WO2023189762A1

WO2023189762A1 - Secondary battery

Info

Publication number: WO2023189762A1
Application number: PCT/JP2023/010712
Authority: WO
Inventors: 陽介河野; 亜未大沼; 武夫浅沼; 淳史黄木; 真純福田
Original assignee: 株式会社村田製作所
Priority date: 2022-03-30
Filing date: 2023-03-17
Publication date: 2023-10-05

Abstract

Provided is a secondary battery comprising: a positive electrode which includes a positive electrode active material layer; a negative electrode; a separator which is arranged between the positive electrode and the negative electrode; and an electrolytic solution. The positive electrode active material layer includes a positive electrode active material and a first binder. The separator includes a porous layer and a coating layer arranged between this porous layer and the positive electrode active material layer and this coating layer includes a plurality of insulating particles and a second binder. A part of the coating layer is not adjacent to the porous layer and is adjacent to the positive electrode active material layer.

Description

secondary battery

The present technology relates to secondary batteries.

As a variety of electronic devices such as mobile phones have become widespread, secondary batteries are being developed as a power source that is small and lightweight and provides high energy density. This secondary battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, and various studies have been made regarding the configuration of the secondary battery.

Specifically, a protective layer containing an insulating inorganic compound is provided on the surface of the positive electrode, and the surface resistance of the positive electrode is 0.5Ω to 40Ω (see, for example, Patent Document 1).

JP 2019-160556 Publication

Although various studies have been made regarding the configuration of secondary batteries, the battery characteristics of the secondary batteries are still insufficient, so there is room for improvement.

A secondary battery that can provide excellent battery characteristics is desired.

A secondary battery according to an embodiment of the present technology includes a positive electrode including a positive electrode active material layer, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte. The positive electrode active material layer includes a positive electrode active material and a first binder. The separator includes a porous layer and a coating layer disposed between the porous layer and the positive electrode active material layer, and the coating layer includes a plurality of insulating particles and a second binder. A portion of the covering layer is not adjacent to the porous layer and is adjacent to the positive electrode active material layer.

According to a secondary battery according to an embodiment of the present technology, a separator including a porous layer and a coating layer is disposed between a positive electrode and a negative electrode, and the positive active material layer of the positive electrode is connected to the positive active material and the first A coating layer disposed between the porous layer and the positive electrode active material layer includes a plurality of insulating particles and a second binder, and a part of the coating layer includes a binder. Since it is not adjacent to the porous layer and is adjacent to the positive electrode active material layer, excellent battery characteristics can be obtained.

Note 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.

FIG. 1 is a perspective view showing the configuration of a secondary battery in an embodiment of the present technology. FIG. 2 is a cross-sectional view showing the configuration of the battery element shown in FIG. 1. FIG. 3 is a plan view showing the configuration of the positive electrode shown in FIG. 2. FIG. 3 is a plan view showing the configuration of the negative electrode shown in FIG. 2. FIG. FIG. 2 is a cross-sectional view showing the configuration of a battery element after a heating test of a secondary battery. FIG. 2 is a perspective view for explaining a method for manufacturing a secondary battery. FIG. 2 is a block diagram showing the configuration of an application example of a secondary battery.

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. Overall composition 1-2. Physical properties 1-3. Operation 1-4. Manufacturing method 1-5. Action and effect 2. Modification example 3. Applications of secondary batteries

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

The secondary battery described here is a secondary battery whose battery capacity is obtained by utilizing the intercalation and desorption of electrode reactants, and includes a positive electrode, a negative electrode, a separator, and an electrolyte.

In this secondary battery, the charging capacity of the negative electrode is larger than the discharging 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.

In the following, a case where the electrode reactant is lithium will be exemplified. A secondary battery whose battery capacity is obtained by utilizing intercalation and desorption of lithium is a so-called lithium ion secondary battery. In this lithium ion secondary battery, lithium is intercalated and released in an ionic state.

<1-1. Overall configuration>
FIG. 1 shows a perspective configuration of a secondary battery, and FIG. 2 shows a cross-sectional configuration of a battery element 20 shown in FIG. 3 shows the planar structure of the positive electrode 21 shown in FIG. 2, and FIG. 4 shows the planar structure of the negative electrode 22 shown in FIG. However, FIG. 1 shows a state in which the exterior film 10 and the battery element 20 are separated from each other.

As shown in FIGS. 1 and 2, this secondary battery includes an exterior film 10, a battery element 20, a plurality of positive electrode terminals 31, a plurality of negative electrode terminals 32, a positive electrode lead 41, and a negative electrode lead 42. , sealing

films

51 and 52.

As mentioned above, the secondary battery described here uses the exterior film 10 as an exterior member for accommodating the battery element 20, the plurality of positive electrode terminals 31, and the plurality of negative electrode terminals 32, so it is of the so-called laminate film type. This is a secondary battery.

[Exterior film]
The exterior film 10 is a flexible or pliable film-like exterior member, and as shown in FIG. are doing. Thereby, the exterior film 10 accommodates a positive electrode 21, a negative electrode 22, a separator 23, and an electrolytic solution, which will be described later.

Here, the exterior film 10 is a single film-like member, and is folded in the folding direction F. This exterior film 10 is provided with a recessed portion 10U (so-called deep drawn portion) for accommodating the battery element 20.

Specifically, the exterior film 10 is a three-layer laminate film in which a fusing layer, a metal layer, and a surface protection layer are laminated in this order from the inside, and when the exterior film 10 is folded, they face each other. The outer peripheral edges of the fusion layers are fused to each other. The adhesive layer contains a polymer compound such as polypropylene. The metal layer contains a metal material such as aluminum. The surface protective layer contains a polymer compound such as nylon.

However, the structure (number of layers) of the exterior film 10 is not particularly limited and may be one or two layers, or four or more layers.

[Battery element]
As shown in FIGS. 1 to 4, the battery element 20 is a power generating element that includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown), and is housed inside the exterior film 10. has been done.

Here, the battery element 20 is a so-called laminated electrode body. That is, the positive electrode 21 and the negative electrode 22 are alternately stacked with the separator 23 in between. The numbers of positive electrodes 21, negative electrodes 22, and separators 23 are not particularly limited and can be set arbitrarily.

(positive electrode)
As shown in FIGS. 2 and 3, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B. In FIG. 3, the positive electrode active material layer 21B is shaded.

The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. The positive electrode current collector 21A includes a conductive material such as a metal material, and a specific example of the conductive material is aluminum.

The positive electrode active material layer 21B contains a positive electrode active material and a positive electrode binder. However, the positive electrode active material layer 21B may further contain one or more types of other materials such as a positive electrode conductive agent.

Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. However, the positive electrode active material layer 21B may be provided only on one side of the positive electrode current collector 21A on the side where the positive electrode 21 faces the negative electrode 22. The method for forming the positive electrode active material layer 21B is not particularly limited, and specifically, a coating method or the like is used.

The positive electrode active material contains one or more materials capable of intercalating and deintercalating lithium. Here, the positive electrode active material contains a lithium-containing compound. This lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements, and may further contain one or more other elements as constituent elements. The type of other element is not particularly limited as long as it is an element other than lithium and transition metal elements, but specifically, it is an element belonging to Groups 2 to 15 in the long period periodic table. The type of lithium-containing compound is not particularly limited, but specifically includes oxides, phosphoric acid compounds, silicic acid compounds, and boric acid compounds.

Specific examples of oxides include LiNiO ₂ , LiCoO ₂ , LiCo _0.98 Al _0.01 Mg _0.01 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O ₂ , LiNi _{0.3 3} Co _0.33 Mn _0.33 O ₂ , Li _1.2 Mn _0.52 Co _0.175 Ni _0.1 O ₂ , Li _1.15 (Mn _0.65 Ni _0.22 Co _0.13 )O ₂ and LiMn ₂ O ₄ . Specific examples of phosphoric acid compounds include LiFePO ₄ , LiMnPO ₄ , LiFe _0.5 Mn _0.5 PO ₄ and LiFe _0.3 Mn _0.7 PO ₄ .

The positive electrode binder is a first binder that binds the positive electrode active materials and the like to each other. In the secondary battery assembly process described below, the laminate 20Z is hot-pressed in a state where the positive electrode 21 (positive electrode active material layer 21B) is adjacent to the separator 23 (positive electrode side coating layer 23B described later). The laminate 20Z is being pressed while being heated. Thereby, the positive electrode active material layer 21B is in close contact with the positive electrode side coating layer 23B.

This positive electrode binder contains one or more of materials such as synthetic rubber and polymer compounds. Specific examples of synthetic rubber include fluorine rubber and ethylene propylene diene. Specific examples of the polymer compound include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

Among these, it is preferable that the positive electrode binder contains the same material as the constituent material of the separator binder described below. This is because the constituent materials of the positive electrode binder and the separator binder are common to each other, so that the positive electrode binder easily adheres to the separator binder.

Specifically, the positive electrode binder preferably contains one or both of a vinylidene fluoride homopolymer and a vinylidene fluoride copolymer. This is because when the constituent materials of the positive electrode binder and the constituent materials of the separator binder are common to each other, the positive electrode binder is likely to adhere sufficiently to the separator binder.

In this case, the positive electrode binder is likely to be thermally fused to the separator binder, especially during heating of the secondary battery (after a heating test of the secondary battery described below).

The homopolymer of vinylidene fluoride is so-called polyvinylidene fluoride. A copolymer of vinylidene fluoride is a compound in which vinylidene fluoride and other monomers are copolymerized with each other. Specific examples of other monomers include monomers such as hexafluoropropylene. Any one type or two or more types. The copolymerization amount (% by weight) of other monomers can be set arbitrarily.

The positive electrode conductive agent contains one or more of conductive materials such as carbon materials, metal materials, and conductive polymer compounds. Specific examples of carbon materials include graphite, carbon black, acetylene black, and Ketjen black.

Here, as shown in FIG. 3, since a part of the positive electrode current collector 21A protrudes, the positive electrode current collector 21A has a portion (hereinafter referred to as (referred to as "the protrusion of the positive electrode current collector 21A"). Since the positive electrode active material layer 21B is not provided on the protruding portion of the positive electrode current collector 21A, the protruding portion of the positive electrode current collector 21A functions as the positive electrode terminal 31. Note that details of the positive electrode terminal 31 will be described later.

(Negative electrode)
As shown in FIGS. 2 and 4, the negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B. In FIG. 4, the negative electrode active material layer 22B is shaded.

The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. This negative electrode current collector 22A includes a conductive material such as a metal material, and a specific example of the conductive material is copper.

The negative electrode active material layer 22B contains a negative electrode active material. However, the negative electrode active material layer 22B may further contain one or more of other materials such as a negative electrode binder and a negative electrode conductive agent.

Here, the negative electrode active material layer 22B is provided on both sides of the negative electrode current collector 22A. However, the negative electrode active material layer 22B may be provided only on one side of the negative electrode current collector 22A on the side where the negative electrode 22 faces the positive electrode 21. The method for forming the negative electrode active material layer 22B is not particularly limited, but specifically, any one of a coating method, a gas phase method, a liquid phase method, a thermal spraying method, a firing method (sintering method), etc. There are two or more types.

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

Details regarding the negative electrode binder are the same as those regarding the positive electrode binder, except that the specific example of the synthetic rubber may further be styrene-butadiene rubber. Details regarding the negative electrode conductive agent are the same as those regarding the positive electrode conductive agent.

Here, as shown in FIG. 4, since a part of the negative electrode current collector 22A protrudes, the part of the negative electrode current collector 22A that protrudes outward from the negative electrode active material layer 22B (hereinafter referred to as (referred to as "the protrusion of the negative electrode current collector 22A"). Since the negative electrode active material layer 22B is not provided on the protruding portion of the negative electrode current collector 22A, the protruding portion of the negative electrode current collector 22A functions as the negative electrode terminal 32. Note that details of the negative electrode terminal 32 will be described later.

(Separator)
As shown in FIG. 2, the separator 23 is disposed between the positive electrode 21 and the negative electrode 22, and allows lithium ions to pass through while preventing contact (short circuit) between the positive electrode 21 and negative electrode 22.

In this battery element 20, as described above, the positive electrodes 21 and the negative electrodes 22 are alternately stacked with the separators 23 in between, so the battery element 20 includes a plurality of separators 23.

Here, the separator 23 includes a porous layer 23A, a positive electrode side coating layer 23B, and a negative electrode side coating layer 23C.

The porous layer 23A has a plurality of pores to allow lithium ions to pass through, and has a pair of surfaces on which the positive electrode side coating layer 23B and the negative electrode side coating layer 23C are provided. This porous layer 23A contains an insulating material such as a polymer compound, and a specific example of the insulating material is polyethylene.

The positive electrode side coating layer 23B is disposed between the porous layer 23A and the positive electrode 21 (positive electrode active material layer 21B), and is adjacent to the positive electrode active material layer 21B. This positive electrode side coating layer 23B includes a plurality of insulating particles and a separator binder, and the separator binder is a second binder that binds the plurality of insulating particles and the like to each other.

The plurality of insulating particles function to promote heat dissipation during heat generation and heating of the secondary battery. This improves the heat resistance of the secondary battery, thereby improving safety.

Each of the plurality of insulating particles contains one or more types of insulating materials such as inorganic materials, and specific examples of the insulating materials include metal hydroxides, metal oxides, and metal nitrides, etc. This is because sufficient heat dissipation properties can be obtained in the positive electrode side coating layer 23B. More specifically, metal hydroxides include magnesium hydroxide and aluminum hydroxide. Metal oxides include magnesium oxide, aluminum oxide, titanium oxide, silicon oxide, and zirconium oxide. Metal nitrides include aluminum nitride.

The separator binder is a material that holds a plurality of insulating particles, and contains one or more types of polymer compounds. Details regarding the polymer compound are the same as those regarding the polymer compound contained in the positive electrode binder.

Among these, as described above, the separator binder preferably contains the same material as the constituent material of the positive electrode binder, and more specifically, a vinylidene fluoride homopolymer (polyvinylidene fluoride). and a copolymer of vinylidene fluoride, or both thereof. This is because the separator binder easily adheres sufficiently to the positive electrode binder.

In this case, the separator binder is likely to be thermally fused to the positive electrode binder, particularly during heating of the secondary battery (after a heating test of the secondary battery described below).

The negative electrode side coating layer 23C is disposed between the porous layer 23A and the negative electrode 22 (negative electrode active material layer 22B), and is adjacent to the negative electrode active material layer 22B. This negative electrode side coating layer 23C contains a separator binder, and the details regarding the separator binder are as described above. Note that the negative electrode side coating layer 23C may include a plurality of insulating particles or may not include the plurality of insulating particles.

(electrolyte)
The electrolyte is a liquid electrolyte. This electrolytic solution is impregnated into each of the positive electrode 21, negative electrode 22, and separator 23, and contains a solvent and an electrolyte salt.

Here, the solvent contains one or more types of non-aqueous solvents (organic solvents), and the electrolytic solution containing the non-aqueous solvent is a so-called non-aqueous electrolytic solution. This nonaqueous solvent includes esters and ethers, and more specifically includes carbonate ester compounds, carboxylic ester compounds, and lactone compounds. This is because the dissociability of the electrolyte salt and the mobility of ions are improved.

The carbonate ester compounds are cyclic carbonate esters and chain carbonate esters. 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. Specific examples of chain carboxylic acid esters include ethyl acetate, ethyl propionate, propyl propionate, and ethyl trimethylacetate.

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

Note that the ethers may include 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, and 1,4-dioxane.

The electrolyte salt contains one or more 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 ), and lithium bis(fluorosulfonyl)imide (LiN). (FSO ₂ ) ₂ ), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF ₃ SO ₂ ) ₂ ), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF ₃ SO ₂ ) ₃ ), bis(oxalato)boro These include lithium oxide (LiB(C ₂ O ₄ ) ₂ ), lithium monofluorophosphate (Li ₂ PFO ₃ ), and lithium difluorophosphate (LiPF ₂ O ₂ ). This is because high battery capacity can be obtained.

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

Note that the electrolytic solution may further contain any one type or two or more types of additives. The types of additives are not particularly limited, but specifically include unsaturated cyclic carbonates, fluorinated cyclic carbonates, sulfonic esters, phosphoric esters, acid anhydrides, nitrile compounds, and isocyanate compounds.

Specific examples of unsaturated cyclic carbonate esters include vinylene carbonate, vinylethylene carbonate, and methyleneethylene carbonate. Specific examples of fluorinated cyclic carbonate esters include monofluoroethylene carbonate and difluoroethylene carbonate. Specific examples of sulfonic acid esters include propane sultone and propene sultone. Specific examples of phosphoric acid esters include trimethyl phosphate and triethyl phosphate. Specific examples of acid anhydrides include succinic anhydride, 1,2-ethanedisulfonic anhydride, and 2-sulfobenzoic anhydride. Specific examples of nitrile compounds include succinonitrile. A specific example of the isocyanate compound is hexamethylene diisocyanate.

[Multiple positive terminals and multiple negative terminals]
As shown in FIG. 3, the positive electrode terminal 31 is electrically connected to the positive electrode 21, and more specifically, to the positive electrode current collector 21A. The constituent material of the positive electrode terminal 31 is not particularly limited, but specifically, it is the same as the constituent material of the positive electrode current collector 21A.

In the battery element 20, as described above, the positive electrodes 21 and the negative electrodes 22 are alternately stacked with the separator 23 in between, so the battery element 20 includes a plurality of positive electrodes 21. As a result, the positive electrode terminal 31 is connected to each of the plurality of positive electrodes 21, so that the secondary battery includes the plurality of positive electrode terminals 31. As described later, the plurality of positive electrode terminals 31 are joined to each other, so as shown in FIG. 1, they form one lead-shaped joint portion 31Z.

Here, as described above, since the protrusion of the positive electrode current collector 21A functions as the positive electrode terminal 31, the positive electrode terminal 31 is physically integrated with the positive electrode current collector 21A. This is because the connection resistance between the positive electrode current collector 21A and the positive electrode terminal 31 is reduced, so that the electrical resistance of the entire secondary battery is reduced.

As shown in FIG. 4, the negative electrode terminal 32 is electrically connected to the negative electrode 22, and more specifically, to the negative electrode current collector 22A. This negative electrode terminal 32 is arranged at a position that does not overlap with the positive electrode terminal 31 in a state where the positive electrode 21 and the negative electrode 22 are alternately stacked with the separator 23 in between. The constituent material of the negative electrode terminal 32 is not particularly limited, but specifically, it is the same as the constituent material of the negative electrode current collector 22A.

As described above, in the battery element 20, the positive electrodes 21 and the negative electrodes 22 are alternately stacked with the separator 23 in between, so the battery element 20 includes a plurality of negative electrodes 22. Thereby, the negative electrode terminal 32 is connected to each of the plurality of negative electrodes 22, so that the secondary battery includes the plurality of negative electrode terminals 32. As described later, the plurality of negative electrode terminals 32 are joined to each other, so as shown in FIG. 1, they form one lead-shaped joint 32Z.

Here, as described above, since the protrusion of the negative electrode current collector 22A functions as the negative electrode terminal 32, the negative electrode terminal 32 is physically integrated with the negative electrode current collector 22A. This is because the connection resistance between the negative electrode current collector 22A and the negative electrode terminal 32 is reduced, so that the electrical resistance of the entire secondary battery is reduced.

[Positive lead and negative lead]
As shown in FIG. 1, the positive electrode lead 41 is connected to a joint portion 31Z, which is a plurality of positive electrode terminals 31 joined to each other, and is led out from the exterior film 10. The constituent material of the positive electrode lead 41 is not particularly limited, but specifically, it is the same as the constituent material of the positive electrode current collector 21A. Although the shape of the positive electrode lead 41 is not particularly limited, specifically, it is either a thin plate shape or a mesh shape.

As shown in FIG. 1, the negative electrode lead 42 is connected to a joint portion 32Z, which is a plurality of negative electrode terminals 32 joined to each other, and is led out from the exterior film 10. The constituent material of the negative electrode lead 42 is not particularly limited, but specifically, it is the same as the constituent material of the negative electrode current collector 22A. Note that the direction in which the negative electrode lead 42 is led out is the same direction as the direction in which the positive electrode lead 41 is led out. Further, the details regarding the shape of the negative electrode lead 42 are the same as the details regarding the shape of the positive electrode lead 41.

[Sealing film]
Each of the sealing

films

51 and 52 is a sealing member that prevents outside air from entering the exterior film 10. The sealing film 51 is inserted between the exterior film 10 and the positive electrode lead 41, and the sealing film 52 is inserted between the exterior film 10 and the negative electrode lead 42. However, one or both of the sealing

films

51 and 52 may be omitted.

This sealing film 51 contains a polymer compound such as polyolefin that has adhesiveness to the positive electrode lead 41, and a specific example of the polymer compound is polypropylene.

The configuration of the sealing film 52 is similar to that of the sealing film 51 except that it has adhesiveness to the negative electrode lead 42. That is, the sealing film 52 contains a polymer compound such as polyolefin that has adhesiveness to the negative electrode lead 42.

<1-2. Physical properties＞
FIG. 5 shows a cross-sectional configuration of the battery element 20 after the secondary battery heating test, and corresponds to FIG. 2.

In this secondary battery, the physical properties have been optimized to improve battery characteristics.

[Physical property conditions]
In the secondary battery (battery element 20) after the heating test, as shown in FIG. 5, the porous layer 23A undergoes thermal contraction in the in-plane direction of the XY plane. More specifically, in a state where the secondary battery is charged under the following charging conditions, after the secondary battery is heated at 130° C. for 60 minutes (heating test), the porous layer 23A is As in, heat shrinks. As a result, a part of the positive electrode side coating layer 23B is peeled off from the porous layer 23A and is in close contact with the positive electrode active material layer 21B. That is, a part of the positive electrode side coating layer 23B is not adjacent to the porous layer 23A and is adjacent to the positive electrode active material layer 21B. However, in FIG. 5, a part of the negative electrode side coating layer 23C is peeled off from the negative electrode active material layer 22B due to thermal contraction of the porous layer 23A, so a part of the negative electrode side coating layer 23C is removed from the negative electrode active material layer 22B. A case is shown in which the material layer 22B is not adjacent to the material layer 22B.

Charging conditions: In a 25°C environment, constant current charging with a current of 0.2C until the voltage reaches 4.25V, then constant voltage charging with a voltage of 4.25V until the total charging time reaches 6 hours. do. However, 0.2C is a current value that completely discharges the battery capacity (rated capacity) in 5 hours.

Note that the heating temperature is not limited to 130°C, but may be 130°C±2°C. Further, the heating time is not limited to 60 minutes, but may be 60 minutes±10 minutes.

In the battery element 20 after the heating test, a portion of the positive electrode side coating layer 23B that has peeled off from the porous layer 23A is in close contact with the positive electrode active material layer 21B because the discharge reaction between the positive electrode 21 and the negative electrode 22 is progressing. This is because the short circuit caused by the contact between the positive electrode 21 and the negative electrode 22 is suppressed from occurring while ensuring this.

Specifically, in the state before the charged secondary battery is heated (before the heating test), the discharge reaction tends to proceed stably, so the discharge characteristics are improved. In this case, the discharge reaction proceeds stably even if the discharge current increases.

Moreover, after the charged secondary battery is heated (after the heating test), the positive electrode side coating layer 23B (separator binder) is thermally fused to the positive electrode active material layer 21B (positive electrode binder). Therefore, the positive electrode side coating layer 23B tightly adheres to the positive electrode active material layer 21B. In this case, as shown in FIG. 5, even if the separator 23 shrinks due to heat generation and heating of the secondary battery, a part of the positive electrode side coating layer 23B does not peel off from the positive electrode active material layer 21B. remains on the surface of the positive electrode active material layer 21B. As a result, the state in which the insulating positive electrode side coating layer 23B is interposed between the positive electrode 21 and the negative electrode 22 is easily maintained without being affected by the thermal contraction of the separator 23, thereby suppressing the occurrence of short circuits. be done.

[Basic weight]
The basis weight is a parameter representing the amount of the positive electrode side coating layer 23B formed, and the basis weight is not particularly limited. Among these, the basis weight of the positive electrode side coating layer 23B is preferably 3 g/m ² to 7 g/m ² . This is because the amount of the positive electrode side coating layer 23B formed is optimized. Thereby, even if the positive electrode side coating layer 23B is interposed between the positive electrode 21 and the negative electrode 22, the progress of the discharge reaction is less likely to be inhibited. Moreover, when the positive electrode side coating layer 23B is thermally fused to the positive electrode active material layer 21B during heating of the secondary battery, a part of the positive electrode side coating layer 23B tends to remain on the surface of the positive electrode active material layer 21B. Become. Therefore, it becomes easier to ensure the progress of the discharge reaction and to suppress the occurrence of short circuits.

[Calculation procedure]
The procedure for calculating the basis weight is as explained below. In the following, a case will be described in which the positive electrode 21 includes two positive electrode active material layers 21B, and the separator 23 includes a positive electrode side coating layer 23B and a negative electrode side coating layer 23C.

First, the separator 23 is recovered by disassembling the secondary battery in a normal temperature environment (temperature = 25° C.).

Next, the weight (g) of the separator 23 is measured. Next, by dissolving and removing the positive electrode side coating layer 23B and the negative electrode side coating layer 23C from the porous layer 23A using a solvent for dissolving and removing, the porous layer 23A is recovered. Measure the weight (g). The type of solvent is not particularly limited, but specifically, it is an organic solvent such as N-methyl-2-pyrrolidone that can dissolve the separator binder. Subsequently, by subtracting the weight of the porous layer 23A from the weight of the separator 23, the weights (g) of the positive electrode side coating layer 23B and the negative electrode side coating layer 23C are calculated.

Finally ^, the basis weight (g /cm ² ). Note that since the area of the positive electrode side coating layer 23B and the area of the negative electrode side coating layer 23C are almost the same, the area used to calculate the basis weight may be the area of the positive electrode side coating layer 23B, or the area of the negative electrode side coating layer 23B. The area of the side covering layer 23C may also be used.

This basis weight is calculated based on the calculation formula expressed by the following formula (4). That is, the basis weight is a parameter representing the amount of the positive electrode side coating layer 23B and the negative electrode side coating layer 23C formed per unit area. However, the value of the basis weight shall be the value obtained by rounding off the value to the first decimal place.

Area weight = sum of the weight of the positive electrode side coating layer 23B and the weight of the negative electrode side coating layer 23C/area of the positive electrode side coating layer 23B or area of the negative electrode side coating layer 23C... (4)

[Confirmation procedure]
A procedure for checking the state of the battery element 20 after the heating test, that is, a procedure for checking whether a part of the positive electrode side coating layer 23B peeled off from the porous layer 23A after the heating test is in close contact with the positive electrode active material layer 21B. is as explained below.

First, a heating test is performed on the secondary battery according to the above-described procedure, and then the battery element 20 is recovered by disassembling the secondary battery after the heating test.

Next, the cross section of the battery element 20 is exposed by cutting the battery element 20 using a cutting tool in the direction in which the positive electrodes 21 and the negative electrodes 22 are alternately stacked with the separators 23 in between (Z-axis direction). let Subsequently, by observing the cross section (cross section along the XZ plane) of the battery element 20 using an electron microscope, the observation results (cross-sectional configuration) shown in FIG. 5 are obtained.

As the cutting tool, Cross Section Polisher (registered trademark) manufactured by JEOL Ltd. or the like can be used.

As the electron microscope, it is possible to use one or more types of electron microscopes such as a scanning electron microscope (SEM) and a transmission electron microscope. Note that the observation magnification is not particularly limited, but specifically, it is 20,000 times.

Finally, as shown in FIG. 5, the state of the positive electrode side coating layer 23B is confirmed based on an electron micrograph. As a result, if a part of the positive electrode side coating layer 23B is still adjacent to the positive electrode active material layer 21B even though the porous layer 23A has thermally shrunk, the positive electrode side coating layer 23B is Although the entirety of the positive electrode side coating layer 23B was in close contact with the porous layer 23A, after the heating test, it was found that part of the positive electrode side coating layer 23B that had peeled off from the porous layer 23A was in close contact with the positive electrode active material layer 21B. Become.

<1-3. Operation＞
When charging the secondary battery, in the battery element 20, lithium is released from the positive electrode 21, and at the same time, the lithium is inserted into the negative electrode 22 via the electrolyte. On the other hand, when the secondary battery is discharged, lithium is released from the negative electrode 22 in the battery element 20, and the lithium is inserted into the positive electrode 21 via the electrolyte. During charging and discharging, lithium is intercalated and released in an ionic state.

<1-4. Manufacturing method>
FIG. 6 shows a perspective configuration corresponding to FIG. 1 in order to explain a method for manufacturing a secondary battery. However, in FIG. 6, instead of the battery element 20, a laminate 20Z used for manufacturing the battery element 20 is shown. Note that details of the laminate 20Z will be described later.

When manufacturing a secondary battery, the positive electrode 21, the negative electrode 22, and the separator 23 are each manufactured according to the procedure described below, and after preparing the electrolyte, the positive electrode 21, negative electrode 22, and separator 23 are prepared. A secondary battery is assembled using the electrolyte and the secondary battery is stabilized.

[Preparation of positive electrode]
First, a paste-like positive electrode mixture slurry is prepared by adding a mixture of a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent (positive electrode mixture) to a solvent. This solvent may be an aqueous solvent or an organic solvent. Subsequently, a positive electrode mixture slurry is applied to both surfaces of the positive electrode current collector 21A (excluding the positive electrode terminal 31) on which the positive electrode terminal 31 is integrated, thereby forming the positive electrode active material layer 21B. Finally, the positive electrode active material layer 21B is compression molded using a roll press machine or the like. In this case, the positive electrode active material layer 21B may be heated or compression molding may be repeated multiple times. Thereby, the positive electrode active material layers 21B are formed on both sides of the positive electrode current collector 21A, so that the positive electrode 21 is manufactured.

[Preparation of negative electrode]
The negative electrode 22 is formed by the same procedure as the positive electrode 21 described above. Specifically, first, a paste-like negative electrode mixture slurry is prepared by adding a mixture (negative electrode mixture) in which a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent are mixed together into a solvent. Subsequently, a negative electrode active material layer 22B is formed by applying a negative electrode mixture slurry to both surfaces (excluding the negative electrode terminal 32) of the negative electrode current collector 22A in which the negative electrode terminal 32 is integrated. Finally, the negative electrode active material layer 22B is compression molded. Thereby, the negative electrode active material layers 22B are formed on both sides of the negative electrode current collector 22A, so that the negative electrode 22 is manufactured.

[Preparation of separator]
First, a paste-like slurry is prepared by adding a mixture of a plurality of insulating particles and a separator binder to a solvent. Details regarding the solvent are as described above. Subsequently, by applying slurry to one surface of the porous layer 23A, a positive electrode side coating layer 23B containing a plurality of insulating particles is formed.

Finally, a paste-like slurry is prepared by adding a separator binder to a solvent, and then the slurry is applied to one surface of the porous layer 23A on which the positive electrode side coating layer 23B is not formed. A negative electrode side coating layer 23C containing no insulating particles is formed.

As a result, the positive electrode side coating layer 23B is formed on one side of the porous layer 23A, and the negative electrode side coating layer 23C is formed on the opposite side of the porous layer 23A, so that the separator 23 is produced.

[Preparation of electrolyte]
Add electrolyte salt to the solvent. As a result, the electrolyte salt is dispersed or dissolved in the solvent, so that an electrolytic solution is prepared.

[Assembling the secondary battery]
First, the positive electrode 21 and the negative electrode 22 are alternately laminated with the separator 23 in between, thereby producing a laminate 20Z as shown in FIG. This laminate 20Z has the same configuration as the battery element 20, except that the positive electrode 21, the negative electrode 22, and the separator 23 are not impregnated with an electrolytic solution.

Subsequently, a joint portion 31Z is formed by joining the plurality of positive electrode terminals 31 to each other using a joining method such as a welding method, and then the positive electrode lead 41 is connected to the joint portion 31Z. Further, after a joint portion 32Z is formed by joining the plurality of negative electrode terminals 32 to each other using a joining method such as a welding method, the negative electrode lead 42 is connected to the joint portion 32Z.

Subsequently, after accommodating the laminate 20Z inside the recess 10U, the exterior films 10 (fusion layer/metal layer/surface protection layer) are folded to face each other. Subsequently, the outer peripheral edges of two sides of the fusion layers facing each other are adhered to each other using an adhesive method such as a heat fusion method, thereby forming the laminate 20Z inside the bag-shaped exterior film 10. to store. In this case, each of the positive electrode lead 41 and the negative electrode lead 42 is led out from the exterior film 10.

Next, after injecting an electrolytic solution into the inside of the bag-shaped exterior film 10, the outer peripheral edges of the remaining one side of the facing adhesive layers are bonded together using an adhesive method such as a heat fusion method. Glue them together. In this case, a sealing film 51 is inserted between the exterior film 10 and the positive electrode lead 41, and a sealing film 52 is inserted between the exterior film 10 and the negative electrode lead 42.

Finally, using a press machine equipped with a pair of press plates (not shown), the exterior film 10 containing the laminate 20Z is hot-pressed. In this case, after arranging the exterior film 10 between a pair of press plates, the exterior film 10 is heated in the direction in which the positive electrode 21 and the negative electrode 22 are alternately laminated with the separator 23 in between (Z-axis direction), and then the exterior film 10 is moved up and down. Press from As a result, the porous layer 23A is brought into close contact with the positive electrode 21 via the positive electrode side covering layer 23B, and the porous layer 23A is brought into close contact with the negative electrode 22 through the negative electrode side covering layer 23C.

As a result, the stacked body 20Z is impregnated with the electrolytic solution, so that the battery element 20, which is a stacked electrode body, is manufactured. Therefore, since the battery element 20 is sealed inside the bag-shaped exterior film 10, a secondary battery is assembled.

[Stabilization of secondary batteries]
Charge and discharge the assembled secondary battery. Conditions such as environmental temperature, number of charging/discharging times (number of cycles), and charging/discharging conditions can be set arbitrarily. As a result, a film is formed on each surface of the positive electrode 21 and the negative electrode 22, so that the state of the secondary battery is electrochemically stabilized. Thus, the secondary battery is completed.

<1-5. Action and effect>
According to this secondary battery, the separator 23 including the porous layer 23A and the positive electrode side coating layer 23B is arranged between the positive electrode 21 and the negative electrode 22. Further, the positive electrode active material layer 21B of the positive electrode 21 contains a positive electrode active material and a positive electrode binder, and the positive electrode side coating layer 23B disposed between the porous layer 23A and the positive electrode active material layer 21B has a plurality of insulating layers. containing particles and a separator binder. Further, a part of the positive electrode side coating layer 23B is not adjacent to the porous layer 23A and is adjacent to the positive electrode active material layer 21B.

In this case, as described above, before the charged secondary battery is heated, the discharge reaction tends to proceed stably, so the discharge characteristics are improved.

Moreover, in a state after the charged secondary battery is heated, the positive electrode side coating layer 23B is thermally fused to the positive electrode active material layer 21B. As a result, even if the separator 23 thermally shrinks during heat generation and heating of the secondary battery, a portion of the positive electrode side coating layer 23B remains on the surface of the positive electrode active material layer 21B. Therefore, the state in which the insulating positive electrode side coating layer 23B is interposed between the positive electrode 21 and the negative electrode 22 is easily maintained, so that the occurrence of short circuits is suppressed.

For these reasons, since the occurrence of short circuits is suppressed while ensuring discharge characteristics, excellent battery characteristics can be obtained.

In particular, if each of the positive electrode binder and the separator binder contains one or both of vinylidene fluoride homopolymer and vinylidene fluoride copolymer, when the secondary battery is heated, Since the positive electrode active material layer 21B (positive electrode binder) and the positive electrode side coating layer 23B (separator binder) are easily thermally fused to each other, higher effects can be obtained.

Further, if each of the plurality of insulating particles contains one or more types of metal hydroxide, metal oxide, and metal nitride, sufficient heat dissipation properties can be achieved in the positive electrode side coating layer 23B. Therefore, higher effects can be obtained.

Furthermore, if the positive electrodes 21 and negative electrodes 22 are alternately stacked with the separator 23 in between, the occurrence of short circuits can be effectively suppressed even if the positive electrodes 21 are stacked with the separator 23 in between, resulting in a higher effect. can be obtained.

In this case, a positive electrode terminal 31 is connected to each of the plurality of positive electrodes 21, a negative electrode terminal 32 is connected to each of the plurality of negative electrodes 22, a plurality of positive electrode terminals 31 are joined to each other, and a plurality of positive electrode terminals 31 are connected to each of the plurality of negative electrodes 22. If the negative electrode terminals 32 of the two are connected to each other, the battery capacity is guaranteed and the occurrence of short circuits is effectively suppressed, so that even higher effects can be obtained.

Moreover, the battery element 20 is housed inside the exterior film 10, the positive electrode lead 41 joined to the joint 31Z is led out from the exterior film 10, and the negative electrode lead 42 joined to the joint 32Z is connected to the exterior film. 10, even if a plurality of positive electrode terminals 31 and a plurality of negative electrode terminals 32 are used, the sealing performance of the exterior film 10 is improved, and a significantly high effect can be obtained.

Specifically, when the joint portion 31Z is led out from the exterior film 10, the thickness of the joint portion 31Z, which is a joined body of a plurality of positive electrode terminals 31, increases. gaps are likely to occur. This makes it difficult to seal the exterior film 10 using the sealing film 51, and thus the sealability of the exterior film 10 is reduced.

On the other hand, when the positive electrode lead 41 is led out from the exterior film 10, the thickness of the positive electrode lead 41 becomes smaller compared to the thickness of the joint part 31Z, which is a joined body of the plurality of positive electrode terminals 31. , a gap is less likely to occur between the exterior film 10 and the positive electrode lead 41. This makes it easier to seal the exterior film 10 using the sealing film 51, so that the sealability of the exterior film 10 is improved.

Note that the advantages described here based on leading out the positive electrode lead 41 from the exterior film 10 can be similarly obtained based on leading out the negative electrode lead 42 from the exterior film 10. That is, by leading out the negative electrode lead 42 instead of the joint portion 32Z from the exterior film 10, it becomes easier to seal the exterior film 10 using the sealing film 52, so that the sealability of the exterior film 10 is improved.

Furthermore, if the secondary battery is a lithium ion secondary battery, a sufficient battery capacity can be stably obtained by utilizing intercalation and desorption of lithium, so higher effects can be obtained.

<2. Modified example>
The configuration of the secondary battery described above can be modified as appropriate, as described below.

[Modification 1]
In FIG. 2, the separator 23 includes both a positive electrode side coating layer 23B and a negative electrode side coating layer 23C. However, the separator 23 may include only the positive electrode side coating layer 23B without including the negative electrode side coating layer 23C. Also in this case, the adhesion of the separator 23 to the positive electrode 21 is increased using the positive electrode side coating layer 23B, so that the same effect can be obtained.

[Modification 2]
In FIG. 3, since the protrusion of the positive electrode current collector 21A also serves as the positive electrode terminal 31, the positive electrode terminal 31 is physically integrated with the positive electrode current collector 21A. However, since the positive electrode terminal 31 is physically separated from the positive electrode current collector 21A, it may be separate from the positive electrode current collector 21A. In this case, the positive electrode terminal 31 may be connected to the positive electrode current collector 21A using a joining method such as a welding method.

Also in this case, since the positive electrode terminal 31 is electrically connected to the positive electrode 21, the same effect can be obtained. However, in order to reduce the electrical resistance of the entire secondary battery in accordance with the reduction in connection resistance, it is preferable that the positive electrode terminal 31 is physically integrated with the positive electrode current collector 21A.

Similarly, in FIG. 4, the protrusion of the negative electrode current collector 22A also serves as the negative electrode terminal 32, so the negative electrode terminal 32 is physically integrated with the negative electrode current collector 22A. However, since the negative electrode terminal 32 is physically separated from the negative electrode current collector 22A, it may be separate from the negative electrode current collector 22A. In this case, the negative electrode terminal 32 may be connected to the negative electrode current collector 22A using a joining method such as a welding method.

Also in this case, since the negative electrode terminal 32 is electrically connected to the negative electrode 22, the same effect can be obtained. However, in order to reduce the electrical resistance of the entire secondary battery in accordance with the reduction in connection resistance, it is preferable that the negative electrode terminal 32 is physically integrated with the negative electrode current collector 22A.

[Modification 3]
In FIG. 1, a battery element 20 which is a laminated electrode body is used. However, although not specifically illustrated here, the battery element 20 which is a wound electrode body may also be used. In this case, the positive electrode 21 has a band-like structure, and the positive electrode lead 41 is connected to the positive electrode current collector 21A, and the negative electrode 22 has a band-like structure, and the negative electrode current collector 22A A negative electrode lead 42 is connected to. However, the number of positive electrode leads 41 may be one or two or more, and the number of negative electrode leads 42 may be one or two or more. Thereby, the positive electrode 21 and the negative electrode 22 are wound while facing each other with the separator 23 in between.

Even in this case, the secondary battery can be charged and discharged using the battery element 20, so similar effects can be obtained.

<3. Applications of secondary batteries>
The use (application example) of the secondary battery is not particularly limited. A secondary battery used as a power source may be a main power source or an auxiliary power source in applications such as electronic equipment and electric vehicles. The main power source is a power source that is used preferentially, regardless of the presence or absence of other power sources. The auxiliary power source may be a power source used in place of the main power source, or may be a power source that can be switched from the main power source.

Specific examples of uses of the secondary battery are as described below. Electronic devices such as video cameras, digital still cameras, mobile phones, notebook computers, headphone stereos, portable radios, and portable information terminals. Backup power supplies and storage devices such as memory cards. Power tools such as power drills and power saws. This is a battery pack installed in electronic devices. Medical electronic devices such as pacemakers and hearing aids. Electric vehicles such as electric vehicles (including hybrid vehicles). A power storage system such as a household or industrial battery system that stores power in case of an emergency. In these applications, one secondary battery or a plurality of secondary batteries may be used.

The battery pack may use single cells or assembled batteries. An electric vehicle is a vehicle that runs using a secondary battery as a driving power source, and may be a hybrid vehicle that also includes a driving source other than the secondary battery. In a household power storage system, household electrical appliances and the like can be used by using the electric power stored in a secondary battery, which is a power storage source.

Here, an example of the application of the secondary battery will be specifically described. The configuration of the application example described below is just an example and can be modified as appropriate.

FIG. 7 shows the block configuration of the battery pack. The battery pack described here is a battery pack (so-called soft pack) using one secondary battery, and is installed in electronic devices such as smartphones.

As shown in FIG. 7, this battery pack includes a power source 71 and a circuit board 72. This circuit board 72 is connected to a power source 71 and includes a positive terminal 73, a negative terminal 74, and a temperature detection terminal 75.

The power source 71 includes one secondary battery. In this secondary battery, the positive electrode lead is connected to the positive electrode terminal 73, and the negative electrode lead is connected to the negative electrode terminal 74. This power source 71 can be connected to an external power source via the positive terminal 73 and the negative terminal 74, and therefore can be charged and discharged using the external power source. The circuit board 72 includes a control section 76 , a switch 77 , a PTC element 78 , and a temperature detection section 79 . However, the PTC element 78 may be omitted.

The control unit 76 includes a central processing unit (CPU), memory, etc., and controls the operation of the entire battery pack. This control unit 76 detects and controls the usage status of the power source 71 as necessary.

Note that when the voltage of the power source 71 (secondary battery) reaches the overcharge detection voltage or overdischarge detection voltage, the control unit 76 prevents the charging current from flowing in the current path of the power source 71 by cutting off the switch 77. Make it. Although the overcharge detection voltage is not particularly limited, specifically, it is 4.20V±0.05V, and the overdischarge detection voltage is not particularly limited, but specifically, it is 2.40V±0.1V. It is.

The switch 77 includes a charging control switch, a discharging control switch, a charging diode, a discharging diode, and the like, and switches whether or not the power supply 71 is connected to an external device according to an instruction from the control unit 76. This switch 77 includes a field effect transistor (MOSFET) using a metal oxide semiconductor, and the charging/discharging current is detected based on the ON resistance of the switch 77.

The temperature detection section 79 includes a temperature detection element such as a thermistor. The temperature detection section 79 measures the temperature of the power supply 71 using the temperature detection terminal 75 and outputs the temperature measurement result to the control section 76 . The measurement result of the temperature measured by the temperature detection unit 79 is used when the control unit 76 performs charge/discharge control during abnormal heat generation and when the control unit 76 performs correction processing when calculating the remaining capacity.

Although the present technology has been described above with reference to one embodiment, the configuration of the present technology is not limited to the configuration described in the one embodiment and can be modified in various ways.

Specifically, the case where the element structure of the battery element is a stacked type has been described. However, since the element structure of the battery element is not particularly limited, other element structures such as a ninety-nine fold type may be used. In the ninety-nine fold type, a positive electrode and a negative electrode are folded in a zigzag pattern while facing each other with a separator in between.

Furthermore, although the case where the electrode reactant is lithium has been described, the electrode reactant is not particularly limited. Specifically, 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. In addition, the electrode reactant may be other light metals such as aluminum.

The effects described in this specification are merely examples, so the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with the present technology.

Claims

a positive electrode including a positive electrode active material layer;
a negative electrode;
a separator disposed between the positive electrode and the negative electrode;
Equipped with an electrolyte and
The positive electrode active material layer includes a positive electrode active material and a first binder,
The separator is
a porous layer;
a coating layer disposed between the porous layer and the positive electrode active material layer,
The coating layer includes a plurality of insulating particles and a second binder,
A part of the coating layer is not adjacent to the porous layer and is adjacent to the positive electrode active material layer,
Secondary battery.
Each of the first binder and the second binder includes at least one of a vinylidene fluoride homopolymer and a vinylidene fluoride copolymer.
The secondary battery according to claim 1.
Each of the plurality of insulating particles includes at least one of a metal hydroxide, a metal oxide, and a metal nitride.
The secondary battery according to claim 1 or 2.
The positive electrode and the negative electrode are alternately stacked with the separator interposed therebetween.
The secondary battery according to any one of claims 1 to 3.
comprising a plurality of the positive electrodes, a plurality of the negative electrodes, and a plurality of the separators,
moreover,
a positive electrode terminal connected to each of the plurality of positive electrodes;
and a negative electrode terminal connected to each of the plurality of negative electrodes,
The plurality of positive electrode terminals are joined to each other,
the plurality of negative electrode terminals are joined to each other,
The secondary battery according to claim 4.
moreover,
a film-like exterior member that houses a plurality of the positive electrodes, a plurality of the negative electrodes, a plurality of the separators, the electrolytic solution, a plurality of the positive electrode terminals, and a plurality of the negative electrode terminals;
a positive electrode lead connected to the plurality of positive electrode terminals that are joined to each other;
and a negative electrode lead connected to the plurality of negative electrode terminals that are joined to each other,
The positive electrode lead is led out from the exterior member,
The negative electrode lead is led out from the exterior member.
The secondary battery according to claim 5.
A lithium ion secondary battery,
The secondary battery according to any one of claims 1 to 6.