CN110544796B

CN110544796B - Secondary battery, battery pack, electric vehicle, electricity storage system, electric tool, and electronic device

Info

Publication number: CN110544796B
Application number: CN201810522762.6A
Authority: CN
Inventors: 松井贵昭; 国分崇; 本多一辉; 木暮太一; 山川直子
Original assignee: Murata Manufacturing Co Ltd
Current assignee: Murata Manufacturing Co Ltd
Priority date: 2018-05-28
Filing date: 2018-05-28
Publication date: 2022-09-02
Anticipated expiration: 2038-05-28
Also published as: CN110544796A

Abstract

Provided are a secondary battery, a battery pack, an electric vehicle, an electricity storage system, an electric power tool, and an electronic device, which can obtain excellent battery characteristics. The secondary battery includes a wound electrode body having a flat shape defined by a major axis and a minor axis, a first positive/negative electrode wound portion including a positive/negative electrode terminal attached thereto and extending in a winding direction at an end portion on a winding inner side in the winding direction, the first negative electrode wound portion facing the first positive electrode wound portion with a separator interposed therebetween, the negative electrode terminal not overlapping the positive electrode terminal in the minor axis direction; the step-relaxing member is provided in at least one of the first to third regions, the first region is located further outward in a winding direction of the positive electrode than the positive electrode terminal in a longitudinal direction than the positive electrode terminal, the second region is located further outward in a winding direction of the negative electrode than the negative electrode terminal in the longitudinal direction than the negative electrode terminal, and the third region is located between the positive electrode terminal and the negative electrode terminal.

Description

Secondary battery, battery pack, electric vehicle, electricity storage system, electric tool, and electronic device

Technical Field

The present technology relates to a secondary battery including a wound electrode body including a positive electrode and a negative electrode, and a battery pack, an electric vehicle, an electric storage system, an electric power tool, and an electronic device using the secondary battery.

Background

With the widespread use of various electronic devices such as cellular phones, there is a demand for downsizing, weight reduction, and long life of these electronic devices. Therefore, development of a small-sized and lightweight secondary battery capable of obtaining high energy density as a power source has been advanced.

The application of the secondary battery is not limited to the electronic devices, and is being studied for other applications. Examples of such a battery pack include a battery pack detachably mounted on an electronic device or the like, an electric vehicle such as an electric car, an electricity storage system such as a home power server, and an electric tool such as an electric drill.

Specifically, the secondary battery includes a wound electrode body as a battery element. The wound electrode body is formed by laminating a positive electrode and a negative electrode with a separator interposed therebetween and then winding the positive electrode, the negative electrode, and the separator. The positive electrode is connected to a positive electrode lead, and the negative electrode is connected to a negative electrode lead.

The structure of a secondary battery including a wound electrode assembly greatly affects the structural stability of the wound electrode assembly, and further, the battery characteristics. Therefore, various studies have been made on the structure of a secondary battery including a wound electrode assembly.

Specifically, in order to prevent the winding displacement of the electrode, when an electrode tab (tab) is welded to an upper region provided in an uncoated portion of the current collector, an insulating tape is attached to a lower region in the uncoated portion (see, for example, patent document 1).

[ Prior Art document ]

[ patent document ]

[ patent document 1] specification of Japanese patent No. 5535465.

Disclosure of Invention

[ problem to be solved by the invention ]

Electronic devices and the like have been increasingly high in performance and multi-functional. Therefore, the frequency of use of electronic devices and the like is increasing, and the use environments of these electronic devices and the like are expanding. Therefore, the current situation is that the configuration of a secondary battery including a wound electrode body is more likely to affect the battery characteristics, and there is still room for improvement in the battery characteristics.

The present technology has been made in view of the above-described problems, and an object of the present technology is to provide a secondary battery, a battery pack, an electric vehicle, an electricity storage system, an electric power tool, and an electronic device, which can obtain excellent battery characteristics.

[ MEANS FOR SOLVING PROBLEMS ] to solve the problems

A secondary battery according to an embodiment of the present technology includes: a positive terminal; a negative terminal; a wound electrode assembly, (a) the wound electrode assembly including a positive electrode and a negative electrode that are laminated on each other with a separator interposed therebetween and are wound around a winding shaft as a center, (B) a cross section intersecting the winding shaft has a flat shape defined by a major axis and a minor axis, (C) the positive electrode includes a positive electrode collector and a positive electrode active material layer provided on a part of the positive electrode collector, (D) the negative electrode includes a negative electrode collector and a negative electrode active material layer provided on a part of the negative electrode collector, (E) a winding-inner end of the positive electrode in a winding direction includes a first positive electrode winding portion that extends in the major axis direction and is provided with a positive electrode terminal, and (F) a winding-inner end of the negative electrode in the winding direction includes a first negative electrode winding portion that extends in the major axis direction and is opposed to the first positive electrode winding portion with the separator interposed therebetween, a negative electrode terminal is attached to the first negative electrode wound portion so as not to overlap the positive electrode terminal in the direction of the minor axis; and one or more step relaxing members provided in at least one of the first positive electrode wound portion and the first negative electrode wound portion in at least one of a first region, a second region, and a third region, the first region being located further outward in a winding direction of the positive electrode than the positive electrode terminal in a longitudinal direction, the second region being located further outward in a winding direction of the negative electrode than the negative electrode terminal in the longitudinal direction, and the third region being located between the positive electrode terminal and the negative electrode terminal.

The battery pack, the electric vehicle, the power storage system, the electric power tool, and the electronic device according to the embodiment of the present technology each include a secondary battery having the same configuration as that of the secondary battery according to the embodiment of the present technology.

Here, the forming position and the number of the step relaxing members will be described in detail below.

First, the step alleviating member may be provided only in the first region, only in the second region, or only in the third region. The step alleviating member may be provided in both the first region and the second region, in both the second region and the third region, or in both the first region and the third region. The step relaxing member may be provided in all of the first region, the second region, and the third region.

Second, the step relaxing member may be provided only in the first positive electrode wound portion, only in the first negative electrode wound portion, or in both the first positive electrode wound portion and the first negative electrode wound portion.

Third, the number of the step relaxing members may be only one, or two or more.

[ Effect of the invention ]

According to the secondary battery of one embodiment of the present technology, since the step relaxing member is provided in at least one of the first region, the second region, and the third region, at least one of the first positive wound portion and the first negative wound portion is provided, excellent battery characteristics can be obtained. In addition, the battery pack, the electric vehicle, the power storage system, the electric power tool, and the electronic device according to the embodiment of the present technology can also obtain the same effects.

It is needless to say that the present invention is not limited to the effects described herein, and may be any effects described in the present technology.

Drawings

Fig. 1 is a perspective view showing a configuration of a secondary battery according to an embodiment of the present technology.

Fig. 2 is a sectional view showing the configuration of the wound electrode body along the line II-II shown in fig. 1.

Fig. 3 is an enlarged cross-sectional view of a part of the structure of the wound electrode body shown in fig. 2.

Fig. 4 is a view schematically showing each of the positive electrode and the negative electrode shown in fig. 2.

Fig. 5 is an enlarged cross-sectional view of the main portion of each of the positive and negative electrodes shown in fig. 2.

Fig. 6 is a cross-sectional view showing a modification example relating to the configuration of the main portion of each of the positive electrode and the negative electrode shown in fig. 5.

Fig. 7 is a cross-sectional view showing another modification example relating to the configuration of the main portion of each of the positive electrode and the negative electrode shown in fig. 5.

Fig. 8 is a perspective view showing a structure of an application example (battery module: unit cell) of the secondary battery.

Fig. 9 is a block diagram showing the configuration of the battery pack shown in fig. 8.

Fig. 10 is a block diagram showing a configuration of an application example (battery pack: assembled battery) of the secondary battery.

Fig. 11 is a block diagram showing a configuration of an application example (electric vehicle) of the secondary battery.

Fig. 12 is a block diagram showing a configuration of an application example (power storage system) of the secondary battery.

Fig. 13 is a block diagram showing a configuration of an application example (electric power tool) of the secondary battery.

Description of the reference numerals

1: exterior member, 2: positive electrode lead, 3: negative electrode lead, 10: positive electrode, 10X: first positive electrode wound portion, 10Y: second positive electrode wound portion, 11: positive electrode current collector, 12: positive electrode active material layer, 20: negative electrode, 20W: fourth negative electrode wound portion, 20X: first negative electrode wound portion, 20Y: second negative electrode wound portion, 20Z: third negative electrode wound portion, 21: negative electrode current collector, 22: negative electrode active material layer, 30: separator, 40(40A to 40N, 40P to 40S): step relief band, 50(50A to 50G): protective tape, J: and (4) winding the shaft.

Detailed Description

Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description sequence is as follows.

1. Secondary battery

1-1. integral formation

1-2. constitution of wound electrode body

1-3. construction of step relief band

1-4. actions

1-5. method of manufacture

1-6. action and Effect

1-7 modifications

2. Use of secondary battery

2-1. Battery component (Single cell)

2-2. Battery component (Battery set)

2-3. electric vehicle

2-4. electricity storage system

2-5. electric tool

Secondary battery

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

The secondary battery to be described here is, for example, a secondary battery using lithium as an electrode reactant, and more specifically, a lithium ion secondary battery in which a battery capacity (negative electrode capacity) is obtained by utilizing a lithium occlusion phenomenon and a lithium release phenomenon. The "electrode reactant" is a substance used for an electrode reaction (charge/discharge reaction).

(1-1. integral constitution)

First, the entire structure of the secondary battery is explained. Fig. 1 shows a three-dimensional configuration of the secondary battery, and fig. 2 shows a cross-sectional configuration of the wound electrode body 100 along the line II-II shown in fig. 1.

Hereinafter, the dimension in the X-axis direction is referred to as "width", the dimension in the Y-axis direction is referred to as "thickness", and the dimension in the Z-axis direction is referred to as "height".

This secondary battery is, for example, a laminated film type secondary battery using the film-like exterior member 1.

Specifically, for example, as shown in fig. 1, the secondary battery includes a film-shaped exterior member 1, a wound electrode assembly 100, a positive electrode lead 2, and a negative electrode lead 3. In fig. 1, in order to facilitate the observation of the structure of the exterior member 1 and the structure of the wound electrode assembly 100, the exterior member 1 is shown before the wound electrode assembly 100 is housed therein (in a state where the exterior member 1 and the wound electrode assembly 100 are separated from each other).

[ exterior component ]

The exterior member 1 is a housing member that mainly houses the wound electrode assembly 100 and the like.

For example, as shown in fig. 1, the exterior member 1 is a single film foldable in the direction of arrow R, and the exterior member 1 is provided with a recess 1U for accommodating the wound electrode assembly 100, for example.

Specifically, the exterior member 1 is a laminate film or the like, for example. The laminated film is not particularly limited in its structure, and has a multilayer structure in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order.

In the manufacturing process of the secondary battery, one exterior member 1 is folded so that the fusion layers face each other with the wound electrode body 100 interposed therebetween, and then the outer peripheral edge portions of the fusion layers facing each other are fused to each other, thereby sealing the exterior member 1. However, two exterior members 1 may be arranged to face each other with wound electrode assembly 100 interposed therebetween, and then the mutually facing fusion layers may be fused to each other. Alternatively, two exterior members 1 may be arranged to face each other with wound electrode assembly 100 interposed therebetween, and then the outer peripheral edge portions of the two exterior members 1 may be bonded to each other with an adhesive.

The fusion layer includes, for example, one or two or more of films of polyethylene, polypropylene, and the like. The metal layer includes one or more metal foils such as aluminum foil. The surface protective layer includes, for example, one or two or more of films of nylon, polyethylene terephthalate, and the like.

Among them, the exterior member 1 is preferably an aluminum laminated film in which a polyethylene film, an aluminum foil, and a nylon film are laminated in this order. This is because excellent sealing properties, durability, and the like can be obtained. However, the exterior member 1 may be a laminate film having another multilayer structure, for example. Alternatively, the exterior member 1 is not limited to the laminate film, and may be one film containing one or two or more kinds of polypropylene or the like, or may be one metal foil containing one or two or more kinds of aluminum or the like.

[ wound electrode Assembly ]

The wound electrode body 100 is a battery element mainly responsible for charge and discharge reactions, and includes, for example, a positive electrode 10, a negative electrode 20, a separator 30, and an electrolytic solution as a liquid electrolyte.

Specifically, as shown in fig. 2, the wound electrode assembly 100 is formed by stacking the positive electrode 10 and the negative electrode 20 with the separator 30 interposed therebetween, and then winding the positive electrode 10, the negative electrode 20, and the separator 30 around a winding axis J. The electrolyte solution is impregnated into each of the positive electrode 10, the negative electrode 20, and the separator 30, for example. The outermost periphery of the wound electrode body 100 may be protected by a protective tape, for example.

In particular, the wound electrode body 100 is pressed after being formed through the above steps, and has a flat shape. That is, the cross-sectional shape of the wound electrode body 100 is a flat shape. The "cross section" refers to a cross section intersecting the winding axis J, and the cross section is a plane along the XY plane. The "flat shape" is a shape defined by a major axis (X axis) and a minor axis (Y axis), and more specifically, is a substantially elliptical shape having a width larger than a thickness.

The detailed structure of the wound electrode assembly 100 will be described later (see fig. 3).

[ Positive electrode lead ]

The positive electrode lead 2 is a positive electrode terminal attached to the positive electrode 10, and more specifically, is attached to a positive electrode current collector 11 described later, for example.

The positive electrode lead 2 is led out from the inside to the outside of the exterior member 1, and contains one or two or more kinds of conductive materials such as aluminum. The positive electrode lead 2 has, for example, any one or two or more of a thin plate shape and a mesh shape.

[ negative electrode lead ]

The negative electrode lead 3 is a negative electrode terminal attached to the negative electrode 20, and more specifically, is attached to a negative electrode current collector 21 described later, for example.

The negative electrode lead 3 is led out from the inside to the outside of the exterior member 1, and includes any one or two or more of conductive materials such as copper, nickel, and stainless steel. The lead-out direction of the negative electrode lead 3 is, for example, the same as the lead-out direction of the positive electrode lead 2, and the shape of the negative electrode lead 3 is, for example, the same as the shape of the positive electrode lead 2.

[ adhesive film ]

Further, for example, an adhesion film 4 is inserted between the exterior member 1 and the positive electrode lead 2, and an adhesion film 5 is inserted between the exterior member 1 and the negative electrode lead 3.

The adhesive films 4 and 5 are members for mainly preventing the intrusion of the outside air into the exterior member 1, and include, for example, one or two or more kinds of adhesive materials. The "adhesive material" refers to a material having adhesion to each of the positive electrode lead 2 and the negative electrode lead 3, and is, for example, a polyolefin resin. Examples of the polyolefin resin include polyethylene, polypropylene, modified polyethylene, modified polypropylene, and the like.

< 1-2 > constitution of wound electrode body >

Next, the structure of the wound electrode assembly 100 will be described. Fig. 3 is an enlarged view of a part of the cross-sectional structure of the wound electrode body 100 shown in fig. 2. Fig. 4 schematically shows each of the positive electrode 10 and the negative electrode 20 shown in fig. 2. Fig. 5 is an enlarged cross-sectional view of a main portion of each of the positive electrode 10 and the negative electrode 20 shown in fig. 2. In fig. 4, the positive electrode 10 and the negative electrode 20 are each illustrated as a single line. In this case, in order to distinguish the positive electrode 10 and the negative electrode 20 from each other, the positive electrode 10 is indicated by a thick line, and the negative electrode 20 is indicated by a thin line.

[ Positive electrode ]

For example, as shown in fig. 3, the positive electrode 10 includes a positive electrode current collector 11 and two positive electrode active material layers 12 provided on both surfaces of the positive electrode current collector 11. However, the positive electrode active material layer 12 is provided only on a part of the positive electrode current collector 11. The range of the positive electrode active material layer 12 to be provided to the positive electrode current collector 11 will be described in detail later.

(Positive electrode collector)

The positive electrode current collector 11 contains, for example, one or two or more kinds of conductive materials such as aluminum, nickel, and stainless steel. The positive electrode current collector 11 may be a single layer or a plurality of layers.

(Positive electrode active Material layer)

The positive electrode active material layer 12 contains, as a positive electrode active material, any one or two or more kinds of positive electrode materials capable of occluding and releasing lithium. However, the positive electrode active material layer 12 may further contain one or two or more of other materials such as a positive electrode binder and a positive electrode conductive agent.

In particular, as described above, the positive electrode active material layers 12 are provided on both surfaces of the positive electrode current collector 11. Therefore, the positive electrode 10 includes, for example, an inner peripheral side positive electrode active material layer 12A provided on an inner peripheral side surface of the positive electrode collector 11, and an outer peripheral side positive electrode active material layer 12B provided on an outer peripheral side surface of the positive electrode collector 11. The "inner peripheral side" refers to a side close to the winding axis J, and the "outer peripheral side" refers to a side away from the winding axis J.

The positive electrode material is preferably a lithium-containing compound. This is because a high energy density can be obtained. The type of the lithium-containing compound is not particularly limited, and examples thereof include a lithium-containing composite oxide and a lithium-containing phosphoric acid compound.

The lithium-containing composite oxide is a generic term for oxides including lithium and one or two or more other elements as constituent elements, and has, for example, any of a layered rock-salt type, a spinel type, and the like crystal structure. The lithium-containing phosphoric acid compound is a generic term for a phosphoric acid compound containing lithium and one or two or more other elements as constituent elements, and has a crystal structure such as an olivine type. The "other element" means an element other than lithium.

The kind of the other elements is not particularly limited, but among them, elements belonging to groups 2 to 15 in the long period periodic table are preferable. Specifically, the other elements include nickel (Ni), cobalt (Co), manganese (Mn), iron (Fe), and the like. This is because a high voltage can be obtained.

The lithium-containing composite oxide having a layered rock-salt crystal structure is, for example, a compound represented by each of the following formulae (1) to (3).

Li _a Mn _(1-b-c) Ni _b M11 _c O _(2-d) F _e …(1)

(M11 represents at least one of cobalt (Co), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), zirconium (Zr), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). a to e satisfy 0.8 ≦ a ≦ 1.2, 0 < B < 0.5, 0 ≦ c ≦ 0.5, (B + c) < 1, -0.1 ≦ d ≦ 0.2 and 0 ≦ e ≦ 0.1. however, the composition of lithium differs depending on the state of charge and discharge, a is the value in the fully discharged state.)

Li _a Ni _(1-b) M12 _b O _(2-c) F _d …(2)

(M12 represents at least one of cobalt (Co), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). a-d satisfy 0.8 ≦ a ≦ 1.2, 0.005 ≦ B ≦ 0.5, -0.1 ≦ c ≦ 0.2 and 0 ≦ d ≦ 0.1. however, the composition of lithium differs depending on the charge/discharge state, and a represents a value of the full discharge state.)

Li _a Co _(1-b) M13 _b O _(2-c) F _d …(3)

(M13 represents at least one of nickel (Ni), manganese (Mn), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). a-d satisfy 0.8 ≦ a ≦ 1.2, 0 ≦ B < 0.5, -0.1 ≦ c ≦ 0.2 and 0 ≦ d ≦ 0.1. however, the composition of lithium varies depending on the charge and discharge state, and a represents a value in a full discharge state.)

A specific example of the lithium-containing composite oxide having a layered rock-salt type crystal structure is 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 _0.33 Co _0.33 Mn _0.33 O ₂ 、Li _1.2 Mn _0.52 Co _0.175 Ni _0.1 O ₂ And Li _1.15 (Mn _0.65 Ni _0.22 Co _0.13 )O ₂ And the like.

When the lithium-containing composite oxide having a layered rock-salt crystal structure contains nickel, cobalt, manganese, and aluminum as constituent elements, the atomic ratio of nickel is preferably 50 atomic% or more. This is because a high energy density can be obtained.

The lithium-containing composite oxide having a spinel-type crystal structure is, for example, a compound represented by the following formula (4).

Li _a Mn _(2-b) M14 _b O _c F _d …(4)

(M14 represents at least one of cobalt (Co), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), chromium (Cr), iron (Fe), copper (Cu), zinc (Zn), molybdenum (Mo), tin (Sn), calcium (Ca), strontium (Sr) and tungsten (W). a-d satisfy 0.9 ≦ a ≦ 1.1, 0 ≦ B ≦ 0.6, 3.7 ≦ c ≦ 4.1 and 0 ≦ d ≦ 0.1. however, the composition of lithium varies depending on the state of charge and discharge, and a represents a value in a full discharge state.)

Specific example of the lithium-containing composite oxide having a spinel-type crystal structure is LiMn ₂ O ₄ And so on.

The lithium-containing phosphate compound having an olivine-type crystal structure is, for example, a compound represented by the following formula (5).

Li _a M15PO ₄ …(5)

(M15 represents at least one of cobalt (Co), manganese (Mn), iron (Fe), nickel (Ni), magnesium (Mg), aluminum (Al), boron (B), titanium (Ti), vanadium (V), niobium (Nb), copper (Cu), zinc (Zn), molybdenum (Mo), calcium (Ca), strontium (Sr), tungsten (W), and zirconium (Zr). a satisfies 0.9 ≦ a ≦ 1.1. however, the composition of lithium differs depending on the charge/discharge state, and a represents a value in a full discharge state.)

A specific example of a lithium-containing phosphoric acid compound having an olivine-type crystal structure is LiFePO ₄ 、LiMnPO ₄ 、LiFe _0.5 Mn _0.5 PO ₄ And LiFe _0.3 Mn _0.7 PO ₄ And the like.

The lithium-containing composite oxide may be a compound represented by the following formula (6).

(Li ₂ MnO ₃ ) _x (LiMnO ₂ ) _1-x …(6)

(x satisfies 0 ≦ x ≦ 1. however, the composition of lithium differs depending on the charge/discharge state, and x is a value in a completely discharged state.)

The positive electrode material may be an oxide, a disulfide, a chalcogenide, a conductive polymer, or the like. Examples of the oxide include titanium oxide, vanadium oxide, and manganese dioxide. Examples of the disulfide include titanium disulfide and molybdenum sulfide. The chalcogenide compound is, for example, niobium selenide. Examples of the conductive polymer include sulfur, polyaniline, and polythiophene. Of course, the positive electrode material may be other materials than the series of materials.

The positive electrode binder contains, for example, one or two or more of synthetic rubber, a polymer compound, and the like. Examples of the synthetic rubber include styrene butadiene rubber, fluorine rubber, ethylene propylene diene rubber (epdm), and the like. The polymer compound is, for example, polyvinylidene fluoride, polyimide, or the like.

The positive electrode conductive agent contains, for example, any one or two or more of carbon materials and the like. The carbon material is, for example, graphite, carbon black, acetylene black, ketjen black, or the like. However, the positive electrode conductive agent may be a metal material, a conductive polymer, or the like as long as it is a material having conductivity.

[ negative electrode ]

For example, as shown in fig. 3, the anode 20 includes an anode current collector 21 and two anode active material layers 22, and the two anode active material layers 22 are provided on both surfaces of the anode current collector 21. However, only a part of the anode current collector 21 is provided with the anode active material layer 22. The range of arrangement of the anode active material layer 22 with respect to the anode current collector 21 will be described in detail later.

(negative electrode collector)

The negative electrode current collector 21 contains, for example, any one or two or more of conductive materials such as copper, aluminum, nickel, and stainless steel. The negative electrode current collector 21 may be a single layer or a plurality of layers.

The surface of the negative electrode current collector 21 is preferably roughened. This is because the adhesion of the anode active material layer 22 to the anode current collector 21 is improved by the so-called anchor effect. In this case, the surface of the negative electrode current collector 21 may be roughened at least in the region facing the negative electrode active material layer 22. The roughening method includes, for example, a method of forming fine particles by electrolytic treatment. In the electrolytic treatment, since fine particles are formed on the surface of the negative electrode current collector 21 by an electrolytic method in an electrolytic bath, irregularities are formed on the surface of the negative electrode current collector 21. The copper foil produced by the electrolytic method is generally called electrolytic copper foil.

(negative electrode active material layer)

The negative electrode active material layer 22 contains, as a negative electrode active material, any one or two or more kinds of negative electrode materials that can occlude and release lithium. However, the anode active material layer 22 may further contain one or two or more of other materials such as an anode binder and an anode conductive agent.

In addition, the anode active material layer 22 is provided on both surfaces of the anode current collector 21 as described above. Therefore, the anode 20 includes, for example, an inner peripheral side anode active material layer 22A provided on the inner peripheral side surface of the anode current collector 21, and an outer peripheral side anode active material layer 22B disposed on the outer peripheral side surface of the anode current collector 21.

In order to suppress the lithium metal from being accidentally deposited on the surface of the negative electrode 20 during charging, the chargeable capacity of the negative electrode material is preferably larger than the discharge capacity of the positive electrode 10. That is, the electrochemical equivalent of the negative electrode material capable of occluding and releasing lithium is preferably larger than that of the positive electrode 10.

The negative electrode material is, for example, a carbon material. Since the crystal structure changes very little during lithium occlusion and lithium release, a high energy density can be stably obtained. In addition, since the carbon material also functions as an anode conductive agent, the conductivity of the anode active material layer 22 is improved.

The carbon material is, for example, graphitizable carbon, graphite, or the like. However, the (002) plane spacing of the non-graphitizable carbon is preferably 0.37nm or more, and the (002) plane spacing of the graphite is preferably 0.34nm or less. More specifically, the carbon material is, for example, pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, activated carbon, carbon blacks or the like. The coke includes pitch coke, needle coke, petroleum coke, etc. The organic polymer compound fired body is obtained by firing (carbonizing) a polymer compound such as a phenol resin or a furan resin at an appropriate temperature. The carbon material may be low crystalline carbon heat-treated at a temperature of about 1000 ℃ or lower, or may be amorphous carbon. The shape of the carbon material may be any of a fibrous shape, a spherical shape, a granular shape, and a scaly shape.

Further, the anode material is, for example, a metal-based material. The "metal-based material" is a general term for a material containing any one or two or more of a metal element and a semimetal element as a constituent element. This is because a high energy density can be obtained.

The metal-based material may be a single body, an alloy, a compound, two or more kinds thereof, or a material at least partially containing one or two or more kinds of phases thereof. However, the alloy includes a material containing one or more metal elements and one or more semimetal elements, in addition to a material formed of two or more metal elements. Further, the alloy may contain a non-metallic element. The structure of the metal-based material includes, for example, a solid solution, a eutectic crystal (eutectic mixture), an intermetallic compound, and a coexisting substance of two or more of them.

The metal element and the semimetal element are, for example, elements capable of forming an alloy with lithium. Specifically, examples of the metal element and the semimetal element include magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc, hafnium (Hf), zirconium, yttrium (Y), palladium (Pd), and platinum (Pt).

Among them, one or both of silicon and tin are preferable. This is because the capacity of occluding and releasing lithium is excellent and a high energy density can be obtained.

The material containing silicon as an element may be a single body of silicon, may be an alloy of silicon, may be a compound of silicon, may be two or more of them, or may be a material at least partially containing one or two or more phases of them.

The material containing tin as an element may be a single substance of tin, may be an alloy of tin, may be a compound of tin, may be two or more kinds of them, or may be a material containing at least a part of one or two or more kinds of phases thereof.

The "monomer" as referred to herein means a monomer in a general sense, and therefore the monomer may contain a slight amount of impurities. That is, the purity of the monomer does not have to be 100%.

The alloy of silicon contains, for example, any one or two or more of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, and the like as a constituent element other than silicon. The compound of silicon contains, for example, one or two or more of carbon, oxygen, and the like as a constituent element other than silicon. The compound of silicon may contain any one or two or more of the series of elements described for the alloy of silicon, for example.

Specific examples of alloys of silicon and compounds of silicon are SiB ₄ 、SiB ₆ 、Mg ₂ Si、Ni ₂ Si、TiSi ₂ 、MoSi ₂ 、CoSi ₂ 、NiSi ₂ 、CaSi ₂ 、CrSi ₂ 、Cu ₅ Si、FeSi ₂ 、MnSi ₂ 、NbSi ₂ 、TaSi ₂ 、VSi ₂ 、WSi ₂ 、ZnSi ₂ 、SiC、Si ₃ N ₄ 、Si ₂ N ₂ O、SiO _v (0 < v ≦ 2), LiSiO, and the like. In addition, SiO _v V in (1) may also be 0.2 < v < 1.4.

The alloy of tin contains, for example, any one or two or more of silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony, chromium, and the like as a constituent element other than tin. The tin compound contains, for example, any one or two or more of carbon, oxygen, and the like as a constituent element other than tin. The tin compound may contain, for example, any one or two or more of the series of elements described for the tin alloy as a constituent element other than tin.

Specific examples of the alloy of tin and the compound of tin are SnO _w (0＜w≦2)、SnSiO ₃ LiSnO and Mg ₂ Sn, and the like.

In particular, the material containing tin as a constituent element is preferably, for example, a material containing tin as a first constituent element and tin as a second constituent element and a third constituent element (tin-containing material). The second constituent element is, for example, any one or two or more of cobalt, iron, magnesium, titanium, vanadium, chromium, manganese, nickel, copper, zinc, gallium, zirconium, niobium, molybdenum, silver, indium, cesium (Ce), hafnium (Hf), tantalum, tungsten, bismuth, silicon, and the like. The third constituent element is, for example, one or two or more of boron, carbon, aluminum, phosphorus, and the like. This is because a high battery capacity, excellent cycle characteristics, and the like can be obtained.

Among them, the tin-containing material is preferably a material containing tin, cobalt, and carbon as constituent elements (a material containing tin, cobalt, and carbon). In the material containing tin, cobalt and carbon, for example, the carbon content is 9.9 to 29.7 mass%, and the ratio of the tin and cobalt contents (Co/(Sn + Co)) is 20 to 70 mass%. This is because a high energy density can be obtained.

The material containing tin, cobalt and carbon has a phase containing tin, cobalt and carbon as constituent elements, and this phase is preferably low crystalline or amorphous. This phase is a phase (reaction phase) that can react with lithium, so excellent characteristics are obtained due to the presence of the reaction phase. When CuK α rays are used as the specific X-rays and the scanning speed is 1 °/min, the half width (diffraction angle 2 θ) of the diffraction peak obtained by X-ray diffraction of the reaction phase is preferably 1 ° or more. This is because lithium can be smoothly stored and released, and the reactivity with the electrolyte solution is lowered. In addition, the tin-cobalt-carbon-containing material may have a phase containing a monomer or a part of each constituent element in addition to a low crystalline or amorphous phase.

It is judged whether or not the diffraction peak obtained by X-ray diffraction is a diffraction peak corresponding to a reaction phase which can react with lithium, for example, by comparing X-ray diffraction patterns before and after electrochemical reaction with lithium. If the position of the diffraction peak is changed before and after the electrochemical reaction with lithium, the diffraction peak is a diffraction peak corresponding to a reaction phase that can react with lithium. In this case, for example, a diffraction peak of a low-crystalline or amorphous reaction phase is detected in a range of 20 ° to 50 ° 2 θ. It is considered that the reaction phase contains, for example, the above-mentioned series of constituent elements and is low-crystallized or amorphous mainly due to the presence of carbon.

In the tin-cobalt-carbon-containing material, at least a part of carbon as a constituent element is preferably bonded to a metal element or a semimetal element as another constituent element. This is because aggregation of tin, crystallization of tin, and the like can be suppressed. The bonding state of the element can be confirmed, for example, by X-ray photoelectron spectroscopy (XPS). In a commercially available apparatus, for example, Al-Ka rays or Mg-Ka rays are used as soft X-rays. When part or all of carbon is bonded to a metal element, a semimetal element, or the like, the peak of the composite wave of the 1s orbital (C1s) of carbon is detected in a region lower than 284.5 eV. However, in order to detect the peak of the 4f orbital (Au4f) of the gold atom at the energy position of 84.0eV, an energy calibration was performed. In this case, since surface contamination carbon is usually present on the surface of the substance, the energy position at which the peak of C1s of this surface contamination carbon is detected is 284.8eV, and the peak is set as the energy reference. In the XPS measurement, the waveform of the peak of C1s is generally obtained in a state containing the peak of surface contamination carbon and the peak of carbon in the SnCoC-containing material. Therefore, for example, the peak is analyzed using commercially available software, and the peak of the surface contamination carbon and the peak of the carbon in the SnCoC-containing material are separated. In the waveform analysis, the energy position of the main peak existing on the lowest bound energy side is set as an energy reference (284.8 eV).

The material containing tin, cobalt, and carbon is not limited to a material (SnCoC) in which only tin, cobalt, and carbon are constituent elements. The tin-cobalt-carbon-containing material may further contain, for example, one or two or more of silicon, iron, nickel, chromium, indium, niobium, germanium, titanium, molybdenum, aluminum, phosphorus, gallium, bismuth, and the like as a constituent element in addition to tin, cobalt, and carbon.

In addition to the material containing tin, cobalt, carbon, and tin, cobalt, iron, and carbon as constituent elements (the material containing tin, cobalt, iron, and carbon) are also suitable. The composition of the material containing tin, cobalt, iron and carbon is arbitrary. For example, when the content of iron is set to be small, the content of carbon is 9.9 to 29.7 mass%, the content of iron is 0.3 to 5.9 mass%, and the ratio of the contents of tin and cobalt (Co/(Sn + Co)) is 30 to 70 mass%. When the iron content is set to be large, the carbon content is 11.9 to 29.7 mass%, the ratio of the tin, cobalt, and iron contents ((Co + Fe)/(Sn + Co + Fe)) is 26.4 to 48.5 mass%, and the ratio of the cobalt and iron contents (Co/(Co + Fe)) is 9.9 to 79.5 mass%. This is because a high energy density can be obtained. The physical properties (half-value width, etc.) of the material containing tin, cobalt, iron and carbon are, for example, the same as those of the material containing tin, cobalt and carbon.

The negative electrode material may be, for example, a metal oxide, a polymer compound, or the like. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide. The polymer compound is, for example, polyacetylene, polyaniline, polypyrrole, or the like.

Among them, the negative electrode material preferably contains both a carbon material and a metal material for the reason described below.

The metal-based material, particularly a material containing one or both of silicon and tin as a constituent element has an advantage of high theoretical capacity, but may be susceptible to severe expansion and contraction during charging and discharging. On the other hand, the carbon material may have a low theoretical capacity, but has an advantage that it is less likely to expand and contract during charge and discharge. Thus, by using both the carbon material and the metal-based material, it is possible to obtain a high theoretical capacity (in other words, battery capacity) and to suppress expansion and contraction of the negative electrode material during charge and discharge.

The negative electrode active material layer 22 is formed by any one of, for example, a coating method, a gas phase method, a liquid phase method, a firing method (sintering method), and the like, or by two or more methods.

The coating method is as follows: for example, a mixture of a particulate (powder) negative electrode active material and a negative electrode binder or the like is dissolved or dispersed in an organic solvent or the like to prepare a solution, and the solution is applied to the negative electrode current collector 21. The vapor phase method is, for example, a physical deposition method, a chemical deposition method, or the like. More specifically, the method includes, for example, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a thermal Chemical Vapor Deposition (CVD) method, a plasma CVD method, and the like. The liquid phase method is, for example, an electrolytic plating method, an electroless plating method, or the like. The meltblowing method is a method of spraying a negative electrode active material in a molten state or a semi-molten state onto the negative electrode current collector 21. The firing method is a method of applying the solution to the negative electrode current collector 21, and then heat-treating the solution at a temperature higher than the melting point of the negative electrode binder or the like. The firing method is, for example, an atmosphere firing method, a reaction firing method, a hot press firing method, or the like.

In the secondary battery, as described above, in order to prevent lithium metal from being accidentally deposited on the surface of the negative electrode 20 during charging, the electrochemical equivalent of the negative electrode material capable of storing and releasing lithium is preferably larger than that of the positive electrode. In addition, when the open circuit voltage (that is, the battery voltage) at the time of full charge is 4.25V or more, the amount of lithium discharged per unit mass is larger than that in the case where the open circuit voltage at the time of full charge is 4.20V even if the same positive electrode active material is used, and therefore, the amount of the positive electrode active material and the amount of the negative electrode active material are preferably adjusted to each other in consideration of this point. Thereby, a high energy density is obtained.

[ separator ]

For example, as shown in fig. 3, the separator 30 is interposed between the positive electrode 10 and the negative electrode 20. Thus, the separator 30 allows lithium ions to pass therethrough while preventing a short circuit of current caused by contact between the positive electrode 10 and the negative electrode 20. In fig. 2, the diaphragm 30 is shown in a thick line shape for simplifying the illustration.

The separator 30 may be a laminated film including one or more kinds of porous films such as a synthetic resin and a ceramic. Examples of the synthetic resin include polytetrafluoroethylene, polypropylene, and polyethylene.

In particular, the separator 30 may include, for example, the porous film (substrate layer) and a polymer compound layer provided on one or both surfaces of the substrate layer. This is because the adhesion of the separator 30 to the positive electrode 10 is improved, and the adhesion of the separator 30 to the negative electrode 20 is improved, so that deformation of the wound electrode assembly 100 can be suppressed. This can suppress the decomposition reaction of the electrolyte solution and also suppress the leakage of the electrolyte solution impregnated in the base material layer, and therefore, even if the charge and discharge are repeated, the resistance is less likely to increase and the secondary battery is less likely to bulge.

The polymer compound layer contains one or more of polymer compounds such as polyvinylidene fluoride. This is because the physical strength is excellent and the electrochemical stability is stable. In forming the polymer compound layer, for example, a solution in which a polymer compound is dissolved such as an organic solvent is applied to a base material layer, and then the base material layer is dried. Alternatively, for example, the substrate layer may be immersed in a solution and then dried.

The polymer compound layer may contain any one or two or more kinds of insulating particles such as inorganic particles. Examples of the inorganic particles include alumina and aluminum nitride.

[ electrolyte ]

The electrolyte solution contains a solvent and an electrolyte salt. However, the electrolyte may further contain one or two or more of other materials such as additives.

(solvent)

The solvent includes one or more kinds of non-aqueous solvents such as organic solvents. The electrolyte containing a nonaqueous solvent is a so-called nonaqueous electrolyte.

Examples of the nonaqueous solvent include cyclic carbonates, chain carbonates, lactams, chain carboxylates, and nitriles (mononitriles). This is because excellent battery capacity, cycle characteristics, storage characteristics, and the like can be obtained.

Examples of the cyclic carbonate include ethylene carbonate, propylene carbonate, and butylene carbonate. Examples of the chain carbonate include dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and propyl methyl carbonate. The lactams include, for example, gamma-butyrolactone and gamma-valerolactone. Examples of the chain carboxylic acid ester include methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, methyl pivalate, and ethyl pivalate. As the nitrile, acetonitrile, methoxyacetonitrile, 3-methoxypropionitrile, etc. can be mentioned.

The nonaqueous solvent may be, for example, 1, 2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1, 3-dioxolane, 4-methyl-1, 3-dioxolane, 1, 3-dioxane, 1, 4-dioxane, N-dimethylformamide, N-methylpyrrolidone, N-methyloxazolidinone, N' -dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, trimethyl phosphate, dimethylsulfoxide, or the like. The same advantages can be obtained.

Among them, one or more of cyclic carbonates and chain carbonates are preferable, and one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like are more preferable. This is because a high battery capacity, excellent cycle characteristics, excellent storage characteristics, and the like can be obtained. In this case, a combination of a high-viscosity (high dielectric constant) solvent (e.g., a relative dielectric constant ≧ 30) such as ethylene carbonate and propylene carbonate, and a low-viscosity solvent (e.g., a viscosity ≦ 1mPa · s) such as dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate is more preferable. This is because the dissociation property and ion mobility of the electrolyte salt are improved.

Examples of the nonaqueous solvent include unsaturated cyclic carbonates, halogenated carbonates, sulfonates, acid anhydrides, dicyan compounds (dinitrile compounds), diisocyanate compounds, phosphates, and chain compounds having triple bonds between carbons. This is because the chemical stability of the electrolyte is improved.

The unsaturated cyclic carbonate is a general term for cyclic carbonates having one or more unsaturated bonds (double bonds between carbons or triple bonds between carbons). Examples of the unsaturated cyclic carbonate include vinylene carbonate, vinyl ethylene carbonate, and methylene ethylene carbonate. The content of the unsaturated cyclic carbonate in the nonaqueous solvent is not particularly limited, and is, for example, 0.01 to 10% by weight.

The halogenated carbonates are a general term for cyclic or chain carbonates containing one or more halogen elements as constituent elements. When the halogenated carbonate contains two or more halogen elements as constituent elements, the kind of the two or more halogen elements may be one kind, or two or more kinds. Examples of the cyclic halogenated carbonates include 4-fluoro-1, 3-dioxolan-2-one and 4, 5-difluoro-1, 3-dioxolan-2-one. As the chain halogenated carbonates, for example, fluoromethyl methyl carbonate (fluoromethyl ester), bis (fluoromethyl) carbonate (fluoromethyl ester) and difluoromethyl methyl carbonate (fluoromethyl ester) are mentioned. The content of the halogenated carbonate in the nonaqueous solvent is not particularly limited, and is, for example, 0.01 to 50% by weight.

Examples of the sulfonic acid ester include monosulfonic acid ester and disulfonic acid ester. The content of the sulfonic acid ester in the nonaqueous solvent is not particularly limited, and is, for example, 0.01 to 10% by weight.

The monosulfonate may be a cyclic monosulfonate or a linear monosulfonate. Examples of the cyclic monosulfonate include sultones such as 1, 3-propane sultone and 1, 3-propene sultone. Examples of the chain monosulfonate include compounds in which a cyclic monosulfonate is interrupted. The disulfonate ester may be a cyclic disulfonate ester or a linear disulfonate ester.

Examples of the acid anhydride include carboxylic acid anhydride, disulfonic acid anhydride, and carboxylic acid sulfonic acid anhydride. Examples of the carboxylic acid anhydride include succinic anhydride, glutaric anhydride, and maleic anhydride. The disulfonic anhydride includes, for example, ethane disulfonic anhydride and propane disulfonic anhydride. Examples of the carboxylic sulfonic anhydride include sulfobenzoic anhydride, sulfopropionic anhydride, and sulfobutyric anhydride. The content of the acid anhydride in the nonaqueous solvent is not particularly limited, and is, for example, 0.5 to 5% by weight.

The dinitrile compound is represented by, for example, NC-R1-CN (R1 is any of an alkylene group and an arylene group). The dinitrile compound is, for example, succinonitrile (NC-C) ₂ H ₄ -CN), glutaronitrile (NC-C) ₃ H ₆ -CN), adiponitrile (NC-C) ₄ H ₈ -CN) and phthalonitrile (NC-C) ₆ H ₄ -CN) and the like. The content of the dinitrile compound in the nonaqueous solvent is not particularly limited, and is, for example, 0.5 to 5% by weight.

The diisocyanate compound is, for example, a compound represented by OCN-R2-NCO (R2 is either an alkylene group or an arylene group). Such as hexamethylene diisocyanate (OCN-C) ₆ H ₁₂ -NCO), etc. The content of the diisocyanate compound in the nonaqueous solvent is not particularly limited, and is, for example, 0.5 to 5% by weight.

Examples of the phosphate ester include trimethyl phosphate and triethyl phosphate. The content of the phosphate ester in the nonaqueous solvent is not particularly limited, and is, for example, 0.5 to 5% by weight.

The chain compound having a triple bond between carbons is a general term for a chain compound having one or more triple bonds between carbons (-C.ident.C-). Examples of the chain compound having a triple bond between carbons include methyl carboxylic acid-2-propynyl ester (CH.ident.C-CH) ₂ -O-C(＝O)-O-CH ₃ ) And propylene methanesulfonate (CH ≡ C-CH) ₂ -O-S(＝O) ₂ -CH ₃ ) And the like. The content of the chain compound having a triple bond between carbons in the nonaqueous solvent is not particularly limited, and is, for example, 0.5 to 5% by weight.

(electrolyte salt)

The electrolyte salt contains, for example, any one or two or more of lithium salts. However, the electrolyte salt may also contain, for example, a salt other than a lithium salt. Examples of the salt other than lithium include salts of light metals other than lithium.

The lithium salt is, for example, lithium hexafluorophosphate (LiPF) ₆ ) Lithium tetrafluoroborate (LiBF) ₄ ) Lithium perchlorate (LiClO) ₄ ) Lithium hexafluoroarsenate (LiAsF) ₆ ) Lithium tetraphenylborate (LiB (C) ₆ H ₅ ) ₄ ) Lithium methanesulfonate (LiCH) ₃ SO ₃ ) Lithium trifluoromethanesulfonate (LiCF) ₃ SO ₃ ) Lithium aluminum tetrachloride (LiAlCl) ₄ ) Dilithium hexafluorosilicate (Li) ₂ SiF ₆ ) Lithium chloride (LiCl), lithium bromide (LiBr), and the like. This is because excellent battery capacity, cycle characteristics, storage characteristics, and the like can be obtained.

Among these, one or two or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate and lithium hexafluoroarsenate are preferable, and lithium hexafluorophosphate is more preferable. This is because the internal resistance becomes low.

The content of the electrolyte salt is not particularly limited, but is preferably 0.3mol/kg to 3.0mol/kg with respect to the solvent. High ion conductivity can be obtained.

[ winding Structure of Positive electrode ]

For example, as shown in fig. 2, the positive electrode 10 and the negative electrode 20 are wound such that the positive electrode 10 is disposed on the outer side and the negative electrode 20 is disposed on the inner side.

The positive electrode active material layer 12 is provided only on a part of the positive electrode current collector 11 as described above. Therefore, the inner peripheral side positive electrode active material layer 12A is provided only on a partial surface on the inner peripheral side of the positive electrode collector 11, for example, and the outer peripheral side positive electrode active material layer 12B is provided only on a partial surface on the outer peripheral side of the positive electrode collector 11, for example.

Specifically, at the end of the positive electrode 10 on the outside of the roll, for example, the inner peripheral side positive electrode active material layer 12A is not provided on the inner peripheral side surface of the positive electrode collector 11, and the outer peripheral side positive electrode active material layer 12B is not provided on the outer peripheral side surface of the positive electrode collector 11. Therefore, the positive electrode current collector 11 is exposed at the end of the positive electrode 10 on the outside of the roll, for example. The "outside winding" described here refers to the outside (the side near the outer end) of the positive electrode 10 in the winding direction.

The end portion on the roll outer side of the positive electrode 10 can be arbitrarily set because the range in which the inner peripheral side positive electrode active material layer 12A is not provided on the inner peripheral side surface of the positive electrode current collector 11, in other words, the position of the end portion of the inner peripheral side positive electrode active material layer 12A on the roll outer side of the positive electrode 10 is not particularly limited.

In addition, the end portion of the positive electrode 10 on the outside of the roll is not particularly limited in the range where the outer peripheral side positive electrode active material layer 12B is not provided on the outer peripheral side surface of the positive electrode current collector 11, in other words, the position of the end portion of the outer peripheral side positive electrode active material layer 12B on the outside of the roll of the positive electrode 10 is not particularly limited, and thus can be set arbitrarily.

Here, the end portion of the inner peripheral side positive electrode active material layer 12A on the roll outer side is located, for example, on the roll outer side than the end portion of the outer peripheral side positive electrode active material layer 12B on the roll outer side.

On the other hand, at the end portion of the positive electrode 10 on the inner side of the roll, for example, the inner peripheral side positive electrode active material layer 12A is not provided on the inner peripheral side surface of the positive electrode collector 11, and the outer peripheral side positive electrode active material layer 12B is not provided on the outer peripheral side surface of the positive electrode collector 11. Therefore, the positive electrode current collector 11 is exposed at the end of the positive electrode 10 on the inside of the roll. The "roll inside" described here means the inside (the side close to the inner end) of the positive electrode 10 in the winding direction, that is, the so-called roll core side.

The end portion on the roll inner side of the positive electrode 10 can be arbitrarily set because the range in which the inner peripheral side positive electrode active material layer 12A is not provided on the inner peripheral side surface of the positive electrode current collector 11, in other words, the position of the end portion of the inner peripheral side positive electrode active material layer 12A on the roll inner side of the positive electrode 10 is not particularly limited.

In addition, the end portion of the positive electrode 10 on the inner side of the roll is not particularly limited in the range where the outer peripheral side positive electrode active material layer 12B is not provided on the outer peripheral side surface of the positive electrode current collector 11, in other words, the position of the end portion of the outer peripheral side positive electrode active material layer 12B on the inner side of the roll of the positive electrode 10.

Here, the end of the inner peripheral side positive electrode active material layer 12A on the winding inner side is located, for example, on the winding inner side than the end of the outer peripheral side positive electrode active material layer 12B on the inner peripheral side.

[ winding constitution of negative electrode ]

The anode active material layer 22 is provided only on a part of the anode current collector 21 as described above. Therefore, the inner peripheral side anode active material layer 22A is provided only on a partial surface on the inner peripheral side of the anode current collector 21, for example, and the outer peripheral side anode active material layer 22B is provided only on a partial surface on the outer peripheral side of the anode current collector 21, for example.

Specifically, at the end of the anode 20 on the roll outer side, for example, the inner side anode active material layer 22A is not provided on the inner side surface of the anode current collector 21, and the outer side anode active material layer 22B is not provided on the outer side surface of the anode current collector 21. Therefore, the negative electrode current collector 21 is exposed at the end of the negative electrode 20 on the outside of the roll, for example.

The end portion on the roll outer side of the negative electrode 20 is not particularly limited in the range where the inner periphery side negative electrode active material layer 22A is not provided on the inner periphery side surface of the negative electrode current collector 21, in other words, the position of the end portion of the inner periphery side negative electrode active material layer 22A on the roll outer side of the negative electrode 20, and thus can be arbitrarily set.

In addition, the end portion on the roll outer side of the negative electrode 20 is not particularly limited in the range where the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21, in other words, the position of the end portion of the outer peripheral side negative electrode active material layer 22B on the roll outer side of the negative electrode 20.

Here, the end portion of the inner-side negative electrode active material layer 22A on the roll outer side is located on the roll inner side than the end portion of the outer-side negative electrode active material layer 22B on the roll outer side, for example.

On the other hand, at the end of the negative electrode 20 on the roll inner side, for example, the inner peripheral side negative electrode active material layer 22A is not provided on the inner peripheral side surface of the negative electrode current collector 21, and the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21. Therefore, at the end portion of the negative electrode 20 on the roll inner side, for example, the negative electrode current collector 21 is exposed.

The end portion on the roll inner side of the negative electrode 20 is not particularly limited in the range where the inner peripheral side negative electrode active material layer 22A is not provided on the inner peripheral side surface of the negative electrode current collector 21, in other words, the position of the end portion of the inner peripheral side negative electrode active material layer 22A on the roll inner side of the negative electrode 20.

In addition, the end portion of the negative electrode 20 on the roll inner side is not particularly limited in the range where the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21, in other words, the position of the end portion of the outer peripheral side negative electrode active material layer 22B on the roll inner side of the negative electrode 20.

Here, the end of the inner-periphery side negative electrode active material layer 22A on the roll inner side is located on the roll outer side than the end of the outer-periphery side negative electrode active material layer 22B on the roll inner side, for example.

[ Positive electrode lead and negative electrode lead ]

The positive electrode lead 2 is attached to the positive electrode current collector 11, which is an end portion of the positive electrode 10 on the inner side of the roll. Here, the positive electrode lead 2 is provided on, for example, a surface on the outer peripheral side of the positive electrode current collector 11. However, the positive electrode lead 2 may be provided on the inner peripheral surface of the positive electrode current collector 11. The method for attaching the positive electrode lead 2 to the positive electrode current collector 11 is not particularly limited, and for example, a welding method or the like is used.

The negative electrode lead 3 is attached to a negative electrode current collector 21 which is an end portion of the negative electrode 20 on the inner side of the roll. Here, the negative electrode lead 3 is attached to, for example, an outer peripheral surface of the negative electrode current collector 21. However, the negative electrode lead 3 may be provided on the inner circumferential surface of the negative electrode current collector 21. The negative electrode lead 3 is disposed so as not to overlap the positive electrode lead 2 in the direction of the minor axis (Y axis). The method of attaching the negative electrode lead 3 to the negative electrode current collector 21 is the same as the method of attaching the positive electrode lead 2 to the positive electrode current collector 11, for example.

A winding fixing tape 58 is attached to the positive electrode current collector 11, which is the end portion of the positive electrode 10 on the outside of the roll, for example. Here, the winding fixing tape 58 is attached to, for example, the outer peripheral surface of the positive electrode current collector 11. In this way, the positive electrode collector 11, which is the end portion of the positive electrode 10 on the outside of the roll, is fixed to the main body of the wound electrode assembly 100. The roll fixing tape 58 is, for example, an adhesive tape or the like.

[ protective tape ]

For example, a protective tape 50 is joined to the positive electrode 10 and the negative electrode 20. The protective tape 50 includes, for example, one or two or more kinds of insulating polymer compounds. The kind of the insulating polymer compound is not particularly limited, and examples thereof include polypropylene (PP). The thickness of the protective tape 50 is not particularly limited, and is, for example, 5 to 40 μm.

The number of the protective tape 50 is not particularly limited, and may be one or two or more. Here, for example, 7 guard bands 50(50A to 50G) are used. As for detailed description of the positions where the protective tapes 50A to 50G are provided, for example, as shown in the following description.

The protective tape 50A mainly covers (protects) the end (corner) of the positive electrode active material layer 12A on the inner peripheral side outside the positive electrode 10 in the roll and the periphery thereof, thereby suppressing defects caused by the corner. That is, the protective tape 51 covers, for example, the inner peripheral side cathode active material layer 12A and the cathode current collector 11 together.

In detail, when the corner portion of the inner peripheral side cathode active material layer 12A is exposed, the corner portion is easily cut into the anode 20 (the outer peripheral side anode active material layer 22) and the like via the separator 30. This may cause deformation or breakage of the negative electrode 20 due to the presence of the corner. The "breakage" is, for example, a phenomenon in which the negative electrode 20 cracks, a phenomenon in which the negative electrode 20 and the separator 30 are cut, or the like. In this case, the separator 30 may be deformed or broken as in the negative electrode 20.

In contrast, when the corner portion of the inner peripheral side positive electrode active material layer 12A is covered with the protective tape 50A, the acute angle of the corner portion can be alleviated by the protective tape 50A, and therefore the corner portion is less likely to cut into the negative electrode 20. Accordingly, the influence of the corner portions is reduced, so that the negative electrode 20 is less likely to be deformed or broken, and the separator 30 is less likely to be deformed or broken.

Since the installation range of the protective tape 50A can be set arbitrarily, it can be extended to one side or both of the roll inside and the roll outside. In fig. 2, the situation is shown: for example, the protective tape 50A is provided so as to extend outward from the roll, and the protective tape 50A covers the inner circumferential surface of the positive electrode collector 11 over a wide range.

The protective tape 50B covers the end (corner) of the positive electrode active material layer 12B on the outer peripheral side of the roll outer side of the positive electrode 10 and the periphery thereof, and thus suppresses defects caused by the corner.

Since the installation range of the protective tape 50B can be set arbitrarily, it can be extended to one side or both of the roll inside and the roll outside. In fig. 2, the situation is shown: for example, since the protective tape 50B is provided over a wide range extending outward from the roll, the protective tape 50B covers the outer peripheral surface of the positive electrode collector 11 over a wide range.

The protective tape 50C mainly covers the end (corner) of the outer peripheral side positive electrode active material layer 12B inside the roll of the positive electrode 10 and the periphery thereof, thereby suppressing defects caused by the corner.

Since the installation range of the protective tape 50C can be set arbitrarily, it can be extended to one side or both of the roll inside and the roll outside. In fig. 2, the situation is shown: for example, since the protective tape 50C is provided over a wide range extending toward the roll inner side, the protective tape 50C covers the outer peripheral surface of the positive electrode collector 11 over a wide range.

The protective tape 50D mainly covers the end (corner) of the positive electrode active material layer 12A on the inner peripheral side inside the roll of the positive electrode 10 and the periphery thereof, thereby suppressing defects caused by the corner.

Since the installation range of the protective tape 50D can be set arbitrarily, it can be extended to one side or both of the roll inside and the roll outside. In fig. 2, the situation is shown: for example, since the protective tape 50D is provided over a wide range extending toward the roll inner side, the protective tape 50D covers the inner circumferential surface of the positive electrode collector 11 over a wide range. Here, the protective tape 50D is provided in a range extending to, for example, a region overlapping with the positive electrode lead 2 and the periphery thereof.

The protective tape 50E is a positive electrode terminal protection member, and covers the positive electrode lead 2 and its periphery, thereby suppressing a problem caused by an end portion (corner portion) of the positive electrode lead 2. That is, the protective tape 50E covers, for example, the positive electrode lead 2 and the positive electrode collector 11 together. The reason why the defect occurs at the corner of the positive electrode lead 2 is the same as the reason why the defect occurs at the corner of the inner peripheral side positive electrode active material layer 12A.

Since the installation range of the protective tape 50E can be set arbitrarily, it can be extended to one side or both of the roll inside and the roll outside. In fig. 2, the situation is shown: for example, the protective tape 50E is provided over a wide range extending outward from the roll, and the protective tape 50E covers the outer peripheral surface of the positive electrode collector 11 over a wide range. Here, the protective tape 50E is connected to (integrated with) the protective tape 50C, for example.

The protective tape 50F is a negative electrode terminal protection member, and covers the negative electrode lead 3 and its periphery, thereby suppressing a problem caused by an end portion (corner portion) of the negative electrode lead 3. That is, the protective tape 50F covers, for example, the anode lead 3 and the anode current collector 21 together.

Since the installation range of the protective tape 50F can be set arbitrarily, it can be extended to one side or both of the roll inside and the roll outside.

The protective tape 50G covers mainly the end portion of the negative electrode 20 on the roll inner side, that is, the region overlapping the negative electrode lead 3 in the negative electrode current collector 21 and the periphery thereof, and suppresses defects caused by the corner portion of the negative electrode lead 3, as with the protective tape 50F.

Since the range of the protective tape 50G can be set arbitrarily, it can be extended to one or both of the roll inside and the roll outside.

[ constitution of the main portion of each of the positive and negative electrodes ]

As shown in fig. 4, the positive electrode 10 is wound around a winding axis J. Therefore, the positive electrode 10 includes a plurality of long axis direction extending portions 10A which are a part of the positive electrode 10 and a plurality of short axis direction extending portions 10B which are the other part of the positive electrode 10. That is, the positive electrode 10 has a structure in which a plurality of long-axis direction extending portions 10A and a plurality of short-axis direction extending portions 10B are alternately connected. The "plurality of long axis direction extending portions 10A" refers to a plurality of portions extending in the long axis (X axis) direction in the positive electrode 10 wound around the winding axis J, and the "plurality of short axis direction extending portions 10B" refers to a plurality of portions extending in the short axis (Y axis) direction in the positive electrode 10.

In addition, in fig. 4, in order to easily distinguish the plurality of long-axis direction extending portions 10A and the plurality of short-axis direction extending portions 10B from each other, the plurality of long-axis direction extending portions 10A are indicated by solid lines, and the plurality of short-axis direction extending portions 10B are indicated by broken lines. In order to simplify the illustration, each of the plurality of short-axis direction extending portions 10B is shown in a straight line. As clearly shown in fig. 2, actually, each of the plurality of short-axis direction extending portions 10B is curved.

As shown in fig. 4, the negative electrode 20 is wound around a winding axis J, and therefore has the same configuration as the positive electrode 10. That is, the negative electrode 20 includes a plurality of long axis direction extending portions 20A and a plurality of short axis direction extending portions 20B, and has a structure in which the plurality of long axis direction extending portions 20A and the plurality of short axis direction extending portions 20B are alternately connected. The detailed description of each of the plurality of long-axis direction extending portions 20A and the plurality of short-axis direction extending portions 20B is the same as the detailed description of each of the plurality of long-axis direction extending portions 10A and the plurality of short-axis direction extending portions 20B, except that, for example, the negative electrode 20 is a part thereof.

In fig. 4, as in the case of the plurality of long-axis direction extending portions 10A and the plurality of short-axis direction extending portions 10B, the plurality of long-axis direction extending portions 20A are indicated by solid lines, and the plurality of short-axis direction extending portions 20B are indicated by broken lines. Note that, for simplicity of illustration, each of the plurality of short-axis direction extending portions 20B is shown in a straight line shape, but actually, each of the plurality of short-axis direction extending portions 10B is in a curved line shape.

As shown in fig. 2, 4, and 5, the positive electrode 10 (the plurality of long-axis direction extending portions 10A) and the negative electrode 20 (the plurality of long-axis direction extending portions 20A) include six portions divided according to the winding position in the vicinity of the winding axis J. The six portions are a first positive electrode wound portion 10X and a second positive electrode wound portion 10Y which are a portion of the positive electrode 10 (the long axis direction extending portion 10A), and a first negative electrode wound portion 20X, a second negative electrode wound portion 20Y, a third negative electrode wound portion 20Z, and a fourth negative electrode wound portion 20W which are a portion of the negative electrode 20 (the long axis direction extending portion 20A).

Specifically, the positive electrode 10 includes a first positive electrode wound portion 10X extending in the longitudinal direction at the end portion inside the wound portion, and the positive electrode lead 2 is attached to the first positive electrode wound portion 10X. In the first positive electrode wound section 10X, for example, the inner peripheral side positive electrode active material layer 12A is not provided on the inner peripheral side surface of the positive electrode collector 11, and the outer peripheral side positive electrode active material layer 12B is not provided on the outer peripheral side surface of the positive electrode collector 11.

Further, the protective tape 50D is joined to the inner peripheral side of the first wound positive electrode portion 10X, for example, as described above, and the protective tape 50E is joined to the outer peripheral side of the first wound positive electrode portion 10X, for example, as described above.

The positive electrode 10 includes, for example, a second positive electrode wound portion 10Y disposed further outward than the first positive electrode wound portion 10X and extending in the longitudinal direction. The second positive electrode wound portion 10Y faces the first positive electrode wound portion 10X through the separator 30, for example. In the second positive electrode wound section 10Y, for example, an inner peripheral side positive electrode active material layer 12A is provided on a partial surface on the inner peripheral side of the positive electrode current collector 11, and an outer peripheral side positive electrode active material layer 12B is provided on a partial surface on the outer peripheral side of the positive electrode current collector 11.

The protective tape 50D is joined to the inner peripheral side of the second positive electrode wound portion 10Y, for example, as described above, and the protective tape 50C is joined to the outer peripheral side of the second positive electrode wound portion 10Y, for example, as described above.

On the other hand, the negative electrode 20 includes a first negative electrode wound portion 20X extending in the longitudinal direction at the end portion inside the winding, and the negative electrode lead 3 is attached to the first negative electrode wound portion 20X. The first negative electrode wound portion 20X faces the first positive electrode wound portion 10X with the separator 30 interposed therebetween. In the first negative electrode wound portion 20X, for example, an inner peripheral side negative electrode active material layer 22A is provided on an inner peripheral side surface of the negative electrode current collector 21, and an outer peripheral side negative electrode active material layer 22B is provided on an outer peripheral side partial surface of the negative electrode current collector 21.

Further, the protective tape 50F is joined to the outer peripheral side of the first negative electrode wound portion 20X, for example, as described above.

The negative electrode 20 includes a second negative electrode wound portion 20Y, and the second negative electrode wound portion 20Y is disposed further outside than the first negative electrode wound portion 20X and extends in the longitudinal direction. The second negative electrode wound portion 20Y faces the first negative electrode wound portion 20X through the separator 30, for example. In the second anode wound portion 20Y, for example, the inner peripheral side anode active material layer 22A is not provided on the inner peripheral side of the anode current collector 21, and the outer peripheral side anode active material layer 22B is provided on the outer peripheral side surface of the anode current collector 21.

The negative electrode 20 includes a third negative electrode wound portion 20Z, and the third negative electrode wound portion 20Z is disposed further outside than the second negative electrode wound portion 20Y and extends in the longitudinal direction. The third negative electrode wound portion 20Z faces the second negative electrode wound portion 20Y with the separator 30 interposed therebetween, for example. In the third negative electrode wound portion 20Z, for example, an inner peripheral side negative electrode active material layer 22A is provided on a partial surface on the inner peripheral side of the negative electrode current collector 21, and an outer peripheral side negative electrode active material layer 22B is provided on a surface on the outer peripheral side of the negative electrode current collector 21.

Further, the protective tape 50G is joined to the inner peripheral side of the third negative electrode wound portion 20Z, for example, as described above.

The negative electrode 20 includes a fourth negative electrode wound portion 20W, and the fourth negative electrode wound portion 20W is disposed further inside than the first negative electrode wound portion 20X and extends in the longitudinal direction. The fourth negative electrode wound portion 20W faces the first negative electrode wound portion 20X through the separator 30, for example. In the fourth negative electrode wound section 20W, for example, the inner peripheral side negative electrode active material layer 22A is not provided on the inner peripheral side surface of the negative electrode current collector 21, and the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21.

< 1-3 > construction of step alleviating belt >

The step reducing tape 40 is joined to the positive electrode 10 and the negative electrode 20 in addition to the protective tape 50.

[ function ]

The step reducing tape 40 is a step reducing member that mainly reduces the influence of steps caused by the presence of each of the positive electrode lead 2 and the negative electrode lead 3, and thereby brings the shape (flat shape) of the wound electrode assembly 100 into a nearly flat state as much as possible. By using this step-relaxation band 40, the charge-discharge reaction between the positive electrode 10 and the negative electrode 20 is easily and stably performed, and thus the battery characteristics are improved.

Specifically, since the positive electrode lead 2 is attached to the positive electrode 10 (positive electrode current collector 11), a step is generated by the presence of the positive electrode lead 2, and the negative electrode lead 3 is attached to the negative electrode 20 (negative electrode current collector 21), a step is generated by the presence of the negative electrode lead 3.

When the step-relaxing tapes 40 are not provided in the positive electrode 10 and the negative electrode 20, the steps affect the winding state of the positive electrode 10 and the negative electrode 20 when the positive electrode 10 and the negative electrode 20 are wound in the manufacturing process of the wound electrode assembly 100, and therefore the wound electrode assembly 100 is likely to be deformed by the steps.

Specifically, the winding strength of the positive electrode 10 and the negative electrode 20 is unexpectedly high in the region near each of the positive electrode lead 2 and the negative electrode lead 3, whereas the winding strength of the positive electrode 10 and the negative electrode 20 is unexpectedly low in the other regions. The "winding strength is high" means that the wound state of the positive electrode 10 and the negative electrode 20 is tight, and the "winding strength is low" means that the wound state of the positive electrode 10 and the negative electrode 20 is loose. In this case, the distance (charge/discharge distance) between the positive electrode 10 and the negative electrode 20 is likely to vary due to the difference in the winding state, and therefore, the charge amount and the discharge amount are likely to vary during charge/discharge.

In the regions near the positive electrode lead 2 and the negative electrode lead 3, the winding strength of the positive electrode 10 and the negative electrode 20 is high at the beginning, but the winding state of the positive electrode 10 and the negative electrode 20 is relaxed as the charging and discharging are repeated, and the winding strength varies. In this case, when the secondary battery is continuously used, since the charge/discharge distance is likely to change, the charge amount and the discharge amount are also likely to change.

Accordingly, it is difficult to smoothly and stably perform charge and discharge reactions between the positive electrode 10 and the negative electrode 20, and the charge amount and the discharge amount are likely to vary and to fluctuate, thereby deteriorating battery characteristics.

In contrast, when the step alleviating zone 40 is provided in the positive electrode 10 and the negative electrode 20, as described above, the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20 can be alleviated. Accordingly, when the positive electrode 10 and the negative electrode 20 are wound in the manufacturing process of the wound electrode assembly 100, the shape (flat shape) of the wound electrode assembly 100 is closer to a flat state than in the case where the step-relaxing tape 40 is not provided for the positive electrode 10 and the negative electrode 20, and therefore the wound electrode assembly 100 is less likely to deform.

In this case, the winding strength of the positive electrode 10 and the negative electrode 20 becomes substantially uniform, regardless of whether the regions are in the vicinity of the positive electrode lead 2 and the negative electrode lead 3, respectively. Thus, the charging/discharging distance is less likely to vary, and therefore, the charging amount and the discharging amount are less likely to vary during charging and discharging.

Further, since the winding strength of the positive electrode 10 and the negative electrode 20 becomes substantially uniform, the winding strength is not easily changed even when charging and discharging are repeated. Thus, even when the secondary battery is continuously used, the charge/discharge distance is not easily changed, and thus the charge amount and the discharge amount are not easily changed.

Accordingly, the charge and discharge reaction between the positive electrode 10 and the negative electrode 20 proceeds smoothly and stably, and the charge amount and the discharge amount are stabilized, so that the battery characteristics are improved.

[ Material ]

The step reducing belt 40 includes, for example, one or two or more kinds of insulating polymer compounds. The kind of the insulating polymer compound is not particularly limited, and examples thereof include polypropylene (PP), polyethylene terephthalate (PET), and Polyimide (PI). The insulation of the step relaxing tape 40 can be ensured.

[ form ]

The form of the step reducing belt 40 is not limited at all as long as it can be fixed to each of the positive electrode 10 and the negative electrode 20.

Specifically, the step reducing tape 40 may be an adhesive tape having an adhesive layer, or may be a non-adhesive tape having no adhesive layer. The step reducing tape 40 as a non-adhesive tape is bonded to the positive electrode 10 and the negative electrode 20 with an adhesive, for example. The step alleviating belt 40 may be a film having flexibility (pliability), or may be a sheet having rigidity.

[ size ]

The thickness of the step reducing tape 40 is not particularly limited, but is preferably not extremely thin and is equal to or less than the thickness of each of the positive electrode lead 2 and the negative electrode lead 3. If the thickness of the step reducing tape 40 is extremely thin, it becomes difficult to reduce the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20. On the other hand, if the thickness of the step reducing tape 40 is larger than the thickness of each of the positive electrode lead 2 and the negative electrode lead 3, the influence of the step on the winding state of the positive electrode 10 and the negative electrode 20 may be increased.

Specifically, the ratio T of the thickness T2 of the step-relaxing tape 40 to the thickness T1 of each of the positive electrode lead 2 and the negative electrode lead 3 is preferably 15% to 80%. The influence of the steps on the winding state of the positive electrode 10 and the negative electrode 20 can be sufficiently alleviated. The ratio T is calculated by the ratio T (%) (thickness T2/thickness T1) × 100. Here, regarding the value of (thickness T2/T1), the value of the second decimal place is rounded.

More specifically, the thickness T1 is, for example, 50 to 100 μm, and the thickness T2 is, for example, 8 to 80 μm.

The width of the step moderating belt 40 is not limited at all. However, when the step reducing band 40 is disposed in a third region R3 (see fig. 5) described later, the width of the step reducing band 40 is preferably not extremely small and is sufficiently smaller than the distance between the positive electrode lead 2 and the negative electrode lead 3. If the width of the step reducing tape 40 is extremely thin, it becomes difficult to reduce the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20. On the other hand, if the width of the step reducing tape 40 is not sufficiently smaller than the distance between the positive electrode lead 2 and the negative electrode lead 3, the influence of the step on the winding state of the positive electrode 10 and the negative electrode 20 may be increased.

Specifically, the ratio W of the width W2 of the step relaxing tape 40 to the distance W1 between the positive electrode lead 2 and the negative electrode lead 3 is preferably 50% to 90%. The influence of the steps on the winding state of the positive electrode 10 and the negative electrode 20 can be sufficiently reduced. The ratio W is calculated by the ratio W (%) (width W2/distance W1) × 100. Wherein, regarding the value of (width W2/distance W1), the value of the second digit of the decimal point is rounded.

More specifically, the distance W1 is, for example, 8mm to 30mm, and the width W2 is, for example, 4mm to 27 mm.

The height of the step reducing band 40 is not particularly limited, but is preferably not extremely small and not extremely larger than the height of each of the positive electrode current collector 11 and the negative electrode current collector 21. If the height of the step reducing tape 40 is extremely small, it becomes difficult to reduce the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20. On the other hand, if the height of the step-reducing tape 40 is extremely larger than the height of each of the positive electrode current collector 11 and the negative electrode current collector 21, the influence of the step on the wound state of the positive electrode 10 and the negative electrode 20 may be increased.

Specifically, the ratio H of the height H2 of the step reducing band 40 to the height H1 of each of the positive electrode current collector 11 and the negative electrode current collector 21 is preferably 20% to 105%. The influence of the steps on the winding state of the positive electrode 10 and the negative electrode 20 can be sufficiently reduced. The ratio H is calculated by the ratio H (%) (height H2/height H1) × 100. Wherein, regarding the values of (height H2/height H1), the value of the second digit of the decimal point is rounded.

More specifically, the height H1 is, for example, 30mm to 180mm, and the height H2 is, for example, 6mm to 189 mm.

[ number of set ]

The number of the step alleviating belts 40 may be one, or two or more. However, the larger the number of the step reducing belts 40, the more easily the steps are provided, the more easily the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20 is reduced.

When the number of the step relaxing belts 40 is two or more, the two or more step relaxing belts 40 may be the same or different in material, form, and size. Of course, any two or more of the two or more step reducing belts 40 may be made of the same material, form, and size.

[ setting position ]

The details of the installation position of the step reducing belt 40 are as follows. In addition, the case shown in fig. 5 is: in order to easily distinguish a series of installation positions of the step reducing belt 40, the step reducing belt 40 is provided at all the installation positions as candidates. Therefore, the step alleviation belt 40 need not be provided in all of the installation positions described below with reference to fig. 5.

(Main setting position)

The step reducing belt 40 is provided in one or both of the first positive wound portion 10X and the first negative wound portion 20X in one or more regions among the first region R1, the second region R2, and the third region R3.

Therefore, the step alleviating belt 40 may be provided only in the first region R1, only in the second region R2, or only in the third region R3. The step reducing belt 40 may be provided in both the first region R1 and the second region R2, in both the second region R2 and the third region R3, or in both the first region R1 and the third region R3. The step reducing belts 40 may be provided in all of the first region R1, the second region R2, and the third region R3.

The step-relaxing tape 40 may be provided only in the first positive wound portion 10X, only in the first negative wound portion 20X, or in both the first positive wound portion 10X and the first negative wound portion 20X.

When the step reducing tape 40 is provided in the first positive wound portion 10X, the step reducing tape 40 may be provided only on the inner peripheral side, only on the outer peripheral side, or on both the inner peripheral side and the outer peripheral side.

When the step relaxing tape 40 is provided in the first negative electrode wound portion 20X, the step relaxing tape 40 may be provided only on the inner peripheral side, only on the outer peripheral side, or both the inner peripheral side and the outer peripheral side.

Of course, the number of the step reducing belts 40 may be one as described above, or two or more. Hereinafter, the step reducing belts 40A to 40I will be described as specific examples of the step reducing belt 40. However, all the step reducing belts 40A to 40I are not necessarily provided, and one or more of the step reducing belts 40A to 40I may be provided.

Specifically, the step alleviating belts 40(40A to 40D) are provided in the first positive electrode wound portion 10X to which the positive electrode lead 2 is attached. Here, the first positive electrode wound portion 10X extends to the second region R2 through the first region R1, for example.

In the first positive electrode wound section 10X, for example, the inner peripheral side positive electrode active material layer 12A is not provided on the inner peripheral side surface of the positive electrode collector 11, and the outer peripheral side positive electrode active material layer 12B is not provided on the outer peripheral side surface of the positive electrode collector 11. Thus, since the positive electrode collector 11 in the first positive electrode wound section 10X includes, for example, the first positive electrode exposed section 11XP in which the inner peripheral side positive electrode active material layer 12A and the outer peripheral side positive electrode active material layer 12B are not provided, the step reducing belt 40 is provided, for example, in the first positive electrode exposed section 11 XP.

That is, the step alleviating belt 40A is provided on the surface of the first positive electrode exposed portion 11XP in the first region R1. However, when the protective tape 50D is pasted to the exposed surface on the inner peripheral side of the first positive electrode exposed portion 11XP, the step reducing tape 40A may be provided on the protective tape 50D.

The step alleviating belt 40B is provided on the outer peripheral surface of the first positive electrode exposed portion 11XP in the first region R1. However, when the protective tape 50E is pasted to the exposed surface on the outer peripheral side of the first positive electrode exposed portion 11XP, the step reducing tape 40B may be provided on the protective tape 50E.

A step alleviating belt 40C is provided on the inner circumferential side surface of the first positive electrode exposed portion 11XP in the second region R2. However, when the protective tape 50D is pasted on the inner circumferential side surface of the first positive electrode exposed portion 11XP, the step reducing tape 40C may be provided on the protective tape 50D. The step reducing belt 40C may cover the inner circumferential surface of the first positive electrode exposed portion 11XP together with the protective belt 50D, for example.

The step reducing belt 40D is provided on the outer peripheral surface of the first positive electrode exposed portion 11XP in the second region R2. However, when the protective tape 50E is provided on the outer peripheral surface of the first positive electrode exposed portion 11XP, the step reducing tape 40D may be provided on the protective tape 50E. The step reducing belt 40D may cover the outer peripheral surface of the first positive electrode exposed portion 11XP together with the protective belt 50E, for example.

The step alleviating belts 40(40E to 40I) are provided in the first negative electrode wound portion 20X to which the negative electrode lead 3 is attached. Here, the first negative electrode wound portion 20X extends from the first region R1 to the third region R3 through the second region R2, for example.

In the first negative electrode wound portion 20X, for example, the inner peripheral side negative electrode active material layer 22A is not provided on the inner peripheral side surface of the negative electrode current collector 21, and the outer peripheral side negative electrode active material layer 22B is provided on the outer peripheral side partial surface (first region R1) of the negative electrode current collector 11. Thus, the negative electrode current collector 21 in the first negative electrode wound portion 20X includes, for example, the first negative electrode exposed portion 21XP on which the inner peripheral side negative electrode active material layer 22A and the outer peripheral side negative electrode active material layer 22B are not provided, and therefore, the step-relaxing tape 40 is provided, for example, on the first negative electrode exposed portion 21 XP.

That is, the step alleviating belt 40E is provided on the inner circumferential side surface of the first negative electrode exposed portion 21XP of the first region R1.

A step alleviating belt 40F is provided on the inner circumferential side surface of the first negative electrode exposed portion 21XP of the second region R2.

A step-relaxing belt 40G is provided on the outer peripheral surface of the first negative electrode exposed portion 21XP in the second region R2. However, when the protective tape 50F is joined to the surface on the outer peripheral side of the first negative electrode exposed portion 21XP, the step reducing tape 40G may be provided on the protective tape 50F.

The step alleviating belt 40H is provided on the inner circumferential surface of the first negative electrode exposed portion 21XP of the third region R3.

The step alleviating belt 40I is provided on the outer peripheral surface of the first negative electrode exposed portion 21XP of the third region R3. However, when the protective tape 50F is provided on the surface on the outer peripheral side of the first negative electrode exposed portion 21XP, the step relaxing tape 40I may be provided on the protective tape 50F.

Here, the step-relaxing tape 40 is provided in one or both of the first cathode wound portion 10X and the first anode wound portion 20X because the cathode lead 2 is attached to the first cathode wound portion 10X and the anode lead 3 is attached to the first anode wound portion 20X. That is, by providing the step reducing band 40 in the first positive electrode wound portion 10X itself where the step is generated, the influence of the positive electrode lead 2 (step) is easily and effectively reduced by the step reducing band 40. Further, by providing the step alleviating strip 40 in the first negative electrode wound portion 20X itself where the step is generated, the influence of the step of the negative electrode lead 3 (step) can be easily and effectively alleviated by the step alleviating strip 40.

(optional setting position)

In addition, the step reducing belt 40 may be provided at one or two or more of a series of setting positions described below, in addition to the series of setting positions. The influence of the steps on the winding state of the positive electrode 10 and the negative electrode 20 is further reduced, and thus the battery characteristics are further improved.

The first step reducing belts 40(40R, 40S) may be provided on the second positive electrode wound portion 10Y, for example. The step-relaxing belt 40 may be provided on one or both of the inner peripheral side and the outer peripheral side of the second positive electrode wound portion 10Y. Here, the second positive electrode wound portion 10Y extends from the first region R1 to the third region R3 through the second region R2, for example.

In the second positive electrode wound section 10Y, for example, an inner peripheral side negative electrode active material layer 22A is provided on partial surfaces on the inner peripheral side of the positive electrode collector 11 (the second region R2 and the third region R3), and an outer peripheral side negative electrode active material layer 22B is provided on partial surfaces on the outer peripheral side of the negative electrode collector 11 (the second region R2 and the third region R3). Thus, the positive electrode current collector 11 in the second positive electrode wound section 10Y includes the second positive electrode exposed section 11YP where the inner peripheral side positive electrode active material layer 12A and the outer peripheral side positive electrode active material layer 12B are not provided, and therefore the step reducing tape 40 is provided in the second positive electrode exposed section 11YP, for example.

That is, the step-relaxing belt 40R may be provided on the inner circumferential surface of the second positive electrode exposed portion 11YP of the first region R1. However, when the protective tape 50D is pasted on the inner circumferential surface of the second positive electrode exposed portion 11YP, the step reducing tape 40R may be provided on the protective tape 50D. The step-relaxing belt 40S may be provided on the outer peripheral surface of the second positive electrode exposed portion 11YP of the first region R1. However, when the protective tape 50C is joined to the outer peripheral surface of the second positive electrode exposed portion 11YP, the step reducing tape 40S may be provided on the protective tape 50C.

The second step-relaxing belt 40(40L to 40N) may be provided in the second negative electrode wound portion 20Y, for example. The step-relaxing tape 40 may be provided on one or both of the inner peripheral side and the outer peripheral side of the second negative electrode wound portion 20Y. Here, the second negative electrode wound portion 20Y extends from the first region R1 to the third region R3 through the second region R2, for example.

In the second negative electrode wound section 20Y, for example, the inner peripheral side negative electrode active material layer 22A is not provided on the inner peripheral side surface of the negative electrode current collector 21, and the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 11. Thus, the negative electrode current collector 21 in the second negative electrode wound portion 20Y includes, for example, the second negative electrode exposed portion 21YP where the inner peripheral side negative electrode active material layer 22A and the outer peripheral side negative electrode active material layer 22B are not provided, and therefore the step-relaxing tape 40 is provided, for example, on the second negative electrode exposed portion 21 YP.

That is, the step-relaxing belt 40L may be provided on the inner circumferential surface of the second negative electrode exposed portion 21YP in the first region R1. The step-relaxing belt 40M may be provided on the inner circumferential surface of the second negative electrode exposed portion 21YP of the second region R2, for example. The step-relaxing belt 40N may be provided on the inner circumferential surface of the second negative electrode exposed portion 21YP of the third region R3, for example.

The third step reducing belts 40(40P, 40Q) may be provided on the third negative electrode wound portion 20Z, for example. The step-relaxing tape 40 may be provided on one or both of the inner peripheral side and the outer peripheral side of the third negative electrode wound portion 20Z. Here, the third negative electrode wound portion 20Z extends from the first region R1 to the third region R3 through the second region R2, for example.

In the third negative electrode wound portion 20Z, for example, an inner peripheral side negative electrode active material layer 22A is provided on a partial surface on the inner peripheral side of the negative electrode current collector 21 (first region R1), and an outer peripheral side negative electrode active material layer 22B is provided on a surface on the outer peripheral side of the negative electrode current collector 21. Thus, the negative electrode current collector 21 in the third negative electrode wound portion 20Z includes the third negative electrode exposed portion 21ZP where the inner peripheral side negative electrode active material layer 22A and the outer peripheral side negative electrode active material layer 22B are not provided, and therefore the step-relaxing tape 40 is provided on the third negative electrode exposed portion 21ZP, for example.

That is, the step-relaxing belt 40P may be provided on the inner circumferential surface of the third negative electrode exposed portion 21ZP in the second region R2. The step-relaxing belt 40Q may be provided on the surface of the third region R3 on the inner circumferential side of the third negative electrode exposed portion 21 ZP.

The fourth step reducing band 40(40J, 40K) may be provided in the fourth negative electrode wound portion 20W, for example. The step-relaxing tape 40 may be provided on one or both of the inner peripheral side and the outer peripheral side of the fourth negative electrode wound portion 20W. Here, the fourth negative electrode wound portion 20W extends in the third region R3, for example.

In the fourth negative electrode wound section 20W, for example, the inner peripheral side negative electrode active material layer 22A is not provided on the inner peripheral side surface of the negative electrode current collector 21, and the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 11. Thus, the anode current collector 21 in the fourth anode rolled portion 20W includes, for example, the fourth anode exposed portion 21WP where the inner periphery side anode active material layer 22A and the outer periphery side anode active material layer 22B are not provided, and therefore the step reducing band 40 is provided, for example, on the fourth anode exposed portion 21 WP.

That is, the step reducing band 40J may be provided on the inner circumferential surface of the fourth negative electrode exposed portion 21WP in the third region R3. For example, the step reducing band 40K may be provided on the surface of the third region R3 on the outer peripheral side of the fourth negative electrode exposed portion 21 WP.

Of course, the step reducing tape 40 may be provided only in any one of the second cathode wound portion 10Y, the second anode wound portion 20Y, the third anode wound portion 20Z, and the fourth anode wound portion 20W, or the step reducing tape 40 may be provided in any two or more of the second cathode wound portion 10Y, the second anode wound portion 20Y, the third anode wound portion 20Z, and the fourth anode wound portion 20W.

Here, the step-relaxing tape 40 is provided in each of the second cathode winding portion 10Y, the second anode winding portion 20Y, the third anode winding portion 20Z, and the fourth anode winding portion 20W because each of the second cathode winding portion 10Y, the second anode winding portion 20Y, the third anode winding portion 20Z, and the fourth anode winding portion 20W is arranged next to each of the first cathode winding portion 10X and the first anode winding portion 20X in the vicinity of the winding axis J. That is, the influence of the step is easily alleviated by providing the step alleviating tape 40 in each of the second positive electrode wound portion 10Y, the second negative electrode wound portion 20Y, the third negative electrode wound portion 20Z, and the fourth negative electrode wound portion 20W disposed in the vicinity of each of the positive electrode lead 2 and the negative electrode lead 3 in which the step is generated.

< 1-4 > actions

Next, the operation of the secondary battery will be described. The secondary battery is operated as follows.

During charging, for example, lithium ions are released from the positive electrode 10, and the released lithium ions are absorbed in the negative electrode 20 via the electrolytic solution. On the other hand, during discharge, for example, lithium ions are released from the negative electrode 20, and the released lithium ions are absorbed by the positive electrode 10 via the electrolytic solution.

< 1-5 > method for manufacturing >

Next, a method for manufacturing the secondary battery will be described. The secondary battery is manufactured, for example, in the following steps.

In the production of the positive electrode 10, a positive electrode active material, a positive electrode binder, a positive electrode conductive agent, and the like are mixed to obtain a positive electrode mixture. Next, a positive electrode mixture is dispersed in an organic solvent or the like to obtain a slurry-like positive electrode mixture slurry. Next, a positive electrode mixture slurry is applied to both surfaces of the positive electrode current collector 11, and then the positive electrode mixture slurry is dried, thereby forming the positive electrode active material layers 12 (the inner peripheral side positive electrode active material layer 12A and the outer peripheral side positive electrode active material layer 12B). Finally, the positive electrode active material layer 12 is compression-molded using a roll press or the like. In this case, the positive electrode active material layer 12 may be heated, or compression molding may be repeated a plurality of times.

In the case of producing the negative electrode 20, the negative electrode active material layers 12 (the inner peripheral side negative electrode active material layer 12A and the outer peripheral side negative electrode active material layer 12B) are formed on both surfaces of the negative electrode current collector 11 in the same step as the production step of the positive electrode 10. Specifically, a slurry-like negative electrode mixture slurry is obtained by mixing a negative electrode active material, a negative/positive electrode binder, a negative electrode conductive agent, and the like to obtain a negative electrode mixture, and then dispersing the negative electrode mixture in an organic solvent or the like. Next, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 21, and then the negative electrode mixture slurry is dried, thereby forming the negative electrode active material layer 22. Finally, the anode active material layer 22 is compression-molded using a roll press or the like. Of course, the anode active material layer 22 may be heated, or compression molding may be repeated a plurality of times.

In the preparation of the electrolyte, an electrolyte salt is added to a solvent, and then the solvent is stirred.

When assembling the secondary battery, first, the positive electrode lead 2 is attached to the positive electrode 10 (positive electrode collector 11) by welding or the like, and the negative electrode lead 3 is attached to the negative electrode 20 (negative electrode collector 21) by welding or the like. Next, the step reducing tape 40 and the protective tape 50 are joined to each of the positive electrode 10 and the negative electrode 20. Next, the positive electrode 10 and the negative electrode 20 are laminated with the separator 30 interposed therebetween, and then the positive electrode 10, the negative electrode 20, and the separator 30 are wound around the winding axis J to obtain a wound body. Next, the wind-up fixing tape 58 is attached to the wind-up end portion of the wound body, thereby fixing the wind-up end portion.

Next, after the exterior member 1 is folded with the roll body interposed therebetween, the remaining outer peripheral edge portion of the exterior member 1 excluding one outer peripheral edge portion is welded by a thermal fusion bonding method or the like, thereby housing the roll body inside the bag-like exterior member 1. In this case, the wound body is housed inside the recess 1U provided in the exterior member 1. Next, the electrolyte solution is injected into the bag-like exterior member 1, and the exterior member 1 is sealed by a thermal fusion bonding method or the like. In this way, the wound electrode assembly 100 is obtained by impregnating the wound body with the electrolyte solution, and the wound electrode assembly 100 is sealed inside the exterior member 1. In this case, the adhesion film 4 is inserted between the exterior member 1 and the positive electrode lead 2, and the adhesion film 5 is inserted between the exterior member 1 and the negative electrode lead 3.

Finally, the outer sheathing member 1 enclosing the wound electrode assembly 100 is heated and pressed to mold the wound electrode assembly 100 into a flat shape. In this case, the exterior member 1 may be heated. Thereby, a laminate film type secondary battery is completed.

Action and Effect (1-6)

According to the secondary battery, the step alleviating belts 40(40A to 40I) are provided in one or two or more regions among the first region R1, the second region R2, and the third region R3 in one or both of the first positive wound portion 10X and the first negative wound portion 20X. In this case, as described above, even if the positive electrode lead 2 (step) is provided in the first positive electrode wound portion 10X and the negative electrode lead 3 (step) is provided in the first negative electrode wound portion 20X, the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20 can be alleviated, and therefore, the shape (flat shape) of the wound electrode assembly 100 is not easily deformed. As a result, even when the secondary battery is continuously used, the charge and discharge reaction between the positive electrode 10 and the negative electrode 20 is easily and stably performed, and thus the charge amount and the discharge amount are stable. Thus, battery characteristics can be improved.

In particular, if the step reducing belts 40 are provided on one or both of the inner peripheral side and the outer peripheral side of the first positive electrode wound portion 10X, the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20 can be easily reduced, and therefore, a higher effect can be obtained. Further, if the step alleviating belts 40 are provided on one or both of the inner peripheral side and the outer peripheral side of the first negative electrode wound portion 20X, the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20 can be easily alleviated, and therefore, a higher effect can be obtained.

Further, if the step alleviating belts 40(40J to 40N, 40P to 40S) are provided in one or more of the second cathode wound section 10Y, the second anode wound section 20Y, the third anode wound section 20Z, and the fourth anode wound section 20W, the influence of the steps on the wound state of the cathode 10 and the anode 20 can be further alleviated, and therefore, a higher effect can be obtained.

Further, when the step reducing tape 40 and the protective tape 50(50A to 50G) are used together, the positive electrode 10, the negative electrode 20, and the separator 30 can be prevented from being deformed or damaged, and the charge/discharge reaction between the positive electrode 10 and the negative electrode 20 can be easily and stably performed, so that a higher effect can be obtained.

Further, when the ratio T is 15% to 80%, the ratio W is 50% to 90%, or the ratio H is 20% to 105%, the influence of the steps on the wound state of the positive electrode 10 and the negative electrode 20 can be sufficiently alleviated, and therefore, a higher effect can be obtained.

Further, if the step reducing tape 40 is made of polypropylene or the like, the insulation property of the step reducing tape 40 can be ensured, and therefore, a higher effect can be obtained.

(1-7. variants)

The configuration of the secondary battery may be appropriately modified.

[ modification 1]

For example, as shown in fig. 6 corresponding to fig. 5, a step-relaxing tape 41(41A to 41L) may be additionally provided to one or both of the first positive electrode wound portion 10X and the first negative electrode wound portion 20X. That is, the step reducing belt 41 may be newly provided at a position where the step reducing belt 40 is not provided in fig. 5. The configuration of the step reducing belt 41 is, for example, the same as that of the step reducing belt 40. However, all the step reducing belts 41A to 41L are not necessarily provided, and one or more of the step reducing belts 41A to 41L may be provided. The same effect can be obtained in this case as well.

Specifically, for example, in the first negative electrode wound section 20X, as shown in fig. 5, since the outer peripheral negative electrode active material layer 22B is provided on the outer peripheral surface of the negative electrode current collector 21 in the first region R1, the step-relaxing band 40 is not provided on the outer peripheral surface of the negative electrode current collector 21.

However, for example, as shown in fig. 6, since the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21 in the first region R1, the step reducing zone 41A may be provided on the outer peripheral side surface of the negative electrode current collector 21 (first negative electrode exposed portion 21 XP).

The second positive electrode wound portion 10Y, the second negative electrode wound portion 20Y, and the third negative electrode wound portion 20Z may be provided with additional step reducing tapes 41 as described above.

For example, in the second positive electrode wound section 10Y, as shown in fig. 5, since the inner peripheral side positive electrode active material layer 12A is provided on the inner peripheral side surface of the positive electrode current collector 11 in each of the second region R2 and the third region R3, the step relaxing band 40 is not provided on the inner peripheral side surface of the positive electrode current collector 11.

However, for example, as shown in fig. 6, since the inner peripheral side positive electrode active material layer 12A is not provided on the inner peripheral side surface of the positive electrode collector 11 in the second region R2, the step reducing zone 41C may be provided on the inner peripheral side surface of the positive electrode collector 11 (second positive electrode exposed portion 11 YP). For example, since the inner peripheral side positive electrode active material layer 12A is not provided on the inner peripheral side surface of the positive electrode collector 11 in the third region R3, the step reducing band 41B may be provided on the inner peripheral side surface of the positive electrode collector 11.

In the second positive electrode wound section 10Y, for example, as shown in fig. 5, since the outer peripheral side positive electrode active material layer 12B is provided on the outer peripheral side surface of the positive electrode current collector 11 in each of the second region R2 and the third region R3, the step reducing band 40 is not provided on the outer peripheral side surface of the positive electrode current collector 11.

However, for example, as shown in fig. 6, since the outer peripheral negative electrode active material layer 12B is not provided on the outer peripheral surface of the positive electrode collector 11 in the second region R2, the step-relaxing zone 41E may be provided on the outer peripheral surface of the positive electrode collector 11 (second positive electrode exposed portion 11 YP). For example, since the outer peripheral positive electrode active material layer 12B is not provided on the outer peripheral surface of the positive electrode collector 11 in the third region R3, the step reducing zone 41D may be provided on the outer peripheral surface of the positive electrode collector 11.

In the second negative electrode wound section 20Y, for example, as shown in fig. 5, since the outer peripheral side negative electrode active material layer 22B is provided on the outer peripheral side surface of the negative electrode current collector 21 in each of the first region R1, the second region R2, and the third region R3, the step-reducing band 40 is not provided on the outer peripheral side surface of the negative electrode current collector 21.

However, for example, as shown in fig. 6, since the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21 in the first region R1, the step reducing zone 41F may be provided on the outer peripheral side surface of the negative electrode current collector 21 (second negative electrode exposed portion 21 YP). For example, since the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21 in the second region R2, the step-relaxing belt 41H may be provided on the outer peripheral side surface of the negative electrode current collector 21. For example, since the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21 in the third region R3, the step-relaxing belt 41G may be provided on the outer peripheral side surface of the negative electrode current collector 21.

In addition, for example, in the third negative electrode wound portion 20Z, as shown in fig. 5, since the inner peripheral side negative electrode active material layer 22A is provided on the surface on the inner peripheral side of the negative electrode current collector 21 in the first region R1, the step reducing band 40 is not provided on the surface on the inner peripheral side of the negative electrode current collector 21.

However, for example, as shown in fig. 6, since the inner peripheral side negative electrode active material layer 22A is not provided on the inner peripheral side surface of the negative electrode current collector 21 in the first region R1, the step relaxing zone 41I may be provided on the inner peripheral side surface of the negative electrode current collector 21 (third negative electrode exposed portion 21 ZP).

In the third negative electrode wound section 20Z, for example, as shown in fig. 5, since the outer peripheral side negative electrode active material layer 22B is provided on the outer peripheral side surface of the negative electrode current collector 21 in each of the first region R1, the second region R2, and the third region R3, the step reducing band 40 is not provided on the outer peripheral side surface of the negative electrode current collector 21.

However, for example, as shown in fig. 6, since the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21 in the first region R1, the step reducing zone 41J may be provided on the outer peripheral side surface of the negative electrode current collector 21 (third negative electrode exposed portion 21 ZP). For example, since the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21 in the second region R2, the step-relaxing tape 41L may be provided on the outer peripheral side surface of the negative electrode current collector 21. For example, since the outer peripheral side negative electrode active material layer 22B is not provided on the outer peripheral side surface of the negative electrode current collector 21 in the third region R3, the step-relaxing belt 41K may be provided on the outer peripheral side surface of the negative electrode current collector 21.

[ modification 2]

For example, as shown in fig. 7 corresponding to fig. 5, the step-relaxing tapes 41(41M, 41N, 41P to 41S) may be provided by changing the extension range of the first cathode wound portion 10X and the extension range of the fourth anode wound portion 20W. However, all of the

step reducing belts

41M, 41N, and 41P to 41S are not necessarily provided, and one or more of the

step reducing belts

41M, 41N, and 41P to 41S may be provided. In this case, the same effect can be obtained.

Specifically, for example, by extending the first positive electrode wound section 10X to the second region R2, the step reducing zone 41M may be provided on the surface of the second region R2 on the inner peripheral side of the positive electrode collector 11 (first positive electrode exposed section 11XP), or the step reducing zone 41N may be provided on the surface of the second region R2 on the outer peripheral side of the positive electrode collector 11.

For example, by extending the fourth negative wound portion 20W to the first region R1 through the third region R3, the step reducing band 41P may be provided on the surface of the first region R1 on the inner peripheral side of the negative electrode collector 21 (fourth negative electrode exposed portion 21WP), or the step reducing band 41Q may be provided on the surface of the first region R1 on the outer peripheral side of the negative electrode collector 21. The step-reducing tape 41R may be provided on the inner circumferential surface of the negative electrode current collector 21 (fourth negative electrode exposed portion 21WP) in the third region R3, and the step-reducing tape 41S may be provided on the outer circumferential surface of the negative electrode current collector 21 in the third region R3.

Of course, when the extending range of the fourth negative electrode wound portion 20W is changed, only the

step alleviating belts

41R and 41S may be provided by extending the fourth negative electrode wound portion 20W not to the first region R1 but to the third region R3.

[ modification 3]

The number of the step reducing belts 40 may be increased at each installation position of the step reducing belts 40.

For example, as shown in fig. 5, in the first positive electrode wound portion 10X, one step alleviating zone 40A is provided on the inner circumferential side surface of the first positive electrode exposed portion 11XP of the first region R1. However, for example, two or more step reducing belts 40A may be provided on the inner circumferential surface of the first positive electrode exposed portion 11 XP. In this case, for example, two or more step reducing belts 40A may be provided in parallel. In this case, the same effect can be obtained.

Of course, two or more step-relaxing belts 40 may be similarly provided at other positions of the first positive electrode wound portion 10X. Two or more step reducing tapes 40 may be provided at each installation position of the second positive electrode wound portion 10Y, the first negative electrode wound portion 20X, the second negative electrode wound portion 20Y, the third negative electrode wound portion 20Z, and the fourth negative electrode wound portion 20W.

[ modification 4]

As shown in fig. 5, by using a protective tape 50, a step mitigating tape 40 is provided over the protective tape 50.

However, the step alleviating belt 40 may be newly provided by not using the protective belt 50 or by changing the installation range of the protective belt 50. In this case, the same effect can be obtained.

Specifically, for example, the step alleviating tape 40A may be provided on the inner circumferential side surface of the first positive electrode exposed portion 11XP in the first region R1 without using the protective tape 50D or changing the installation range of the protective tape 50D. For example, the step reducing belts 40B may be provided on the outer peripheral surfaces of the first positive electrode exposed portions 11XP in the first region R1 without using the protective belts 50E or changing the installation range of the protective belts 50E.

Second, for example, the step alleviating zone 40R may be provided on the inner circumferential surface of the second positive electrode exposed portion 11YP of the first region R1 without using the protective tape 50D or changing the installation range of the protective tape 50D. For example, the step-relaxing belt 40S may be provided on the outer peripheral surface of the second positive electrode exposed portion 11YP in the first region R1 without using the protective belt 50C or changing the installation range of the protective belt 50C.

Third, for example, the step alleviating tape 40G may be provided on the outer peripheral surface of the first negative electrode exposed portion 21XP in the third region R3 without using the protective tape 50F or changing the installation range of the protective tape 50F. For example, the step alleviating belts 40I may be provided on the outer peripheral side surfaces of the first negative electrode exposed portions 11XP in the second regions R2 without using the protective tape 50F or changing the installation range of the protective tape 50F.

Fourth, for example, the step alleviating zone 40P may be provided on the surface of the third region R3 on the inner circumferential side of the third negative electrode exposed portion 21ZP without using the protective tape 50G or changing the installation range of the protective tape 50G. For example, the step reducing belts 40Q may be provided on the inner circumferential side surfaces of the third negative electrode exposed portions 21ZP in the second regions R2 without using the protective belts 50G or changing the installation range of the protective belts 50G.

[ modification 5]

As shown in fig. 5, the step-relaxing tapes 40 are provided in six portions (the first positive wound portion 10X, the second positive wound portion 10Y, the first negative wound portion 20X, the second negative wound portion 20Y, the third negative wound portion 20Z, and the fourth negative wound portion 20W) of the positive electrode 10 and the negative electrode 20, which are disposed in the vicinity of the winding axis J.

However, in the positive electrode 10, the step-relaxing tape 40 may be provided at a portion on the outer peripheral side of the first positive electrode wound portion 10X and the second positive electrode wound portion 10Y. In the negative electrode 20, the step-relaxing tape 40 may be provided on a portion of the negative electrode winding part 20X, the second negative electrode winding part 20Y, the third negative electrode winding part 20Z, and the fourth negative electrode winding part 20W on the outer circumferential side.

However, the more the step alleviating belt 40 is provided at a portion of the positive electrode 10 closer to the winding axis J, the more easily the influence of the steps on the wound state of the positive electrode 10 is alleviated. Therefore, the step-relaxing tape 40 is preferably provided in a portion (the first positive wound portion 10X and the second positive wound portion 10Y) of the positive electrode 10 close to the winding axis J.

Further, the step reducing band 40 is provided in the portion of the negative electrode 20 closer to the winding axis J, and the influence of the step on the wound state of the negative electrode 20 is more easily reduced. Therefore, the step reducing tape 40 is preferably provided in a portion of the negative electrode 20 close to the winding axis J (the first negative electrode wound portion 20X, the second negative electrode wound portion 20Y, the third negative electrode wound portion 20Z, and the fourth negative electrode wound portion 20W).

Use of secondary battery

Next, an application example (use) of the secondary battery will be described.

The secondary battery is not limited in application, and may be a machine, equipment, appliance, device, system (an assembly of a plurality of pieces of equipment, etc.) or the like using the secondary battery as a driving power source, a power storage source for power storage, or the like. The secondary battery used as a power source may be a main power source or an auxiliary power source. The main power source is a power source that is preferentially used regardless of the presence or absence of other power sources. The auxiliary power supply may be, for example, a power supply used in place of the main power supply, or a power supply switched from the main power supply as needed. When a secondary battery is used as the auxiliary power supply, the type of the main power supply is not limited to the secondary battery.

The applications of the secondary battery are, for example, as follows. The present invention is used for electronic devices (including portable electronic devices) such as camcorders, digital still cameras, cellular phones, notebook computers, cordless phones, stereo headphones, portable radios, portable televisions, and portable information terminals. Is used for portable life appliances such as an electric shaver and the like. The power supply is used for a standby power supply and a storage device such as a memory card. The electric drill is used for electric tools such as electric drills and electric saws. A battery pack mounted as a detachable power supply on a notebook computer or the like. Is used in medical electronic devices such as pacemakers and hearing aids. The method is used for electric vehicles such as electric vehicles (including hybrid vehicles). An electricity storage system such as a household battery system for storing electric power in an emergency or the like. Of course, the secondary battery may be used for other applications than those described above.

Among them, the secondary battery is effectively applied to battery packs, electric vehicles, electricity storage systems, electric tools, electronic devices, and the like. Since these applications require excellent battery characteristics, the secondary battery using the present technology can effectively achieve performance improvement. In addition, the battery pack is a power source using a secondary battery. As described later, a single cell may be used for the battery module, or a battery pack may be used. The electrically powered vehicle is a vehicle that operates (moves) using a secondary battery as a driving power source, and may be an automobile (such as a hybrid automobile) that is provided with a driving source other than the secondary battery as described above. The electric storage system is a system that uses a secondary battery as an electric power storage source. For example, in a household electricity storage system, electric power is stored in an electric power storage source secondary battery, and household electric appliances and the like can be used with the electric power. The electric power tool is a tool in which a movable portion (e.g., a drill) is movable using a secondary battery as a driving power source. An electronic device is a device that uses a secondary battery as a driving power source (power supply source) to perform various functions.

Here, several application examples of the secondary battery will be specifically described. The configuration of the application example described below is merely an example, and thus the configuration of the application example can be appropriately modified.

(2-1. Battery pack (cell))

Fig. 8 shows a three-dimensional configuration of a battery module using a single cell, and fig. 9 shows a block configuration of the battery module shown in fig. 8. Fig. 8 shows a state in which the battery pack is disassembled.

The battery pack described here is a simple battery pack (so-called soft pack) using one secondary battery, and is mounted on an electronic device such as a smartphone. For example, as shown in fig. 8, the battery module includes a power supply 111 as a laminate film type secondary battery, and a circuit board 116 connected to the power supply 111. A positive electrode lead 112 and a negative electrode lead 113 are attached to the power source 111.

A pair of

adhesive tapes

118 and 119 are attached to both side surfaces of the power supply 111. A Protection Circuit (PCM) is formed in the Circuit board 116. The circuit board 116 is connected to the positive electrode lead 112 via the tab 114, and is connected to the negative electrode lead 113 via the tab 115. The circuit board 116 is connected to a lead 117 of the connector for external connection. In addition, in a state where the circuit board 116 is connected to the power supply 111, the circuit board 116 is protected by a label (label)120 and an insulating sheet 128. By attaching the label 120, the circuit board 116, the insulating sheet 128, and the like are fixed.

Further, for example, as shown in fig. 9, the battery pack includes a power source 111 and a circuit board 116. The circuit board 116 includes, for example, a control unit 121, a switch unit 122, a thermistor element (PTC element) 123, and a temperature detection unit 124. The power source 111 is connected to the outside through the positive electrode terminal 125 and the negative electrode terminal 127, so that the power source 111 can be charged and discharged through the positive electrode terminal 125 and the negative electrode terminal 127. The temperature detection unit 124 detects the temperature using a temperature detection terminal (so-called T terminal) 126.

The controller 121 controls the operation of the entire battery pack (including the use state of the power source 111). The control unit 121 includes, for example, a Central Processing Unit (CPU), a memory, and the like.

For example, when the battery voltage reaches the overcharge detection voltage, the control unit 121 turns off the switch unit 122, and the charging current is no longer supplied to the current path of the power supply 111. For example, when a large current flows during charging, the control unit 121 switches the disconnecting switch 122 to interrupt the charging current.

On the other hand, for example, when the battery voltage reaches the overdischarge detection voltage, the control unit 121 turns off the switch unit 122, and the discharge current is no longer supplied to the current path of the power supply 111. For example, when a large current flows during discharging, the control unit 121 turns off the switch unit 122 to interrupt the discharging current.

The overcharge detection voltage is not particularly limited, and is, for example, 4.2V ± 0.05V. The overdischarge detection voltage is not particularly limited, and is, for example, 2.4V ± 0.1V.

The switch unit 122 switches the use state of the power supply 111, that is, whether or not the power supply 111 is connected to an external device, in accordance with an instruction from the control unit 121. The switch unit 122 includes, for example, a charge control switch and a discharge control switch. The charge control switch and the discharge control switch are semiconductor switches such as field effect transistors (MOSFETs) using metal oxide semiconductors, for example. The charge/discharge current is detected based on, for example, the on-resistance of the switch unit 122.

Temperature detector 124 measures the temperature of power supply 111 and outputs the temperature measurement result to controller 121. The temperature detection unit 124 includes a temperature detection element such as a thermistor. The temperature measurement result measured by the temperature detector 124 is used when the controller 121 performs charge/discharge control in the event of abnormal heat generation, when the controller 121 performs correction processing in the case of calculating the remaining capacity, and the like.

The circuit board 116 may not include the PTC element 123. In this case, a PTC element may be additionally provided on the circuit board 116.

(2-2. Battery pack)

Fig. 10 shows a block configuration of a battery pack using battery packs.

The battery module includes, for example, a control unit 61, a power supply 62, a switch unit 63, a current measuring unit 64, a temperature detecting unit 65, a voltage detecting unit 66, a switch control unit 67, a memory 68, a temperature detecting element 69, a current detecting resistor 70, a positive electrode terminal 71, and a negative electrode terminal 72 in a case 60. The housing 60 comprises, for example, a plastic material or the like.

The control unit 61 controls the operation of the entire battery pack (including the use state of the power source 62). The control section 61 includes, for example, a CPU. The power source 62 is a battery pack including two or more secondary batteries, and the two or more secondary batteries may be connected in series, in parallel, or in a hybrid manner. In one example, the power source 62 includes six secondary batteries connected in series in two parallel connections.

The switch 63 switches the use state of the power source 62, that is, switches whether or not the power source 62 is connected to the external device, in accordance with an instruction from the control unit 61. The switch unit 63 includes, for example, a charge control switch, a discharge control switch, a charge diode, a discharge diode, and the like. The charge control switch and the discharge control switch are semiconductor switches such as field effect transistors (MOSFETs) using metal oxide semiconductors, for example.

The current measuring unit 64 measures a current using the current detection resistor 70, and outputs the current measurement result to the control unit 61. The temperature detection unit 65 measures the temperature using the temperature detection element 69, and outputs the temperature measurement result to the control unit 61. The temperature measurement results are used, for example, when the control unit 61 performs charge and discharge control during abnormal heat generation, when the control unit 61 performs correction processing during calculation of the remaining capacity, and the like. The voltage detection section 66 measures the voltage of the secondary battery in the power supply 62, and supplies the measurement result of the voltage subjected to analog-digital conversion to the control section 61.

The switch control unit 67 controls the operation of the switch unit 63 based on signals input from each of the current measuring unit 64 and the voltage detecting unit 66.

For example, when the battery voltage reaches the overcharge detection voltage, the switch control unit 67 turns off the switch unit 63 (charge control switch) and stops the flow of the charge current to the current path of the power source 62. Thus, the power source 62 can discharge only through the discharge diode. For example, when a large current flows during charging, the switch control unit 67 blocks the charging current.

For example, when the battery voltage reaches the overdischarge detection voltage, the switch control unit 67 turns off the switch unit 63 (discharge control switch) and stops the discharge current from flowing through the current path of the power source 62. Thus, the power source 62 can be charged only via the charging diode. For example, when a large current flows during discharging, the switching control unit 67 blocks the discharging current.

The memory 68 includes, for example, a nonvolatile memory EEPROM or the like. The memory 68 stores, for example, a numerical value calculated by the control unit 61, information of the secondary battery measured in the manufacturing process stage (for example, internal resistance in an initial state, etc.), and the like. Further, when the memory 68 stores the full charge capacity of the secondary battery, the control unit 61 can grasp information such as the remaining capacity.

The temperature detection element 69 measures the temperature of the power source 62 and outputs the temperature measurement result thereof to the control section 61. The temperature detection element 69 includes, for example, a thermistor or the like.

Both the positive electrode terminal 71 and the negative electrode terminal 72 are connected to an external device (e.g., a notebook personal computer) that operates using the battery pack, an external device (e.g., a charger) that charges the battery pack, and the like. The power source 62 can be charged and discharged through the positive electrode terminal 71 and the negative electrode terminal 72.

Electric vehicle (2-3)

Fig. 11 shows a block configuration of a hybrid vehicle as an example of an electric vehicle.

The electric vehicle includes, for example, a control unit 74, an engine 75, a power supply 76, a drive motor 77, a differential device 78, a generator 79, a transmission 80, a clutch 81,

inverters

82 and 83, and various sensors 84 inside a metal case 73. The electric vehicle further includes, for example, a front wheel drive shaft 85 and a front wheel 86 connected to the differential device 78 and the transmission case 80, and a rear wheel drive shaft 87 and a rear wheel 88.

The electric vehicle can be moved using, for example, any one of the engine 75 and the motor 77 as a drive source. The engine 75 is a main power source, such as a gasoline engine or the like. When the engine 75 is used as a power source, a driving force (rotational force) of the engine 75 is transmitted to the front wheels 86 and the rear wheels 88 via, for example, a differential device 78, a transmission 80, and a clutch 81, which are drive units. Since the rotational force of the engine 75 is transmitted to the generator 79, the generator 79 generates ac power by using the rotational force and converts the ac power into dc power via the inverter 83, and the dc power is stored in the power source 76. On the other hand, when the motor 77 as the conversion unit is used as the power source, the electric power (dc power) supplied from the power source 76 is converted into ac power via the inverter 82, and therefore the motor 77 is driven by the ac power. The driving force (rotational force) converted from electric power by the motor 77 is transmitted to the front wheels 86 and the rear wheels 88 via, for example, the differential device 78, the transmission 80, and the clutch 81 as the driving portion.

Further, when the electric vehicle is decelerated by the brake mechanism, the resistance at the time of deceleration is transmitted to the motor 77 as the rotational force, and therefore the motor 77 may generate the ac power by the rotational force. Since the ac power is converted into dc power via the inverter 82, the dc regenerated power is preferably stored in the power supply 76.

The control unit 74 controls the operation of the entire electric vehicle. The control unit 74 includes, for example, a CPU. The power source 76 includes one or more secondary batteries. The power supply 76 may be connected to an external power supply and receive power from the external power supply, thereby accumulating power. The various sensors 84 are used, for example, to control the number of revolutions of the engine 75 and to control the opening degree of a throttle valve (throttle opening degree). The various sensors 84 include, for example, one or two or more of a speed sensor, an acceleration sensor, and an engine revolution sensor.

Although the case where the electric vehicle is a hybrid vehicle is described as an example, the electric vehicle may be a vehicle (electric vehicle) that is operated only by the power source 76 and the motor 77 without using the engine 75.

(2-4. Electricity storage System)

Fig. 12 shows a block configuration of the power storage system.

The power storage system includes a control unit 90, a power supply 91, a smart meter 92, and a power hub 93 in a house 89 such as a general residence or a commercial office building.

Here, power supply 91 is connected to, for example, electric equipment 94 provided inside house 89 and to electric vehicle 96 stopped outside house 89. The power source 91 is connected to a home generator 95 installed in the house 89 via a power hub 93, and is connected to an external centralized power system 97 via a smart meter 92 and the power hub 93.

The electric device 94 includes, for example, one or two or more home electric appliances, such as a refrigerator, an air conditioner, a television, and a water heater. The home generator 95 includes, for example, one or two or more of a solar generator and a wind turbine generator. The electric vehicle 96 includes, for example, one or two or more of an electric vehicle, an electric motorcycle, and a hybrid vehicle. The concentrated power system 97 includes one or more of a thermal power plant, a nuclear power plant, a hydroelectric power plant, and a wind power plant.

The control unit 90 controls the operation of the entire power storage system (including the use state of the power source 91). The control unit 90 includes, for example, a CPU. The power source 91 includes one or more secondary batteries. The smart meter 92 is, for example, a network-supported power meter installed in the house 89 on the power demand side, and can communicate with the power supply side. Accordingly, the smart meter 92 can control the balance of the power demand and supply of the house 89 while communicating with the outside, for example, thereby enabling stable energy supply with high efficiency.

In this power storage system, for example, electric power is stored from a concentrated power system 97 as an external power source to the power source 91 via the smart meter 92 and the power hub 93, and electric power is stored from a home power generator 95 as an independent power source to the power source 91 via the power hub 93. The electric power stored in the power supply 91 is supplied to the electric device 94 and the electric vehicle 96 in accordance with the instruction of the control unit 90, so that the electric device 94 can be operated and the electric vehicle 96 can be charged. That is, the electricity storage system is a system capable of storing and supplying electric power in house 89 using power supply 91.

The electric power stored in the power supply 91 can be used as needed. Therefore, for example, it is possible to store electric power from the concentrated power system 97 to the power supply 91 in the late night when the electric power rate is low, and then use the electric power stored in the power supply 91 in the daytime when the electric power rate is high.

In addition, the electricity storage system can be set in one household (one household unit) or in multiple households (multiple household units).

Electric tool (2-5)

Fig. 13 shows a block configuration of the electric power tool.

The electric tool described here is, for example, an electric drill. The electric power tool includes, for example, a control unit 99 and a power supply 100 inside a tool main body 98. The tool main body 98 is attached with a drill 101, which is a movable part capable of running (rotating), for example.

The tool body 98 comprises, for example, a plastic material or the like. The control unit 99 controls the operation of the entire electric power tool (including the use state of the power supply 100). The control unit 99 includes, for example, a CPU. The power supply 100 includes one or more secondary batteries. The controller 99 supplies power from the power source 100 to the drill 101 in response to the operation of the operation switch.

[ examples ] A method for producing a compound

Embodiments of the present technology are illustrated.

(Experimental examples 1 to 59)

A laminate film type secondary battery (lithium ion secondary battery) shown in fig. 1 to 5 was produced in accordance with the following procedure, and then the battery characteristics of this secondary battery were evaluated.

[ production of Secondary Battery ]

When the positive electrode 10 was produced, first, 91 parts by mass of a positive electrode active material (lithium cobaltate), 3 parts by mass of a positive electrode binder (polyvinylidene fluoride), and 6 parts by mass of a positive electrode conductive agent (graphite) were mixed to obtain a positive electrode mixture. Next, a positive electrode mixture was put into an organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to obtain slurry-like positive electrode mixture slurry. Next, a positive electrode mixture slurry was applied to both surfaces of a strip-shaped positive electrode collector 11 (aluminum foil, thickness 12 μm, height 90mm) using an application device, and then the positive electrode mixture slurry was dried, thereby forming positive electrode active material layers 12 (inner peripheral side positive electrode active material layer 12A and outer peripheral side positive electrode active material layer 12B). Finally, the positive electrode active material layer 12 is compression-molded using a roll press.

In order to produce the negative electrode 20, first, 97 parts by mass of a negative electrode active material (artificial graphite) and 3 parts by mass of a negative electrode binder (polyvinylidene fluoride) were mixed to obtain a negative electrode mixture. Next, the negative electrode mixture was put into the organic solvent (N-methyl-2-pyrrolidone), and the organic solvent was stirred to obtain slurry-like negative electrode mixture slurry. Next, the negative electrode mixture slurry was applied to both sides of the strip-shaped negative electrode current collector 21 (copper foil, thickness: 10 μm, height: 91.2mm) using a coating device, and then the negative electrode mixture slurry was dried, thereby forming the negative electrode active material layer 22 (inner peripheral side negative electrode active material layer 22A and outer peripheral side negative electrode active material layer 22B). Finally, the anode active material layer 22 was compression-molded using a roll press.

In the preparation of the electrolyte, an electrolyte salt (lithium hexafluoro-carbonate) was added to a solvent (ethylene carbonate, propylene carbonate, diethyl carbonate, and vinylene carbonate), and then the solvent was stirred. The mixing ratio (weight ratio) of the solvents is ethylene carbonate: propylene carbonate: diethyl carbonate: vinylene carbonate ═ 20: 20: 59: 1. the content of the electrolyte salt in the electrolyte solution was set to 1 mol/kg.

When assembling the secondary battery, first, an aluminum cathode lead 2 (width 10mm and thickness 80 μm) is welded to the cathode 10 (cathode current collector 11), and a nickel anode lead 3 (width 10mm and thickness 80 μm) is welded to the anode 20 (anode current collector 21). In this case, the distance between the cathode lead 2 and the anode lead 3 was set to 12 mm.

Then, a step-reducing tape 40 (polypropylene adhesive tape) and a protective tape 50(50A to 50G: polypropylene adhesive tape) were attached to each of the positive electrode 10 and the negative electrode 20. The installation position, the number (number) and the type of the step reducing belts 40 are shown in tables 1 to 4. In this case, as shown in tables 1 to 4, the thickness (μm), the ratio T (%), the width (mm), the ratio W (%), the height (mm), and the ratio H (%) of the step-relaxation belt 40 are set. In table 4 (experimental examples 54 to 58), the thickness (μm), the ratio T (%), the width (mm), the ratio W (%), the height (mm), and the ratio H (%) of each step-relaxation zone 40 are shown.

For comparison, the step reducing tape 40 was not attached to each of the positive electrode 10 and the negative electrode 20. The presence or absence of the step reducing belt 40 is shown in tables 1 to 4.

Next, the positive electrode 10 and the negative electrode 20 were laminated with the separator 30 (microporous polyethylene film, thickness 15 μm) interposed therebetween, to obtain a laminate. Next, after the laminate is wound in the longitudinal direction, a winding-fixing tape 58 is attached to the winding-completed portion of the laminate, thereby obtaining a wound body. Next, the exterior member 1 is folded with the wound body interposed therebetween, and then the outer peripheral edge portions of three sides of the exterior member 1 are heat-welded to each other in a reduced pressure environment. As the exterior member 1, an aluminum laminate film in which a nylon film (thickness: 25 μm), an aluminum foil (thickness: 40 μm), and a polypropylene film (thickness: 30 μm) are laminated in this order from the outside was used. In this case, a close-fitting film 4 (polypropylene film, thickness 60 μm) is inserted between the exterior member 1 and the cathode lead 2, and a close-fitting film 5 (polypropylene film, thickness 60 μm) is inserted between the exterior member 1 and the anode lead 3.

Next, an electrolyte solution is injected into the interior of the exterior member 1 to impregnate the wound body with the electrolyte solution, and thereafter, the remaining peripheral edge portions of the exterior member 1 are thermally fused together in a reduced pressure environment. Thereby, wound electrode assembly 100 is obtained, and wound electrode assembly 100 is enclosed inside exterior member 1. Finally, the outer sheathing member 1 enclosing the wound electrode assembly 100 is heated and pressed to mold the wound electrode assembly 100 into a flat shape.

Thus, a laminate film type secondary battery (width: 40mm, height: 100mm) was completed.

[ evaluation of Battery characteristics ]

In order to evaluate the battery characteristics of the secondary battery, the cycle characteristics of the secondary battery were analyzed, and the results shown in tables 1 to 4 were obtained. When the cycle characteristics were analyzed, a cycle test was performed to determine the capacity retention (%).

Specifically, first, in order to stabilize the state of the secondary battery, the secondary battery is charged and discharged (one cycle) in a normal temperature environment (temperature ═ 23 ℃). In the charging, after the voltage reached 4.2V by constant current charging at a current of 1C, the voltage reached 0.05C by constant voltage charging at a voltage of 4.2V. During discharge, constant current discharge was performed at a current of 1C until the voltage reached 3.0V. In addition, "1C" refers to a current value at which the battery capacity (theoretical capacity) is discharged within 1 hour, and "0.05C" refers to a current value at which the battery capacity is discharged within 20 hours.

Next, the secondary battery was charged and discharged again in the same environment, and the discharge capacity in the second cycle was measured. The charge and discharge conditions were the same as those in the case of stabilizing the state of the secondary battery, except that the current at the time of charge was changed to 0.7C and the current at the time of discharge was changed to 0.7C. "0.7C" is a current value at which the battery capacity is discharged within 10/7 hours.

Next, in the same environment, the discharge capacity at the 500 th cycle was measured by repeating charge and discharge of the secondary battery until the total number of cycles reached 500 cycles. The charge and discharge conditions were the same as those of the 2 nd cycle.

Finally, the capacity retention rate (%) was calculated as (discharge capacity at 500 cycles/discharge capacity at 2 cycles) × 100.

[ TABLE 1]

[ TABLE 2]

[ TABLE 3]

[ TABLE 4]

[ examination ]

As shown in tables 1 to 4, the capacity retention rate was increased when the step relaxation belt 40 was used (experimental examples 1 to 58) as compared with the case where the step relaxation belt 40 was not used (experimental example 59).

In particular, when the step reducing belt 40 is used, the following tendency is obtained. First, when the number of the step reducing belts 40 is increased, the capacity retention rate is further increased. Second, if the ratio T is 15% to 80%, the capacity retention rate further increases. Third, if the ratio W is 50% to 90%, the capacity retention rate further increases. Fourth, when the ratio H is 20% to 105%, the capacity retention rate further increases.

From the results shown in tables 1 to 4, if the step reducing belts 40 are provided in one or two or more regions among the first region R1, the second region R2, and the third region R3, one or both of the positive electrode 10 (first positive electrode wound portion 10X) and the negative electrode 20 (first negative electrode wound portion 20X) can improve the cycle characteristics. Thereby, the secondary battery obtains excellent battery characteristics.

The present technology has been described above with reference to one embodiment and examples, but the present technology is not limited to the embodiments described in the one embodiment and examples, and various modifications are possible.

Specifically, a secondary battery (lithium ion secondary battery) that obtains a battery capacity by utilizing a lithium occlusion phenomenon and a lithium release phenomenon is described, but the present invention is not limited thereto. For example, a secondary battery (lithium metal secondary battery) may be used in which the battery capacity is obtained by utilizing a precipitation phenomenon and a dissolution phenomenon of lithium. Alternatively, for example, the following secondary battery may be used: the capacity of the negative electrode material capable of occluding and releasing lithium is made smaller than the capacity of the positive electrode, and the battery capacity is expressed by the sum of the capacity utilizing the occlusion phenomenon and the release phenomenon of lithium and the capacity utilizing the precipitation phenomenon and the dissolution phenomenon of lithium.

Further, although the laminate film type secondary battery is described, it is not limited thereto. For example, a rectangular secondary battery or the like in which a flat wound electrode assembly is housed inside a flat battery can may be used.

In addition, the case of using lithium as an electrode reaction material has been described, but the present invention is not limited thereto. The electrode reactant may be, for example, other group 1 elements in the periodic table such as sodium and potassium, group 2 elements in the periodic table such as magnesium and calcium, or other light metals such as aluminum. The electrode reactant may be an alloy containing any one or two or more of the above-described series of elements.

The effects described in the present specification are merely illustrative and not restrictive, and other effects may be obtained.

In addition, the present technology can also be configured as follows.

(1) A secondary battery is provided with:

a positive terminal;

a negative terminal;

a wound electrode assembly, (a) the wound electrode assembly including a positive electrode and a negative electrode that are stacked on each other with a separator interposed therebetween and wound around a winding shaft as a center, (B) a cross section intersecting the winding shaft having a flat shape defined by a major axis and a minor axis, (C) the positive electrode including a positive electrode collector and a positive electrode active material layer provided on a part of the positive electrode collector, (D) the negative electrode including a negative electrode collector and a negative electrode active material layer provided on a part of the negative electrode collector, (E) a winding-direction-inside end portion of the positive electrode in a winding direction including a first positive electrode winding portion that extends in a direction of the major axis and to which the positive electrode terminal is attached, (F) a winding-direction-inside end portion of the negative electrode in the winding direction including a first negative electrode winding portion that extends in the direction of the major axis, and is opposed to the first positive electrode wound portion via the separator, and the negative electrode terminal is attached to the first negative electrode wound portion so as not to overlap with the positive electrode terminal in the direction of the short axis; and

one or two or more step relaxing members provided in at least one of the first positive electrode wound portion and the first negative electrode wound portion in at least one of a first region, a second region, and a third region, the first region being located further outward in a winding direction of the positive electrode than the positive electrode terminal in the direction of the long axis, the second region being located further outward in the winding direction of the negative electrode than the negative electrode terminal in the direction of the long axis, and the third region being located between the positive electrode terminal and the negative electrode terminal.

(2) The secondary battery according to item (1), wherein the step-relaxing member is provided on at least one of an inner peripheral side and an outer peripheral side of the first positive wound portion, and the step-relaxing member is provided on the at least one of the inner peripheral side and the outer peripheral side of the first positive wound portion

The step relaxing member is provided on at least one of an inner peripheral side and an outer peripheral side of the first negative electrode wound portion.

(3) The secondary battery according to the item (1) or (2), wherein the positive electrode current collector in the first positive electrode wound portion includes a first positive electrode exposed portion where the positive electrode active material layer is not provided,

the step alleviating member is provided in the first positive electrode exposing portion.

(4) The secondary battery according to item (3), wherein a positive electrode terminal protection member is provided in the first positive electrode exposed portion so as to cover the positive electrode terminal and the periphery thereof,

the step alleviating member is provided on the positive electrode terminal protection member.

(5) The secondary battery according to any one of the above (1) to (4), wherein the anode current collector in the first anode wound part includes a first anode exposed part where the anode active material layer is not provided,

the step alleviating member is provided in the first negative electrode exposed portion.

(6) The secondary battery according to item (5), wherein a negative electrode terminal protection member is provided in the first negative electrode exposed portion so as to cover the negative electrode terminal and the periphery thereof,

the step alleviating member is provided on the negative electrode terminal protection member.

(7) The secondary battery according to any one of (1) to (6), wherein the positive electrode further includes a second positive electrode wound portion that is disposed on a winding outer side in a winding direction of the positive electrode than the first positive electrode wound portion, extends in the direction of the long axis, and is opposed to the first positive electrode wound portion with the separator interposed therebetween,

the positive electrode collector in the second positive electrode wound portion includes a second positive electrode exposed portion where the positive electrode active material layer is not provided in at least one of the first region, the second region, and the third region,

the step alleviating member is provided in the second positive electrode exposing portion.

(8) The secondary battery according to any one of the above (1) to (7), wherein the negative electrode further includes a second negative electrode wound portion that is disposed on a winding outer side in a winding direction of the negative electrode than the first negative electrode wound portion, extends in the direction of the long axis, and is opposed to the first negative electrode wound portion with the separator interposed therebetween,

the negative electrode current collector in the second negative electrode wound portion includes a second negative electrode exposed portion where the negative electrode active material layer is not provided in at least one of the first region, the second region, and the third region,

the step alleviating member is provided in the second negative electrode exposed portion.

(9) The secondary battery according to the item (8), wherein the negative electrode further includes a third negative electrode wound portion that is disposed further outside in a winding direction of the negative electrode than the second negative electrode wound portion, the third negative electrode wound portion extending in the direction of the long axis and facing the second negative electrode wound portion via the separator,

the negative electrode current collector in the third negative electrode wound portion includes a third negative electrode exposed portion where the negative electrode active material layer is not provided in at least one of the first region, the second region, and the third region,

the step alleviating member is provided in the third negative electrode exposed portion.

(10) The secondary battery according to any one of (1) to (9), wherein the negative electrode further includes a fourth negative electrode wound portion that is disposed further inside than the first negative electrode wound portion in a winding direction of the negative electrode, extends in the direction of the long axis, and faces the first negative electrode wound portion with the separator interposed therebetween,

the negative electrode current collector in the fourth negative electrode wound portion includes a fourth negative electrode exposed portion where the negative electrode active material layer is not provided in at least one of the first region, the second region, and the third region,

the step alleviating member is provided in the fourth negative electrode exposed portion.

(11) The secondary battery according to any one of the items (1) to (10), wherein a ratio of a thickness of the step relaxing member to a thickness of each of the positive electrode terminal and the negative electrode terminal is 15% to 80%.

(12) The secondary battery according to any one of the above (1) to (11), wherein the step relaxing member is disposed in the third region,

the ratio of the width of the step relaxing member to the distance between the positive electrode terminal and the negative electrode terminal is 50% to 90%.

(13) The secondary battery according to any one of the items (1) to (12), wherein a ratio of a height of the step reducing member to a height of each of the positive electrode current collector and the negative electrode current collector is 20% or more and 105% or less.

(14) The secondary battery according to any one of (1) to (13), wherein the step relaxing member includes at least one of polypropylene, polyethylene terephthalate, and polyimide.

(15) The secondary battery according to any one of the (1) to (14), which is a lithium-ion secondary battery.

(16) A battery pack is provided with: the secondary battery according to any one of (1) to (15) above;

a control unit for controlling the operation of the secondary battery; and

and a switch unit for switching the operation of the secondary battery according to the instruction of the control unit.

(17) An electric vehicle is provided with: the secondary battery according to any one of (1) to (15) above;

a conversion unit that converts electric power supplied from the secondary battery into driving force;

a driving unit that drives the motor according to the driving force; and

and a control unit for controlling the operation of the secondary battery.

(18) An electricity storage system is provided with: the secondary battery according to any one of (1) to (15) above;

one or more than two electrical devices powered by the secondary battery; and

and a control unit that controls power supply from the secondary battery to the electrical device.

(19) An electric power tool is provided with: the secondary battery according to any one of (1) to (15) above; and

and a movable part powered by the secondary battery.

(20) An electronic device comprising the secondary battery according to any one of (1) to (15) above as a power supply source.

Claims

1. A secondary battery is characterized by comprising:

a positive terminal;

a negative terminal;

a wound electrode assembly, (a) the wound electrode assembly including a positive electrode and a negative electrode that are stacked on each other with a separator interposed therebetween and wound around a winding shaft as a center, (B) a cross section intersecting the winding shaft having a flat shape defined by a major axis and a minor axis, (C) the positive electrode including a positive electrode collector and a positive electrode active material layer provided on a part of the positive electrode collector, (D) the negative electrode including a negative electrode collector and a negative electrode active material layer provided on a part of the negative electrode collector, (E) a winding-direction-inner-side end portion of the positive electrode in a winding direction including a first positive electrode winding portion that extends in the direction of the major axis and to which the positive electrode terminal is attached, (F) a winding-direction-inner-side end portion of the negative electrode in the winding direction including a first negative electrode winding portion that extends in the direction of the major axis, and is opposed to the first positive electrode wound portion with the separator interposed therebetween, the negative electrode terminal being attached to the first negative electrode wound portion so as not to overlap the positive electrode terminal in the direction of the short axis; and

one or two or more step relaxing members provided in at least one of the first positive wound portion and the first negative wound portion in at least one of a first region, a second region, and a third region, the first region being located further outward in a winding direction of the positive electrode than the positive terminal in the direction of the long axis, the second region being located further outward in the winding direction of the negative electrode than the negative terminal in the direction of the long axis, the third region being located between the positive terminal and the negative terminal,

the positive electrode current collector in the first positive electrode wound portion includes a first positive electrode exposed portion where the positive electrode active material layer is not provided,

the step alleviating member is provided in the first positive electrode exposed portion,

a positive electrode terminal protection member is provided in the first positive electrode exposed portion so as to cover the positive electrode terminal and the periphery thereof,

2. A secondary battery is characterized by comprising:

a positive terminal;

a negative terminal;

a wound electrode assembly, (a) the wound electrode assembly including a positive electrode and a negative electrode that are stacked on each other with a separator interposed therebetween and wound around a winding shaft as a center, (B) a cross section intersecting the winding shaft having a flat shape defined by a major axis and a minor axis, (C) the positive electrode including a positive electrode collector and a positive electrode active material layer provided on a part of the positive electrode collector, (D) the negative electrode including a negative electrode collector and a negative electrode active material layer provided on a part of the negative electrode collector, (E) a winding-direction-inner-side end portion of the positive electrode in a winding direction including a first positive electrode winding portion that extends in the direction of the major axis and to which the positive electrode terminal is attached, (F) a winding-direction-inner-side end portion of the negative electrode in the winding direction including a first negative electrode winding portion that extends in the direction of the major axis, and is opposed to the first positive electrode wound portion with the separator interposed therebetween, the negative electrode terminal being attached to the first negative electrode wound portion so as not to overlap with the positive electrode terminal in the direction of the minor axis; and

the anode current collector in the first anode rolled portion includes a first anode exposed portion where the anode active material layer is not provided,

the step alleviating member is provided in the first negative electrode exposed portion,

a negative electrode terminal protection member is provided in the first negative electrode exposed portion so as to cover the negative electrode terminal and the periphery thereof,

the step alleviating member is provided on the negative terminal protection member.

3. The secondary battery according to claim 1 or 2, wherein the step-relaxing member is provided on at least one of an inner peripheral side and an outer peripheral side of the first positive wound portion, and the step-relaxing member is provided on at least one of the inner peripheral side and the outer peripheral side of the first positive wound portion

4. The secondary battery according to claim 1 or 2, wherein the positive electrode further includes a second positive electrode wound portion that is disposed outside the first positive electrode wound portion in a winding direction of the positive electrode, extends in the direction of the long axis, and faces the first positive electrode wound portion with the separator interposed therebetween,

the positive electrode current collector in the second positive electrode wound portion includes a second positive electrode exposed portion where the positive electrode active material layer is not provided in at least one of the first region, the second region, and the third region,

the step alleviating member is provided in the second positive electrode exposed portion.

5. The secondary battery according to claim 1 or 2, wherein the negative electrode further comprises a second negative electrode wound portion that is disposed outside the first negative electrode wound portion in a winding direction of the negative electrode, extends in the direction of the long axis, and faces the first negative electrode wound portion with the separator interposed therebetween,

6. The secondary battery according to claim 5, wherein the negative electrode further comprises a third negative electrode wound portion that is disposed outside the second negative electrode wound portion in the winding direction of the negative electrode, extends in the direction of the long axis, and faces the second negative electrode wound portion with the separator interposed therebetween,

7. The secondary battery according to claim 1 or 2, wherein the negative electrode further comprises a fourth negative electrode wound portion that is disposed further inside than the first negative electrode wound portion in a winding direction of the negative electrode, extends in the direction of the long axis, and faces the first negative electrode wound portion with the separator interposed therebetween,

8. The secondary battery according to claim 1 or 2, wherein a ratio of a thickness of the step relaxing member to a thickness of each of the positive electrode terminal and the negative electrode terminal is 15% or more and 80% or less.

9. The secondary battery according to claim 1 or 2, wherein the step alleviating member is disposed in the third region,

10. The secondary battery according to claim 1 or 2, wherein a ratio of a height of the step-relaxing member to a height of each of the positive electrode current collector and the negative electrode current collector is 20% or more and 105% or less.

11. The secondary battery according to claim 1 or 2, wherein the step relaxation member comprises at least one of polypropylene, polyethylene terephthalate, and polyimide.

12. The secondary battery according to claim 1 or 2, characterized in that it is a lithium-ion secondary battery.

13. A battery pack is characterized by comprising: a secondary battery;

a control unit that controls an operation of the secondary battery; and

a switch unit for switching the operation of the secondary battery according to the instruction of the control unit,

the secondary battery includes:

a positive terminal;

a negative terminal;

14. A battery pack is characterized by comprising: a secondary battery;

a control unit that controls an operation of the secondary battery; and

the secondary battery includes:

a positive terminal;

a negative terminal;

one or more step-relaxing members provided in at least one of the first positive wound part and the first negative wound part in at least one of a first region, a second region, and a third region, the first region being located further outside in a winding direction of the positive electrode than the positive terminal in the direction of the major axis, the second region being located further outside in the winding direction of the negative electrode than the negative terminal in the direction of the major axis, the third region being located between the positive terminal and the negative terminal,

15. An electric vehicle is characterized by comprising:

a secondary battery;

a conversion portion that converts electric power supplied from the secondary battery into driving force;

a driving unit that drives the motor according to the driving force; and

a control unit for controlling the operation of the secondary battery,

the secondary battery includes:

a positive terminal;

a negative terminal;

16. An electric vehicle is characterized by comprising:

a secondary battery;

a driving unit that drives the motor according to the driving force; and

a control unit for controlling the operation of the secondary battery,

the secondary battery includes:

a positive terminal;

a negative terminal;

17. An electricity storage system is characterized by comprising:

a secondary battery;

one or more electrical devices powered by the secondary battery; and

a control unit that controls power supply from the secondary battery to the electrical device,

the secondary battery includes:

a positive terminal;

a negative terminal;

18. An electricity storage system is characterized by comprising:

a secondary battery;

one or more electrical devices powered by the secondary battery; and

the secondary battery includes:

a positive terminal;

a negative terminal;

19. An electric power tool is characterized by comprising:

a secondary battery; and

a movable portion powered by the secondary battery,

the secondary battery includes:

a positive terminal;

a negative terminal;

a wound electrode assembly (a) including a positive electrode and a negative electrode that are stacked on each other with a separator interposed therebetween and wound around a winding axis, (B) having a cross section intersecting the winding axis and having a flat shape defined by a major axis and a minor axis, (C) the positive electrode including a positive electrode collector and a positive electrode active material layer provided on a part of the positive electrode collector, (D) the negative electrode including a negative electrode collector and a negative electrode active material layer provided on a part of the negative electrode collector, (E) a winding-direction winding-inner-side end portion of the positive electrode in a winding direction including a first positive electrode winding portion extending in the direction of the major axis and to which the positive electrode terminal is attached, (F) a winding-direction winding-inner-side end portion of the negative electrode in the winding direction including a first negative electrode winding portion extending in the direction of the major axis, and is opposed to the first positive electrode wound portion with the separator interposed therebetween, the negative electrode terminal being attached to the first negative electrode wound portion so as not to overlap with the positive electrode terminal in the direction of the minor axis; and

20. An electric power tool is characterized by comprising:

a secondary battery; and

a movable portion powered by the secondary battery,

the secondary battery includes:

a positive electrode terminal;

a negative terminal;

21. An electronic device comprising a secondary battery as a power supply source,

the secondary battery includes:

a positive terminal;

a negative terminal;

22. An electronic device comprising a secondary battery as a power supply source,

the secondary battery includes:

a positive electrode terminal;

a negative terminal;