WO2022264526A1

WO2022264526A1 - Secondary battery

Info

Publication number: WO2022264526A1
Application number: PCT/JP2022/007293
Authority: WO
Inventors: 敏高橋
Original assignee: 株式会社村田製作所
Priority date: 2021-06-14
Filing date: 2022-02-22
Publication date: 2022-12-22

Abstract

This secondary battery is provided with: a conductive outer package member which has a through hole; a battery element which is contained in the outer package member, while comprising a first electrode and a second electrode; an electrode terminal which is arranged outside the outer package member, while blocking the through hole; an insulating sealing member which is arranged between the outer package member and the electrode terminal; a wiring member which is connected to the first electrode and the electrode terminal through the through hole; and an insulating cover member which covers the surface of the wiring member. The wiring member comprises a turn-back part in which the wiring member is turned back within the through hole in the radially inward direction of the through hole; and the cover member covers at least the outer surface of the turn-back part.

Description

secondary battery

This technology relates to secondary batteries.

Due to the widespread use of various electronic devices such as mobile phones, the development of secondary batteries is underway as a power source that is compact, lightweight, and provides high energy density. This secondary battery has battery elements (a positive electrode, a negative electrode, and an electrolyte) inside an exterior member, and various studies have been made on the configuration of the secondary battery.

Specifically, an electrode body is housed inside an exterior case, a flat electrode terminal member is arranged outside the exterior case via a sealing member, and a lead body connected to the electrode body is It is connected to the flat electrode terminal member via an insertion hole provided in the exterior case (see, for example, Patent Document 1).

A wound electrode body is housed inside an exterior body having a crimped sealing structure, a lead connected to the wound electrode body is connected to a safety valve, and the lead is folded back in the middle ( For example, see Patent Document 2.).

An electrode group is housed inside a battery can having a crimped sealing structure, a lead connected to the electrode group is connected to an explosion-proof valve body, and the surface of the lead is covered with an insulating tape. (For example, see Patent Document 3.).

JP 2019-046639 A JP 2016-001615 A JP-A-10-302751

Various studies have been conducted on the configuration of secondary batteries, but the battery capacity characteristics, physical durability, and operational reliability of the secondary batteries are still insufficient, so there is room for improvement.

Therefore, a secondary battery capable of obtaining excellent battery capacity characteristics, excellent physical durability, and excellent operational reliability is desired.

A secondary battery according to an embodiment of the present technology includes a conductive exterior member having a through hole, a battery element housed inside the exterior member and including a first electrode and a second electrode, and the exterior member. An electrode terminal disposed outside and shielding the through-hole; an insulating sealing member disposed between the exterior member and the electrode terminal; and a first electrode and the electrode terminal via the through-hole. It is provided with wiring members connected to each other and an insulating covering member covering the surface of the wiring members. The wiring member includes a folded portion in which the wiring member is folded back in the inner diameter direction of the through hole inside the through hole, and the covering member covers at least the outer surface of the folded portion.

Here, the “outer surface” of the folded portion means that when the wiring member is folded inside the through hole provided in the exterior member, the folded wiring members face each other (or approach each other). It is the surface on the side opposite to the surface on the side that touches. More specifically, the outer surface is the surface on the side facing the inner wall surface of the exterior member inside the through hole and the exposed surface of the electrode terminal in the through hole. Details of the "outer surface" will be described later.

According to the secondary battery of one embodiment of the present technology, the battery element including the first electrode and the second electrode is housed inside the exterior member having the through hole, and the electrode is arranged outside the exterior member. A terminal shields the through-hole, a wiring member is connected to the first electrode and the electrode terminal via the through-hole, and an insulating covering member covers the surface of the wiring member. The wiring member includes a folded portion, the wiring member is folded back in the inner diameter direction of the through hole inside the through hole at the folded portion, and the covering member covers at least the outer surface of the folded portion, Excellent battery capacity characteristics, excellent physical durability and excellent operational reliability can be obtained.

It should be noted that the effects of the present technology are not necessarily limited to the effects described here, and may be any of a series of effects related to the present technology described below.

It is a perspective view showing composition of a secondary battery in one embodiment of this art. 2 is an enlarged cross-sectional view showing the configuration of the secondary battery shown in FIG. 1; FIG. 3 is an enlarged sectional view showing the configuration of the battery element shown in FIG. 2; FIG. 3 is an enlarged cross-sectional view showing the configuration of the positive electrode lead shown in FIG. 2; FIG. FIG. 3 is an enlarged cross-sectional view showing the structure of the sealant shown in FIG. 2; FIG. 4 is a cross-sectional view for explaining the operation of the secondary battery; It is a perspective view for explaining a manufacturing process of a secondary battery. FIG. 8 is a cross-sectional view for explaining the manufacturing process of the secondary battery continued from FIG. 7; 3 is a cross-sectional view showing the configuration of a secondary battery in Modification 1. FIG. 10 is a cross-sectional view showing another configuration of the secondary battery in Modification 1. FIG. FIG. 12 is a cross-sectional view showing the configuration of a secondary battery in Modification 4; 14 is a cross-sectional view showing the configuration of a secondary battery in Modification 5. FIG.

Hereinafter, one embodiment of the present technology will be described in detail with reference to the drawings. The order of explanation is as follows.

1. Secondary Battery 1-1. Configuration 1-2. Detailed Configuration of Positive Electrode Lead and Sealant 1-3. Operation 1-4. Manufacturing method 1-5. Action and effect 2 . Modification

<1. Secondary battery>
First, a secondary battery according to an embodiment of the present technology will be described.

The secondary battery described here has a flat and columnar three-dimensional shape, and is a so-called coin-shaped or button-shaped secondary battery. As will be described later, this secondary battery has a pair of bottom portions facing each other and side wall portions connected to each of the pair of bottom portions. Also, the secondary battery has an outer diameter and a height, and the height is smaller than the outer diameter. The "outer diameter" is the diameter (maximum diameter) of each of the pair of bottoms, and the "height" is the distance (maximum distance) from one bottom to the other bottom.

Although the charging and discharging principle of the secondary battery is not particularly limited, the case where the battery capacity is obtained by utilizing the absorption and release of the electrode reactant will be described below. The secondary battery includes a positive electrode, a negative electrode, and an electrolyte, and the charge capacity of the negative electrode is greater than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of the negative electrode is set to be larger than the electrochemical capacity per unit area of the positive electrode. This is to prevent electrode reactants from depositing on the surface of the negative electrode during charging.

The type of electrode reactant is not particularly limited, but specifically light metals such as alkali metals and alkaline earth metals. Examples of alkali metals are lithium, sodium and potassium, and examples of alkaline earth metals are beryllium, magnesium and calcium.

In the following, the case where the electrode reactant is lithium will be taken as an example. A secondary battery whose battery capacity is obtained by utilizing the absorption and release of lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is intercalated and deintercalated in an ionic state.

<1-1. Configuration>
FIG. 1 shows a perspective configuration of a secondary battery. FIG. 2 shows an enlarged cross-sectional configuration of the secondary battery shown in FIG. FIG. 3 shows an enlarged cross-sectional configuration of the battery element 40 shown in FIG. However, in FIG. 2, each of the positive lead 51 and the negative lead 52 is shaded. In FIG. 3, only part of the battery element 40 is shown.

In the following description, for convenience, the upper, lower, right, and left sides in FIG. 2 are the upper, lower, right, and left sides of the secondary battery.

The secondary battery shown in FIGS. 1 and 2 is a button type secondary battery and has an outer diameter D and a height H. This secondary battery has a three-dimensional shape in which the height H is smaller than the outer diameter D, that is, a flat and columnar three-dimensional shape. Here, the three-dimensional shape of the secondary battery is flat and cylindrical (columnar), and the ratio D/H of the outer diameter D to the height H is greater than one.

Although the specific dimensions of the secondary battery are not particularly limited, for example, the outer diameter D is 3 mm to 30 mm and the height H is 0.5 mm to 70 mm. The ratio D/H is preferably 25 or less.

1 to 3, the secondary battery includes an outer can 10, an external terminal 20, a gasket 30, a battery element 40, a positive electrode lead 51, a negative electrode lead 52, and a sealant 60. and an insulating film 70 .

[Outer can]
As shown in FIGS. 1 and 2, the exterior can 10 is a hollow exterior member that houses the battery element 40 and the like, and has a through hole 10K.

Here, the outer can 10 has a three-dimensional shape similar to the three-dimensional shape of the secondary battery, that is, it has a flat and columnar (cylindrical) three-dimensional shape. Thus, the outer can 10 has an upper bottom portion M1 and a lower bottom portion M2 facing each other, and a side wall portion M3. The side wall portion M3 is arranged between the upper base portion M1 and the lower base portion M2, and is connected to the upper base portion M1 and the lower base portion M2, respectively. Here, the planar shape of each of the upper base portion M1 and the lower base portion M2 is circular, and the surface of the side wall portion M3 is an outwardly convex curved surface.

The outer can 10 includes a storage portion 11 and a lid portion 12, and the storage portion 11 and the lid portion 12 are joined together. Here, as will be described later, since the storage portion 11 and the lid portion 12 are welded together, the storage portion 11 is sealed by the lid portion 12 .

The housing portion 11 is a substantially cylindrical member (lower bottom portion M2 and side wall portion M3) for housing the battery element 40 and the like therein. Here, the storage portion 11 has a structure in which the lower bottom portion M2 and the side wall portion M3 are integrated with each other. Since the housing portion 11 has a hollow structure with an open upper end and a closed lower end, it has an opening 11K at its upper end.

The lid portion 12 is a substantially disc-shaped member (upper bottom portion M1) that closes the opening portion 11K, and has the above-described through hole 10K. The through hole 10K is used as a connection path for electrically connecting the battery element 40 and the external terminal 20 to each other, as will be described later.

In the secondary battery after completion, the lid portion 12 is already joined to the housing portion 11 as described above, so that the opening portion 11K is closed by the lid portion 12 . For this reason, even if the external appearance of the secondary battery is observed, it may not be possible to confirm after the fact whether or not the storage portion 11 has the opening portion 11K.

However, in the manufacturing process of the secondary battery, when the storage portion 11 and the lid portion 12 are welded together in order to join the storage portion 11 and the lid portion 12 together, the surface of the outer can 10, more specifically, Ideally, there should be a weld mark left on the boundary between the storage portion 11 and the lid portion 12 . Therefore, based on the presence or absence of welding marks, it can be confirmed after the fact whether or not the storage portion 11 has the opening portion 11K.

That is, when the welding marks remain on the surface of the outer can 10 (the welding marks are visible), it means that the storage portion 11 has the opening 11K. On the other hand, if no welding marks remain on the surface of the outer can 10 (the welding marks cannot be visually recognized), it means that the storage portion 11 did not have the opening 11K.

Here, the lid portion 12 has a recessed portion 12U, and the through hole 10K is provided in the recessed portion 12U. In this recessed portion 12U, the lid portion 12 is bent so as to be partially recessed toward the inside of the storage portion 11, so that a portion of the lid portion 12 is bent so as to form a downward step.

The shape of the recessed portion 12U, that is, the shape defined by the outer edge of the recessed portion 12U when the secondary battery is viewed from above is not particularly limited. Here, the shape of the recessed portion 12U is circular. In addition, since the inner diameter and depth of the recessed portion 12U are not particularly limited, they can be set arbitrarily.

As described above, the outer can 10 is a can in which two members (the storage portion 11 and the lid portion 12) that are physically separated from each other are joined to each other, a so-called joined can. More specifically, the outer can 10 in which the storage portion 11 and the lid portion 12 are welded together is a so-called welded can. As a result, since the outer can 10 after bonding is physically one member as a whole, it cannot be separated into two members (the storage portion 11 and the lid portion 12) afterwards.

The outer can 10, which is a bonded can, is a so-called crimpless can, which is different from a crimped can formed using caulking. This is because the volumetric energy density increases because the element space volume increases inside the outer can 10 . This “element space volume” is the volume (effective volume) of the internal space of the outer can 10 that can be used to house the battery element 40 .

In addition, the outer can 10, which is a joint can, does not have a portion where two or more members overlap each other, and does not have a portion where two or more members overlap each other.

"Does not have a portion folded over" means that the outer can 10 is not processed (bent) so that a part of the outer can 10 is folded over. Further, "not having a portion where two or more members overlap each other" means that the outer can 10 is physically one member after the completion of the secondary battery. It literally means that it cannot be separated into two or more members. That is, the state of the outer can 10 in the secondary battery after completion is not a state in which two or more members are combined while overlapping each other so that they can be separated later.

Since the outer can 10 is an electrically conductive exterior member, each of the storage portion 11 and the lid portion 12 is electrically conductive. As a result, the outer can 10 is connected to the battery element 40 (negative electrode 42 to be described later) through the negative electrode lead 52 , and thus is electrically connected to the negative electrode 42 . Therefore, the outer can 10 functions as an external connection terminal for the negative electrode 42 . Since the secondary battery does not need to be provided with an external connection terminal for the negative electrode 42 separately from the outer can 10, the decrease in the element space volume due to the presence of the external connection terminal for the negative electrode 42 is suppressed. is. As a result, the element space volume increases, so the volumetric energy density increases.

Specifically, the outer can 10 contains one or more of conductive materials such as metallic materials and alloy materials. Specific examples of the metallic materials and alloy materials include iron, copper, , nickel, stainless steel, iron alloys, copper alloys and nickel alloys. The type of stainless steel is not particularly limited, but specific examples include SUS304 and SUS316. However, the material for forming the storage portion 11 and the material for forming the lid portion 12 may be the same as or different from each other.

Above all, the outer can 10 is preferably a so-called metal can. This is because the rigidity of the outer can 10 is improved, so that the outer can 10 is less likely to be deformed. This metal can is a can containing one or more of the metal materials and alloy materials described above.

Note that the lid portion 12 is insulated via a gasket 30 from the external terminal 20 functioning as an external connection terminal for the positive electrode 41, as will be described later. This is because contact (short circuit) between the outer can 10 (terminal for external connection of the negative electrode 42) and the external terminal 20 (terminal for external connection of the positive electrode 41) is prevented.

[External terminal]
The external terminal 20 is an electrode terminal connected to an electronic device when the secondary battery is mounted on the electronic device, as shown in FIGS. The external terminal 20 is arranged outside the outer can 10 and shields the through hole 10K.

Note that the external terminal 20 is supported by the outer can 10 via a gasket 30 . More specifically, the external terminal 20 is thermally welded to the lid portion 12 via a gasket 30, as will be described later. Thereby, the external terminal 20 is fixed to the lid portion 12 via the gasket 30 while being insulated from the lid portion 12 via the gasket 30 .

The external terminal 20 is electrically connected to the positive electrode 41 because it is connected to the battery element 40 (positive electrode 41 ) through the positive electrode lead 51 . Thereby, the external terminal 20 functions as an external connection terminal for the positive electrode 41 . When the secondary battery is used, the secondary battery is connected to the electronic device via the external terminal 20 (terminal for external connection of the positive electrode 41) and the outer can 10 (terminal for external connection of the negative electrode 42). becomes operable using a secondary battery as a power source.

Also, the external terminal 20 is a substantially plate-shaped member. Although the three-dimensional shape of the external terminal 20 is not particularly limited, it is specifically a flat plate shape.

Here, the external terminal 20 is arranged inside the recess 12U. That is, the external terminal 20 is housed inside the recessed portion 12U so as not to protrude outward (upward) from the recessed portion 12U. This is because the volume energy density is increased because the height H of the secondary battery is smaller than when the external terminal 20 protrudes outward beyond the recessed portion 12U.

Since the outer diameter of the external terminal 20 is smaller than the inner diameter of the recessed portion 12U, the external terminal 20 is separated from the lid portion 12 on the periphery. Thereby, the gasket 30 is arranged in at least part of the space between the lid portion 12 and the external terminal 20 inside the recess portion 12U. The lid portion 12 and the external terminal 20 are arranged at locations where they can come into contact with each other.

In addition, the external terminal 20 includes one or more of conductive materials such as metal materials and alloy materials, and specific examples of the metal materials and alloy materials are aluminum and aluminum alloys. be.

However, the external terminal 20 may contain a clad material. This clad material includes an aluminum layer and a nickel layer in order from the side closer to the gasket 30, and the aluminum layer and the nickel layer are roll-bonded to each other. The clad material may contain a nickel alloy layer instead of the nickel layer.

In particular, the external terminal 20 functions as an external connection terminal for the positive electrode 41, and also functions as a release valve for releasing the internal pressure of the outer can 10 when the internal pressure rises excessively, as will be described later. The cause of this increase in internal pressure is the generation of gas due to the decomposition reaction of the electrolyte during charging and discharging, and the cause of promoting the decomposition reaction of the electrolyte is internal short circuit of the secondary battery, secondary battery heating and discharge of a secondary battery due to high current conditions.

The details of the operation of the external terminal 20 functioning as an open valve will be described later (see FIG. 6).

[gasket]
The gasket 30 is an insulating sealing member arranged between the outer can 10 and the external terminal 20, as shown in FIG. Here, the gasket 30 is arranged between the lid portion 12 and the external terminal 20, and has a through hole 30K at a position overlapping the through hole 10K. Thereby, the gasket 30 is arranged so as not to block the through hole 10K.

Since the gasket 30 contains one or more of insulating and thermally fusible polymer compounds, the external terminal 20 is connected to the lid portion via the gasket 30 as described above. 12 is heat-sealed. The type of polymer compound is not particularly limited, but specific examples include polypropylene and polyethylene.

The installation range of the gasket 30 is not particularly limited and can be set arbitrarily. Here, the gasket 30 is arranged in the space between the upper surface of the lid portion 12 and the lower surface of the external terminal 20 inside the recess portion 12U. However, the installation range of the gasket 30 may extend outside the space between the upper surface of the lid portion 12 and the lower surface of the external terminal 20 .

[Battery element]
The battery element 40, as shown in FIGS. 1 to 3, is a power generation element that advances charge/discharge reactions, and is housed inside the outer can 10. As shown in FIG. The battery element 40 includes a positive electrode 41 as a first electrode, a negative electrode 42 as a second electrode, a separator 43, and an electrolytic solution (not shown) as a liquid electrolyte.

Here, since the battery element 40 is a so-called wound electrode body, the element structure of the battery element 40 is a so-called wound type. In this case, the positive electrode 41 and the negative electrode 42 are laminated with the separator 43 interposed therebetween, and the positive electrode 41, the negative electrode 42 and the separator 43 are wound. As a result, the positive electrode 41 and the negative electrode 42 are wound while facing each other with the separator 43 interposed therebetween, so that the battery element 40 has a winding center space 40K as a winding core.

Since the battery element 40 has a three-dimensional shape similar to that of the outer can 10, it has a flat and cylindrical three-dimensional shape. Compared to the case where the battery element 40 has a three-dimensional shape different from the three-dimensional shape of the outer can 10, when the battery element 40 is accommodated inside the outer can 10, dead space (the outer can 10 and the battery element 40), the internal space of the outer can 10 is effectively utilized. As a result, the element space volume increases, so the volumetric energy density increases.

(positive electrode)
The positive electrode 41 includes a positive electrode current collector 41A and a positive electrode active material layer 41B, as shown in FIGS.

The positive electrode current collector 41A is a conductive support that supports the positive electrode active material layer 41B, and has a pair of surfaces on which the positive electrode active material layer 41B is provided. The positive electrode current collector 41A contains a conductive material such as a metal material, and a specific example of the metal material is aluminum.

Here, the positive electrode active material layer 41B is provided on both sides of the positive electrode current collector 41A and contains one or more of positive electrode active materials capable of intercalating and deintercalating lithium. However, the positive electrode active material layer 41B may be provided only on one side of the positive electrode current collector 41A on the side where the positive electrode 41 faces the negative electrode 42 . Moreover, the positive electrode active material layer 41B may further contain one or more of materials such as a positive electrode binder and a positive electrode conductive agent. A method for forming the positive electrode active material layer 41B is not particularly limited, but a specific example is a coating method.

The positive electrode active material contains a lithium compound. This is because a high energy density can be obtained. This lithium compound is a compound containing lithium as a constituent element, and more specifically, a compound containing lithium and one or more transition metal elements as constituent elements. However, the lithium compound may further contain one or more of other elements (elements other than lithium and transition metal elements).

The type of lithium compound is not particularly limited, but specific examples include oxides, phosphoric acid compounds, silicic acid compounds and boric acid compounds. Specific examples of oxides include LiNiO ₂ , LiCoO ₂ and LiMn ₂ O ₄ . Specific examples of phosphoric acid compounds include _LiFePO4 and _LiMnPO4 .

The positive electrode binder contains one or more of synthetic rubber and polymer compounds. A specific example of the synthetic rubber is styrene-butadiene rubber, and a specific example of the polymer compound is polyvinylidene fluoride. The positive electrode conductive agent contains one or more of conductive materials such as carbon materials, and specific examples of the carbon materials include graphite, carbon black, acetylene black, and ketjen black. . However, the conductive material may be a metal material, a polymer compound, or the like.

(negative electrode)
The negative electrode 42 includes a negative electrode current collector 42A and a negative electrode active material layer 42B, as shown in FIGS.

The negative electrode current collector 42A is a conductive support that supports the negative electrode active material layer 42B, and has a pair of surfaces on which the negative electrode active material layer 42B is provided. The negative electrode current collector 42A contains a conductive material such as a metal material, and a specific example of the metal material is copper.

Here, the negative electrode active material layer 42B is provided on both sides of the negative electrode current collector 42A, and contains one or more of negative electrode active materials capable of intercalating and deintercalating lithium. However, the negative electrode active material layer 42B may be provided only on one side of the negative electrode current collector 42A on the side where the negative electrode 42 faces the positive electrode 41 . In addition, the negative electrode active material layer 42B may further contain one or more of materials such as a negative electrode binder and a negative electrode conductor. The details of the negative electrode binder and the negative electrode electrical conductor are the same as the details of the positive electrode binder and the positive electrode electrical conductor. The method of forming the negative electrode active material layer 42B is not particularly limited, but specifically, any one of a coating method, a vapor phase method, a liquid phase method, a thermal spraying method, a firing method (sintering method), and the like, or Two or more types.

The negative electrode active material contains one or more of a carbon material, a metal-based material, and the like. This is because a high energy density can be obtained. Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon and graphite (natural graphite and artificial graphite). A metallic material is a material containing as constituent elements one or more of metallic elements and semi-metallic elements capable of forming an alloy with lithium. , silicon and tin. However, the metallic material may be a single substance, an alloy, a compound, a mixture of two or more thereof, or a material containing two or more phases thereof. Specific examples of metallic materials include TiSi ₂ and SiO _x (0<x≦2 or 0.2<x<1.4).

(separator)
The separator 43 is an insulating porous film interposed between the positive electrode 41 and the negative electrode 42, as shown in FIGS. Allows lithium ions to pass through. This separator 43 contains a polymer compound such as polyethylene.
(Electrolyte)
The electrolyte is impregnated in each of the positive electrode 41, the negative electrode 42 and the separator 43, and contains a solvent and an electrolyte salt.

Here, the solvent contains one or more of non-aqueous solvents (organic solvents), and the electrolytic solution containing the non-aqueous solvent is a so-called non-aqueous electrolytic solution. The non-aqueous solvents are esters, ethers, and the like, and more specifically, carbonate compounds, carboxylic acid ester compounds, lactone compounds, and the like.

The carbonate compounds include cyclic carbonates and chain carbonates. Specific examples of the cyclic carbonate include ethylene carbonate and propylene carbonate, and specific examples of the chain carbonate include dimethyl carbonate, diethyl carbonate and ethylmethyl carbonate.

The carboxylic acid ester compound is a chain carboxylic acid ester or the like. Specific examples of chain carboxylic acid esters include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, propyl propionate, ethyl trimethylacetate, methyl butyrate and ethyl butyrate.

Lactone-based compounds include lactones. Specific examples of lactones include γ-butyrolactone and γ-valerolactone.

The ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, etc., in addition to the lactone compounds described above.

Electrolyte salts are light metal salts such as lithium salts. Specific examples of lithium salts include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium trifluoromethanesulfonate (LiCF ₃ SO ₃ ), lithium bis(fluorosulfonyl)imide (LiN (FSO2) ₂ ), bis(trifluoromethanesulfonyl)imidolithium (LiN( _CF3SO2 ) ₂ ), lithium tris(trifluoromethanesulfonyl)methide ( _LiC ( _CF3SO2 ) ₃ ) _, _bis (oxalato)boron lithium oxide (LiB _(C2O4)2 ₎ _and lithium difluoro(oxalato)borate ₍ LiB ₍ _C2O4 )F2).

The content of the electrolyte salt is not particularly limited, but specifically, it is 0.3 mol/kg to 3.0 mol/kg with respect to the solvent. This is because high ionic conductivity can be obtained.

[Positive lead]
The positive electrode lead 51 is a wiring member for electrically connecting the positive electrode 41 to the external terminal 20, as shown in FIGS. Since the positive electrode lead 51 is connected to the positive electrode current collector 41A of the positive electrode 41 and the external terminal 20 via the through hole 10K, the positive electrode lead 51 is electrically connected to the positive electrode 41 and the external terminal 20, respectively. It is The positive electrode lead 51 is connected to the positive electrode 41 on the side closer to the lid portion 12 .

Here, the secondary battery has one positive electrode lead 51 . However, the secondary battery may have two or more positive electrode leads 51 . This is because the electrical resistance of the battery element 40 decreases as the number of the positive electrode leads 51 increases.

The details of the material forming the positive electrode lead 51 are the same as the details of the material forming the positive electrode current collector 41A. However, the material for forming the positive electrode lead 51 and the material for forming the positive electrode current collector 41A may be the same as or different from each other.

Because the positive electrode lead 51 is physically separated from the positive electrode current collector 41A, it is a separate member from the positive electrode current collector 41A. However, since the positive electrode lead 51 is physically continuous with the positive electrode current collector 41A, it may be a member integrated with the positive electrode current collector 41A.

It should be noted that the positive electrode lead 51 is connected to the external terminal 20 by folding back halfway between the positive electrode 41 and the external terminal 20 . The details of the configuration of the positive electrode lead 51 will be described later (see FIG. 4).

[Negative electrode lead]
The negative electrode lead 52 is a member for electrically connecting the negative electrode 42 to the outer can 10, as shown in FIG. Since the negative electrode lead 52 is connected to the negative electrode current collector 42A of the negative electrode 42 and the housing portion 11, it is electrically connected to the negative electrode 42 and the outer can 10, respectively. Since the negative electrode lead 52 is connected to the negative electrode 42 on the far side from the lid portion 12, it is connected to the lower bottom portion M2.

Here, the secondary battery has one negative electrode lead 52 . However, the secondary battery may have two or more negative electrode leads 52 . This is because the electrical resistance of the battery element 40 decreases as the number of the negative electrode leads 52 increases.

The details of the material forming the negative electrode lead 52 are the same as the details of the material forming the negative electrode current collector 42A. However, the material for forming the negative electrode lead 52 and the material for forming the negative electrode current collector 42A may be the same as or different from each other.

Since the negative electrode lead 52 is physically separated from the negative electrode current collector 42A, it is a separate member from the negative electrode current collector 42A. However, since the negative electrode lead 52 is physically continuous with the negative electrode current collector 42A, it may be a member integrated with the negative electrode current collector 42A.

[Sealant]
The sealant 60 is an insulating covering member covering the surface of the positive electrode lead 51, as shown in FIG. Thereby, the positive electrode lead 51 is insulated from each of the outer can 10 and the negative electrode 42 via the sealant 60 .

The sealant 60 contains one or more of insulating materials such as insulating polymer compounds, and a specific example of the polymer compound is polyimide.

Note that the sealant 60 covers the surface of a part of the positive electrode lead 51 that is folded back midway between the positive electrode 41 and the external terminal 20 . Details of the configuration of the sealant 60 will be described later (see FIG. 5).

[insulating film]
The insulating film 70 is an insulating member arranged between the lid portion 12 and the battery element 40, as shown in FIG. Since this insulating film 70 has a through hole 70K at a position overlapping with the through hole 10K, it is arranged so as not to shield the through hole 10K.

Here, since the insulating film 70 is an insulating tape including an adhesive layer (not shown), it is adhered to the inner surface (lower surface) of the lid portion 12 via the adhesive layer. More specifically, the insulating film 70 is adhered to the lower surface of the portion of the lid portion 12 where the recess portion 12U is provided. As a result, a portion of the insulating film 70 is arranged between the lid portion 12 and the positive electrode lead 51 .

The insulating film 70 contains one or more of insulating materials such as insulating polymer compounds, and a specific example of the insulating material is polyimide.

[others]
Note that the secondary battery may further include one or more of other components (not shown).

Specifically, the other component is another insulating film or the like arranged between the storage portion 11 (lower bottom portion M2) and the battery element 40. In this case, part of the other insulating film is arranged between the housing portion 11 and the negative electrode lead 52 . Materials for forming other insulating films are the same as those for forming the insulating film 70 .

<1-2. Detailed Configuration of Positive Electrode Lead and Sealant>
FIG. 4 shows an enlarged cross-sectional configuration of the positive electrode lead 51 shown in FIG. FIG. 5 shows an enlarged cross-sectional configuration of the sealant 60 shown in FIG. However, in FIG. 4, only the main part of the positive electrode lead 51 is shown. FIG. 5 shows a state in which an outer sealant portion 61 and an inner sealant portion 62, which will be described later, are separated from each other.

[Detailed configuration of positive electrode lead]
As shown in FIG. 2 , the positive electrode lead 51 is connected to the positive electrode 41 on the side closer to the lid portion 12 , and thus is connected to the upper end portion of the positive electrode 41 . Also, since the positive electrode lead 51 is routed from the upper end of the positive electrode 41 to the external terminal 20 via the through hole 10K, the positive electrode lead 51 is connected to the lower surface of the external terminal 20 . A method for connecting the positive electrode lead 51 is not particularly limited, but specifically, one or more of welding methods such as resistance welding and laser welding are used. The details of the welding method described here are the same hereinafter.

Since the battery element 40 is a wound electrode body, when the positive electrode 41 and the negative electrode 42 are wound with the separator 43 interposed therebetween, the connection position of the positive electrode lead 51 to the positive electrode 41 is not particularly limited. Here, the positive electrode lead 51 is connected to the positive electrode 41 in the middle of winding. However, the positive electrode lead 51 may be connected to the positive electrode 41 on the outermost winding side, or may be connected to the positive electrode 41 on the innermost winding side.

As shown in FIG. 4, the positive electrode lead 51 includes a folded portion 51Z and is connected to the external terminal 20 beyond the folded portion 51Z. More specifically, the positive electrode lead 51 includes two extending

portions

51X and 51Y and a folded portion 51Z, and is connected to the external terminal 20 at a portion (tip portion 51YN) of the extending portion 51Y. .

Here, the extending

portions

51X, 51Y and the folded portion 51Z are connected to each other and integrated with each other. In FIG. 4, the boundary between the extending portion 51X and the folded portion 51Z is indicated by a broken line, and the boundary between the extending portion 51Y and the folded portion 51Z is indicated by a broken line.

The extending portion 51X is a first extending portion extending in the direction toward the folded portion 51Z (left direction in FIGS. 2 and 4). One end of the extending portion 51X is connected to the positive electrode 41, and the other end of the extending portion 51X is connected to one end of the folded portion 51Z.

However, the extending portion 51X may be bent into a crank shape in the middle. The number of times the extending portion 51X is bent halfway in a crank shape is not particularly limited, and may be one time or two or more times.

The extending portion 51Y is a second extending portion that extends in the opposite direction (to the right in FIGS. 2 and 4) to the direction in which the extending portion 51X extends. One end of the extending portion 51Y is connected to the external terminal 20, and the other end of the extending portion 51Y is connected to the other end of the folded portion 51Z. In particular, the extension portion 51Y includes a tip portion 51YN whose surface is not covered with the sealant 60, and is connected to the external terminal 20 at the tip portion 51YN.

However, like the extension 51X, the extension 51Y may be bent into a crank shape in the middle.

The folded portion 51Z is a portion where the positive electrode lead 51 is folded, and at the folded portion 51Z, the positive electrode lead 51 is folded inside the through hole 10K in the radial direction of the through hole 10K. 2 and 4, the positive electrode lead 51 extends leftward and then rightward as described above. It is folded back to extend. As a result, the positive electrode lead 51 is not arranged beyond the through hole 10K, but is folded back inside the through hole 10K so as to change direction. This folded portion 51Z is connected to each of the

extension portions

51X and 51Y as described above.

At the folded portion 51Z, the positive electrode lead 51 may be folded back so as to be bent, or may be folded back so as to be curved. 2 and 4 show the case where the positive electrode lead 51 is folded back so as to be curved.

The angle at which the positive electrode lead 51 is folded back at the folded portion 51Z, that is, the angle defined by the extending direction of the extending portion 51X and the extending direction of the extending portion 51Y is not particularly limited. The angle may be slightly increased or decreased from 180°.

The positive electrode lead 51 has an outer surface S1 and an inner surface S2. The outer surface S1 is one of the two areas when the surface of the positive electrode lead 51 is classified into two areas, and the inner surface S2 is the other area. In FIG. 4, the boundary between the outer surface S1 and the inner surface S2 is indicated by a dashed line.

Specifically, when the positive electrode lead 51 is folded inside the through hole 10K provided in the outer can 10 as described above, the outer surface S1 is formed such that the folded positive electrode leads 51 It is the surface opposite to the surface facing (or approaching each other). More specifically, the outer surface S1 is a surface on the side facing the inner wall surface of the outer can 10 (lid portion 12) inside the through hole 10K and the exposed surface of the external terminal 20 in the through hole 10K.

The inner surface S2 is the surface of the positive electrode lead 51 opposite to the outer surface S1. That is, the inner surface S2 is the surface on the side where the folded positive electrode leads 51 face each other. More specifically, the inner surface S2 is opposite to the surface on the side facing the inner wall surface of the outer can 10 (lid portion 12) inside the through hole 10K and the exposed surface of the external terminal 20 in the through hole 10K. side surface.

Here, the positive electrode lead 51 includes the folded portion 51Z because the excess length (length margin) of the positive electrode lead 51 can be obtained as compared with the case where the positive electrode lead 51 does not include the folded portion 51Z. because it will be

As a result, when the secondary battery receives an external force such as vibration or impact, the external force is mitigated by using the length margin of the positive electrode lead 51, so the positive electrode lead 51 is less likely to be damaged. The breakage includes cutting of the positive electrode lead 51 , detachment of the positive electrode lead 51 from the external terminal 20 , and cracking of the positive electrode lead 51 . In this case, the strength of the connection of the positive lead 51 to the external terminal 20 is improved because the positive lead 51 is less likely to be damaged.

In addition, as will be described later, when the outer can 10 is formed using the storage portion 11 and the lid portion 12 in the manufacturing process of the secondary battery, the length margin of the positive electrode lead 51 is used for the storage portion 11. Since the lid portion 12 can be erected (see FIG. 8), the secondary battery can be easily assembled.

The positive electrode lead 51 is folded back inside the through hole 10K to form the folded portion 51Z because the volume energy density is higher than that in the case where the positive electrode lead 51 is folded outside the through hole 10K. This is because the external terminal 20 becomes more likely to function as an on-off valve as it increases.

Specifically, when the positive electrode lead 51 is folded back between the lid portion 12 and the battery element 40, the folded portion 51Z is arranged in the inner space of the outer can 10 in which the battery element 40 is housed. In this case, the element space volume is reduced by the amount that the folded portion 51Z is arranged in the inner space of the outer can 10, so the height of the battery element 40 is reduced. As a result, the volume of the battery element 40 is reduced by the amount corresponding to the reduction in height, thereby reducing the volumetric energy density.

On the other hand, when the positive electrode lead 51 is folded inside the through hole 10K, the folded portion 51Z is arranged in the internal space of the through hole 10K. In this case, the height of the battery element 40 is increased because the element space volume is increased by the amount that the folded portion 51Z is not arranged in the inner space of the outer can 10 . As a result, the volume of the battery element 40 increases by the amount corresponding to the increase in height, so the volumetric energy density increases.

Further, when the positive electrode lead 51 is folded back between the lid portion 12 and the battery element 40, when the external terminal 20 is separated from the lid portion 12 when an abnormality occurs (when the internal pressure increases), the folded portion Since 51Z is caught on the lid portion 12, the external terminal 20 becomes difficult to separate from the lid portion 12.例文帳に追加This makes it difficult for the external terminal 20 to function as an on-off valve.

On the other hand, when the positive electrode lead 51 is folded back inside the through hole 10K, when the external terminal 20 is separated from the lid portion 12 when the internal pressure increases, the folded portion 51Z is prevented from being caught by the lid portion 12. Therefore, the external terminal 20 can be easily separated from the lid portion 12 . This makes it easier for the external terminal 20 to function as an on-off valve.

[Detailed configuration of sealant]
The sealant 60 covers at least the outer surface S1 of the folded portion 51Z.

The reason why the sealant 60 covers at least the outer surface S1 of the folded portion 51Z is that even if the positive electrode lead 51 is folded back inside the through hole 10K, the positive electrode lead 51 is covered with the sealant 60 through the outer can 10 (the lid of the outer can 10). This is because it is insulated from the portion 12). This prevents the occurrence of a short circuit between the positive electrode lead 51 and the lid portion 12 .

In particular, when the positive electrode lead 51 is folded back inside the through hole 10K, if the connection area of the positive electrode lead 51 (tip portion 51YN) to the external terminal 20 is to be sufficiently increased, the cover inside the through hole 10K will The positive electrode lead 51 approaches the inner wall surface of the portion 12 . However, since the outer surface S1 of the folded portion 51Z is covered with the sealant 60, even if the positive electrode lead 51 approaches the inner wall surface of the lid portion 12, the sealant 60 is used to effectively and sufficiently short-circuit the lead. prevented.

As long as the sealant 60 covers the outer surface S1 of the folded portion 51Z, the sealant 60 may further cover the inner surface S2 of the folded portion 51Z. One or both of them may be covered, or one or both of the outer surface S1 and the inner surface S2 of the extension portion 51Y may be covered.

Here, the sealant 60 includes an outer sealant portion 61 and an inner sealant portion 62, as shown in FIG. The outer sealant portion 61 covers at least the outer surface S1 of the folded portion 51Z, and the inner sealant portion 62 covers at least the inner surface S2 of the folded portion 51Z. The reason why the outer sealant portion 61 not only covers the outer surface S1 of the folded portion 51Z but also the inner sealant portion 62 covers the inner surface S2 of the folded portion 51Z is that the positive electrode lead 51 passes through the sealant 60. This is because it becomes easier to insulate from the lid portion 12, so that the occurrence of a short circuit is further prevented.

Each of the outer sealant portion 61 and the inner sealant portion 62 is an adhesive tape including an adhesive layer (not shown). As a result, the outer sealant portion 61 and the inner sealant portion 62 are bonded to each other via their adhesive layers while facing each other via the positive electrode lead 51 . That is, the positive electrode lead 51 is sandwiched between the outer sealant portion 61 and the inner sealant portion 62 from above and below. 5 shows a state in which the outer sealant portion 61 and the inner sealant portion 62 are separated from each other, as described above, before the outer sealant portion 61 and the inner sealant portion 62 are attached to each other.

Above all, it is preferable that the sealant 60 (the outer sealant portion 61 and the inner sealant portion 62) covers the surface (the outer surface S1 and the inner surface S1) of the extension portion 51Y. As will be described later, when the positive electrode lead 51 (extending portion 51Y) is welded to the external terminal 20 using a laser welding method in the manufacturing process of the secondary battery, the extending portion 51Y is covered with the sealant 60. This is because the portion where the contact is made is not welded to the external terminal 20 . As a result, the portion of the extension portion 51Y that is covered with the sealant 60, in other words, the portion that is not connected to the external terminal 20 of the extension portion 51Y becomes the length margin of the positive electrode lead 51. It becomes easy to obtain the advantage derived from the length margin of the positive electrode lead 51 .

In addition, the sealant 60 (the outer sealant portion 61 and the inner sealant portion 62) preferably covers up to the surface (the outer surface S1 and the inner surface S1) of the extension portion 51X. This is because the extended portion 51X is insulated from the lid portion 12 and the negative electrode 42 via the sealant 60, so that the occurrence of a short circuit between the positive electrode lead 51 and the lid portion 12 is further prevented.

<1-3. Operation>
FIG. 6 shows a cross-sectional configuration corresponding to FIG. 2 in order to explain the operation of the secondary battery. The operation during charging and discharging will be described below, and then the operation when an abnormality occurs will be described.

[Operation during charging and discharging]
During charging, in the battery element 40, lithium is released from the positive electrode 41 and absorbed into the negative electrode 42 via the electrolyte. On the other hand, during discharge, in the battery element 40, lithium is released from the negative electrode 42 and absorbed into the positive electrode 41 via the electrolyte. Lithium is intercalated and deintercalated in an ionic state during charging and discharging.

[Operation when an error occurs]
As described above, the external terminal 20 is arranged outside the lid portion 12 and is thermally welded to the lid portion 12 via the gasket 30 . Accordingly, in a normal state, the external terminal 20 is fixed to the lid portion 12 via the gasket 30, so that the through hole 10K is shielded by the external terminal 20 and the outer can 10 is sealed. A battery element 40 is sealed inside the outer can 10 .

On the other hand, when an abnormality occurs, that is, when the internal pressure of the outer can 10 rises excessively, the external terminal 20 is pushed outward (upward) via the through hole 10K according to the rise in internal pressure. In this case, if the strength of the force pushing the external terminal 20 outward becomes greater than the strength (so-called sealing strength) with which the external terminal 20 is fixed to the lid portion 12 via the gasket 30, the external terminal 20 separates partially or wholly from the lid 12 . As a result, as shown in FIG. 6, a gap 20G (an internal pressure release path) is formed between the lid portion 12 and the external terminal 20, and the internal pressure is released using the gap 20G. Note that FIG. 6 shows a case where the external terminal 20 is partially separated from the lid portion 12 .

As described above, the housing portion 11 is joined to the lid portion 12, whereas the external terminals 20 are thermally welded to the lid portion 12 via the gasket 30. It is smaller than the bonding strength of the lid portion 12 to the portion 11 . In this case, if the internal pressure of the outer can 10 rises excessively, the external terminal 20 separates from the lid portion 12 before the lid portion 12 separates from the storage portion 11 . Since the external terminal 20 functions as a release valve before the outer can 10 bursts, the outer can 10 is prevented from bursting.

<1-4. Manufacturing method>
FIG. 7 shows a perspective configuration corresponding to FIG. 1 in order to explain the manufacturing process of the secondary battery. FIG. 8 shows a cross-sectional structure corresponding to FIG. 2 in order to explain the manufacturing process of the secondary battery following FIG.

However, each of FIGS. 7 and 8 shows the state before the lid portion 12 is joined to the storage portion 11 . As a result, the lid portion 12 is separated from the storage portion 11 in FIG. 7, and the lid portion 12 is erected with respect to the storage portion 11 in FIG.

In the case of manufacturing a secondary battery, the positive electrode 41 and the negative electrode 42 are prepared and the electrolytic solution is prepared according to the procedure illustrated below, and then the secondary battery is assembled using the positive electrode 41, the negative electrode 42 and the electrolytic solution. At the same time, the secondary battery after assembly is stabilized. In the following description, both FIGS. 7 and 8 will refer to FIGS. 1 to 5 which have already been described.

Here, as shown in FIG. 7, a housing portion 11 and a lid portion 12 that are physically separated from each other are used to form the outer can 10 . As described above, the storage portion 11 has the opening portion 11K, and the lid portion 12 has the recess portion 12U. Further, as described above, the external terminals 20 are thermally welded to the lid portion 12 via the gasket 30 in advance, and the tape-like insulating film 70 is adhered thereto.

[Preparation of positive electrode]
First, a paste-like positive electrode mixture slurry is prepared by putting a positive electrode mixture in which a positive electrode active material, a positive electrode binder, and a positive electrode conductor are mixed together into a solvent. This solvent may be an aqueous solvent or an organic solvent. The details of the solvent explained here are the same for the following. Subsequently, the cathode active material layer 41B is formed by applying the cathode mixture slurry to both surfaces of the cathode current collector 41A. Finally, the cathode active material layer 41B is compression-molded using a roll press or the like. In this case, the positive electrode active material layer 41B may be heated and the compression molding may be repeated multiple times. As a result, the cathode active material layers 41B are formed on both surfaces of the cathode current collector 41A, so that the cathode 41 is produced.

[Preparation of negative electrode]
First, a paste-like negative electrode mixture slurry is prepared by putting a negative electrode mixture in which a negative electrode active material, a negative electrode binder, and a negative electrode conductor are mixed together into a solvent. Subsequently, the anode active material layer 42B is formed by applying the anode mixture slurry to both surfaces of the anode current collector 42A. Finally, the negative electrode active material layer 42B is compression-molded using a roll press or the like. The details of the compression molding of the negative electrode active material layer 42B are the same as the details of the compression molding of the positive electrode active material layer 41B. As a result, the negative electrode 42 is manufactured because the negative electrode active material layers 42B are formed on both surfaces of the negative electrode current collector 42A.

[Preparation of electrolytic solution]
Add the electrolyte salt to the solvent. This disperses or dissolves the electrolyte salt in the solvent, thus preparing an electrolytic solution.

[Assembly of secondary battery]
First, after preparing the positive electrode lead 51 , the sealant 60 is used to cover the surface of the positive electrode lead 51 . In this case, as described above, the sealant 60 is used to cover at least the outer surface S1 of the folded portion 51Z. It covers the side S1 and the inner side S2.

Subsequently, the positive electrode lead 51 is connected to the positive electrode current collector 41A of the positive electrode 41 by welding or the like, and the negative electrode lead 52 is connected to the negative electrode current collector 42A of the negative electrode 42 by welding or the like. to connect.

Subsequently, after the positive electrode 41 and the negative electrode 42 are laminated with the separator 43 interposed therebetween, the positive electrode 41, the negative electrode 42 and the separator 43 are wound to form a winding center space 40K as shown in FIG. A wound body 40Z having the following is produced. The wound body 40Z has the same structure as the battery element 40 except that the positive electrode 41, the negative electrode 42 and the separator 43 are not impregnated with the electrolytic solution. 7, illustration of each of the positive electrode lead 51 and the negative electrode lead 52 is omitted.

Subsequently, the wound body 40Z is stored inside the storage section 11 through the opening 11K. In this case, a welding method or the like is used to connect the negative electrode lead 52 to the storage portion 11 .

Subsequently, after preparing the lid portion 12 to which the external terminals 20 are thermally welded via the gasket 30 and to which the insulating film 70 is adhered in advance, the external terminals are welded through the through holes 10K using a welding method or the like. A positive lead 51 is connected to 20 .

As a result, the positive electrode 41 of the wound body 40Z housed inside the housing portion 11 and the external terminal 20 attached to the lid portion 12 are connected to each other via the positive electrode lead 51. Therefore, as shown in FIG. 8, in a state in which the wound body 40Z and the external terminal 20 are connected to each other through the positive electrode lead 51, the lid portion 12 is held by using a holding jig (not shown). is held, the lid portion 12 can be erected with respect to the storage portion 11 .

As is clear from FIG. 8, this "standing the lid portion 12 against the storage portion 11" means that the lid portion 12 does not block the opening portion 11K. It means that the lid portion 12 can be arranged so as to be substantially perpendicular to the bottom surface (lower bottom portion M2) of the storage portion 11 in a state where 40Z and the external terminal 20 are connected to each other. In this case, by making the length of the positive electrode lead 51 sufficiently large, the positive electrode lead 51 is not excessively pulled even when the cover portion 12 is erected against the storage portion 11, and the positive electrode lead 51 is not damaged. become difficult.

Here, the housing portion 11 is arranged so that the lid portion 12 is arranged inside (the inside side of the housing portion 11) and the positive electrode lead 51 is arranged outside (the side opposite to the inside side of the housing portion 11). The lid portion 12 is erected against it. As a result, when the positive electrode lead 51 is welded to the external terminal 20 using a laser welding method or the like, foreign matter generated during welding is less likely to enter the housing portion 11 .

Subsequently, the electrolytic solution is injected into the storage portion 11 through the opening portion 11K. In this case, as described above, even if the wound body 40Z and the external terminal 20 are connected to each other through the positive electrode lead 51, the lid portion 12 does not obstruct the opening portion 11K. This makes it easier to inject the electrolytic solution into the storage portion 11 . As a result, the wound body 40Z (the positive electrode 41, the negative electrode 42, and the separator 43) is impregnated with the electrolytic solution, so that the battery element 40, which is a wound electrode body, is produced.

In this case, part of the electrolytic solution is particularly supplied to the inside of the winding center space 40K. As a result, the winding center space 40K is used as an impregnation path for the electrolytic solution, so that the wound body 40Z is easily impregnated with the electrolytic solution.

Subsequently, by inclining the lid portion 12 so as to approach the storage portion 11, the lid portion 12 is used to shield the opening portion 11K. to join. In this case, the portion of the positive electrode lead 51 covered with the sealant 60 is folded inside the through hole 10K. As a result, the outer can 10 is formed, and the battery element 40 and the like are housed inside the outer can 10, so that the secondary battery is assembled as shown in FIG.

[Stabilization of secondary battery]
The secondary battery after assembly is charged and discharged. Various conditions such as environmental temperature, number of charge/discharge times (number of cycles), and charge/discharge conditions can be arbitrarily set. As a result, films are formed on the respective surfaces of the positive electrode 41 and the negative electrode 42 in the battery element 40, so that the state of the secondary battery is electrochemically stabilized.

Therefore, since the battery element 40 and the like are sealed inside the outer can 10, the secondary battery is completed.

<1-5. Action and effect>
According to this secondary battery, the battery element 40 is housed inside the outer can 10 having the through hole 10K, and the external terminal 20 arranged outside the outer can 10 shields the through hole 10K. . Also, the positive electrode lead 51 is connected to the positive electrode 41 and the external terminal 20 via the through hole 10K, and the sealant 60 covers the surface of the positive electrode lead 51 . Further, the positive electrode lead 51 includes a folded portion 51Z, in which the positive electrode lead 51 is folded back in the inner diameter direction of the through hole 10K inside the through hole 10K at the folded portion 51Z, and the sealant 60 is at least outside the folded portion 51Z. It covers the side surface S1.

In this case, as described above, based on the configurations of the positive electrode lead 51 and the sealant 60, a series of actions described below are obtained.

First, since the positive electrode lead 51 includes the folded portion 51Z, a length margin of the positive electrode lead 51 can be obtained. As a result, when the secondary battery receives an external force, the external force is relieved using the length margin of the positive electrode lead 51, so that the positive electrode lead 51 is less likely to be damaged.

Second, since the positive electrode lead 51 is folded inside the through hole 10K to form the folded portion 51Z, the folded portion 51Z is not arranged in the internal space of the outer can 10. As a result, the element space volume increases, so the volumetric energy density increases.

Thirdly, since the sealant 60 covers at least the outer surface S1 of the folded portion 51Z, even if the positive electrode lead 51 is folded inside the through-hole 10K, the positive electrode lead 51 is inserted through the sealant 60 into the outer can. 10 (lid portion 12). This prevents the occurrence of a short circuit between the positive electrode lead 51 and the lid portion 12, thereby facilitating stable operation of the secondary battery.

Fourthly, since the positive electrode lead 51 is folded back inside the through hole 10K, when the external terminal 20 is separated from the lid portion 12 when the internal pressure of the outer can 10 rises, the folded portion 51Z does not get caught on the lid portion 12. No. As a result, the external terminal 20 can be easily separated from the lid portion 12, so that the external terminal 20 can stably function as an on-off valve.

As a result, a high volumetric energy density can be obtained, the positive electrode lead 51 can be prevented from being damaged by an external force, and the occurrence of a short circuit can be prevented. From the viewpoint of securing the function of the external terminal 20 as a valve, the secondary battery can easily operate stably. Therefore, excellent battery capacity characteristics, excellent physical durability, and excellent operational reliability can be obtained.

In this case, as described above, it is possible to use the length margin of the positive electrode lead 51 to stand the lid portion 12 against the storage portion 11 in the manufacturing process of the secondary battery. Even when the battery element 40 (positive electrode 41) and the external terminal 20 are connected to each other through the positive electrode lead 51, the electrolytic solution is easily injected into the storage portion 11 through the opening 11K. Therefore, since the secondary battery can be easily assembled, the ease of manufacturing the secondary battery can be improved.

In addition, if the sealant 60 also covers the inner surface S2 of the folded portion 51Z, short-circuiting between the positive electrode lead 51 and the lid portion 12 can be further prevented, and a higher effect can be obtained.

Also, if the sealant 60 covers the surface of the extending portion 51Y, the portion of the extending portion 51Y that is covered with the sealant 60 provides a length margin for the positive electrode lead 51. Therefore, since the length margin of the positive electrode lead 51 is sufficiently large, a higher effect can be obtained.

Also, if the sealant 60 covers the surface of the extension 51X, the extension 51X is insulated from the lid 12 and the negative electrode 42 via the sealant 60. Therefore, the occurrence of a short circuit between the positive electrode lead 51 and the lid portion 12 is further suppressed, and a higher effect can be obtained.

In addition, if the outer can 10 includes the storage portion 11 and the lid portion 12, and the storage portion 11 and the lid portion 12 are joined to each other, the outer can 10, which is a so-called crimpless joining can, can be used for the two-piece construction. Since the secondary battery is constructed, the volumetric energy density is further increased. Therefore, since the battery capacity characteristic is further improved, a higher effect can be obtained.

In this case, if the lid portion 12 has the recessed portion 12U and the external terminals 20 are arranged inside the recessed portion 12U, the height H of the secondary battery is reduced, and the volumetric energy density is reduced. further increases. Therefore, since the battery capacity characteristics are further improved, a higher effect can be obtained.

Also, if the outer can 10 is electrically connected to the negative electrode 42 , the outer can 10 functions as an external connection terminal for the negative electrode 42 . As a result, the secondary battery does not need to be provided with an external connection terminal for the negative electrode 42 separately from the outer can 10, so that the volumetric energy density is further increased. Therefore, since the battery capacity characteristic is further improved, a higher effect can be obtained.

In addition, if the outer can 10 has a flat and columnar three-dimensional shape, excellent physical durability and excellent operational reliability can be achieved even in a small secondary battery in which the internal pressure of the outer can 10 tends to increase. Therefore, a higher effect can be obtained.

Also, if the outer can 10 is a metal can, the outer can 10 is less likely to deform. Therefore, physical durability is improved in terms of deformation of the outer can 10, and a higher effect can be obtained.

Also, if the secondary battery is a lithium-ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and release of lithium, so a higher effect can be obtained.

<2. Variation>
The configuration of the secondary battery described above can be changed as appropriate, as described below. However, any two or more of the series of modifications described below may be combined with each other.

[Modification 1]
2, 4 and 5, sealant 60 (outer sealant portion 61 and inner sealant portion 62) covers respective surfaces (outer surface S1 and inner surface S2) of

extension portions

51X and 51Y and folded portion 51Z. ing. However, as described above, as long as the sealant 60 covers at least the outer surface S1 of the folded portion 51Z, the coverage range of the sealant 60 is not particularly limited.

Specifically, as shown in FIG. 9 corresponding to FIG. 2, the sealant 60 (outer sealant portion 61 and inner sealant portion 62) covers only the surface (outer surface S1 and inner surface S2) of the folded portion 51Z. may be

Also, as shown in FIG. 10 corresponding to FIG. 2, the sealant 60 (outer sealant portion 61) may cover only the outer surface S1 of the folded portion 51Z.

Even in these cases, the sealant 60 is used to obtain a high volumetric energy density and to prevent damage to the positive electrode lead 51 due to external force. Since the secondary battery can operate stably more easily from the viewpoint of ensuring the function, the same effect as the case shown in FIG. 2 can be obtained.

[Modification 2]
In FIG. 2, since the positive electrode lead 51 is folded only once inside the through hole 10K, the positive electrode lead 51 includes only one folded portion 51Z. Thereby, the sealant 60 covers only the surface of one folded portion 51Z.

However, although not specifically illustrated here, since the positive electrode lead 51 is folded two or more times inside the through hole 10K, the positive electrode lead 51 may include two or more folded portions 51Z. Thereby, the sealant 60 may cover the surface of each of the two or more folded portions 51Z. Note that the two or more folded portions 51Z may or may not overlap each other. Of course, only a part of two or more folded portions 51Z may overlap each other.

In this case as well, two or more folded portions 51Z and a sealant 60 covering the surface of each of the two or more folded portions 51Z are used to obtain the same effect as in the case shown in FIG. can be done.

In this case, in particular, when the number of folded portions 51Z increases, the length margin of the positive electrode lead 51 increases, so a higher effect can be obtained.

[Modification 3]
2, 4 and 5, the sealant 60 includes an outer sealant portion 61 and an inner sealant portion 62 to cover both the outer surface S1 and the inner surface S2 of the positive lead 51, the outer sealant portion 61 and inner sealant portion 62 are attached to each other via positive electrode lead 51 .

However, if the sealant 60 can cover both the outer surface S1 and the inner surface S2 of the positive electrode lead 51, the configuration of the sealant 60 is not particularly limited. Although not specifically illustrated here, the sealant 60 may have a tubular structure. That is, sealant 60 may be a single piece having a tubular structure.

Also in this case, since the positive electrode lead 51 is insulated from the outer can 10 (cover portion 12) via the sealant 60, the same effect as in the case shown in FIG. 2 can be obtained.

[Modification 4]
In FIG. 2, the lid portion 12 has a recessed portion 12U, and the external terminal 20 is arranged inside the recessed portion 12U.

However, as shown in FIG. 11 corresponding to FIG. 2, even if the lid portion 12 is substantially flat without the recessed portion 12U and the external terminals 20 are arranged on the lid portion 12, good. Also in this case, the same effect as in the case shown in FIG. 2 can be obtained. However, it should be noted that increasing the height H of the secondary battery may decrease the volumetric energy density.

[Modification 5]
In FIG. 2 , the positive electrode 41 as the first electrode is connected to the external terminal 20 via the positive lead 51 , and the negative electrode 42 as the second electrode is connected to the housing portion 11 via the negative lead 52 . . As a result, the external terminal 20 functions as an external connection terminal for the positive electrode 41 , and the outer can 10 functions as an external connection terminal for the negative electrode 42 .

However, as shown in FIG. 12 corresponding to FIG. 2, the positive electrode 41 which is the second electrode is connected to the housing portion 11 via the positive electrode lead 51, and the negative electrode 42 which is the first electrode is connected to the negative electrode lead 52. may be connected to the external terminal 20 via the . As a result, the outer can 10 may function as an external connection terminal for the positive electrode 41 , and the external terminal 20 may function as an external connection terminal for the negative electrode 42 .

In this case, the external terminal 20 contains one or more of conductive materials such as a metal material and an alloy material in order to function as a terminal for external connection of the negative electrode 42, and the metal material and alloy materials include iron, copper, nickel, stainless steel, iron alloys, copper alloys and nickel alloys. Each of the outer can 10, that is, the storage portion 11 and the lid portion 12, is made of one or more of conductive materials such as a metal material and an alloy material in order to function as an external connection terminal for the positive electrode 41. Specific examples of metal materials and alloy materials include aluminum, aluminum alloys and stainless steel.

Although not specifically illustrated here, the negative lead 52, which is a wiring member connected to the external terminal 20, has the same configuration as the positive lead 51 shown in FIG. Includes a stay section and a folded section. Thereby, the sealant 60 covers the surface of the negative electrode lead 52, and more specifically covers at least the surface of the folded portion.

Even in this case, the secondary battery can be connected to the electronic device via the external terminal 20 (terminal for external connection of the negative electrode 42) and the outer can 10 (terminal for external connection of the positive electrode 41). It is possible to obtain the same effect as in the case of

[Modification 6]
A separator 43, which is a porous membrane, was used. However, although not specifically illustrated here, instead of the separator 43, a laminated separator including a polymer compound layer may be used.

Specifically, a laminated separator includes a porous membrane having a pair of surfaces and a polymer compound layer provided on one or both sides of the porous membrane. This is because the adhesiveness of the separator to each of the positive electrode 41 and the negative electrode 42 is improved, so that the winding misalignment of the battery element 40 is suppressed. As a result, even if a decomposition reaction of the electrolytic solution occurs, the secondary battery is less likely to swell. The polymer compound layer contains a polymer compound such as polyvinylidene fluoride. This is because polyvinylidene fluoride or the like has excellent physical strength and is electrochemically stable.

One or both of the porous film and the polymer compound layer may contain one or more of a plurality of insulating particles. This is because the safety (heat resistance) of the secondary battery is improved because the plurality of insulating particles promote heat dissipation when the secondary battery generates heat. The insulating particles include one or both of inorganic particles and resin particles. Specific examples of inorganic particles are particles such as aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide and zirconium oxide. Specific examples of resin particles are particles of acrylic resins, styrene resins, and the like.

When manufacturing a laminated separator, after preparing a precursor solution containing a polymer compound, a solvent, etc., the precursor solution is applied to one or both sides of the porous membrane. In this case, instead of applying the precursor solution to the porous membrane, the porous membrane may be immersed in the precursor solution. Also, a plurality of insulating particles may be added to the precursor solution.

Even when this laminated separator is used, lithium ions can move between the positive electrode 41 and the negative electrode 42, so the same effect can be obtained. In this case, particularly, as described above, the safety of the secondary battery is improved, so that a higher effect can be obtained.

[Modification 7]
An electrolytic solution, which is a liquid electrolyte, was used. However, although not specifically illustrated here, an electrolyte layer that is a gel electrolyte may be used instead of the electrolyte solution.

In the battery element 40 using the electrolyte layer, the positive electrode 41 and the negative electrode 42 are laminated with the separator 43 and the electrolyte layer interposed therebetween, and the positive electrode 41, the negative electrode 42, the separator 43 and the electrolyte layer are wound. This electrolyte layer is interposed between the positive electrode 41 and the separator 43 and interposed between the negative electrode 42 and the separator 43 . However, the electrolyte layer may be interposed only between the positive electrode 41 and the separator 43 , or may be interposed only between the negative electrode 42 and the separator 43 .

Specifically, the electrolyte layer contains a polymer compound together with an electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented. The composition of the electrolytic solution is as described above. Polymer compounds include polyvinylidene fluoride and the like. When forming the electrolyte layer, after preparing a precursor solution containing an electrolytic solution, a polymer compound, a solvent, and the like, the precursor solution is applied to one side or both sides of each of the positive electrode 41 and the negative electrode 42 .

Even when this electrolyte layer is used, lithium ions can move between the positive electrode 41 and the negative electrode 42 through the electrolyte layer, so that similar effects can be obtained. In this case, especially, as described above, leakage of the electrolytic solution is prevented, so that a higher effect can be obtained.

Although the present technology has been described above while citing one embodiment, the configuration of the present technology is not limited to the configuration described in the one embodiment, and can be variously modified.

Specifically, the case where the element structure of the battery element is a wound type has been described, but the element structure is not particularly limited, and may be a laminated type or a folded type. In the laminate type, positive electrodes and negative electrodes are alternately laminated with separators interposed therebetween, and in the multifold type, positive electrodes and negative electrodes are folded in zigzags with separators interposed therebetween.

Also, the case where the electrode reactant is lithium has been described, but the electrode reactant is not particularly limited. Thus, the electrode reactants may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium and calcium, as described above. Alternatively, the electrode reactant may be other light metals such as aluminum.

Since the effects described in this specification are merely examples, the effects of the present technology are not limited to the effects described in this specification. Accordingly, other advantages may be obtained with respect to the present technology.

Claims

a conductive exterior member having a through hole;
a battery element housed inside the exterior member and including a first electrode and a second electrode;
an electrode terminal arranged outside the exterior member and shielding the through hole;
an insulating sealing member disposed between the exterior member and the electrode terminal;
a wiring member connected to each of the first electrode and the electrode terminal via the through hole;
and an insulating coating member that coats the surface of the wiring member,
The wiring member includes a folded portion in which the wiring member is folded back in an inner diameter direction of the through hole inside the through hole,
The covering member covers at least the outer surface of the folded portion,
secondary battery.
The covering member further covers the inner surface of the folded portion,
The secondary battery according to claim 1.
The wiring member further includes:
a first extending portion extending in a direction toward the folded portion and connected to each of the first electrode and the folded portion;
a second extending portion extending in a direction opposite to the direction in which the first extending portion extends and connected to each of the electrode terminal and the folded portion;
The covering member covers up to the surface of at least one of the first extending portion and the second extending portion,
The secondary battery according to claim 1 or 2.
The exterior member is
a storage section having an opening and housing the battery element therein;
a lid that has the through hole and closes the opening,
The lid portion and the storage portion are joined to each other,
The secondary battery according to any one of claims 1 to 3.
The lid portion has a recess portion provided with the through hole,
In the recessed portion, the lid portion is bent so as to be partially recessed toward the interior of the storage portion,
The electrode terminal is arranged inside the recess,
The secondary battery according to claim 4.
The exterior member is electrically connected to the second electrode,
The secondary battery according to any one of claims 1 to 5.
The exterior member has a flat and columnar three-dimensional shape,
The secondary battery according to any one of claims 1 to 6.
The exterior member is a metal can,
The secondary battery according to any one of claims 1 to 7.
A lithium ion secondary battery,
The secondary battery according to any one of claims 1 to 8.