JP7237054B2 - secondary battery - Google Patents

Description

The present invention relates to secondary batteries.

For example, Patent Literature 1 discloses a secondary battery including a wound electrode body. In the wound electrode body, active material layers containing a powdery active material are formed on both sides of a long metal foil current collector. A plurality of discontinuous linear slits are formed throughout the metal foil current collector.

When manufacturing the secondary battery disclosed in Patent Document 1, first, an active material layer is formed on one surface of a metal foil current collector. After that, a plurality of slits are formed in the metal foil current collector from the other side of the metal foil current collector. Then, an active material layer is formed on the other surface of the metal foil current collector. As a result, when the metal foil current collector is wound, the slits allow the metal foil current collector to follow the elongation of the active material layer, making it difficult for twisting and distortion to occur.

Further, Patent Document 2 discloses a technique of permeating a wound electrode body with a non-aqueous electrolyte in a secondary battery. In the secondary battery disclosed in Patent Document 2, the positive electrode plate and the negative electrode plate of the wound electrode body are provided with an uncoated portion where no active material layer is formed at one end in the winding axial direction. there is A plurality of slits extending in the winding axis direction are formed in this uncoated portion. As a result, the non-aqueous electrolyte enters the wound electrode body through the slits and permeates the wound electrode body.

JP-A-7-192726 JP 2006-221817 A

By the way, in the secondary battery disclosed in Patent Document 2, the non-aqueous electrolytic solution is easily permeated into both end portions of the wound electrode body in the winding axial direction, but the non-aqueous electrolyte is easily penetrated over the entire wound electrode body. It took time to allow the electrolyte to permeate. Further, in the secondary battery disclosed in Patent Document 1, even if the non-aqueous electrolyte can pass through the slits of the metal foil current collector and permeate the wound electrode body, Since the slits are formed over the entire metal foil current collector, it is difficult to ensure strength for the wound electrode assembly.

The secondary battery proposed here includes a wound electrode body, a non-aqueous electrolyte, and a battery case. In the wound electrode body, at least a positive electrode sheet and a negative electrode sheet are superimposed and wound in a predetermined winding direction about a winding axis. The battery case accommodates the wound electrode assembly and the non-aqueous electrolyte. Each of the positive electrode sheet and the negative electrode sheet has a sheet-like current collector and an electrode active material layer formed on the current collector and containing an electrode active material. A slit is formed in the current collector of at least one of the positive electrode sheet and the negative electrode sheet at the central portion in the winding axis direction in the region where the positive electrode sheet and the negative electrode sheet overlap. Slits are not formed in the portion of the current collector other than the central portion.

According to the secondary battery proposed here, both ends of the wound electrode assembly in the winding axial direction are open. The non-aqueous electrolyte permeates into the wound electrode body through slits formed in the current collector in addition to the openings at both ends in the winding axis direction of the wound electrode body. Therefore, the non-aqueous electrolyte can be easily permeated into the wound electrode body. Moreover, since the slit is not formed in the portion of the current collector 82 other than the central portion in the winding axial direction, the strength of the wound electrode assembly can be ensured.

In the secondary battery proposed here, slits may be formed in the current collectors of both the positive electrode sheet and the negative electrode sheet. The electrode active material layer may not be formed on the portion of the current collector where the slits are formed. Also, a plurality of slits may be formed in the current collector along the winding direction.

In the secondary battery proposed here, the wound electrode body may be formed by stacking and winding a positive electrode sheet, a negative electrode sheet, and a separator. In this case, the slit may be formed in the portion of the separator that overlaps the positive electrode sheet and the negative electrode sheet.

In the secondary battery proposed here, the slit is formed in a portion of the current collector located on one side in the longitudinal direction of the wound electrode body relative to the winding axis of the wound electrode body, and It may not be formed on the portion of the current collector positioned on the other side in the longitudinal direction of the winding axis of the electrode assembly.

1 is a cross-sectional view schematically showing the internal structure of a secondary battery according to an embodiment; FIG. FIG. 2 is a schematic diagram showing the configuration of a wound electrode body of a secondary battery according to an embodiment, and is a partially developed diagram. FIG. 3 is a schematic diagram showing the unfolded state of the positive electrode sheet, the negative electrode sheet, and the separator. FIG. 5 is a schematic diagram showing the configuration of a wound electrode body of a secondary battery according to a modification; FIG. 10 is a schematic diagram showing a state in which a positive electrode sheet according to a modified example is unfolded;

Hereinafter, one embodiment of the secondary battery disclosed herein will be described with reference to the drawings. Matters other than those specifically referred to in this specification that are necessary for implementation can be grasped as design matters for those skilled in the art based on the prior art in the relevant field. The present invention can be implemented based on the contents disclosed in this specification and common general technical knowledge in the field. In the drawings below, members and portions having the same function are denoted by the same reference numerals. Also, the dimensional relationships (length, width, thickness, etc.) in each drawing do not reflect the actual dimensional relationships.

As used herein, the term “battery” is a general term for power storage devices from which electrical energy can be extracted, and is a concept that includes primary batteries and secondary batteries. "Secondary battery" generally refers to an electricity storage device that can be repeatedly charged and discharged, and includes so-called storage batteries such as lithium secondary batteries, nickel-hydrogen batteries, and nickel-cadmium batteries. Hereinafter, the secondary battery disclosed herein will be described in detail by exemplifying a lithium-ion secondary battery, which is a type of secondary battery. However, the secondary battery disclosed here is not limited to the embodiments described here.

FIG. 1 is a cross-sectional view schematically showing the internal structure of a secondary battery 100 according to this embodiment. As shown in FIG. 1 , a secondary battery 100 according to this embodiment is a sealed lithium ion secondary battery that includes a battery case 30 , a wound electrode assembly 20 , and a non-aqueous electrolyte 10 .

The battery case 30 accommodates the wound electrode body 20 and the non-aqueous electrolyte 10 in a sealed state. In this embodiment, the shape of the battery case 30 is a rectangular parallelepiped, which is a flat square. Battery case 30 includes main body 31 and lid 32 . The main body 31 is a rectangular hollow member having an opening (not shown) at one end (for example, upper end). The lid 32 is a plate-like member that closes the opening of the main body 31 . The lid 32 is attached to the main body 31 .

The lid 32 is provided with a positive terminal 42 and a negative terminal 44 for external connection, and a safety valve 36 . The safety valve 36 releases the internal pressure when the internal pressure of the battery case 30 rises above a predetermined pressure. Further, the battery case 30 is provided with an injection port (not shown) for injecting the non-aqueous electrolyte 10 into the main body 31 . Although the material of the battery case 30 is not particularly limited, as the material of the battery case 30, for example, a metal material such as aluminum that is lightweight and has high thermal conductivity is used.

FIG. 2 is a schematic diagram showing the structure of the wound electrode body 20 of the secondary battery 100 according to this embodiment. As shown in FIG. 2 , the wound electrode assembly 20 has a long positive electrode sheet 50 , a long negative electrode sheet 60 , and a long separator 70 . In this embodiment, the separator 70 has a first separator 71 and a second separator 72, and is composed of two separators. In the wound electrode body 20, at least a positive electrode sheet 50 and a negative electrode sheet 60 are superimposed and wound in a predetermined winding direction D11 around a winding axis W1. In the wound electrode body 20 according to the present embodiment, the positive electrode sheet 50 and the negative electrode sheet 60 are overlapped with the separator 70 and wound. Specifically, the positive electrode sheet 50, the first separator 71, the negative electrode sheet 60, and the second separator 72 are stacked in this order in the winding direction D11 and wound around the winding axis W1.

The positive electrode sheet 50 and the negative electrode sheet 60 each have a current collector 82 and an electrode active material layer 84 containing an electrode active material. The current collector 82 is long and sheet-like. The electrode active material layer 84 is formed on one side or both sides (both sides in this embodiment) of the current collector 82 so as to extend in the winding direction D11.

In the present embodiment, in the positive electrode sheet 50 , the current collector 82 is also referred to as the positive electrode current collector 52 , and the electrode active material layer 84 is also referred to as the positive electrode active material layer 54 . The positive electrode active material layer 54 contains a positive electrode active material, which is an example of an electrode active material. Here, the positive electrode active material layer 54 is formed at one end (the left end in FIG. 2) of the sheet-like positive electrode current collector 52 in the direction in which the winding axis W1 extends (here, the winding axis direction D12). A non-formed portion 52a is provided. Here, the winding axial direction D12 is the direction along the lateral direction of the positive electrode sheet 50 when unfolded. The non-formed portion 52a of the positive electrode sheet 50 is a portion where the positive electrode current collector 52 is exposed. As shown in FIG. 1 , the positive electrode current collecting plate 42 a is joined to the unformed portion 52 a of the positive electrode sheet 50 . A positive terminal 42 is electrically connected to the positive collector plate 42a.

In this embodiment, for the positive electrode current collector 52, a material used as a positive electrode current collector for this type of secondary battery can be used without particular limitation. As the positive electrode current collector 52, it is preferable to use a positive electrode current collector made of metal having good conductivity. Metal materials such as aluminum, nickel, titanium, and stainless steel can be used as the positive electrode current collector 52 . In particular, it is preferable to use aluminum (for example, aluminum foil) as the positive electrode current collector 52 .

Examples of the positive electrode active material contained in the positive electrode active material layer 54 include lithium composite metal oxides having a layered structure or a spinel structure (eg, LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNiO ₂ , LiCoO ₂ , _{LiFeO2 , LiMn2O4} , _{LiNi0.5Mn1.5O4} , _LiCrMnO4 , _{LiFePO4 ,} etc.) _. The positive electrode active material layer 54 is formed by dispersing a positive electrode active material and optionally used materials (eg, conductive materials, binders, etc.) in an appropriate solvent (eg, N-methyl-2-pyrrolidone: NMP) to form a paste. It can be formed by preparing a composition in the form of a slurry (or slurry), applying an appropriate amount of the composition to the surface of the positive electrode current collector 52, and drying the composition.

As shown in FIG. 2 , in the negative electrode sheet 60 , the current collector 82 is also called the negative electrode current collector 62 , and the electrode active material layer 84 is also called the negative electrode active material layer 64 . The negative electrode active material layer 64 contains a negative electrode active material, which is an example of an electrode active material. Here, an unformed portion 62a where the negative electrode active material layer 64 is not formed is formed on the end portion of the sheet-like negative electrode current collector 62 on the other end side (the right end side in FIG. 2) in the direction in which the winding axis W1 extends. is provided. The unformed portion 62a of the negative electrode sheet 60 is a portion where the negative electrode current collector 62 is exposed. As shown in FIG. 1, the negative electrode current collecting plate 44a is joined to the unformed portion 62a of the negative electrode sheet 60. As shown in FIG. A negative electrode terminal 44 is electrically connected to the negative electrode current collecting plate 44a.

In this embodiment, for the negative electrode current collector 62, a material that is used as a negative electrode current collector for this type of secondary battery can be used without particular limitation. As the negative electrode current collector 62, a metal negative electrode current collector having good conductivity is preferably used. As the negative electrode current collector 62, for example, copper (for example, copper foil) or an alloy mainly composed of copper can be used.

As the negative electrode active material contained in the negative electrode active material layer 64, for example, a particulate (or spherical or scale-like) carbon material having a graphite structure (for example, a layered structure) at least in part, a lithium transition metal composite oxide (for example, Li ₄ Ti ₅ O ₁₂ and other lithium-titanium composite oxides), lithium-transition metal composite nitrides, and the like. The negative electrode active material layer 64 is formed by dispersing a negative electrode active material and optionally used materials (such as a binder) in an appropriate solvent (such as ion-exchanged water) to prepare a paste (or slurry) composition. is adjusted, an appropriate amount of the composition is applied to the surface of the negative electrode current collector 62, and dried.

As shown in FIG. 2, as separators 70 (specifically, first separator 71 and second separator 72), conventionally known separators made of porous sheets can be used without particular limitation. Examples of the separator 70 include a porous sheet (eg, film, nonwoven fabric, etc.) made of resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such a porous sheet may have a single-layer structure or a multi-layer structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). Moreover, one side or both sides of the porous sheet may be provided with a porous heat-resistant layer. This heat-resistant layer can be, for example, a layer containing an inorganic filler and a binder (for example, a filler layer). As inorganic fillers, for example, alumina, boehmite, silica, etc. can be preferably employed.

As shown in FIG. 1, the non-aqueous electrolyte 10 contained in the battery case 30 together with the wound electrode body 20 contains a supporting salt in an appropriate non-aqueous solvent. It can be used without any particular restrictions. Examples of non-aqueous solvents that can be used include ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), and ethylmethyl carbonate (EMC). Also, as the supporting salt, for example, a lithium salt (eg, LiBOB, _LiPF6, etc.) can be preferably used. In this embodiment, LiBOB is employed as the supporting electrolyte. In this case, the LiBOB content in the non-aqueous electrolyte 10 is preferably 0.3 wt % to 0.6 wt %.

Next, the wound electrode body 20 according to this embodiment will be described in more detail. As shown in FIG. 2 , the wound electrode body 20 has a first R portion 21 , a second R portion 22 and a flat portion 23 . The first R portion 21 and the second R portion 22 are portions of the wound electrode body 20 formed with a radius when viewed from the winding axial direction D12. As shown in FIG. 1, the first R portion 21 constitutes one end portion of the wound electrode body 20 in a longitudinal direction D13 perpendicular to the direction of the winding axis W1 (here, the winding axis direction D12). The second R portion 22 faces the first R portion 21 across the winding axis W1, and constitutes the other end of the wound electrode body 20 in the longitudinal direction D13. The flat portion 23 is arranged between the first R portion 21 and the second R portion 22, and has two flat surfaces 24 facing each other as shown in FIG. The flat surface 24 is a flat surface extending in the longitudinal direction D13.

In this embodiment, the wound electrode body 20 is relatively long in the winding axial direction D12. For example, in the wound electrode assembly 20 according to the present embodiment, the length in the winding axial direction D12 is in the range of 2 to 100 times the length in the longitudinal direction D13, preferably in the range of 5 to 50 times. and particularly preferably in the range of 10 to 35 times.

As shown in FIG. 2, slits 90 are formed in the current collector 82 of at least one of the positive electrode sheet 50 and the negative electrode sheet 60 in the overlap region AR1 where the positive electrode sheet 50 and the negative electrode sheet 60 overlap. In this embodiment, the slits 90 are formed in the current collectors 82 of both the positive electrode sheet 50 and the negative electrode sheet 60 (specifically, the positive electrode current collector 52 and the negative electrode current collector 62). Furthermore, the slit 90 is formed in the portion of the separator 70 that overlaps the positive electrode sheet 50 and the negative electrode sheet 60 (in other words, overlaps the overlapping region AR1). That is, the slits 90 are also formed in the first separator 71 and the second separator 72 . Hereinafter, the slits 90 formed in the positive electrode current collector 52, the negative electrode current collector 62, and the separator 70 are also referred to as a positive electrode slit 91, a negative electrode slit 92, and a separator slit 93, respectively.

FIG. 3 is a schematic diagram showing a state in which the positive electrode sheet 50, the negative electrode sheet 60 and the separator 70 are unfolded. In the present embodiment, as shown in FIG. 3, the slits 90 are formed in the winding direction D11 in each of the current collector 82 (specifically, the positive electrode current collector 52 and the negative electrode current collector 62) and the separator 70. A plurality of them are formed so as to line up. Specifically, a plurality of positive electrode slits 91 are formed in the positive electrode current collector 52 so as to be aligned in the winding direction D11. Similarly, a plurality of negative electrode slits 92 are formed in the negative electrode current collector 62 so as to line up in the winding direction D11, and a plurality of separator slits 93 are formed in the separator 70 to line up in the winding direction D11. These slits 90 are arranged discontinuously.

Here, the slits 90 are arranged in a row along the winding direction D11 in each of the current collector 82 and the separator 70 . However, the number of rows in which the slits 90 are arranged in each of the current collector 82 and the separator 70 is not limited to one, and may be two or three. That is, in each of the current collector 82 and the separator 70, the number of rows in which the slits 90 are arranged may be plural.

As described above, as shown in FIG. 2, the region where the positive electrode sheet 50 and the negative electrode sheet 60 overlap is called an overlapping region AR1. This overlap region AR1 is a region where the positive electrode current collector 52 and the negative electrode current collector 62 overlap, and is also a region where the separator 70 overlaps. The slits 90 are formed in the portion of the current collector 82 (specifically, the positive electrode current collector 52 and the negative electrode current collector 62) located in the overlap region AR1 and the separator 70 portion. Here, the slits 90 are formed in the portion of the current collector 82 and the portion of the separator 70 located in the central portion of the overlapping region AR1 in the winding axis direction D12. Moreover, the slits 90 are not formed in the current collector 82 and separator 70 portions other than the central portion in the winding axial direction D12. Here, the central portion in the winding axial direction D12 refers to, for example, the central portion when the current collector 82 is divided into three equal parts in the winding axial direction D12.

In the present embodiment, as shown in FIG. 2, a portion of the current collector 82 located on the central axis W2 along the winding direction D11 passing through the center C1 of the winding axis direction D12 in the overlap region AR1, and A slit 90 is formed in the separator 70 portion. Here, in the state where the wound electrode body 20 is wound, the position of the positive electrode slit 91 in the winding axial direction D12, the position of the negative electrode slit 92 in the winding axial direction D12, and the winding axial direction of the separator slit 93 are shown. The position of D12 is the same.

In the present embodiment, as shown in FIG. 3, the slits 90 are formed in each of the current collector 82 and the separator 70 from the end of the winding start side (for example, the lower side of FIG. 3) to the winding end side (for example, the lower side of FIG. For example, they are formed at predetermined intervals (for example, constant intervals) over the edge of the upper side of FIG. However, in each of current collector 82 and separator 70, slits 90 may not be formed in a portion of winding direction D11. For example, taking the slit 90 formed in the current collector 82 as an example, the slit 90 may be formed only in a portion of the current collector 82 from the winding start to a predetermined number of turns. Alternatively, the slits 90 may be formed only in a portion of the current collector 82 from the winding end to a predetermined number of turns.

Note that the shape and size of the slit 90 are not particularly limited. In this embodiment, the plurality of slits 90 have the same shape and size. However, some slits 90 among the plurality of slits 90 may differ from other slits 90 in shape or size. In other words, in the present embodiment, the positive electrode slit 91, the negative electrode slit 92, and the separator slit 93 have the same shape and the same size, but may have different shapes or different sizes. . In addition, although the plurality of positive electrode slits 91 (or the plurality of negative electrode slits 92 or the separator slits 93) have the same shape and the same size, some of the slits may have different shapes or different sizes. may be

In this embodiment, as shown in FIG. 3, the slits 90 (specifically, the positive electrode slit 91, the negative electrode slit 92 and the separator slit 93) are cuts extending in the winding direction D11. The shape of the slit 90 is linear. The length of the slit 90 (specifically, the length in the winding direction D11) is 1 mm to 50 mm, preferably 1 mm to 10 mm, particularly preferably 1 mm to 5 mm. However, the slits 90 may be short in the winding direction D11, that is, in the form of dots. In the present embodiment, the slit 90 allows the non-aqueous electrolyte 10 to pass through and penetrates the current collector 82 and the separator 70. shall be included. In the present embodiment, the intervals between the slits 90 arranged in the winding direction D11 are the same in each of the current collector 82 and the separator 70, but they may be different.

In this embodiment, the electrode active material layer 84 is not formed on the portion of the current collector 82 where the slits 90 are formed. Here, the portion of the current collector 82 where the electrode active material layer 84 is not formed along the slit 90 is referred to as a slit-side unformed portion 86 . The slit-side unformed portion 86 is different from the unformed portions 52a and 62a to which the positive collector plate 42a (see FIG. 1) and the negative collector plate 44a (see FIG. 1) are joined. Here, as shown in FIG. 3, the slit-side unformed portion 86 of the positive electrode sheet 50 is also referred to as the positive slit-side unformed portion 56, and the slit-side unformed portion 86 of the negative electrode sheet 60 is also referred to as the negative electrode slit. It is also called side unformed portion 66 .

In this embodiment, a slit 90 is formed in the slit-side unformed portion 86 . The slit-side unformed portion 86 extends along the winding direction D11. Current collectors 82 are arranged on both sides of the slit-side unformed portion 86 in the winding axial direction D12. In the present embodiment, the slit-side unformed portion 86 is continuous in the winding direction D11. The electrode active material layer 84 may be formed without the unformed portion 86 . That is, the slit-side unformed portion 86 is provided at least in the portion of the current collector 82 where the slit 90 is formed, and may be provided discontinuously in the winding direction D11.

In the present embodiment, the length of the slit-side unformed portion 86 in the winding axial direction D12 is shorter than the length of the unformed portion 52a of the positive electrode sheet 50 in the winding axial direction D12, but may be longer. The length of the slit-side unformed portion 86 in the winding axial direction D12 is shorter than the length of the unformed portion 62a of the negative electrode sheet 60 in the winding axial direction D12, but may be longer. However, the length of the slit-side unformed portion 86 in the winding axial direction D12 may be the same as the length of the unformed portions 52a and 62a in the winding axial direction D12. The length of the slit-side unformed portion 86 in the winding axis direction D12 is 1 mm to 10 mm, preferably 1 mm to 5 mm, and particularly preferably 1 mm to 3 mm.

In this embodiment, as shown in FIG. 2, the positive slit-side unformed portion 56 and the negative slit-side unformed portion 66 overlap each other when the wound electrode assembly 20 is wound. The length of the positive electrode slit-side unformed portion 56 in the winding axial direction D12 and the length of the negative electrode slit-side unformed portion 66 in the winding axial direction D12 are the same. However, the length of the positive electrode slit-side unformed portion 56 in the winding axial direction D12 may be longer or shorter than the length of the negative electrode slit-side unformed portion 66 in the winding axial direction D12.

The method of forming the slits 90 and the slit-side unformed portions 86 in the current collector 82 of the wound electrode body 20 is not particularly limited. For example, when forming the electrode active material layer 84 on the current collector 82, a paste-like (or slurry-like) composition containing the electrode active material is prepared, and the composition is applied on the current collector 82. An electrode active material layer 84 may be formed. At this time, the slit-side unformed portion 86 is provided on the current collector 82 by not applying the composition containing the electrode active material to the portion of the current collector 82 where the slit-side unformed portion 86 is to be provided. can be done. Then, a slit 90 is formed in the slit-side unformed portion 86 using, for example, a knife. Also, a slit 90 is formed in the separator 70 using, for example, a knife. Thus, the wound electrode body 20 according to this embodiment can be produced.

As described above, in the present embodiment, as shown in FIG. 2, the secondary battery 100 includes at least the positive electrode sheet 50 and the negative electrode sheet 60 that are superimposed and wound in a predetermined winding direction D11 about the winding axis W1. a wound electrode assembly 20, a non-aqueous electrolyte 10 (see FIG. 1), and a battery case 30 (see FIG. 1) that houses the wound electrode assembly 20 and the non-aqueous electrolyte 10. As shown in FIG. 2, each of the positive electrode sheet 50 and the negative electrode sheet 60 has a sheet-like current collector 82 and an electrode active material layer 84 formed on the current collector 82 and containing an electrode active material. . A slit 90 is formed in the current collector 82 of at least one of the positive electrode sheet 50 and the negative electrode sheet 60 at the central portion in the winding axial direction D12 in the overlap region AR1 where the positive electrode sheet 50 and the negative electrode sheet 60 overlap. there is The slit 90 is not formed in the portion of the current collector 82 excluding the central portion in the winding axial direction D12. Both ends of the wound electrode body 20 in the winding axial direction D12 are open. Therefore, the non-aqueous electrolyte 10 permeates into the wound electrode body 20 through the slits 90 formed in the current collector 82 in addition to the openings at both ends of the wound electrode body 20 in the winding axial direction D12. do. Therefore, the non-aqueous electrolytic solution 10 can be more easily permeated into the wound electrode body 20 than in the conventional case, and the non-aqueous electrolytic solution 10 can be efficiently permeated into the wound electrode body 20 . Further, in the present embodiment, since the slit 90 is not formed in the current collector 82 other than the central portion in the winding axial direction D12, the strength of the wound electrode body 20 can be ensured.

In this embodiment, the slits 90 are formed in the current collectors 82 of both the positive electrode sheet 50 and the negative electrode sheet 60 . As a result, the non-aqueous electrolyte 10 passes through the positive electrode sheet 50 through the positive electrode slit 91, which is the slit 90 on the positive electrode sheet 50 side, and passes through the negative electrode slit 92, which is the slit 90 on the negative electrode sheet 60 side, to the negative electrode sheet. 60 can be passed. Therefore, the non-aqueous electrolytic solution 10 can more efficiently permeate the wound electrode assembly 20 .

In this embodiment, the electrode active material layer 84 is not formed on the portion of the current collector 82 where the slits 90 are formed. As a result, it is not necessary to form the slits 90 in the electrode active material layer 84, so that the operation of forming the slits 90 in the current collector 82 can be easily performed.

In this embodiment, as shown in FIG. 3, a plurality of slits 90 are formed in the current collector 82 along the winding direction D11. This makes it easier for the non-aqueous electrolyte 10 to permeate the entire wound electrode assembly 20 efficiently.

In this embodiment, as shown in FIG. 2, the wound electrode body 20 is formed by stacking a positive electrode sheet 50, a negative electrode sheet 60, and a separator 70 and winding them. Slits 90 (specifically, separator slits 93 ) are formed in portions of the separator 70 overlapping the positive electrode sheet 50 and the negative electrode sheet 60 . This allows the non-aqueous electrolyte 10 to pass through the separator 70 through the separator slit 93 . Therefore, the non-aqueous electrolytic solution 10 can more efficiently permeate the wound electrode assembly 20 .

In the above embodiment, the slits 90 are formed in the current collector 82 so as to be evenly spaced along the winding direction D11, and extend along the length of the wound electrode body 20 in the wound state. It was formed from one end to the other end in the direction D13. However, like the wound electrode body 20A shown in the modification of FIGS. 4 and 5, the slit 90A is formed in a part of the wound electrode body 20 in the longitudinal direction D13 and not formed in the other part. It doesn't have to be. Here, as shown in FIG. 4 , the portion of the wound electrode body 20 on one side (here, the first R portion 21 side) of the winding axis W1 is referred to as a first portion 25 . On the other hand, the portion of the wound electrode assembly 20 on the other side (here, the second R portion 22 side) of the winding axis W1 is called a second portion 26 .

Here, slits 90A are formed in the portion of the current collector 82 (specifically, the positive electrode current collector 52 and the negative electrode current collector 62) located in the first portion 25 and the separator 70 portion. On the other hand, slits 90A are not formed in the current collector 82 portion located in the second portion 26 and the separator 70 portion. Therefore, as shown in FIG. 5, the intervals between the slits 90A arranged in the winding direction D11 are not constant. 5 shows only the slit 90A formed in the positive electrode current collector 52 of the positive electrode sheet 50, the slit 90A formed in the negative electrode current collector 62 of the negative electrode sheet 60 is The spacing and the shape, size, and spacing of the slits 90A formed in the separator 70 are the same as those of the slits 90A formed in the positive electrode current collector 52. FIG.

According to this modification, the non-aqueous electrolyte 10 can easily permeate the wound electrode body 20 in the first portion 25 , so that the non-aqueous electrolyte 10 can efficiently permeate the wound electrode body 20 . . Since the slit 90A is not formed in the second portion 26, the strength of the wound electrode body 20 can be ensured. Thus, according to this modification, the strength of the wound electrode body 20 can be secured while the non-aqueous electrolyte solution 10 is allowed to permeate the wound electrode body 20 efficiently.

In the above embodiment, the slits 90 were formed in the current collectors 82 of both the positive electrode sheet 50 and the negative electrode sheet 60 (specifically, the positive electrode current collector 52 and the negative electrode current collector 62). However, the slits 90 may be formed in one of the positive electrode current collector 52 and the negative electrode current collector 62 and not formed in the other. For example, the slits 90 may be formed in the positive electrode current collector 52 and not formed in the negative electrode current collector 62 . Even in this case, the non-aqueous electrolytic solution 10 can be permeated through the slits 90, so that the non-aqueous electrolytic solution 10 can be efficiently permeated into the wound electrode assembly 20 as compared with the conventional case.

In the above embodiment, the slits 90 were formed in the separator 70 . However, slits 90 may not be formed in separator 70 .

In the above-described embodiment, the electrode active material layer 84 is not formed in the portion of the current collector 82 where the slits 90 are formed, and the slits 90 are provided in the slit-side unformed portion 86 . However, the electrode active material layer 84 may be formed on the portion of the current collector 82 where the slits 90 are formed. That is, the slit-side unformed portion 86 may be omitted. In this case, slits may be formed in the electrode active material layer 84 at positions overlapping the slits 90 formed in the current collector 82 .

REFERENCE SIGNS LIST 10 Non-aqueous electrolyte 20 Wound electrode body 30 Battery case 50 Positive electrode sheet 60 Negative electrode sheet 70 Separator 82 Current collector 84 Electrode active material layer 90, 90A Slit 91 Positive electrode slit 92 Negative electrode slit 93 Separator slit 100 Secondary battery AR1 Overlapping region D11 winding direction D12 winding axis direction W1 winding axis

Claims (5)

a wound electrode body in which a positive electrode sheet, a negative electrode sheet , and a separator are superimposed and wound in a predetermined winding direction around a winding axis;
a non-aqueous electrolyte;
a battery case containing the wound electrode body and the non-aqueous electrolyte;
with
The separator is disposed between the positive electrode sheet and the negative electrode sheet,
Each of the positive electrode sheet and the negative electrode sheet has a sheet-like current collector and an electrode active material layer formed on the current collector and containing an electrode active material,
The electrode active material layer is formed on the current collector of at least one of the positive electrode sheet and the negative electrode sheet in the central portion in the winding axis direction in the region where the positive electrode sheet and the negative electrode sheet overlap. A slit side unformed portion that is not formed is provided,
A slit is formed in the slit-side unformed portion of the current collector ,
The secondary battery, wherein the slit is not formed in a portion of the current collector other than the central portion. 2. The secondary battery according to claim 1, wherein said slits are formed in said current collectors of both said positive electrode sheet and said negative electrode sheet. 3. The secondary battery according to claim 1 , wherein a plurality of said slits are formed in said current collector along said winding direction. a wound electrode body in which a positive electrode sheet, a negative electrode sheet, and a separator are superimposed and wound in a predetermined winding direction around a winding axis;
a non-aqueous electrolyte;
a battery case containing the wound electrode body and the non-aqueous electrolyte;
with
The separator is disposed between the positive electrode sheet and the negative electrode sheet,
Each of the positive electrode sheet and the negative electrode sheet has a sheet-like current collector and an electrode active material layer formed on the current collector and containing an electrode active material,
A slit is formed in the current collector of at least one of the positive electrode sheet and the negative electrode sheet at a central portion in the winding axis direction in the region where the positive electrode sheet and the negative electrode sheet overlap,
The slit is not formed in the current collector portion except for the central portion,
The secondary battery, wherein the slit is formed in a portion of the separator that overlaps the positive electrode sheet and the negative electrode sheet. a wound electrode body in which a positive electrode sheet, a negative electrode sheet, and a separator are superimposed and wound in a predetermined winding direction around a winding axis;
a non-aqueous electrolyte;
a battery case containing the wound electrode body and the non-aqueous electrolyte;
with
The separator is disposed between the positive electrode sheet and the negative electrode sheet,
Each of the positive electrode sheet and the negative electrode sheet has a sheet-like current collector and an electrode active material layer formed on the current collector and containing an electrode active material,
A slit is formed in the current collector of at least one of the positive electrode sheet and the negative electrode sheet at a central portion in the winding axis direction in the region where the positive electrode sheet and the negative electrode sheet overlap,
The slit is not formed in the current collector portion except for the central portion,
The slit is formed in a portion of the current collector located on one side in the longitudinal direction of the wound electrode body relative to the winding axis of the wound electrode body, and A secondary battery that is not formed on a portion of the current collector located on the other side in the longitudinal direction of the winding axis.

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