electrode body and a nonaqueous electrolyte are housed in a battery case. The electrode body typically includes a sheet-like positive electrode (hereinafter sometimes referred to as a "positive electrode sheet") in which a positive electrode active material layer is formed on a positive electrode current collector foil, and a sheet-like positive electrode (hereinafter sometimes referred to as a "positive electrode sheet") on which a positive electrode active material layer is formed on a positive electrode current collector foil. It has a laminated structure of positive and negative electrodes in which a plurality of negative electrodes (hereinafter sometimes referred to as "negative electrode sheets") on which a negative electrode active material layer is formed overlap each other with a separator interposed therebetween. As a typical example of an electrode body having the above-mentioned positive and negative electrode laminated structure, a long positive electrode sheet and a similarly long negative electrode sheet are stacked one on top of the other with a separator interposed between them, and are wound in the longitudinal direction to form a flat sheet. A so-called wound electrode body formed by molding may be mentioned.

When manufacturing a secondary battery having such a structure, a non-aqueous electrolyte is poured into the case after reducing the pressure inside the battery case housing the wound electrode body. Then, the battery case is kept open for a predetermined period of time to allow the non-aqueous electrolyte to penetrate into the inside of the electrode body (between the positive electrode and the negative electrode), and then the battery case is sealed. In the manufacture of such secondary batteries, various techniques for adjusting the amount of permeation of the aqueous electrolyte have been proposed. An example of such a technique is Patent Document 1 below.

Japanese Patent Application Publication No. 2016-091870

By the way, in the above manufacturing process, if the permeability of the non-aqueous electrolyte into the electrode body is low, a region with negative pressure remains inside the electrode body, and the non-aqueous electrolyte continues to permeate into the electrode body even after the case is sealed. Therefore, the space between the electrode body and the battery case tends to have negative pressure. In such a secondary battery, when the positive electrode and the negative electrode expand due to charging and discharging, it is difficult for the electrode body to expand outward, so that the gap between the positive electrode and the negative electrode tends to collapse. As a result, the non-aqueous electrolyte that has permeated between the positive electrode and the negative electrode may leak out of the electrode body, and the high rate characteristics may deteriorate.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a non-aqueous electrolyte secondary battery in which the permeability of a non-aqueous electrolyte into the inside of a wound electrode body is suitably improved. It is.

In order to achieve the above object, the non-aqueous electrolyte secondary battery disclosed herein includes a sheet-like positive electrode in which a positive electrode active material layer is formed on a long positive electrode current collector foil, and a long negative electrode current collector. A wound electrode body in which a sheet-shaped negative electrode having a negative electrode active material layer formed on a foil is wound with a separator interposed therebetween to form a flat shape, a non-aqueous electrolyte, and the wound electrode body. Provided is a non-aqueous electrolyte secondary battery comprising: a battery case accommodating the battery; The wound electrode body has a flat part with a flat surface that exists in the longitudinal center of the cross section perpendicular to the winding axis, and exists at both ends of the cross section that sandwich the flat part in the longitudinal direction. It has two R parts with curved surfaces. Further, at one end of the wound electrode body in the winding axis direction, a positive electrode current collector is laminated with an exposed portion of the positive electrode current collector foil on which the positive electrode active material layer is not formed protruding from the negative electrode. There is a foil laminated portion, and on the other side there is a negative electrode current collector foil laminated portion in which the exposed portion of the negative electrode current collector foil on which the negative electrode active material layer is not formed is laminated with the exposed portion protruding from the positive electrode. In the non-aqueous electrolyte secondary battery disclosed herein, in at least one of the positive electrode current collector foil laminated portion and the negative electrode current collector foil laminated portion, at least one R portion of the two R portions is provided. , characterized in that an expanded electrolyte infiltration path is formed in which the nonaqueous electrolyte infiltration path is expanded more than the surrounding area.

In the electrolyte infiltration expanded path as described above, the permeability of the non-aqueous electrolyte is improved better than the surrounding area, so the permeability of the non-aqueous electrolyte into the inside of the wound electrode body is improved as a whole. It is possible.

FIG. 1 is a front sectional view schematically showing the external shape and internal configuration of a lithium ion secondary battery according to an embodiment. FIG. 1 is a perspective view schematically showing a wound electrode body according to an embodiment. 2 is a sectional view taken along line III-III in FIG. 1. FIG. FIG. 2 is a cross-sectional view schematically showing an example of a side surface of a positive electrode current collector foil laminated portion of a lithium ion secondary battery according to an embodiment. FIG. 7 is a schematic cross-sectional view schematically showing another example of the side surface of the positive electrode current collector foil laminated portion of the lithium ion secondary battery according to one embodiment. FIG. 7 is a schematic cross-sectional view schematically showing another example of the side surface of the positive electrode current collector foil laminated portion of the lithium ion secondary battery according to one embodiment. It is a graph showing the relationship between the elapsed time after electrolyte injection and the height of the electrolyte solution level.

Hereinafter, one embodiment of the non-aqueous electrolyte secondary battery disclosed herein will be described with reference to the drawings. Note that matters other than those specifically mentioned in this specification, which are necessary for implementing the technology disclosed herein, can be understood based on conventional technology in the field. That is, the technology disclosed herein can be implemented based on the content explicitly disclosed in this specification and common technical knowledge in the field. Note that the following embodiments are not intended to limit the technology disclosed herein. Further, in the drawings shown in this specification, the same reference numerals are given to members and parts that have the same function. Further, the dimensional relationships (length, width, thickness, etc.) in each figure do not reflect actual dimensional relationships. In addition, in this specification and claims, when a predetermined numerical range is expressed as A to B (A and B are arbitrary numerical values), it means A or more and B or less. Therefore, cases in which the value exceeds A and are lower than B are included.

As used herein, the term "nonaqueous electrolyte secondary battery" refers to a general battery that uses a nonaqueous electrolyte as an electrolyte and can be repeatedly charged and discharged. A typical example of such a nonaqueous electrolyte secondary battery is a lithium ion secondary battery. This lithium ion secondary battery is a secondary battery that uses lithium (Li) ions as electrolyte ions (charge carriers) and charges and discharges by moving lithium ions between a positive electrode and a negative electrode. Furthermore, in this specification, the term "active material" refers to a material that reversibly absorbs and releases charge carriers.
Note that in the embodiments below, a lithium ion secondary battery is used as a nonaqueous electrolyte secondary battery, but the technology disclosed herein is not limited to lithium ion secondary batteries, and can be used with other nonaqueous electrolytes. It can also be applied to secondary batteries (for example, nickel-metal hydride batteries).

A lithium ion secondary battery 100 shown in FIG. 1 is constructed by housing a flat wound electrode body 20 and an electrolyte (not shown) in a battery case (ie, an outer container) 10. The battery case 10 shown in FIG. 1 is a rectangular container with an internal space. Further, as the material for the battery case 10, for example, a metal material such as aluminum that is lightweight and has good thermal conductivity is used. The lid 12 of the battery case 10 includes an external positive terminal 38 and an external negative terminal 48 for external connection, and a thin wall configured to release the internal pressure when the internal pressure of the battery case 10 rises above a predetermined level. A safety valve 14 and an injection port (not shown) for injecting electrolyte are provided. Parts of the external terminals 38 and 48 are connected to the positive current collector terminal 37 and the negative current collector terminal 47, respectively, inside the case.

In the wound electrode body 20, as shown in FIG. 2, a positive electrode sheet 30 and a negative electrode sheet 40 are stacked on top of each other with two separators 50 in between, and are wound in the longitudinal direction around a winding axis WL. It has a different form. The positive electrode sheet 30 is formed by forming a positive electrode active material layer 34 along the longitudinal direction on one or both surfaces (in this case, both surfaces) of a long positive electrode current collector foil 32. Further, the negative electrode sheet 40 is formed by forming a negative electrode active material layer 44 along the longitudinal direction on one or both surfaces (in this case, both surfaces) of a long negative electrode current collector foil 42. A positive electrode active material layer 34 and a negative electrode active material layer 44 are laminated in the central portion of the wound electrode body 20 in the direction of the winding axis, forming a core portion 20a that serves as a main site for charging and discharging reactions. ing.

In addition, in the wound electrode body 20, a positive electrode collector is laminated with an exposed portion 36 of the positive electrode current collector foil on which the positive electrode active material layer 34 is not formed protruding from the negative electrode 40 at one end in the winding axis direction. An electric foil laminated portion 35 is present. In addition, in the wound electrode body 20, the negative electrode is stacked at the other end in the winding axis direction with the negative electrode current collector foil exposed portion 46 on which the negative electrode active material layer 44 is not formed protruding from the positive electrode 30. A collector foil laminated portion 45 is present. Then, such current collector foil laminated parts are bundled (hereinafter also referred to as "foil collectors"), parts of the current collector terminals 37 and 47 of corresponding poles are arranged, and joined by welding means such as ultrasonic welding. In this way, a current collecting structure for each of the positive and negative electrodes is formed.

FIG. 3 is a sectional view taken along the line III-III in FIG. As shown in FIG. 3, in a cross section perpendicular to the winding axis of the core portion 20a of the wound electrode body 20, an upper R portion 21a facing the upper surface of the battery case 10 (i.e., the lid 12) and an upper R portion 21a of the battery case 10 are shown. There are a lower R portion 21b facing the bottom surface of the lower R portion 21b, and a flat portion 22 sandwiched between the upper R portion 21a and the lower R portion 21b. The upper R portion 21a and the lower portion 21b each have a curved surface (curved surface), and the flat portion 22 has a flat surface (see also FIG. 2 regarding the upper R portion 21a and the lower portion 21b).

4 to 6 are cross-sectional views schematically showing an example of a side surface of the positive electrode current collector foil laminated portion of the lithium ion secondary battery 100. Note that although FIGS. 4 to 6 show the structure in the positive electrode current collector foil laminated part, a similar structure can be used in the negative electrode current collector foil laminated part.
The upper R portion 21c of the current collector foil laminated portion represents an R portion that exists in the current collector foil laminated portion and faces the upper surface of the battery case 10 (that is, the lid 12). Further, the lower R portion 21d of the current collector foil laminated portion represents an R portion that exists in the current collector foil laminated portion and faces the bottom surface of the battery case 10. The upper R portion 21c and the lower R portion 21d of these current collector foil laminate portions are formed in each of the positive electrode current collector foil laminate portion 35 and the negative electrode current collector foil laminate portion 45. That is, in the wound electrode body 20, as shown in FIG. 2, there are two upper R parts 21c of the current collecting foil laminated part and two lower R parts 21d of the current collecting foil laminated part.

In the wound electrode body 20 according to the present embodiment, an electrolyte infiltration expansion path in which a non-aqueous electrolyte infiltration path is expanded from the surrounding area is formed in at least one of the four R parts. It is characterized by Such an electrolyte infiltration expansion path may be, for example, a notch O formed in the upper R portion 21c of the negative electrode current collector foil laminated portion 45 shown in FIG. ), a cut P for cutting each current collector foil configuring the upper R portion 21c of the positive electrode current collector foil laminated portion shown in FIG. 4 along the radial direction, and an upper R of the positive electrode current collector foil laminated portion shown in FIG. Examples include a notch Q obtained by cutting out a part of the portion 21c, and a through hole S penetrating the upper R portion 21c of the positive electrode current collector foil laminated portion shown in FIG. 6. In the electrolyte infiltration expansion path as described above, the stress is more relaxed than in the surrounding area, so the amount of non-aqueous electrolyte infiltration increases more favorably than in the surrounding area, and as a whole, the amount of infiltration into the wound electrode body 20 is improved. The permeability of the non-aqueous electrolyte is suitably improved. Further, when forming electrolyte solution infiltration and expansion paths in two or more R portions, the combinations of the electrolyte solution infiltration and expansion paths may be various. For example, when forming electrolyte infiltration and expansion paths in two R portions, both may be notches, or both may be a notch and a notch. The above-mentioned notch/notch can be formed with a scalpel or the like, and the above-mentioned through hole can be formed with a drill or the like. The formation of the electrolyte infiltration expansion path may be performed either before or after welding the current collector terminal, but for example, in consideration of suppressing wrinkles in the current collector foil described later, It is preferable to form it as follows.

Note that the dimensions of the electrolyte infiltration expansion path are preferably adjusted as appropriate depending on the shape of the path and the dimensions of the electrode body, and are not intended to limit the technology disclosed herein. Furthermore, the electrolyte infiltration expansion path can be formed with desired dimensions as long as it does not extend to the core portion 20a. For example, when forming the notch O in FIG. 1, it is preferable to form it in the negative electrode current collector foil laminated portion 45. Further, for example, when forming the notch P in FIG. 4, it is preferable to form it from the end of the wound electrode body 20 along the winding axis. For example, when forming the notch Q in FIG. 5, it is preferable to form it in the positive electrode current collector foil laminated portion 35 of the wound electrode body 20. Furthermore, for example, when forming the through hole S in FIG. 6, it is preferable to form it in the positive electrode current collector foil laminated portion 35.

Note that when the electrolyte infiltration expansion path exists in the upper R portion 21c of the current collector foil laminated portion of the wound electrode body 20, the electrolyte infiltration expansion path is connected to the non-aqueous electrolyte injected from the electrolyte injection hole. Since contact is easy, the permeability of the non-aqueous electrolyte into the wound electrode body 20 can be improved more suitably. If the electrolyte infiltration expansion path exists in the lower R portion 21d of the current collector foil laminated portion of the wound electrode body 20, the electrolyte is discharged from the inside of the wound electrode body 20 due to high rate charging and discharging, etc. This is preferable because the non-aqueous electrolyte accumulated in the lower part can efficiently return to the inside of the wound electrode body. Furthermore, when the electrolyte infiltration expansion path exists in both the upper R portion 21c of the current collecting foil laminated portion of the wound electrode body 20 and the lower R portion 21d of the current collecting foil laminated portion, the above effects can be achieved at the same time. More preferred.

Further, for the positive electrode sheet 30 and the negative electrode sheet 40, materials similar to those used in conventional lithium ion secondary batteries can be used without particular restriction. A typical embodiment is shown below.

Examples of the positive electrode current collector foil 32 constituting the positive electrode sheet 30 include aluminum foil. The positive electrode active material contained in the positive electrode active material layer 34 includes, for example, lithium transition metal oxide (e.g., 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 , etc.), lithium transition metal phosphate compounds (eg, LiFePO ₄ , etc.), and the like. The positive electrode active material layer 34 may contain components other than the active material, such as a conductive material and a binder. As the conductive material, carbon black such as acetylene black (AB) and other carbon materials (eg, graphite, etc.) can be suitably used. As the binder, for example, polyvinylidene fluoride (PVdF) can be used.

Examples of the negative electrode current collector foil 42 constituting the negative electrode sheet 40 include copper foil and the like. As the negative electrode active material contained in the negative electrode active material layer 44, carbon materials such as graphite, hard carbon, and soft carbon can be used, for example. Among them, graphite is preferred. Graphite may be natural graphite or artificial graphite, and may be coated with an amorphous carbon material. The negative electrode active material layer 44 may contain components other than the active material, such as a binder and a thickener. As the binder, for example, styrene butadiene rubber (SBR) can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

As the separator 50, a porous sheet (film) made of polyolefin such as polyethylene (PE) or polypropylene (PP) can be suitably used. Such a porous sheet may have a single-layer structure or a laminate structure of two or more layers (for example, a three-layer structure in which a PP layer is laminated on both sides of a PE layer). A heat resistant layer (HRL) may be provided on the surface of the separator 50.

The electrolytic solution included in the lithium ion secondary battery disclosed herein usually contains a nonaqueous solvent and a supporting salt. As the non-aqueous solvent, conventionally known non-aqueous solvents used as non-aqueous solvents for electrolytes for lithium ion secondary batteries can be used, and specific examples thereof include carbonates, ethers, esters, and nitriles. , sulfones, lactones, etc. Among them, carbonates are preferred. Examples of carbonates include ethylene carbonate (EC), propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethylmethyl carbonate (EMC). These can be used alone or in combination of two or more.

Further, as the supporting salt, conventionally known supporting salts used as supporting salts of electrolytes for lithium ion secondary batteries can be used. Specific examples thereof include LiPF ₆ , LiBF ₄ , lithium bis(fluorosulfonyl ) imide (LiFSI), lithium bis(trifluoromethane)sulfonimide (LiTFSI), and the like. The concentration of the supporting salt in the electrolytic solution is not particularly limited, but is, for example, 0.5 mol/L or more and 5 mol/L or less, preferably 0.7 mol/L or more and 2.5 mol/L or less, and more preferably is 0.7 mol/L or more and 1.5 mol/L or less.

The electrolytic solution may contain other components as long as the effects of the present invention are not significantly impaired. Examples of other components include gas generating agents such as biphenyl (BP) and cyclohexylbenzene (CHB), film forming agents, dispersants, and thickeners.

Note that the electrolytic solution may be prepared by a conventionally known method, and such an electrolytic solution can be used in a lithium ion secondary battery according to a conventionally known method. Furthermore, since the lithium ion secondary battery disclosed herein can be manufactured by a conventionally known method, a detailed explanation of the manufacturing procedure will be omitted.

Examples related to the technology disclosed herein will be described below, but the technology disclosed herein is not intended to be limited to what is shown in these examples.

1. Preparation of Samples In this example, four types of lithium ion secondary batteries (Samples 1 to 4) were used. Each sample will be explained below.

(1) Preparation of sample 1 [Positive electrode]
Lithium transition metal oxide (NCM: LiNi _1/3 Co _1/3 Mn _1/3 O ₂ ) as a positive electrode active material, acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVdF) as a binder. These materials are weighed so that the weight ratio is NCM:AB:PVdF=91:6:3, and N-methylpyrrolidone (NMP) is added and kneaded so that the solid content concentration (NV) is approximately 50% by weight. In this way, a slurry for forming a positive electrode active material layer was prepared. This slurry was applied in a strip form from one end in the longitudinal direction on both sides of a strip-shaped aluminum foil as a cathode current collector foil, and dried to produce a cathode sheet having a cathode active material layer. Note that at the other longitudinal end of the positive electrode sheet, an exposed portion of the current collector foil in which the positive electrode active material layer is not formed is set. Then, this was rolled and pressed to obtain a positive electrode.

[Negative electrode]
Graphite (C) is used as a negative electrode active material, styrene butadiene rubber (SBR) is used as a binder, and carboxymethyl cellulose (CMC) is used as a thickener, so that the weight ratio of these is C:SBR:CMC=98:1:1. A slurry for forming a negative electrode active material layer was prepared by adding ion-exchanged water and kneading. This slurry was applied in a strip form from one end in the longitudinal direction on both sides of a strip-shaped copper foil as a negative electrode current collector foil, and dried to produce a negative electrode sheet having a negative electrode active material layer. Note that an exposed portion of the current collector foil in which the negative electrode active material layer is not formed is set at the other end of the negative electrode sheet in the longitudinal direction. Then, this was rolled and pressed to obtain a negative electrode.

[Separator]
As the separator, a strip-shaped microporous sheet with a three-layer structure (PP/PE/PP) in which polyethylene (PE) was sandwiched between polypropylene (PP) on both sides was used.

The positive electrode and negative electrode produced as described above were stacked on top of each other with a separator interposed therebetween, and wound so that the cross section had an oval shape. At this time, the negative electrode active material layer covers the positive electrode active material layer in the width direction, and the positive electrode and negative electrode and was placed. Moreover, the separator was arranged so as to insulate the active material layers of the positive and negative electrodes. Then, this wound body was pressed into a flat plate at room temperature (25° C.) and formed into a flat shape, thereby obtaining a wound electrode body.
Next, a battery assembly was constructed by accommodating the wound electrode body produced as described above inside a transparent glass case. After reducing the pressure inside the case of the battery assembly, the non-aqueous electrolyte was poured into the case so that the non-aqueous electrolyte reached a height of about 55 mm from the bottom of the case. Then, a lithium ion secondary battery (Sample 1) for evaluation testing was constructed by sealing the liquid injection port and sealing the case. The non-aqueous electrolyte contains approximately 1 mol/L of supporting salt LiPF ₆ in a mixed solvent containing ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) in a volume ratio of 3:4:3. A concentration of L was used.

(2) Preparation of Sample 2 Sample 2 is made by cutting each current collector foil configuring the upper R part of both the positive and negative electrode current collector foil laminated parts of the wound electrode body into 5 mm pieces along the radial direction with a scalpel. It was produced in the same manner as Sample 1.

(3) Preparation of Sample 3 Sample 3 has the following exceptions: Through holes were formed by drilling at locations 3 mm wide from the ends of both upper R portions of the positive and negative electrode current collector foil laminated portions of the wound electrode body. , was produced in the same manner as Sample 1.

(4) Preparation of Sample 4 Sample 4 is made by cutting each current collector foil configuring the lower R portions of both the positive and negative electrode current collector foil laminated portions of the wound electrode body to 5 mm along the radial direction with a scalpel. It was produced in the same manner as Sample 1.

2. Evaluation of Permeability of Nonaqueous Electrolyte In this example, the permeability of the nonaqueous electrolyte in each sample prepared as described above was evaluated. Specifically, as described above, after pouring a non-aqueous electrolyte into a transparent glass case to a height of approximately 55 mm, each sample was visually inspected until the liquid level of the non-aqueous electrolyte no longer decreased. I continued to monitor the liquid level. The graph in FIG. 7 shows the change in liquid level height over time for each sample.

As shown in FIG. 7, in Sample 1, the rate at which the liquid level decreases (that is, the rate at which the non-aqueous electrolyte permeates into the electrode body) decreases significantly from around 400 seconds after injection. confirmed. On the other hand, in Samples 2 to 4, the non-aqueous electrolyte continued to permeate into the electrode body even after 400 seconds had passed since injection, and the liquid level height 600 seconds after injection was significantly higher than in Sample 1. It became low. From the above, it can be seen that the non-aqueous electrolyte secondary battery disclosed herein suitably improves the permeability of the electrolyte.

Further, for example, the following effects are also expected for the wound electrode body according to Sample 2. That is, in the conventional wound electrode body, when the current collector terminal is welded, stress is applied to the R portion of the laminated portion of the current collector foil of the wound electrode body, so that wrinkles may occur in the current collector foil. However, when a notch is provided in the upper R part of the current collecting foil laminated part of the wound electrode body as in sample 2, by welding a terminal to the current collecting part spread out along the notch, the R part can be Since such stress is relaxed, wrinkles are less likely to occur in the current collector foil. This is expected to improve the permeability of the electrolyte.

Although the present invention has been described in detail above, the above description is merely an example. That is, the technology disclosed herein includes various modifications and changes of the above-described specific example.

10 Battery case 12 Lid body 14 Safety valve 20 Wound electrode body 20a Core portion 21a Upper R portion 21b Lower R portion 21c Upper R portion 21d of current collector foil laminated portion Lower R portion 22 of current collector foil laminated portion Flat portion 30 Positive electrode sheet (positive electrode)
32 Positive electrode current collector foil 34 Positive electrode active material layer 35 Positive electrode current collector foil laminated portion 36 Positive electrode current collector foil exposed portion 37 Positive electrode current collector terminal 38 External positive electrode terminal 40 Negative electrode sheet (negative electrode)
42 Negative electrode current collector foil 44 Negative electrode active material layer 45 Negative electrode current collector foil laminated portion 46 Negative electrode current collector foil exposed portion 47 Negative electrode current collector terminal 48 External negative electrode terminal 50 Separator 100 Lithium ion secondary battery WL Winding axis O Notch P Notch Q Notch S Through hole

Claims (1)

A sheet-like positive electrode in which a positive electrode active material layer is formed on a long positive electrode current collector foil, and a sheet-like negative electrode in which a negative electrode active material layer is formed on a long negative electrode current collector foil, with a separator interposed therebetween. A non-aqueous electrolyte secondary battery comprising a wound electrode body formed into a flat shape by being wound while rotating, a non-aqueous electrolyte, and a battery case housing the wound electrode body,
The wound electrode body has a flat portion with a flat surface that is present in the longitudinal center portion of the cross section perpendicular to the winding axis, and exists at both ends of the cross section that sandwich the flat portion in the longitudinal direction. It has two R parts with curved surfaces,
At one end of the wound electrode body in the winding axis direction, a positive electrode current collector foil laminate is laminated with an exposed portion of the positive electrode current collector foil on which the positive electrode active material layer is not formed protruding from the negative electrode. and at the other end, there is a negative electrode current collector foil laminated part in which the exposed part of the negative electrode current collector foil on which the negative electrode active material layer is not formed is laminated with the exposed part of the negative electrode current collector foil protruding from the positive electrode. ,
Here, in at least one of the positive electrode current collector foil laminated portion and the negative electrode current collector foil laminated portion, an infiltration path of the non-aqueous electrolyte is greater than that in the surrounding area in at least one of the two R portions. A non-aqueous electrolyte secondary battery, characterized in that a through hole is formed that penetrates the R portion as an expanded electrolyte infiltration expansion path.

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