JP2004047479A - Secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a secondary battery with a high thermal stability and an improved safety. <P>SOLUTION: For the secondary battery comprising a positive electrode 38 including a positive electrode collector 37 and a positive electrode layer 36 held by the positive electrode collector 37, a negative electrode 35, a flat electrode group 31 including a separator 32 arranged between the positive electrode 38 and the negative electrode 35, a liquid nonaqueous electrolyte impregnated into the electrode group 31, and an outer casing housing the electrode group 31 with a thickness of 0.3 mm or less, the positive electrode collector is located on at least one of two surfaces having a maximum area out of surfaces of the electrode group 31. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a secondary battery.

At present, a thin lithium-ion secondary battery has been commercialized as a nonaqueous electrolyte secondary battery for mobile devices such as mobile phones. This battery comprises a positive electrode containing lithium cobalt oxide (LiCoO ₂ ), a negative electrode containing a graphite or carbonaceous material, a liquid non-aqueous electrolyte comprising an organic solvent in which a lithium salt is dissolved, and a porous membrane. And a cladding made of a cylindrical or square metal can.

A thin lithium ion secondary battery having the liquid non-aqueous electrolyte and the metal can and having a thickness of 4 mm or less has been demanded as a battery is required to be thinner and lighter with the downsizing and thinning of portable devices. Is difficult to put into practical use.

By the way, a lithium ion secondary including an electrode group including a positive electrode, a negative electrode, and a polymer electrolyte layer disposed between the positive electrode and the negative electrode, an electrolyte including a polymer electrolyte, and an exterior material in which the electrode group is housed. A battery has been proposed and is under development. This secondary battery can ensure the adhesion between the positive electrode and the negative electrode and the polymer electrolyte layer even if the thickness of the outer package is reduced. Therefore, a laminate film composed of a thin metal layer and a polymer film can be used as the exterior material. The polymer electrolyte is a gel polymer in which a non-aqueous electrolyte is held.

However, this secondary battery has a higher impedance at the electrode interface and a lower lithium ion conductivity than a lithium ion secondary battery having a liquid non-aqueous electrolyte. There is a problem that the volume energy density and the large current discharge characteristics are inferior to the secondary battery.

From such circumstances, proposals for reducing the thickness of a lithium ion secondary battery including a liquid non-aqueous electrolyte have been made as follows.

The claims of Japanese Patent Application Laid-Open Publication No. 10-177865 (Patent Document 1) include a positive electrode, a negative electrode, a separator having an opposing surface holding an electrolytic solution, an electrolytic solution phase, and an electrolytic solution containing an electrolytic solution. A lithium ion secondary battery comprising a mixed phase of a molecular gel phase and a polymer solid phase, and having an adhesive resin layer for joining the positive electrode and the negative electrode on the opposite surface of the separator is described. Also, in the claims of Japanese Patent Laid-Open Publication No. Hei 10-189054 (Patent Document 2), a step of applying a binder resin solution obtained by dissolving a main component polyvinylidene fluoride in a solvent to a separator, A method for manufacturing a lithium ion secondary battery including a step of forming a battery stack by drying and evaporating a solvent while the electrodes are overlapped and in close contact with each other, and a step of impregnating the battery stack with an electrolyte is described. I have. Furthermore, in the claims of Japanese Patent Application Laid-Open No. 10-172606 (Patent Document 3), a positive electrode, a negative electrode, and an electrolytic solution containing lithium ions are disposed between the positive electrode and the negative electrode. A lithium ion secondary battery including a separator and a porous adhesive resin layer holding the electrolyte and bonding the positive electrode, the negative electrode, and the separator is disclosed. The secondary battery disclosed in Japanese Patent Application Laid-Open No. H10-172606 discloses that the bonding strength between the positive electrode layer and the separator is equal to or higher than the bonding strength between the positive electrode layer and the positive electrode current collector, and the negative electrode layer and the separator Is equal to or higher than the bonding strength between the negative electrode layer and the negative electrode current collector.

However, the lithium ion secondary batteries disclosed in the respective publications have a problem that the cycle life is inferior because the internal resistance is high.
JP-A-10-177865 JP-A-10-189054 JP-A-10-172606

目的 An object of the present invention is to provide a secondary battery with improved thermal stability and improved safety.

Another object of the present invention is to provide a secondary battery that is lightweight, has a thin exterior material, and has improved resistance to external impact.

According to the present invention, a flat electrode group including a positive electrode including a positive electrode current collector and a positive electrode layer supported on the positive electrode current collector, a negative electrode, and a separator disposed between the positive electrode and the negative electrode When,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, and comprises an exterior material having a thickness of 0.3 mm or less,
A secondary battery is provided, wherein a positive electrode current collector is located on at least one of two surfaces having a maximum area on the surface of the electrode group.

Further, according to the present invention, a flat shape including a positive electrode including a positive electrode current collector and a positive electrode layer supported on the positive electrode current collector, a negative electrode, and a separator disposed between the positive electrode and the negative electrode An electrode group;
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, comprising a packaging material having a thickness of 0.5 mm or less including a resin layer,
A secondary battery is provided, wherein a positive electrode current collector is located on at least one of two surfaces having a maximum area on the surface of the electrode group.

According to the present invention, an electrode group having a structure in which a positive electrode including a positive electrode current collector and a positive electrode layer supported on the positive electrode current collector, and a negative electrode are wound in a flat shape via a separator,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, comprising a packaging material having a thickness of 0.5 mm or less including a resin layer,
A secondary battery is provided, wherein the outermost periphery of the electrode group is the positive electrode current collector.

Further, according to the present invention, a flat electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, and comprises an exterior material having a thickness of 0.3 mm or less,
A secondary battery is provided, wherein the separator is located on two surfaces having the maximum area on the surface of the electrode group.

Further, according to the present invention, a flat electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, comprising a packaging material having a thickness of 0.5 mm or less including a resin layer,
A secondary battery is provided, wherein the separator is located on two surfaces having the maximum area on the surface of the electrode group.

Further, according to the present invention, an electrode group having a flat shape including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, and comprises an exterior material having a thickness of 0.3 mm or less,
A secondary battery is provided, wherein an insulating protective sheet is formed so as to straddle two surfaces having a maximum area on the surface of the electrode group.

Furthermore, according to the present invention, a positive electrode, a negative electrode, and a flat electrode group including a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, comprising a packaging material having a thickness of 0.5 mm or less including a resin layer,
A secondary battery is provided, wherein an insulating protective sheet is formed so as to straddle two surfaces having a maximum area on the surface of the electrode group.

In the secondary battery according to the present invention, the flat shape of the electrode group may be such that the positive electrode and the negative electrode are spirally wound with the separator interposed therebetween, and then radially pressurized, or The positive electrode, the laminate comprising the negative electrode and the separator is bent at least once, or the positive electrode, the negative electrode and the separator are laminated, or the positive electrode and the negative electrode are flattened with the separator interposed therebetween. It is desirable that the shape be obtained by winding.

According to the present invention, it is possible to provide a secondary battery having high thermal stability, a suppressed increase in temperature during abnormal heating and abnormal heat generation, and improved safety. Further, according to the present invention, it is possible to provide a secondary battery capable of suppressing damage and short circuit due to impact such as dropping.

Hereinafter, the first to fourth nonaqueous electrolyte secondary batteries according to the present invention will be described in detail.

A first nonaqueous electrolyte secondary battery according to the present invention includes a positive electrode including a positive electrode current collector and a positive electrode layer supported on the positive electrode current collector, and a positive electrode including the negative electrode current collector and the negative electrode current collector. An electrode group including a negative electrode including a negative electrode layer, and a separator disposed between the positive electrode layer and the negative electrode layer;
A non-aqueous electrolyte held by the electrode group; and a packaging material A containing the electrode group and having a thickness of 0.3 mm or less, or a packaging material B including a resin layer and having a thickness of 0.5 mm or less. ;
Is provided.

に お い て In this secondary battery, the positive electrode, the negative electrode, and the separator are integrated. The peel strength between the negative electrode layer and the separator is lower than the peel strength between the negative electrode layer and the negative electrode current collector.

Hereinafter, the positive electrode, the negative electrode, the separator, the non-aqueous electrolyte, and the exterior material will be described.

(1) Negative Electrode The negative electrode includes a negative electrode current collector and a negative electrode layer supported on one or both surfaces of the negative electrode current collector and containing a negative electrode material and a binder.

炭素 The negative electrode material is preferably a carbonaceous material that stores and releases lithium ions. Examples of the carbonaceous material include (I) a graphite material or a carbonaceous material such as graphite, coke, carbon fiber, spherical carbon, and granular carbon; and (II) a thermosetting resin, an isotropic pitch, a mesoface pitch, and a mesophase. Graphite materials or carbonaceous materials obtained by subjecting pitch-based carbon fibers, vapor-grown carbon fibers, mesophase small spheres, and the like to heat treatment at 500 to 3000 ° C. can be mentioned. Among the carbonaceous materials subjected to the heat treatment, preferred are a graphite material or a carbonaceous material of mesophase pitch-based carbon fiber, a graphite material or a carbonaceous material of mesophase spherules, and a granular graphite material. Among such carbonaceous materials, carbonaceous materials a and b described below are preferable.

The carbonaceous material a is obtained by setting the temperature of the heat treatment to 2000 ° C. or higher, and is a graphitic material having graphite crystals having a plane distance doo ₂ of (002) plane of 0.34 nm or less. The shape of the graphitic material is preferably granular. The nonaqueous electrolyte secondary battery provided with the negative electrode containing the carbonaceous material a can greatly improve the battery capacity and the large current characteristics. The plane distance doo ₂ is more preferably 0.336 nm or less.

The carbonaceous material b is at least one selected from a fibrous graphite material heat-treated at 2,000 ° C. or higher and a spheroidal graphite material heat-treated at 2,000 ° C. or higher. Among them, a graphitic material of mesophase pitch-based carbon fiber, a vapor-grown carbon fiber such as carbon whisker, and a graphitic material of mesophase spherules are preferable. The negative electrode containing the carbonaceous material b can reduce the interface impedance between the negative electrode and the separator even when the density is increased to 1.3 g / cm ³ or more. Discharge cycle performance can be improved.

形状 The shape of the carbonaceous material can be, for example, fibrous, spherical, or granular. The negative electrode layer contains one or more carbonaceous materials selected from the group consisting of fibrous carbonaceous materials, spherical carbonaceous materials, and granular carbonaceous materials, thereby maintaining the interface resistance of the negative electrode at a low value over a long period of time. Therefore, the charge / discharge cycle life can be improved.

平均 The average fiber length of the fibrous carbonaceous material is preferably in the range of 5 to 200 µm. A more preferred range is 10 to 50 μm.

平均 The average fiber diameter of the fibrous carbonaceous material is preferably in the range of 0.1 to 20 µm. A more preferred range is 1 to 15 μm.

平均 The average aspect ratio of the fibrous carbonaceous material is preferably in the range of 1.5 to 200. A more preferred range is from 1.5 to 50. However, the aspect ratio is a ratio of the fiber length (fiber length / fiber diameter) to the fiber diameter.

平均 The average particle diameter of the spherical carbonaceous material is preferably in the range of 1 to 100 µm. A more preferred range is 2 to 40 μm.

比 The ratio of the minor radius to the major radius of the spherical carbonaceous material (minor radius / major radius) is preferably 1/10 or more. A more preferred range is 1/2 or more.

The granular carbonaceous material means a carbonaceous material powder having a shape in which a ratio of a minor radius to a major radius (minor radius / major radius) is in the range of 1/100 to 1. A more preferable range of the ratio is 1/10 to 1.

平均 The average particle size of the granular carbonaceous material is preferably in the range of 1 to 100 µm. A more preferred range is 2 to 50 μm.

The binder has a function of binding the negative electrode materials together and a function of binding the negative electrode material and the negative electrode current collector. Examples of such a binder include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC). Can be used. When the positive electrode, the negative electrode, and the separator are integrated by a heat molding method described later, it is desirable to use a thermosetting resin as the binder, and PVdF is particularly preferable.

The compounding ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder. In particular, the content of the carbonaceous material in the negative electrode is preferably in the range of 10 to 80 g / m ^{2 on} one surface. The packing density is desirably in the range of 1.2 to 1.50 g / cm ³ .

負極 The thickness of the negative electrode layer is preferably in the range of 10 to 150 µm. Here, the thickness of the negative electrode layer means the distance between the negative electrode layer surface facing the separator and the negative electrode layer surface contacting the current collector. In addition, when the negative electrode layer is supported on both surfaces of the negative electrode current collector, it is desirable that the thickness of one side of the negative electrode layer be 10 to 150 μm and the total thickness of the negative electrode layer be 20 to 300 μm. A more preferable range of the thickness of the negative electrode layer is 30 to 100 μm. By setting the thickness of the negative electrode layer in the range of 30 to 100 μm, large current discharge characteristics and cycle life can be significantly improved.

As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, copper, stainless steel, or nickel. The current collector preferably has a thickness of 5 to 20 μm. This is because in this range, the balance between electrode strength and weight reduction can be achieved.

剥離 The peel strength between the negative electrode layer and the negative electrode current collector and the peel strength between the negative electrode layer and the separator are measured by a 180 degree peel strength method. The principle of measuring the peel strength between the negative electrode layer and the negative electrode current collector by the 180-degree peel strength method will be described with reference to FIGS. First, the secondary battery is disassembled, and a laminate in which the negative electrode current collector C carries the negative electrode layer L is taken out. The laminate may retain the non-aqueous electrolyte. This laminate is placed on the support 1 with the current collector side facing down. Next, a fixing point 2 is provided on the surface of the negative electrode layer L, and a traction jig 3 such as a string is attached to the fixing point 2. This pulling jig 3 is pulled in the direction indicated by the arrow in FIG. 1, that is, in a direction parallel to the surface of the negative electrode layer L, and the negative electrode layer L is separated from the negative electrode current collector C as shown in FIG. The force required to peel the negative electrode layer fluctuates at the start of peeling, and the traction force at the time when this force becomes constant is defined as the peel strength between the negative electrode layer and the negative electrode current collector.

On the other hand, the principle of measuring the peel strength between the negative electrode layer and the separator by a 180-degree peel strength method will be described. First, the secondary battery is disassembled, and a laminate in which the negative electrode current collector, the negative electrode layer, and the separator are laminated in this order is taken out. The laminate may retain the non-aqueous electrolyte. This laminate is placed on a support base with the current collector side facing down. Next, a fixing point is provided on the surface of the separator, and a traction jig is attached to the fixing point. The pulling jig is pulled in a direction parallel to the separator surface, and the separator is peeled from the negative electrode layer. The force required to peel the separator fluctuates at the beginning of peeling, and the traction force at the time when this force becomes constant is defined as the peel strength between the negative electrode layer and the separator.

In addition, regarding the electrode group taken out by disassembling the secondary battery, those in which the peel strength between the negative electrode layer and the separator is smaller than the peel strength between the negative electrode layer and the negative electrode current collector, Even in the non-aqueous electrolyte non-retained electrode group before being incorporated, the peel strength of the negative electrode layer and the separator by the 180-degree peel strength method is smaller than the peel strength of the negative electrode layer and the negative electrode current collector by the 180-degree peel strength method. It is getting smaller.

剥離 The peel strength between the negative electrode layer and the negative electrode current collector is desirably 10 gf / cm or more and 20 gf / cm or less. By setting the content within this range, it is possible to prevent the negative electrode layer from peeling off from the negative electrode current collector due to repetition of the charge / discharge cycle, so that the charge / discharge cycle life can be further improved.

剥離 It is desirable that the peel strength between the negative electrode layer and the separator be 10 gf / cm or less. If the peel strength exceeds 10 gf / cm, the interface resistance between the negative electrode and the separator increases, and it becomes difficult to obtain excellent large current discharge characteristics and cycle life. The peel strength is preferably 5 gf / cm or less, and more preferably 2 gf / cm or less. When the negative electrode and the separator are not integrated, the peel strength becomes 0 gf / cm.

In addition to the above-mentioned carbonaceous materials that occlude and release lithium ions, metal materials, metal sulfides, metal nitrides, lithium metals, or lithium alloys can be used as the negative electrode material.

Examples of the metal oxide include tin oxide, silicon oxide, lithium titanium oxide, niobium oxide, and tungsten oxide.

Examples of the metal sulfide include tin sulfide and titanium sulfide.

Examples of the metal nitride include lithium cobalt nitride, lithium iron nitride, lithium manganese nitride, and the like.

Examples of the lithium alloy include a lithium aluminum alloy, a lithium tin alloy, a lithium lead alloy, and a lithium silicon alloy.

The area of the negative electrode is preferably larger than the area of the positive electrode. With such a configuration, the end of the negative electrode can be extended as compared with the end of the positive electrode, so that the current concentration on the negative electrode end can be reduced, and the cycle performance of the secondary battery can be improved. Safety can be improved.

(2) Positive electrode This positive electrode has a positive electrode current collector and a positive electrode layer supported on one or both surfaces of the positive electrode current collector and containing an active material and a binder.

Examples of the positive electrode active material include various oxides such as manganese dioxide, lithium manganese composite oxide, lithium-containing nickel oxide, lithium-containing cobalt oxide, lithium-containing nickel-cobalt oxide, lithium-containing iron oxide, and lithium. Vanadium oxides and chalcogen compounds such as titanium disulfide and molybdenum disulfide can be exemplified. Above all, when a lithium-containing cobalt oxide (for example, LiCoO ₂ ), a lithium-containing nickel cobalt oxide (for example, LiNi _0.8 Co _0.2 O ₂ ), and a lithium manganese composite oxide (for example, LiMn ₂ O ₄ , LiMnO ₂ ) are used. This is preferable because a high voltage can be obtained.

The binder has a function of binding the positive electrode active materials and a function of binding the positive electrode active material and the positive electrode current collector. As such a binder, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), ethylene-propylene-diene copolymer (EPDM), styrene-butadiene rubber (SBR) and the like can be used. When the positive electrode, the negative electrode, and the separator are integrated by a heat molding method described later, it is desirable to use a thermosetting resin as the binder, and PVdF is particularly preferable.

The positive electrode layer may further include a conductive agent. Examples of such a conductive agent include acetylene black, carbon black, and graphite.

(4) The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

正極 The thickness of the positive electrode layer is preferably in the range of 10 to 150 µm. Here, the thickness of the positive electrode layer means a distance between the surface of the positive electrode layer facing the separator and the surface of the positive electrode layer contacting the current collector. When the positive electrode layer is supported on both surfaces of the positive electrode current collector, the thickness of one surface of the positive electrode layer is set to 10 to 150 μm, and the total thickness of the positive electrode active material layer is set to 20 to 300 μm. desirable. A more preferable range of the thickness of the positive electrode layer is 30 to 100 μm. By setting the thickness of the positive electrode layer in the range of 30 to 100 μm, large current discharge characteristics and cycle life can be significantly improved.

As the current collector, a conductive substrate having a porous structure or a non-porous conductive substrate can be used. These conductive substrates can be formed from, for example, aluminum, stainless steel, or nickel. The current collector preferably has a thickness of 5 to 20 μm. This is because in this range, the balance between electrode strength and weight reduction can be achieved.

As the current collector, it is desirable to use a conductive substrate having a two-dimensional porous structure in which one or more holes having a diameter of 3 mm or less exist at a rate of one or more per 10 cm ² . That is, if the diameter of the hole formed in the conductive substrate is larger than 3 mm, sufficient positive electrode strength may not be obtained. On the other hand, if the proportion of the holes having a diameter of 3 mm or less is smaller than the above range, it becomes difficult to uniformly infiltrate the non-aqueous electrolyte into the electrode group, so that a sufficient cycle life may not be obtained. More preferably, the diameter of the holes is in the range of 0.1 to 1 mm. Further, it is more preferable that the existence ratio of the holes is in the range of 10 to 20 per 10 cm ² .

The above-mentioned conductive substrate having a two-dimensional porous structure in which one or more holes having a diameter of 3 mm or less exist at a rate of one or more per 10 cm ² , preferably has a thickness in the range of 15 to 100 μm. If the thickness is less than 15 μm, sufficient positive electrode strength may not be obtained. A more preferable range of the thickness is 30 to 80 μm.

(4) The peel strength between the positive electrode layer and the separator is preferably lower than the peel strength between the positive electrode layer and the positive electrode current collector. When the peel strength between the positive electrode layer and the separator is equal to or greater than the peel strength between the positive electrode layer and the positive electrode current collector, the impedance at the interface between the positive electrode and the separator increases, resulting in excellent cycle life and high current discharge characteristics. There is a risk that it will not be available.

剥離 The peel strength between the positive electrode layer and the positive electrode current collector and the peel strength between the positive electrode layer and the separator are measured by a 180-degree peel strength method. The principle of measurement will be described. In order to measure the peel strength between the positive electrode layer and the positive electrode current collector, first, the secondary battery is disassembled, and a laminate in which the positive electrode current collector supports the positive electrode layer is taken out. The laminate may retain the non-aqueous electrolyte. This laminate is placed on a support base with the current collector side facing down. Next, a fixing point is provided on the surface of the positive electrode layer, and a traction jig such as a string is attached to the fixing point. The pulling jig is pulled in a direction parallel to the surface of the positive electrode layer, and the positive electrode layer is separated from the positive electrode current collector. The force required to peel the positive electrode layer fluctuates at the start of peeling, and the traction force at the time when this force becomes constant is defined as the peel strength between the positive electrode layer and the positive electrode current collector.

On the other hand, when the peel strength between the positive electrode layer and the separator is measured by the 180-degree peel strength method, first, the secondary battery is disassembled, and the positive electrode current collector, the positive electrode layer, and the separator are laminated in this order. Take out. The laminate may retain the non-aqueous electrolyte. This laminate is placed on a support base with the current collector side facing down. Next, a fixing point is provided on the surface of the separator, and a traction jig is attached to the fixing point. The pulling jig is pulled in a direction parallel to the separator surface, and the separator is peeled from the positive electrode layer. The force required to peel the separator fluctuates at the beginning of peeling, and the traction force at the time when this force becomes constant is defined as the peel strength between the positive electrode layer and the separator.

Further, regarding the electrode group taken out by disassembling the secondary battery, those having a peel strength between the positive electrode layer and the separator smaller than the peel strength between the positive electrode layer and the positive electrode current collector are considered to be secondary batteries. Even in the non-aqueous electrolyte non-retained electrode group before being incorporated, the peel strength of the positive electrode layer and the separator by the 180-degree peel strength method between the positive electrode layer and the positive electrode current collector is smaller than the peel strength by the 180-degree peel strength method of the positive electrode layer and the separator. It is getting smaller.

剥離 The peel strength between the positive electrode layer and the positive electrode current collector is desirably 10 gf / cm or more and 20 gf / cm or less. By setting the content within this range, it is possible to suppress the positive electrode layer from being separated from the positive electrode current collector due to repetition of the charge / discharge cycle, so that the charge / discharge cycle life can be further improved.

剥離 The peel strength between the positive electrode layer and the separator is desirably 10 gf / cm or less. If the peel strength exceeds 10 gf / cm, the interface resistance between the positive electrode and the separator becomes large, and it becomes difficult to obtain excellent large current discharge characteristics and cycle life. The peel strength is preferably 5 gf / cm or less, and more preferably 2 gf / cm or less. When the positive electrode and the separator are not integrated, the peel strength becomes 0 gf / cm.

(3) Separator A porous separator is used as the separator.

Examples of the porous separator include a porous film containing polyethylene, polypropylene, cellulose, or polyvinylidene fluoride (PVdF), and a nonwoven fabric made of a synthetic resin. Among them, a porous film made of polyethylene, polypropylene, or both is preferable because the safety of the secondary battery can be improved.

The thickness of the separator is preferably 30 μm or less. If the thickness exceeds 30 μm, the distance between the positive electrode and the negative electrode may increase, and the internal resistance may increase. The lower limit of the thickness is preferably set to 5 μm. If the thickness is less than 5 μm, the strength of the separator may be significantly reduced, and an internal short circuit may easily occur. The upper limit of the thickness is more preferably 25 μm, and the lower limit is more preferably 10 μm.

(4) The separator preferably has a heat shrinkage of 20% or less when the separator is present at 120 ° C. for one hour. When the heat shrinkage exceeds 20%, it may be difficult to make the adhesion strength between the positive and negative electrodes and the separator sufficient. More preferably, the heat shrinkage is 15% or less.

The separator preferably has a porosity in the range of 30 to 70%. This is due to the following reasons. If the porosity is less than 30%, it may be difficult to obtain high electrolyte retention in the separator. On the other hand, if the porosity exceeds 70%, sufficient separator strength may not be obtained. A more preferred range of porosity is 35-70%.

The separator preferably has an air permeability of 500 seconds / 100 cm ³ or less. The air permeability means the time (seconds) required for 100 cm ³ of air to pass through the porous sheet. If the air permeability exceeds 500 seconds / 100 cm ³ , it may be difficult to obtain high lithium ion mobility in the separator. The lower limit of the air permeability is preferably 30 seconds / 100 cm ³ . If the air permeability is less than 30 seconds / 100 cm ³ , sufficient separator strength may not be obtained. The upper limit of the air permeability is more preferably set to 150 seconds / 100 cm ³ . Further, the lower limit is more preferably set to 50 seconds / 100 cm ³ .

When the positive electrode, the negative electrode, and the separator are integrated using a polymer having adhesiveness as described later, the end of the separator along the short direction is 0 in comparison with the end of the negative electrode along the short direction. It is preferable that a polymer having adhesiveness is present at the end of the extended separator, which extends from 0.25 mm to 2 mm. By adopting such a configuration, the strength of the end portion of the separator can be improved, so that the occurrence of an internal short circuit when a shock is applied to the battery can be suppressed. Furthermore, when the battery is used in a high-temperature environment of 100 ° C. or higher, the heat shrinkage of the separator can be suppressed, so that an internal short circuit can be suppressed, and safety can be improved.

(4) Non-aqueous electrolyte This non-aqueous electrolyte is held at least by the separator. In particular, the non-aqueous electrolyte is preferably dispersed throughout the electrode group. As the non-aqueous electrolyte, a liquid non-aqueous electrolyte composed of a non-aqueous solvent in which the electrolyte is dissolved (hereinafter, referred to as a non-aqueous solution), a polymer material holding the non-aqueous solution, or a solid non-aqueous electrolyte may be used. it can. As the polymer material in which the non-aqueous solution is retained, a gel-like non-aqueous electrolyte in which the non-aqueous solution is gelled, a part of the non-aqueous solution is gelled, and the remaining non-aqueous solution, Examples thereof include those which are maintained in a liquid state. Especially, it is preferable to use a liquid non-aqueous electrolyte. Since the liquid nonaqueous electrolyte can increase the ionic conductivity of the electrode group, the interface resistance between the positive electrode and the separator and the interface resistance between the negative electrode and the separator can be reduced.

The polymer material holding the non-aqueous solution is prepared, for example, by mixing the non-aqueous solution, the polymer, and the gelling agent, and then performing a heat treatment to gel the mixture.

As the polymer, at least one polymer selected from polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyethylene oxide (PEO), polyvinyl chloride (PVC) and polyacrylate (PMMA) is used. it can.

As the non-aqueous solvent, a known non-aqueous solvent can be used as a solvent for a lithium ion secondary battery, and is not particularly limited, but at least one selected from the group consisting of propylene carbonate (PC) and ethylene carbonate (EC). It is preferable to use a non-aqueous solvent mainly composed of a mixed solvent of a first solvent of a type and a second solvent having a lower viscosity than PC and EC. In particular, the second solvent more preferably has a donor number of 16.5 or less.

Examples of the second solvent include dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), diethyl carbonate (DEC), ethyl propionate, methyl propionate, γ-butyrolactone (BL), acetonitrile (AN), and ethyl acetate ( EA), toluene, xylene, methyl acetate (MA) and the like. These second solvents can be used alone or in the form of a mixture of two or more.

配合 The blending amount of the first solvent in the mixed solvent is preferably 10 to 80% by volume ratio, and more preferably the blending amount of the first solvent is 20 to 75% by volume ratio.

Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetraborate (LiBF ₄ ), lithium arsenic hexafluoride (LiAsF ₆ ), trifluoro Lithium salts such as lithium metasulfonate (LiCF ₃ SO ₃ ) and bistrifluoromethylsulfonylimitolithium [LiN (CF ₃ SO ₂ ) ₂ ] are exemplified. Among them, LiPF ₆ and LiBF ₄ are preferably used.

溶解 The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.5 to 2.0 mol / 1.

A particularly preferred non-aqueous solution is one in which an electrolyte (for example, a lithium salt) is dissolved in a mixed non-aqueous solvent containing γ-butyrolactone (BL), and the composition ratio of BL is 20% by volume or more, 80% or more of the total mixed non-aqueous solvent. % By volume or less. In the mixed non-aqueous solvent, it is preferable to make the composition ratio of BL the largest. If the ratio is less than 20% by volume, gas is likely to be generated at high temperatures. Further, when the mixed non-aqueous solvent contains BL and cyclic carbonate, the ratio of the cyclic carbonate becomes relatively high, so that the solvent viscosity may be significantly increased. When the solvent viscosity increases, the conductivity and permeability of the non-aqueous electrolyte decrease, so that the charge-discharge cycle characteristics, large-current discharge characteristics, and discharge characteristics in a low-temperature environment around -20 ° C decrease. On the other hand, when the ratio exceeds 80% by volume, the reaction between the negative electrode and BL is likely to occur, so that the charge / discharge cycle characteristics may be reduced. In other words, when the negative electrode (for example, a carbonaceous material that absorbs and releases lithium ions) reacts with BL to cause reductive decomposition of the non-aqueous electrolyte, a film that inhibits the charge / discharge reaction is formed on the surface of the negative electrode. . As a result, current concentration tends to occur in the negative electrode, so that lithium metal is deposited on the negative electrode surface, or the impedance at the negative electrode interface increases, so that the charge / discharge efficiency of the negative electrode decreases and the charge / discharge cycle characteristics deteriorate. A more preferred range is 40% by volume or more and 75% by volume or less. By setting the content within this range, the effect of suppressing gas generation during high-temperature storage can be further enhanced, and the discharge capacity in a low-temperature environment around -20 ° C can be further improved.

As the solvent to be mixed with BL, cyclic carbonate is preferable in terms of increasing the charge / discharge efficiency of the negative electrode.

プ ロ ピ レ ン As the cyclic carbonate, propylene carbonate (PC), ethylene carbonate (EC), vinylene carbonate (VC), trifluoropropylene carbonate (TFPC) and the like are desirable. In particular, when EC is used as a solvent mixed with BL, charge / discharge cycle characteristics and large current discharge characteristics can be significantly improved. Further, as another solvent to be mixed with BL, a third solvent consisting of at least one selected from the group consisting of PC, VC, TFPC, diethyl carbonate (DEC), methyl ethyl carbonate (MEC) and an aromatic compound, and EC and It is desirable to use a mixed solvent of from the viewpoint of enhancing charge-discharge cycle characteristics.

か ら From the viewpoint of further lowering the viscosity of the solvent, the low-viscosity solvent may contain 20% by volume or less. Examples of the low-viscosity solvent include chain carbonate, chain ether, and cyclic ether.

More preferable composition of the non-aqueous solvent according to the present invention is BL and EC, BL and PC, BL and EC and DEC, BL and EC and MEC, BL and EC and MEC and VC, BL and EC and VC, BL and PC. And VC, or BL, EC, PC and VC. At this time, the volume ratio of EC is preferably 5 to 40% by volume. This is due to the following reasons. If the EC ratio is less than 5% by volume, it may be difficult to cover the negative electrode surface with the protective film densely, so that a reaction between the negative electrode and BL occurs and the charge / discharge cycle characteristics can be sufficiently improved. Can be difficult. On the other hand, if the EC ratio exceeds 40% by volume, the viscosity of the non-aqueous solution may increase and the ionic conductivity may decrease, so that the charge-discharge cycle characteristics, large-current discharge characteristics, and low-temperature discharge characteristics are sufficiently improved. Can be difficult. A more preferred range of the EC ratio is 10 to 35% by volume. The ratio of the solvent composed of at least one selected from DEC, MEC and VC is preferably in the range of 0.01 to 10% by volume.

Examples of the electrolyte include those similar to those described above. Among them, it is preferable to use LiPF ₆ or LiBF ₄ .

溶解 The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.5 to 2.0 mol / l.

粘度 The viscosity of the non-aqueous solution at 20 ° C. is preferably in the range of 3 cp to 20 cp. This is due to the following reasons. When the viscosity is less than 3 cp, when the secondary battery is stored in a high temperature environment, the vapor pressure may increase or the amount of generated gas may increase, and the exterior material may expand. On the other hand, when the viscosity exceeds 20 cp, the permeability of the non-aqueous solution is reduced, so that the internal resistance may be increased even if the relationship of the peel strength is specified. A more preferable range of the viscosity is 4 cp to 15 cp. A more preferred range is 6 to 8 cp.

Among the non-aqueous solutions whose viscosities at 20 ° C. are in the range of 3 cp to 20 cp, at least one solvent A selected from the group consisting of propylene carbonate (PC), γ-butyrolactone (BL) and diethyl carbonate (DEC) It is preferable to use a solution in which an electrolyte is dissolved in a non-aqueous solvent containing ethylene carbonate (EC).

溶媒 The volume ratio of the solvent A in the non-aqueous solvent is preferably 50 to 90% by volume. This is due to the following reasons. If the volume ratio is less than 50% by volume, low-temperature discharge characteristics may be reduced, and gas may be easily generated at high temperatures. On the other hand, if the volume ratio exceeds 90% by volume, reductive decomposition of the non-aqueous electrolyte may easily occur. When reductive decomposition of the non-aqueous electrolyte occurs, a film that inhibits the charge / discharge reaction is formed on the surface of the negative electrode, and current concentration is likely to occur on the negative electrode, so that lithium metal is deposited on the negative electrode surface, or the impedance at the negative electrode interface is reduced. , The charge / discharge efficiency of the negative electrode is reduced, and the charge / discharge cycle characteristics are reduced. A more preferred range is 60% by volume or more and 80% by volume or less.

ＥＣThe volume ratio of EC in the non-aqueous solvent is preferably 5 to 40% by volume. This is due to the following reasons. If the EC ratio is less than 5% by volume, it is difficult to cover the negative electrode surface with a protective film densely, and it is easy to cause reductive decomposition of the non-aqueous electrolyte. Therefore, it is difficult to sufficiently improve the charge / discharge cycle characteristics. Could be On the other hand, when the EC ratio exceeds 40% by volume, the ratio of the solvent A becomes relatively low, and the amount of gas generated when the secondary battery is stored at a high temperature may increase. A more preferred range of the EC ratio is 10 to 35% by volume.

It is preferable that the non-aqueous solvent further contains vinylene carbonate (VC). The ratio of VC in the non-aqueous solvent is preferably in the range of 0.01 to 10% by volume.

Examples of the electrolyte include those similar to those described above. Among them, it is preferable to use LiPF ₆ or LiBF ₄ .

溶解 The amount of the electrolyte dissolved in the non-aqueous solvent is desirably 0.5 to 2.0 mol / l.

It is preferable that the amount of the liquid non-aqueous electrolyte having each of the above-described compositions is 0.2 to 0.6 g per 100 mAh of battery unit capacity. This is due to the following reasons. If the liquid non-aqueous electrolytic mass is less than 0.2 g / 100 mAh, the ionic conductivity between the positive electrode and the negative electrode may not be able to be sufficiently maintained. On the other hand, if the liquid non-aqueous electrolytic mass exceeds 0.6 g / 100 mAh, the electrolyte becomes large, and thus there is a possibility that sealing may become difficult when using a sheet-made exterior material. A more preferred range of the mass of the liquid non-aqueous electrolyte is 0.4 to 0.55 g / 100 mAh.

(5-1) Exterior material A
This exterior material A has a thickness of 0.3 mm or less.

As the exterior material A, for example, a metal can or a sheet having a function of blocking moisture can be used. The metal can can be formed from, for example, iron, stainless steel, or aluminum. The sheet includes, for example, a multilayer sheet a formed of two or more types of resin layers, one or both sides of which are thermoplastic resins, a flexible metal layer having a protective layer formed on one or both sides of a flexible metal layer. Multilayer sheet b can be mentioned. In particular, the multilayer sheet b is desirable because it is lightweight, has high strength, and can block moisture from entering from the outside.

金属 The metal layer of the multilayer sheet b can be, for example, aluminum, stainless steel, iron, copper, nickel, or the like. Among them, aluminum that is lightweight and has a high function of blocking moisture is preferable. The metal layer may be formed from one type of metal, or may be formed from a combination of two or more types of metal layers.

保護 The protective layer serving as the inner surface of the exterior material has a function as a heat sealing surface and a function of preventing the metal layer from being corroded by the non-aqueous electrolyte. Further, the protective layer serving as the outer surface of the exterior material plays a role of preventing damage to the metal layer. Each protective layer is formed from one type of resin layer or two or more types of resin layers. Each protective layer is desirably formed from a thermoplastic resin. The melting point of the thermoplastic resin forming the protective layer that is to be the inner surface of the exterior material is preferably 120 ° C. or more, and a more desirable range is 140 ° C. to 250 ° C. Examples of the thermoplastic resin include polyethylene and polypropylene. In particular, polypropylene having a melting point of 150 ° C. or higher is preferable because the sealing strength of the heat seal portion can be improved.

(4) When the thickness of the exterior material is more than 0.3 mm, the effect of thinning is small, that is, it is difficult to sufficiently increase the weight energy density and the volume energy density. The thickness of the exterior material is preferably set to 0.25 mm or less, and a more preferable range is 0.2 mm or less. On the other hand, if the thickness is less than 0.05 mm, deformation or breakage tends to occur. Therefore, the lower limit of the thickness is preferably set to 0.05 mm.

(5-2) Exterior material B
The exterior material B is a sheet including a resin layer and having a thickness of 0.5 mm or less.

樹脂 The resin layer of the exterior material B can be formed from, for example, a thermoplastic resin. Examples of the thermoplastic resin include polyethylene and polypropylene.

As the exterior material B, for example, a multilayer sheet including a metal layer and resin layers formed on both surfaces of the metal layer can be exemplified. Examples of the metal layer include those similar to those described in the case of the exterior material A. The resin layer serving as the inner surface of the exterior material has a function as a heat sealing surface and a function of preventing the metal layer from being corroded by the non-aqueous electrolyte. Further, the resin layer serving as the outer surface of the exterior material plays a role of preventing damage to the metal layer. Each resin layer may be formed from one type of resin, or may be formed from two or more types of resins. Each resin layer is desirably formed from a thermoplastic resin. The melting point of the thermoplastic resin forming the resin layer serving as the inner surface of the exterior material is preferably set to 120 ° C. or more, and a more desirable range is from 140 ° C. to 250 ° C. Examples of the thermoplastic resin include polyethylene and polypropylene. In particular, polypropylene having a melting point of 150 ° C. or higher is preferable because the sealing strength of the heat seal portion can be improved.

(4) When the thickness of the exterior material B exceeds 0.5 mm, the capacity per unit weight of the battery and the capacity per unit volume of the battery are reduced. The thickness of the exterior material B is preferably set to 0.3 mm or less, more preferably 0.25 mm or less, and most preferably 0.2 mm or less. On the other hand, if the thickness is less than 0.05 mm, deformation or breakage tends to occur. Therefore, the lower limit of the thickness is preferably set to 0.05 mm.

The thickness of the exterior materials A and B is measured by the method described below. That is, in the area of the exterior materials A and B excluding the heat seal sealing portion, three points that are separated from each other by 1 cm or more are arbitrarily selected, the thickness of each point is measured, and an average value is calculated. Is the thickness of the exterior material. If foreign matter (for example, resin) is attached to the surface of the exterior material, the thickness is measured after removing the foreign matter. For example, when PVdF adheres to the surface of the exterior material, the thickness of the exterior material is measured by removing the PVdF by wiping the surface of the exterior material with a dimethylformamide solution.

When the exterior materials A and B are composed of a multilayer sheet, it is desirable that the electrode group is adhered to the inner surface of the exterior material by an adhesive layer formed on at least a part of the surface. With such a configuration, the exterior material can be fixed to the surface of the electrode group, so that the electrolyte solution can be prevented from permeating between the electrode group and the exterior material.

接着 For the adhesive layer, a material similar to a polymer having adhesiveness described later can be used. The adhesive layer may have a porous structure. The porous adhesive layer can hold the non-aqueous electrolyte in the void.

第 The first nonaqueous electrolyte secondary battery according to the present invention is manufactured by the method described in the following (1) or (2).

(1) Heat molding method (first step)
An electrode group is manufactured by the methods described in (a) to (c) below.

(A) A positive electrode and a negative electrode are spirally wound with a separator interposed therebetween.

(B) The positive electrode and the negative electrode are spirally wound with a separator interposed therebetween, and then compressed in the radial direction.

(C) The positive electrode and the negative electrode are bent at least twice with a separator interposed therebetween.

The positive electrode is manufactured by, for example, suspending a conductive agent and a binder in a positive electrode active material in an appropriate solvent, applying the suspension to a current collector, and drying to form a thin plate. Examples of the positive electrode active material, the conductive agent, the binder, and the current collector include those similar to those described in the section of (2) Positive electrode described above.

The negative electrode is, for example, kneading a carbonaceous material that absorbs and releases lithium ions and a binder in the presence of a solvent, applies the obtained suspension to a current collector, and after drying, applies a desired pressure. By pressing once or multi-stage pressing 2 to 5 times.

炭素 Examples of the carbonaceous material, the binder, and the current collector include the same as those described in the section of (1) Negative electrode described above.

セ パ レ ー タ As the separator, the same one as described in the section of (3) Separator described above can be used.

(2nd process)
After the electrode group is housed in an exterior material, heat molding is performed.

The atmosphere in which the heat molding is performed is preferably a reduced-pressure atmosphere including a vacuum or a normal-pressure atmosphere.

The heating temperature is preferably set to 30 ° C. or higher. A more preferred range is 60 to 100 ° C. In addition, when the molding is performed at a temperature of 60 to 100 ° C. in a reduced pressure atmosphere, the electrode group can be dried simultaneously with the molding.

The molding is performed in the radial direction when the electrode group is manufactured by the method (a), and in the laminating direction when the electrode group is manufactured by the method (b) or (c). It is desirable to do so.

The molding can be performed by, for example, press molding or filling in a molding die.

The pressure applied during molding is preferably in the range of 0.01 to 20 kg / cm ² . If the pressure exceeds 20 kg / cm ² , an internal short circuit is likely to occur. A more preferred range is 0.01 to 15 kg / cm ² . When the pressure is in the range of 0.01 to 15 kg / cm ² , integration can be easily performed.

The heat molding time is preferably in the range of 2 seconds to 120 minutes.

加熱 When the electrode group is subjected to heat molding, the binder contained in the positive electrode and the negative electrode can be thermoset, so that the positive electrode, the negative electrode, and the separator can be integrated. By adjusting the heat molding temperature, the molding pressure and the molding time, the peel strength between the separator and the negative electrode layer, the peel strength between the negative electrode layer and the negative electrode current collector, while integrating the positive electrode, the negative electrode and the separator. It can be lower than.

(3rd step)
The first non-aqueous electrolyte secondary battery according to the present invention is obtained by impregnating a liquid non-aqueous electrolyte into the electrode group in the exterior material and performing sealing treatment.

After the electrode group was subjected to heat molding without being housed in the exterior material, the electrode group was housed in the exterior material, and the electrode group in the exterior material was impregnated with a liquid non-aqueous electrolyte to perform a sealing treatment. By performing the above, the first nonaqueous electrolyte secondary battery according to the present invention can be obtained.

(2) Method of using polymer having adhesiveness (first step)
An electrode group is produced by interposing a porous sheet as a separator between the positive electrode and the negative electrode.

The electrode group is preferably manufactured by a method similar to that described in the above-described heat molding method. When manufactured by such a method, in a second step described later, the solution is applied to the entire boundary between the positive electrode and the separator and the entire boundary between the negative electrode and the separator while infiltrating a solution of an adhesive polymer into the positive electrode, the negative electrode, and the separator. Penetration can be prevented. As a result, it becomes possible to disperse the adhesive polymer on the positive electrode, the negative electrode and the separator, and to disperse the adhesive polymer on the boundary between the positive electrode and the separator and the boundary between the negative electrode and the separator. it can.

正極 The positive electrode and the negative electrode are manufactured by the same method as described in the above-mentioned heat molding method. As the porous sheet of the separator, the same porous sheet as that described in the section of (3) Separator can be used.

(2nd process)
The electrode group is housed in a bag-shaped exterior material such that the lamination surface is visible from the opening. A solution obtained by dissolving a polymer having adhesiveness in a solvent is injected into an electrode group in the exterior material through an opening to impregnate the electrode group with the solution.

高分子 It is desirable that the polymer having adhesiveness can maintain high adhesiveness while holding the non-aqueous electrolyte. Further, such a polymer is more preferably high in lithium ion conductivity. Specific examples include polyacrylonitrile (PAN), polyacrylate (PMMA), polyvinylidene fluoride (PVdF), polyvinyl chloride (PVC), and polyethylene oxide (PEO). Particularly, polyvinylidene fluoride (PVdF) is preferable. Polyvinylidene fluoride (PVdF) can hold a non-aqueous electrolyte, and if it contains a non-aqueous electrolyte, it partially gels, so that the ionic conductivity in the positive electrode can be further improved.

有機 It is desirable to use an organic solvent having a boiling point of 200 ° C. or less as the solvent. Examples of such an organic solvent include dimethylformamide (boiling point: 153 ° C.). When the boiling point of the organic solvent exceeds 200 ° C., when the heating temperature described below is set to 100 ° C. or lower, the drying time may take a long time. The lower limit of the boiling point of the organic solvent is preferably set to 50 ° C. If the boiling point of the organic solvent is lower than 50 ° C., the organic solvent may evaporate while the solution is being injected into the electrode group. The upper limit of the boiling point is more preferably 180 ° C., and the lower limit of the boiling point is more preferably 100 ° C.

濃度 The concentration of the adhesive polymer in the solution is preferably in the range of 0.05 to 2.5% by weight. This is due to the following reasons. If the concentration is less than 0.05% by weight, it may be difficult to bond the positive and negative electrodes and the separator with sufficient strength. On the other hand, if the concentration exceeds 2.5% by weight, it is difficult to obtain sufficient porosity to hold the non-aqueous electrolyte, and the interface impedance of the electrode may be significantly increased. When the interfacial impedance increases, the capacity and the large-current discharge characteristics decrease significantly. A more preferred range of the concentration is from 0.1 to 1.5% by weight.

The amount of the solution to be injected is preferably in the range of 0.1 to 2 ml per 100 mAh of battery capacity when the concentration of the polymer having adhesiveness in the solution is 0.05 to 2.5% by weight. This is due to the following reasons. If the injection amount is less than 0.1 ml, it may be difficult to sufficiently increase the adhesion between the positive electrode, the negative electrode, and the separator. On the other hand, if the injection amount exceeds 2 ml, the lithium ion conductivity of the secondary battery may decrease, or the internal resistance may increase, and the discharge capacity, large current discharge characteristics, and charge / discharge cycle characteristics may be improved. It can be difficult. A more preferable range of the injection amount is 0.15 to 1 ml per 100 mAh of battery capacity.

(3rd step)
Heat molding is performed.

The atmosphere in which the heat molding is performed is preferably a reduced-pressure atmosphere including a vacuum or a normal-pressure atmosphere.

The heating temperature is preferably set to 30 ° C. or higher. A more preferred range is 60 to 100 ° C. In addition, when the molding is performed at a temperature of 60 to 100 ° C. in a reduced pressure atmosphere, the electrode group can be dried simultaneously with the molding.

The molding is performed in the radial direction when the electrode group is manufactured by the method (a), and in the laminating direction when the electrode group is manufactured by the method (b) or (c). It is desirable to do so.

The molding can be performed by, for example, press molding or filling in a molding die.

The pressure applied during molding is preferably in the range of 0.01 to 20 kg / cm ² . A more preferred range is 0.01 to 15 kg / cm ² .

The heat molding time is preferably in the range of 2 seconds to 120 minutes.

加熱 By subjecting the electrode group to heat molding, the solvent can be evaporated, and the positive electrode, the negative electrode, and the separator can be integrated. At the time of this heat molding, the peel strength between the separator and the negative electrode layer while integrating the positive electrode, the negative electrode and the separator by adjusting the adhesive high molecular weight, the heating temperature, the pressure at the time of molding and the heat molding time. Is lower than the peel strength between the negative electrode layer and the negative electrode current collector.

(4th process)
The first non-aqueous electrolyte secondary battery according to the present invention is obtained by impregnating a liquid non-aqueous electrolyte into the electrode group in the exterior material and performing sealing treatment.

Before the electrode group is housed in the exterior material, the electrode group is impregnated with a solution in which an adhesive polymer is dissolved, and the electrode group is subjected to heat molding. The first non-aqueous electrolyte secondary battery according to the present invention can be obtained by injecting the non-aqueous electrolyte, filling the non-aqueous electrolyte, and sealing. Further, after the adhesive is applied to the outer peripheral surface of the electrode group, the electrode group may be housed in the exterior material. Thereby, the electrode group can be bonded to the inner surface of the exterior material.

When a battery is manufactured by a method using an adhesive polymer, the total amount of the polymer having adhesiveness included in the battery (including the one contained in an adhesive portion described later) is 0.1% per 100 mAh of battery capacity. Preferably, the amount is up to 6 mg. This is due to the following reasons. If the total amount of the polymer having adhesiveness is less than 0.1 mg per 100 mAh of battery capacity, it may be difficult to sufficiently improve the adhesion between the positive electrode, the separator, and the negative electrode. On the other hand, if the total amount exceeds 6 mg per 100 mAh of battery capacity, the lithium ion conductivity of the secondary battery may decrease and the internal resistance may increase, and the discharge capacity, large current discharge characteristics and charge / discharge cycle characteristics are improved. Can be difficult to do. A more preferable range of the total amount of the polymer having adhesiveness is 0.2 to 1 mg per 100 mAh of battery capacity.

(4) When a battery is manufactured by a method using an adhesive polymer, it is desirable that the polymer having adhesiveness be held in a gap in the positive electrode layer, the separator, or the negative electrode layer. In addition, it is preferable that the polymer having adhesiveness is scattered in the electrode group because the internal resistance of the battery can be reduced.

高分子 It is preferable that the polymer having adhesiveness has a porous structure having fine pores in the spaces between the positive electrode, the negative electrode, and the separator. An adhesive polymer having a porous structure can hold a large amount of non-aqueous electrolyte. Further, it is desirable that the electrode group is uniformly dispersed and scattered.

A thin lithium ion secondary battery, which is an example of the first nonaqueous electrolyte secondary battery according to the present invention, will be described with reference to FIGS. FIG. 3 is a sectional view showing a thin lithium ion secondary battery as an example of the first nonaqueous electrolyte secondary battery according to the present invention, and FIG. 4 is an enlarged sectional view showing a portion A in FIG.

(3) As shown in FIG. 3, an electrode group 5 is accommodated in an exterior material 4 made of, for example, a multilayer sheet. The electrode group 5 has a structure in which a laminate including a positive electrode, a separator, and a negative electrode is wound into a flat shape. The laminate includes, from the lower side of FIG. 4, a separator 6, a positive electrode 9 including a positive electrode layer 7, a positive electrode current collector 8 and a positive electrode layer 7, a separator 6, a negative electrode layer 10, a negative electrode current collector 11, and a negative electrode layer 10. , A separator 6, a positive electrode layer 7, a positive electrode current collector 8, a positive electrode 9 having a positive electrode layer 7, a separator 6, a negative electrode 12 having a negative electrode layer 10 and a negative electrode current collector 11 are laminated in this order. It has the structure which was done. The negative electrode current collector 11 is located on the outermost periphery of the electrode group 5. The adhesive layer 13 is disposed between the surface of the electrode group 5 and the inner surface of the exterior material 4. The non-aqueous electrolyte is accommodated in the exterior material 4. One end of the strip-shaped positive electrode lead 14 is connected to the positive electrode current collector 8 of the electrode group 5, and the other end is extended from the exterior material 4. On the other hand, one end of the strip-shaped negative electrode lead 15 is connected to the negative electrode current collector 11 of the electrode group 5, and the other end is extended from the exterior material 4.

In addition, in FIG. 3 described above, the adhesive layer 13 is formed on the entire surface of the electrode group 5, but the adhesive layer 13 may be formed on a part of the electrode group 5. When the adhesive layer 13 is formed on a part of the electrode group 5, it is preferable to form the adhesive layer 13 on at least the surface corresponding to the outermost periphery of the electrode group. Further, the adhesive layer 13 may not be provided.

Also, in FIG. 3 described above, an example is described in which an electrode group having a structure in which a laminate including a plurality of positive electrodes and negative electrodes is spirally wound and then radially compressed is used, as shown in FIG. Alternatively, an electrode group having a structure in which one positive electrode 16 and one negative electrode 17 are spirally wound with a separator 18 interposed therebetween and then compressed in the radial direction may be used.

In FIG. 3 described above, an example is described in which an electrode group having a structure in which a positive electrode and a negative electrode are spirally wound therebetween with a separator therebetween, and then compressed in the radial direction is used. An electrode group having a bent structure may be used. An example of this is shown in FIG. As shown in FIG. 6, the electrode group has a structure in which a positive electrode 19 and a negative electrode 20 are bent a plurality of times (for example, five times) so that the negative electrodes 20 are in contact with each other with a separator 21 interposed therebetween. By making the structure of the electrode group a bent structure, it is possible to simplify the production of the electrode group and to improve the mechanical strength of the electrode group.

In FIG. 3 described above, an example is described in which an electrode group having a structure in which a positive electrode and a negative electrode are spirally wound with a separator interposed therebetween and then compressed in the radial direction is used, as shown in FIG. A plurality of positive electrodes 22 and a plurality of negative electrodes 23 may be prepared, and an electrode group manufactured by alternately stacking the positive electrodes 22 and the negative electrodes 23 with a separator 24 interposed therebetween may be used.

The first nonaqueous electrolyte secondary battery according to the present invention is disposed between a positive electrode, a negative electrode including a negative electrode current collector and a negative electrode layer supported on the negative electrode current collector, and the positive electrode and the negative electrode layer. A non-aqueous electrolyte held by the electrode group; and a packaging material containing the electrode group. The positive electrode, the negative electrode, and the separator are integrated. The peel strength between the negative electrode layer and the separator is lower than the peel strength between the negative electrode layer and the negative electrode current collector.

In non-aqueous electrolyte secondary batteries, there is a demand to improve the energy density per battery weight and the energy density per volume. Therefore, it is necessary to use, as the exterior material, an exterior material A having a thickness of 0.3 mm or less or an exterior material B made of a sheet including a resin layer and having a thickness of 0.5 mm or less. However, since the exterior materials A and B have flexibility, they undergo deformation during the charge / discharge reaction following the expansion and contraction of the electrode group accompanying the charge / discharge reaction.

When the peel strength of the negative electrode layer and the separator is equal to or greater than the peel strength of the negative electrode layer and the negative electrode current collector, the expansion and contraction of the electrode group is caused by the progress of the charge / discharge reaction. When repeated, the peel strength is relatively low, that is, the adhesiveness between the negative electrode layer and the negative electrode current collector having a relatively low relative adhesive strength is reduced. In addition, the adhesion strength between the negative electrode layer and the separator becomes uneven. As a result, the interface impedance between the negative electrode and the separator increases, and current concentration occurs in the negative electrode during the charge / discharge reaction, so that lithium dendrite is deposited on the negative electrode, and the charge / discharge cycle life is reduced.

When the peel strength of the negative electrode layer and the separator is made lower than the peel strength of the negative electrode layer and the negative electrode current collector, the expansion and contraction of the electrode group is repeated with the progress of the charge / discharge reaction. In addition, it is possible to suppress a decrease in adhesion between the negative electrode layer and the negative electrode current collector. Further, the adhesion strength between the negative electrode layer and the separator can be made uniform. As a result, the interface impedance between the negative electrode and the separator can be reduced, so that the occurrence of current concentration at the negative electrode during charge / discharge reaction can be avoided. Therefore, while ensuring a high weight energy density and a high volume energy density, the generation of lithium dendrite at the negative electrode can be suppressed, so that the charge / discharge cycle life of the secondary battery can be improved, and the Large current discharge characteristics can be improved.

重量 In the first non-aqueous electrolyte secondary battery according to the present invention, by using the packaging material A, the weight energy density and the volume energy density can be further improved.

In the first nonaqueous electrolyte secondary battery according to the present invention, the interface resistance between the negative electrode and the separator can be further reduced by setting the peel strength between the negative electrode layer and the separator to 10 gf / cm or less. Large current discharge characteristics and cycle life can be further improved.

In the first nonaqueous electrolyte secondary battery according to the present invention, by setting the peel strength between the negative electrode layer and the negative electrode current collector to 10 gf / cm or more and 20 gf / cm or less, the interface resistance between the negative electrode and the separator can be reduced. Since the adhesion strength between the negative electrode layer and the negative electrode current collector can be increased, the large current discharge characteristics and cycle life of the secondary battery can be further improved.

In the first non-aqueous electrolyte secondary battery according to the present invention, by using a non-aqueous electrolyte containing a solution having a viscosity of 3 cp to 20 cp at 20 ° C. which is made of a non-aqueous solvent in which the electrolyte is dissolved, In addition to improving discharge characteristics and cycle life, safety when used in a high-temperature environment can be improved.

That is, since a solution having a viscosity of 3 cp to 20 cp at 20 ° C. has a high viscosity, gas generation when the secondary battery is stored in a high-temperature environment can be suppressed, but permeability to the electrode group is low. When the peel strength of the negative electrode layer and the separator is equal to or greater than the peel strength of the negative electrode layer and the negative electrode current collector, or when the non-aqueous electrolyte is used, the peel strength is reduced. As a result, the non-aqueous electrolyte is unevenly distributed in the electrode group in a situation where the interface resistance between the separator and the negative electrode is originally high, so that the interface resistance becomes extremely high, and the discharge capacity and the large-current discharge characteristics decrease.

As in the present invention, a solution having a viscosity at 20 ° C. of 3 cp to 20 cp was used by lowering the peel strength between the negative electrode layer and the separator compared to the peel strength between the negative electrode layer and the negative electrode current collector. In this case, it is possible to avoid an extremely high interface resistance. As a result, gas generation during high-temperature storage can be suppressed by utilizing the characteristics of the nonaqueous electrolyte containing a solution having a viscosity of 3 cp to 20 cp at 20 ° C., and high-current discharge characteristics and cycle life can be improved. .

By using, as the non-aqueous solvent, a solvent containing at least one solvent A selected from the group consisting of diethyl carbonate (DEC), propylene carbonate (PC) and γ-butyrolactone (BL) and ethylene carbonate (EC) In addition, the large-current discharge characteristics and cycle life can be further improved, and the amount of gas generated during high-temperature storage can be significantly reduced.

That is, since the solvent A is excellent in chemical stability, the inclusion of the solvent A in the non-aqueous solvent allows the positive electrode active material and the non-aqueous electrolyte to react with each other when stored under high-temperature conditions. Oxidative decomposition of the water electrolyte can be suppressed. As a result, the amount of gas generated can be reduced, so that swelling of the exterior material can be suppressed. In addition, since ethylene carbonate can form a protective film on the surface of the negative electrode, it is possible to suppress the reaction between the negative electrode, particularly the negative electrode containing a carbonaceous substance that occludes and releases lithium ions, and the solvent A, The reductive decomposition of the water electrolyte can be suppressed. Therefore, it is possible to provide a non-aqueous electrolyte secondary battery having improved large-current discharge characteristics and charge / discharge cycle characteristics and reduced gas generation during high-temperature storage.

Still another embodiment of the first nonaqueous electrolyte secondary battery according to the present invention is a positive electrode including a positive electrode current collector and a positive electrode layer supported on the positive electrode current collector, a negative electrode current collector, and the negative electrode current collector. An electrode group including a negative electrode including a negative electrode layer supported by a body, and a separator disposed between the positive electrode layer and the negative electrode layer; a non-aqueous electrolyte held by the electrode group; Exterior material; The positive electrode, the negative electrode, and the separator are integrated. The peel strength between the positive electrode layer and the separator is lower than the peel strength between the positive electrode layer and the positive electrode current collector, and the peel strength between the negative electrode layer and the separator is lower than the negative electrode layer and the negative electrode current collector. Is lower than the peel strength.

According to such a secondary battery, not only in the negative electrode, but also in the positive electrode, when the expansion and contraction of the electrode group are repeated with the progress of the charge / discharge reaction, the adhesion between the positive electrode layer and the positive electrode current collector is increased. Can be suppressed from decreasing. Further, the adhesion strength between the positive electrode layer and the separator can be made uniform. As a result, the interface impedance of both the positive electrode and the negative electrode can be reduced, so that the large-current discharge characteristics and cycle life of the secondary battery can be further improved.

重量 In the first non-aqueous electrolyte secondary battery according to the present invention, by using the packaging material A, the weight energy density and the volume energy density can be further improved.

In the first nonaqueous electrolyte secondary battery according to the present invention, by setting the peel strength between the negative electrode layer and the separator, or the peel strength between the positive electrode layer and the separator, or both to 10 gf / cm or less, Large current discharge characteristics and cycle life can be further improved.

In the first nonaqueous electrolyte secondary battery according to the present invention, the peel strength between the negative electrode layer and the negative electrode current collector, or the peel strength between the positive electrode layer and the positive electrode current collector, or both, is 10 gf / cm or more and 20 gf / cm or more. cm or less, the large current discharge characteristics and cycle life of the secondary battery can be further improved.

In the first non-aqueous electrolyte secondary battery according to the present invention, by using a non-aqueous electrolyte containing a solution having a viscosity of 3 cp to 20 cp at 20 ° C. which is made of a non-aqueous solvent in which the electrolyte is dissolved, In addition to improving discharge characteristics and cycle life, safety when used in a high-temperature environment can be improved.

By using, as the non-aqueous solvent, one containing at least one solvent A selected from the group consisting of diethyl carbonate (DEC), propylene carbonate (PC) and γ-butyrolactone (BL) and ethylene carbonate (EC) In addition, the large-current discharge characteristics and cycle life can be further improved, and the amount of gas generated during high-temperature storage can be significantly reduced.

Next, the second nonaqueous electrolyte secondary battery according to the present invention will be described.

The second nonaqueous electrolyte secondary battery includes a flat electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; a liquid nonaqueous liquid held by the electrode group. An electrolyte; and an exterior material in which the electrode group is housed. In this secondary battery, the positive electrode current collector is located on at least one of the two surfaces having the maximum area on the surface of the electrode group. Further, as the exterior material, the aforementioned exterior material A or exterior material B is used. Further, as the separator and the liquid non-aqueous electrolyte, those similar to those described in the first non-aqueous electrolyte secondary battery described above are used.

The positive electrode and the negative electrode will be described.

(1) Positive electrode This positive electrode has a positive electrode current collector and a positive electrode layer supported on one or both surfaces of the positive electrode current collector and containing an active material and a binder.

The positive electrode layer may further include a conductive agent.

と し て Examples of the positive electrode active material, the binder, the conductive agent, and the current collector include the same as those described in the first nonaqueous electrolyte secondary battery.

(4) The mixing ratio of the positive electrode active material, the conductive agent and the binder is preferably in the range of 80 to 95% by weight of the positive electrode active material, 3 to 20% by weight of the conductive agent, and 2 to 7% by weight of the binder.

正極 The thickness of the positive electrode layer is preferably in the range of 10 to 150 μm for the same reason as described in the first nonaqueous electrolyte secondary battery. A more preferable range of the thickness of the positive electrode layer is 30 to 100 μm.

(2) Negative electrode This negative electrode has a negative electrode current collector and a negative electrode layer supported on one or both surfaces of the negative electrode current collector and containing a negative electrode material and a binder.

負極 As the negative electrode material, the binder, and the negative electrode current collector, the same materials as described in the first nonaqueous electrolyte secondary battery described above can be used.

The compounding ratio of the carbonaceous material and the binder is preferably in the range of 90 to 98% by weight of the carbonaceous material and 2 to 20% by weight of the binder. In particular, the content of the carbonaceous material in the negative electrode is preferably in the range of 10 to 80 g / m ^{2 on} one surface. The packing density is desirably in the range of 1.2 to 1.50 g / cm ³ .

負極 The thickness of the negative electrode layer is preferably in the range of 10 to 150 μm for the same reason as described in the first nonaqueous electrolyte secondary battery. A more preferable range of the thickness of the negative electrode layer is 30 to 100 μm.

In addition to the above-mentioned carbonaceous materials that occlude and release lithium ions, metal materials, metal sulfides, metal nitrides, lithium metals, or lithium alloys can be used as the negative electrode material.

As the metal oxide, metal sulfide, metal nitride and lithium alloy, those similar to those described in the first nonaqueous electrolyte secondary battery can be used.

The area of the negative electrode is preferably larger than the area of the positive electrode. With such a configuration, the end of the negative electrode can be extended as compared with the end of the positive electrode, so that the current concentration on the negative electrode end can be reduced, and the cycle performance of the secondary battery can be improved. Safety can be improved.

The flat electrode group is produced, for example, by the methods (1) to (4) described below.

(1) The positive electrode and the negative electrode are spirally wound with a separator interposed therebetween, and then are pressed radially to produce the electrode group.

{Circle around (2)} The electrode group is produced by bending a laminate comprising a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode at least once.

(3) The electrode group is obtained by producing a laminate including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode.

(4) The electrode group is manufactured by flatly winding a positive electrode and a negative electrode with a separator interposed therebetween.

Here, the surface having the maximum area of the flat electrode group means a plane whose area is calculated from the product of the length along the longitudinal direction of the electrode group and the length along the direction orthogonal to the longitudinal direction.

に お い て In this electrode group, it is preferable that the positive electrode, the negative electrode, and the separator are integrated. The integration can be performed by the method (I) or (II) described below.

(I) The positive electrode and the separator are adhered to each other by making the adhesive polymer exist at least at a part of the boundary between the positive electrode and the separator, and the negative electrode is made to exist at least part of the boundary between the negative electrode and the separator. And the separator. Such integration is achieved, for example, by storing the electrode group in an exterior material, injecting a solution of an adhesive polymer into the outer layer, performing heat molding in a reduced-pressure atmosphere, and then applying a liquid This is performed by impregnating with a water electrolyte and performing sealing treatment such as heat sealing under a reduced pressure of 50 Torr or less. The reduced pressure atmosphere is more preferably set to 30 Torr or less.

(II) The positive electrode, the negative electrode, and the separator are integrated by thermally curing the binder contained in the positive electrode and the negative electrode. Such integration is performed, for example, after the electrode group is housed in an exterior material, the binder contained in the positive electrode and the negative electrode is thermoset by performing heat molding in a reduced-pressure atmosphere, and the positive electrode and the negative electrode After integrating the separator, the electrode group is impregnated with a liquid non-aqueous electrolyte, and is subjected to a sealing treatment such as a heat seal under a reduced pressure of 50 Torr or less. The reduced pressure atmosphere is more preferably set to 30 Torr or less.

に お い て In the above (I), it is preferable that the polymer having adhesiveness can maintain high adhesiveness while holding the non-aqueous electrolyte. Further, such a polymer is more preferably high in lithium ion conductivity. Specifically, those similar to those described in the first nonaqueous electrolyte secondary battery can be used.

The total amount of the polymer having adhesiveness included in the battery (including the polymer contained in the bonding portion described later) is determined by the battery capacity for the same reason as described in the first nonaqueous electrolyte secondary battery described above. Preferably, the amount is 0.1 to 6 mg per 100 mAh. A more preferable range of the total amount of the polymer having adhesiveness is 0.2 to 1 mg per 100 mAh of battery capacity.

Hereinafter, the second nonaqueous electrolyte secondary battery according to the present invention will be described in detail with reference to FIGS.

FIG. 8 is a sectional view showing a thin lithium ion secondary battery as an example of the second nonaqueous electrolyte secondary battery according to the present invention, FIG. 9 is an enlarged sectional view showing a portion B in FIG. 8, and FIG. FIG. 5 is a perspective view showing an electrode group incorporated in the lithium ion secondary battery of FIG.

For example, an electrode group 31 is accommodated in an exterior material 30 made of a multilayer sheet. The electrode group 31 has a structure in which a laminate including a positive electrode, a separator, and a negative electrode is wound into a flat shape. The laminated body includes a separator 32, a negative electrode 35 provided with a negative electrode layer 33, a negative electrode current collector 34, and a negative electrode layer 33, a separator 32, a positive electrode layer 36, a positive electrode current collector 37, and a positive electrode layer 36 from below in FIG. , A separator 32, a negative electrode layer 33, a negative electrode current collector 34, a negative electrode 35 having a negative electrode layer 33, a separator 32, a positive electrode 38 having a positive electrode layer 36 and a positive electrode current collector 37 are laminated in this order. It has the structure which was done. The outermost periphery of the electrode group 31 is a positive electrode current collector 37. Therefore, the positive electrode current collector 37 is located on the two surfaces 39 having the maximum area among the surfaces of the electrode group 31. However, the surface having the largest area of the electrode group 31, a surface area thereof is calculated from the product of the length L ₂ along the direction perpendicular to the length L ₁ in the longitudinal direction along the longitudinal direction of the electrode group means. The adhesive layer 40 is disposed between the surface of the electrode group 31 and the inner surface of the exterior member 30. The liquid non-aqueous electrolyte is accommodated in the exterior material 30. One end of the strip-shaped positive electrode lead 41 is connected to the positive electrode current collector 37 of the electrode group 31, and the other end is extended from the exterior material 30. On the other hand, the strip-shaped negative electrode lead 42 has one end connected to the negative electrode current collector 34 of the electrode group 31 and the other end extended from the exterior material 30.

電極 The electrode group 31 preferably has a thickness T of 4 mm or less and a length ratio calculated by the following equation (1) of 1.2 or more.

L ₁ / L _{2 (1)}
However, in the formula (A), L ₁ indicates a length along the longitudinal direction of the electrode group 31, and L ₂ indicates a length in a direction orthogonal to the longitudinal direction of the electrode group 31.

As shown in FIG. 10 described above, the thickness T of the electrode group 31 is a thickness measured when a surface F having a maximum area of the surface of the electrode group 31 is applied with an excess F of 15 to ²⁰ g per 1 cm ^2. Means.

When the thickness T of the electrode group is larger than 4 mm or L ₁ / L ₂ is less than 1.2, the electrode group having a thickness T of 4 mm or less and L ₁ / L ₂ of 1.2 or more In comparison with the above, when the volume of the electrode group is the same, the surface area of the electrode group may be small, and the heat radiation from the electrode group surface may not be quickly performed. A more preferable range of the thickness T is 3.5 mm or less. It is desirable that the upper limit of L ₁ / L ₂ is 10, more preferably 5.

In FIG. 10 described above, the laminated structure is exposed on the side surface 43 on the short side of the electrode group 31. However, as shown in FIG. 11, the laminated structure is exposed on the side surface 43 on the long side of the electrode group 31. It may be exposed. When the laminated structure is exposed on the side surface 43 on the longitudinal direction side of the electrode group, the ratio of the exposed surface of the laminated structure to the entire area of the electrode group increases, so that heat dissipation of the electrode group can be further promoted.

In addition, in FIG. 8 described above, the adhesive layer 40 is formed on the entire surface of the electrode group 31, but the adhesive layer 40 may be formed on a part of the electrode group 31. When the adhesive layer 40 is formed on a part of the electrode group 31, it is preferable to form the adhesive layer 40 on at least the surface corresponding to the outermost periphery of the electrode group. Further, the adhesive layer 40 may not be provided.

Further, in FIG. 10 described above, an example in which an electrode group obtained by winding a positive electrode and a negative electrode into a flat shape with a separator interposed therebetween is described, but a positive electrode, a negative electrode, the positive electrode and the An electrode having a structure in which an electrode group including a laminate including a separator disposed between the negative electrodes and a positive electrode, a negative electrode, and a laminate including the separator disposed between the positive electrode and the negative electrode are bent at least once. Can be applied to groups. An example of this is shown in FIG. As shown in FIG. 12, the electrode group 31 is formed by bending a laminate including the positive electrode current collector 37, the positive electrode layer 36, the separator 32, the negative electrode layer 33, and the negative electrode current collector a plurality of times (for example, five times). It is formed. The outermost layer of the electrode group 31 is a positive electrode current collector 37. Therefore, the positive electrode current collector 37 is located on the surface 39 having the largest area among the surfaces of the electrode group 31. In the case where a laminate including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode is used as the electrode group, at least one of the outermost layers of the laminate is used as the positive electrode current collector 37. good.

The second nonaqueous electrolyte secondary battery according to the present invention described in detail above has a flat electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; A liquid non-aqueous electrolyte to be held; and a packaging material to house the electrode group. In this secondary battery, the positive electrode current collector is located on at least one of the two surfaces having the maximum area on the surface of the electrode group. Further, as the exterior material, an exterior material A having a thickness of 0.3 mm or less or an exterior material B made of a sheet including a resin layer and having a thickness of 0.5 mm or less is used.

According to such a secondary battery, when the battery is abnormally heated by being thrown into a fire or the like, or when an internal short circuit or heat is generated due to an increase in internal resistance, the battery temperature is prevented from excessively increasing. Therefore, dangers such as rupture and fire can be avoided.

That is, since a secondary battery having a liquid non-aqueous electrolyte has a high energy density, when abnormal heating is applied or abnormal heat is generated, self-heating due to a chemical reaction inside the battery is promoted, and the battery temperature is increased. Rises, gas is generated and the internal pressure rises, and there is a danger of leakage, rupture or ignition. Further, in the secondary battery provided with the above-mentioned exterior material A or exterior material B, since reduction in thickness and weight is demanded, for example, a hard mechanism for enhancing safety of a PTC element (positive temperature coefficient) or the like is provided. It is difficult to mount. Without a safety mechanism, the risk of overcharging or short-circuiting increases.

Generally, self-heating due to a chemical reaction inside the battery caused by abnormal heating or heat generation often starts from a reaction originating from the positive electrode. Therefore, it is considered that the heat radiation characteristics of the battery at the start of the chemical reaction derived from the positive electrode greatly affect the safety of the battery. As in the present invention, by locating the positive electrode current collector on at least one of the two surfaces having the maximum area on the surface of the electrode group, the positive electrode, which easily generates self-heating, can be rapidly cooled. In addition, the temperature of the electrode group can be prevented from rising due to abnormal heating or heat generation. As a result, when abnormal heating or abnormal heat is generated by throwing into a fire, short-circuiting, overcharging, or the like, rupture or ignition can be prevented from occurring, and safety can be improved.

In the second nonaqueous electrolyte secondary battery according to the present invention, by exposing the laminated structure including the positive electrode, the negative electrode, and the separator on the side surface on the longitudinal direction side of the electrode group, the entire electrode group having the area of the laminated structure region is exposed. Since the ratio of the electrode group to the area can be increased, the heat radiation of the electrode group can be further promoted, and the temperature of the electrode group can be significantly prevented from rising due to abnormal heating or heat generation.

In the second nonaqueous electrolyte secondary battery according to the present invention, such a condition is satisfied by setting the thickness of the electrode group to 4 mm or less and setting the value of L ₁ / L ₂ to 1.2 or more. It is possible to increase the electrode group surface area with the same electrode group volume as compared with an electrode group that is not satisfied. As a result, since the heat radiation of the electrode group can be further promoted, it is possible to greatly suppress the temperature of the electrode group from rising due to abnormal heating or heat generation.

In the second nonaqueous electrolyte secondary battery according to the present invention, by using a liquid nonaqueous electrolyte including a nonaqueous solvent containing 20% by volume or more and 80% by volume or less of γ-butyrolactone, Oxidative decomposition can be suppressed, and the amount of gas generated when the battery temperature rises due to abnormal heating or abnormal heat generation can be reduced, so that swelling of the exterior material can be suppressed and safety is further improved. can do.

Hereinafter, the third nonaqueous electrolyte secondary battery according to the present invention will be described.

A third nonaqueous electrolyte secondary battery according to the present invention is a flat electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; a liquid held by the electrode group. A non-aqueous electrolyte; and an exterior material in which the electrode group is housed. In this secondary battery, separators are located on two surfaces having the maximum area on the surface of the electrode group. Further, as the exterior material, the aforementioned exterior material A or exterior material B is used. Further, as the positive electrode, the negative electrode, the separator, and the nonaqueous electrolyte, the same ones as described in the second nonaqueous electrolyte secondary battery described above are used.

The flat electrode group is manufactured by the same method as described in the second nonaqueous electrolyte secondary battery.

Here, the surface having the maximum area of the flat electrode group means a plane whose area is calculated from the product of the length along the longitudinal direction of the electrode group and the length along the direction orthogonal to the longitudinal direction.

に お い て In this electrode group, it is preferable that the positive electrode, the negative electrode, and the separator are integrated. For the integration, the same method as described in the second nonaqueous electrolyte can be employed.

Hereinafter, the third nonaqueous electrolyte secondary battery according to the present invention will be described in detail with reference to FIG.

FIG. 13 is an enlarged sectional view showing a main part of a third nonaqueous electrolyte secondary battery according to the present invention.

The thin lithium ion secondary battery, which is an example of the third nonaqueous electrolyte secondary battery, has the same structure as that described with reference to FIG. 8 except for the stacked structure of the electrode group. The electrode group has a structure in which a laminate including a positive electrode, a separator, and a negative electrode is wound into a flat shape. The laminated body includes a separator 44, a negative electrode 47 provided with a negative electrode layer 45, a negative electrode current collector 46 and a negative electrode layer 45, a separator 44, a positive electrode layer 48, a positive electrode current collector 49, and a positive electrode layer 48 from the lower side in FIG. , A separator 44, a negative electrode layer 45, a negative electrode current collector 46, a negative electrode 47 having a negative electrode layer 45, a separator 44, a positive electrode 50 having a positive electrode layer 48 and a positive electrode current collector 49, and a separator 44. It has a structure laminated in order. The outermost periphery of the electrode group is a separator 44. Therefore, the separators 44 are located on the two surfaces having the maximum area on the surface of the electrode group. However, the surface having the largest area of the flat-shaped electrode group, the surface area thereof is calculated from the product of the length L ₂ along the direction perpendicular to the length L ₁ in the longitudinal direction along the longitudinal direction of the electrode group Means

Note that, in FIG. 13 described above, an example is described in which the inside of one layer of the outermost separator is the positive electrode current collector 49, but a negative electrode current collector can be used instead of the positive electrode current collector.

In FIG. 13 described above, the adhesive layer 40 is formed on the entire surface of the electrode group. However, the adhesive layer 40 may be formed on a part of the electrode group. When the adhesive layer 40 is formed on a part of the electrode group, it is preferable to form the adhesive layer on at least the surface corresponding to the outermost periphery of the electrode group. Further, the adhesive layer 40 may not be provided.

Further, in FIG. 13 described above, an example is described in which an electrode group obtained by winding a positive electrode and a negative electrode into a flat shape with a separator interposed therebetween is used, but the positive electrode, the negative electrode, and the positive electrode and the positive electrode An electrode having a structure in which an electrode group including a laminate including a separator disposed between the negative electrodes and a positive electrode, a negative electrode, and a laminate including the separator disposed between the positive electrode and the negative electrode are bent at least once. Can be applied to groups. An example of this is shown in FIG. As shown in FIG. 14, the electrode group is a laminate of a positive electrode 50, a negative electrode 47, and a separator 44 disposed between the positive electrode 50 and the negative electrode 47. The outermost layer of the electrode group is the separator 44.

The third nonaqueous electrolyte secondary battery according to the present invention described in detail above has a flat electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; A liquid non-aqueous electrolyte to be held; and a packaging material to house the electrode group. In this secondary battery, separators are located on two surfaces having the maximum area on the surface of the electrode group. Further, as the exterior material, an exterior material A having a thickness of 0.3 mm or less or an exterior material B made of a sheet including a resin layer and having a thickness of 0.5 mm or less is used.

The non-aqueous electrolyte secondary battery provided with the outer packaging material A or the outer packaging material B can improve the weight energy density, but has poor mechanical strength. Tends to occur.

ADVANTAGE OF THE INVENTION According to this invention, since the mechanical strength of an electrode group can be made high, when an impact is given to a secondary battery by dropping by mistake etc., it is possible to avoid the electrode group being damaged or causing a short circuit. be able to. In addition, after forming a positive electrode and a negative electrode in a spiral shape with a separator interposed therebetween, and then pressing this in the radial direction, the impact applied to the electrode group at the time of pressurization is reduced when the electrode group is manufactured. Therefore, damage to the electrode group during pressurization can be reduced. Further, since it is possible to enhance the impact resistance of the electrode group itself, when using a packaging material including a resin layer, the resin layer on the side in contact with the electrode group is reduced to 15 μ or less, and more preferably eliminated. Can be.

Hereinafter, the fourth nonaqueous electrolyte secondary battery according to the present invention will be described.

The fourth nonaqueous electrolyte secondary battery includes a flat electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; A water electrolyte; and an exterior material in which the electrode group is housed. The insulating protective sheet is formed over two surfaces having the maximum area of the surface of the electrode group. Further, as the exterior material, the aforementioned exterior material A or exterior material B is used.

As the positive electrode, the negative electrode, the separator, and the nonaqueous electrolyte, the same ones as described in the second nonaqueous electrolyte secondary battery described above are used.

The flat electrode group is manufactured by the same method as described in the second nonaqueous electrolyte secondary battery. In the flat electrode group obtained by the methods (1), (2) and (4), it is preferable that the insulating protective sheet does not cover the exposed surface of the laminated structure. If the insulating protective sheet covers the exposed surface of the laminated structure, it may be difficult to impregnate the electrode group with the liquid non-aqueous electrolyte.

Here, the surface having the maximum area of the flat electrode group means a plane whose area is calculated from the product of the length along the longitudinal direction of the electrode group and the length along the direction orthogonal to the longitudinal direction.

に お い て In this electrode group, it is preferable that the positive electrode, the negative electrode, and the separator are integrated. For the integration, the same method as described in the second nonaqueous electrolyte can be employed.

材料 The material of the insulating protective sheet is preferably formed from an organic polymer insoluble in the liquid non-aqueous electrolyte. As such a material, for example, at least one kind selected from the group consisting of a polyimide resin, a fluorine resin, and a polyolefin resin can be given. As the polyimide resin, for example, Kapton (trade name, manufactured by DuPont) can be mentioned. On the other hand, examples of the polyolefin resin include a polyethylene resin and a polypropylene resin. Examples of the fluorine resin include polyvinylidene fluoride (PVdF).

The insulating protective sheet can be formed from a nonwoven fabric or a film. When a porous insulating protective sheet is used, the impregnation of the electrode group with the electrolytic solution can be improved. Further, an adhesive may be present between the insulating protective sheet and the electrode group.

(4) The insulating protective sheet is formed so as to straddle two surfaces having the maximum area on the surface of the electrode group, and it is preferable that both ends contact each other or both ends are separated by a desired distance. When the insulative protective sheet is formed so as to straddle two surfaces having the maximum area on the surface of the electrode group, if both ends of the protective sheet overlap, the expansion and contraction of the electrode group is hindered during the charge / discharge reaction, and the electrode Since the group is distorted, there is a possibility that the electrode group may be folded due to repetition of the charge / discharge cycle, and a long cycle life may not be obtained. For this reason, it is preferable that both ends of the protective sheet face each other with the electrode group surface interposed therebetween, and the distance X between the ends satisfies the following expression (2).

0 ≦ X ≦ 0.4 × L ₃ (2)
However, L _3, as shown in FIG. 15 to be described later, it along a circumferential direction of the insulating protective sheet among the length L ₂ along the length L ₁ and the lateral direction along the longitudinal direction of the electrode group of flattened shape Indicates the length of Note that when both ends are in contact, the distance X is zero. When both ends of the protective sheet are brought into contact when the electrode group is covered with the protective sheet, the manufacturing cost of the electrode group may be increased because the operation of manufacturing the electrode group becomes complicated.

If the distance X is larger than 0.4 × L _3, it may be difficult to suppress a short circuit and damage to the electrode group when an impact such as a drop is applied. Above all, it is more preferable that the distance X between both ends of the protective sheet satisfies the following expression (3).

0 ≦ X ≦ 0.3 × L ₃ (3)
It is desirable that the width of the insulating protective sheet be shorter than the dimensions of the electrode group. If the width of the insulating protective sheet is equal to or longer than the dimensions of the electrode group, it may be difficult to uniformly infiltrate the liquid nonaqueous electrolyte into the electrode group. However, as shown in FIG. 15 described later, the width H of the insulating protective sheet is a length in a direction orthogonal to the circumferential direction.

厚 The thickness of the insulating protective sheet is preferably 0.5 mm or less. If the sheet thickness exceeds 0.5 mm, the electrode group may be inhibited from expanding and contracting during the charge / discharge reaction. There is fear. Further, when the sheet thickness is less than 0.05 mm, it may be difficult to suppress a short circuit and damage to the electrode group when an impact such as a drop is applied. The sheet thickness is preferably set to 0.25 mm or less, and more preferably, 0.05 to 0.2 mm. The most preferred range is 0.05-0.15 mm.

Next, a fourth non-aqueous electrolyte secondary battery according to the present invention will be specifically described with reference to FIGS.

FIG. 15 is a schematic diagram for explaining an electrode group incorporated in the fourth nonaqueous electrolyte secondary battery according to the present invention, and FIG. 16 is a partially enlarged sectional view showing a portion C in FIG.

The thin lithium ion secondary battery, which is an example of the fourth nonaqueous electrolyte secondary battery, has the same structure as that described with reference to FIG. 8 except for the electrode group. As shown in the perspective view of the electrode group shown in the upper part of FIG. 15, the electrode group 51 has a structure in which a laminate including a positive electrode, a separator, and a negative electrode is wound into a flat shape. A sectional view of the electrode group is shown in the lower part of FIG. According to FIG. 16 showing a portion C of this cross-sectional view, the laminated body is composed of a separator 52, a negative electrode 55 provided with a negative electrode layer 53, a negative electrode current collector 54 and a negative electrode layer 53, and a separator 52 from the lower side of FIG. A positive electrode 58 having a positive electrode layer 56, a positive electrode current collector 57 and a positive electrode layer 56, a separator 52, a negative electrode 55 having a negative electrode layer 53, a negative electrode current collector 54 and a negative electrode layer 53, a separator 52, a positive electrode layer 56 and a positive electrode The positive electrode 58 having the current collector 57 and the separator 52 have a structure in which the positive electrode 58 and the separator 52 are stacked in this order. For example, the rectangular insulative protective sheet 59 covers a part of the outermost periphery of the electrode group 51 and straddles two surfaces having the maximum area. Here, the surface having the largest area of the electrode group 51, the area is calculated from the product of the length L ₂ along the direction perpendicular to the length L ₁ in the longitudinal direction along the longitudinal direction of the electrode group surface Means Further, both end portions 60a and 60b of the insulating protective sheet 59 are not in contact with each other but are separated. The distance X between both ends 60a, 60b satisfies the above-mentioned expression (2); 0 ≦ X ≦ 0.4 × L ₃ . However, L _3, of the direction of the length L ₂ perpendicular to the longitudinal length L ₁ and the electrode group in the longitudinal direction of the electrode group is the length of the direction along the circumferential direction of the insulating protective sheet 59 . L ₃ in this case, the direction perpendicular to the longitudinal direction of the electrode group is the length L _2. The width H of the insulating protective sheet 59 is shorter or as compared to the length L ₁ along the longitudinal direction of the electrode group.

Note that, in FIG. 15 described above, an example is described in which the inside of one layer of the insulating protective sheet 59 is the separator 52, but a positive electrode current collector or a negative electrode current collector can be used instead of the separator.

Further, in FIG. 15 described above, an example is described in which an electrode group obtained by winding a positive electrode and a negative electrode into a flat shape with a separator interposed therebetween is used, but the positive electrode, the negative electrode, and the positive electrode and the positive electrode An electrode having a structure in which an electrode group including a laminate including a separator disposed between the negative electrodes and a positive electrode, a negative electrode, and a laminate including the separator disposed between the positive electrode and the negative electrode are bent at least once. Can be applied to groups.

The fourth non-aqueous electrolyte secondary battery according to the present invention described in detail above is a flat electrode group including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode; , A liquid non-aqueous electrolyte held by the battery; and an exterior material in which the electrode group is housed. The insulating protective sheet is formed so as to straddle two surfaces having a maximum area on the surface of the electrode group. Further, as the exterior material, an exterior material A having a thickness of 0.3 mm or less or an exterior material B made of a sheet including a resin layer and having a thickness of 0.5 mm or less is used.

ADVANTAGE OF THE INVENTION According to this invention, since the mechanical strength of an electrode group can be made high, when an impact is given to a secondary battery by dropping by mistake etc., it is possible to avoid the electrode group being damaged or causing a short circuit. be able to. Further, since it is possible to increase the impact resistance of the electrode group itself, when using a packaging material including a resin layer, the resin layer on the side in contact with the electrode group is reduced to 15 μm or less, more preferably eliminated. Can be.

In the fourth nonaqueous electrolyte secondary battery according to the present invention, when the insulating protective sheet is formed so as to straddle the two surfaces having the maximum area on the surface of the electrode group, both ends are not in contact with each other, By setting the distance X between the sections to be equal to or less than the range defined by 0.4 × L ₃ in the above equation (2), the following effects (a) to (c) can be obtained.

(A) It is possible to avoid a short circuit and damage to the electrode group when an impact is applied.

(B) Distortion of the electrode group due to expansion and contraction of the electrode group during the charge / discharge reaction can be suppressed, and the electrode group can be prevented from folding due to repeated charge / discharge, thereby improving the charge / discharge cycle life. be able to.

(C) An electrode group can be manufactured by a simple method.

Hereinafter, embodiments of the present invention will be described in detail.

Example 1
<Preparation of positive electrode>
First, lithium cobalt oxide (LixCoO ₂ ; X is 0 ≦ X ≦ 1) powder 90.5% by weight, acetylene black 2.5% by weight, graphite 3% by weight, polyvinylidene fluoride (PVdF) 4% by weight % And N-methylpyrrolidone (NMP) solution was prepared by mixing the slurry. The slurry was applied to a positive electrode current collector made of an aluminum foil having a thickness of 10 μm, dried, and pressed to prepare a positive electrode having an electrode density of 3.0 g / cm ³ . The obtained positive electrode had a structure in which a positive electrode layer having a thickness of 48 μm was supported on both surfaces of the positive electrode current collector. Note that the total thickness of the positive electrode layer is 96 μm.

<Preparation of negative electrode>
A mesophase pitch-based carbon fiber heat-treated at 3000 ° C. was prepared as a carbonaceous material. The carbon fibers had an average fiber diameter of 8 μm, an average fiber length of 20 μm, and an average interplanar spacing (doo ₂ ) of 0.3360 nm. A slurry was prepared by mixing 93% by weight of the carbonaceous material powder, 7% by weight of polyvinylidene fluoride (PVdF) as a binder, and an NMP solution. The obtained slurry was applied to both surfaces of a negative electrode current collector made of a copper foil having a thickness of 10 μm, dried, and pressed to produce a negative electrode having an electrode density of 1.35 g / cm ³ . The obtained negative electrode had a structure in which a negative electrode layer having a thickness of 45 μm was supported on both surfaces of the negative electrode current collector. Note that the total thickness of the negative electrode layer is 90 μm.

<Preparation of electrode group>
A polyethylene separator having a thickness of 27 μm, a porosity of 50%, and an air permeability of 90 seconds / 100 cm ³ was prepared. The positive electrode and the negative electrode are spirally wound with a separator interposed therebetween, and then formed into a flat shape by pressing radially, and have a thickness of 2.7 mm, a width of 30 mm, and a height of 30 mm. Produced an electrode group having a thickness of 50 mm.

<Preparation of non-aqueous electrolyte>
1.5 mol / 1 of lithium tetrafluoroborate (LiBF ₄ ) was dissolved in a mixed solvent of ethylene carbonate (EC) and γ-butyrolactone (BL) (mixing volume ratio 40:60) to prepare a non-aqueous electrolyte (liquid Was prepared.

<Battery assembly>
A laminate film having a thickness of 0.1 mm (100 μm) in which both surfaces of the aluminum foil were covered with polypropylene was formed into a bag shape. The electrode group was housed in this, and the obtained one was sandwiched between holders so that the battery thickness became 2.7 mm. Immediately after insertion into the holder, the pressure applied to the electrode group was 0.5 kg / cm ² . 0.3% by weight of polyvinylidene fluoride (PVdF), which is an adhesive polymer, was dissolved in dimethylformamide (DMF) (boiling point: 153 ° C.) which was an organic solvent. The obtained solution was injected into the electrode group in the laminate film so as to have a battery capacity of 0.6 ml, and the solution was permeated into the electrode group and adhered to the entire surface of the electrode group.

Next, the organic solvent is evaporated by performing vacuum drying at 80 ° C. for 12 hours to the electrode group in the laminate film, and the positive electrode, the negative electrode, The separator was integrated, and a porous adhesive portion was formed on the surface of the electrode group.

Next, the holder was released. The total time during which the electrode group was held between the holders was 120 minutes. 2 g of the non-aqueous electrolyte is injected into the electrode group in the laminate film, and has the structure shown in FIGS. 3 and 4 described above, and has a thickness of 2.7 mm, a width of 32 mm, and a height of 55 mm. A non-aqueous electrolyte secondary battery was assembled.

Example 2
An electrode group was produced in the same manner as described in Example 1 described above. Next, the electrode group was housed in a laminate film similar to that described in Example 1 described above, and an organic solvent in which an adhesive polymer was dissolved was injected into the laminate film.

Subsequently, the positive electrode, the negative electrode, and the separator are united by an adhesive polymer by performing a press at a pressure of 0.1 kg / cm ² for 120 minutes along a thickness direction of the electrode group in a vacuum atmosphere at 80 ° C. At the same time, a porous bonded portion was formed on the surface of the electrode group.

Next, the same non-aqueous electrolyte solution as described in Example 1 was injected into the electrode group in the laminate film, and the electrode group had the structure shown in FIGS. A thin non-aqueous electrolyte secondary battery having a width of 32 mm and a height of 55 mm was assembled.

Example 3
An electrode group was produced in the same manner as described in Example 1 described above. Next, the electrode group was housed in a laminate film similar to that described in Example 1 described above.

Subsequently, the positive electrode, the negative electrode, and the separator were integrated by performing a press at a pressure of 1 kg / cm ² for 60 minutes along a thickness direction of the electrode group in a vacuum atmosphere at 80 ° C.

Next, the same non-aqueous electrolyte solution as described in Example 1 was injected into the electrode group in the laminate film, and the electrode group had the structure shown in FIGS. A thin non-aqueous electrolyte secondary battery having a width of 32 mm and a height of 55 mm was assembled.

Example 4
A thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Example 3 except that the pressure for press molding was 10 kg / cm ² and the pressing time was 5 minutes.

Example 5
Except that the electrode group is sandwiched by the holder so that the battery thickness becomes 2.7 mm and the pressure applied to the electrode group immediately after the holder insertion becomes 0.1 kg / cm ² , and the holder holding time is set to 120 minutes, A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 1 described above.

Example 6
An electrode group was produced in the same manner as described in Example 1 described above. Next, the electrode group was housed in a laminate film similar to that described in Example 1 described above.

Subsequently, the positive electrode, the negative electrode, and the separator were integrated by holding the electrode group in a vacuum atmosphere at 80 ° C. with a holder so that the battery thickness became 2.68 mm for 120 minutes. The pressure applied to the electrode group immediately after insertion into the holder was 0.1 kg / cm ² .

Next, the same non-aqueous electrolyte solution as described in Example 1 was injected into the electrode group in the laminate film, and the electrode group had the structure shown in FIGS. A thin non-aqueous electrolyte secondary battery having a width of 32 mm and a height of 55 mm was assembled.

Example 7
Thin non-aqueous electrolyte secondary battery in the same manner as in Example 1 except that the air permeability of the separator is 30 seconds / 100 cm ³ and the composition ratio of γ-butyrolactone in the non-aqueous solvent is 20% by volume. Was assembled.

Example 8
Thin non-aqueous electrolyte secondary battery in the same manner as in Example 1 except that the air permeability of the separator is 90 seconds / 100 cm ³ and the composition ratio of γ-butyrolactone in the non-aqueous solvent is 50% by volume. Was assembled.

Example 9
Thin non-aqueous electrolyte secondary battery in the same manner as in Example 1 except that the air permeability of the separator is 450 seconds / 100 cm ³ and the composition ratio of γ-butyrolactone in the non-aqueous solvent is 80% by volume. Was assembled.

Examples 10 to 15
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 3 except that the pressure for press molding and the press time were changed as shown in Table 1 below.

Example 16
Non-aqueous electrolyte prepared by dissolving 1.5 mol / 1 lithium tetrafluoroborate (LiBF ₄ ) in a mixed solvent of 25 vol% ethylene carbonate (EC) and 75 vol% propylene carbonate (PC) A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 3 except for using.

Example 17
Nonaqueous electrolyte prepared by dissolving 1.5 mol / 1 lithium tetrafluoroborate (LiBF ₄ ) in a mixed solvent of 10 vol% ethylene carbonate (EC) and 90 vol% propylene carbonate (PC) A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 3 except for using.

Example 18
A thin non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 1 except that the positive electrode produced by the following method was used, and the pressure and press time of press molding were changed as shown in Table 1 below. Assembled.

That is, 90.5% by weight of lithium cobalt nickel oxide powder having a composition represented by LiCo _0.2 Ni _0.8 O ₂ , 2.5% by weight of acetylene black, 3% by weight of graphite, 4% by weight of polyvinylidene fluoride (PVdF) and N- A slurry was prepared by mixing a methylpyrrolidone (NMP) solution. The slurry was applied to a positive electrode current collector made of an aluminum foil having a thickness of 10 μm, dried, and pressed to prepare a positive electrode having an electrode density of 3.0 g / cm ³ . The obtained positive electrode had a structure in which a positive electrode layer having a thickness of 48 μm was supported on both surfaces of the positive electrode current collector. Note that the total thickness of the positive electrode layer is 96 μm.

Example 19
A thin non-aqueous electrolyte secondary battery was prepared in the same manner as in Example 3 except that the positive electrode produced by the following method was used, and the pressure and press time of press molding were changed as shown in Table 1 below. Assembled.

That is, 90.5% by weight of lithium cobalt nickel oxide powder having a composition represented by LiCo _0.2 Ni _0.8 O ₂ , 2.5% by weight of acetylene black, 3% by weight of graphite, 4% by weight of polyvinylidene fluoride (PVdF) and N- A slurry was prepared by mixing a methylpyrrolidone (NMP) solution. The slurry was applied to a positive electrode current collector made of an aluminum foil having a thickness of 10 μm, dried, and pressed to prepare a positive electrode having an electrode density of 3.0 g / cm ³ . The obtained positive electrode had a structure in which a positive electrode layer having a thickness of 48 μm was supported on both surfaces of the positive electrode current collector. Note that the total thickness of the positive electrode layer is 96 μm.

Example 20
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 3 except that the carbonaceous material described below was used.

As a carbonaceous material, a mixed powder of 60% by weight of mesophase pitch-based carbon fibers heat-treated at 3000 ° C. and 40% by weight of mesophase spheres heat-treated at 3000 ° C. was prepared. The carbon fiber had an average fiber diameter of 8 μm, an average fiber length of 20 μm, an average aspect ratio of 2.5, and an average interplanar spacing (doo ₂ ) of 0.3360 nm. On the other hand, the small spheres had an average particle diameter of 6 μm, a ratio of a minor radius to a major radius of 0.95, and an average interplanar spacing (doo ₂ ) of 0.3361 nm.

Example 21
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 3 except that the carbonaceous material described below was used.

That is, a mixed powder of 50% by weight of mesophase pitch-based carbon fiber heat-treated at 3000 ° C. and 50% by weight of granular graphite was prepared as a carbonaceous material. The carbon fibers had an average fiber diameter of 3 μm, an average fiber length of 15 μm, an average aspect ratio of 5, and an average interplanar spacing (doo ₂ ) of 0.3362 nm. On the other hand, the granular graphite had an average particle size of 6 μm, a ratio of a minor radius to a major radius of 5, and an average interplanar spacing (doo ₂ ) of 0.3355 nm.

Comparative Example 1
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 1 except that a solution of PVdF dissolved in dimethylformamide (DMF) at 5% by weight was used as the polymer solution having adhesiveness. .

Comparative Example 2
5% by weight of PVdF was dissolved in dimethylformamide (DMF), and the obtained solution was applied to a separator similar to that described in Example 1. An electrode group was prepared by interposing the separator between the positive electrode and the negative electrode as described in Example 1.

After the electrode group was housed in the same laminated film as described in Example 1 described above, the same non-aqueous electrolyte as described in Example 1 was injected, and the thickness was 2.7 mm. Thus, a thin nonaqueous electrolyte secondary battery having a width of 32 mm and a height of 55 mm was assembled.

Comparative Example 3
A non-aqueous electrolyte prepared by dissolving lithium tetrafluoroborate (LiBF ₄ ) in a mixed solvent of 10% by volume of ethylene carbonate (EC) and 90% by volume of diethyl carbonate (DEC) at 1 mol / 1 is used. Except for this, a thin nonaqueous electrolyte secondary battery was assembled in the same manner as in Comparative Example 2 described above.

初 The obtained secondary batteries of Examples 1 to 20 and Comparative Examples 1 to 3 were initially charged and discharged. Next, after carrying out a constant voltage charge of 4.2 V at 1 C for 3 hours, a discharge capacity at the time of discharging to 3 V at 1 C was measured, and this was defined as a discharge capacity at 1 C. Subsequently, after carrying out a constant voltage charge of 4.2 V at 1 C for 3 hours, the discharge capacity at the time of discharging to 3 V at 3 C was measured, and this was defined as the discharge capacity at 3 C. Table 3 below shows the discharge capacity at 3C when the discharge capacity at 1C is 100%.

In addition, for the secondary batteries of Examples 1 to 21 and Comparative Examples 1 to 3, charging and discharging cycles of charging at 1 C and discharging at 1 C are repeated, and 500 cycles when the first cycle discharge capacity is 100%. The discharge capacity at the time was determined, and this is shown in Table 3 below as the capacity retention rate at the time of 500 cycles.

Further, for the secondary batteries of Examples 1 to 21, after charging to 4.2 V, swelling after storage at 85 ° C for 24 hours was measured. The swelling ratio was based on the thickness of the battery before storage.

For the secondary batteries of Examples 1 to 21 and Comparative Examples 1 to 3, after the initial charge and discharge, the secondary battery was disassembled, and the peel strength between the positive electrode layer and the separator by the 180-degree peel strength method, the positive electrode layer and the positive electrode The peel strength between the current collector, the peel strength between the negative electrode layer and the separator, and the peel strength between the negative electrode layer and the negative electrode current collector were measured by the methods described below. As a measuring device, a device manufactured by Fudo Kogyo Co., Ltd., whose trade name is a rheometer (Rheo meater) and whose model number is NRM / 1010J-CW was used. First, the secondary battery is disassembled to take out a target laminate (for example, a laminate in which a negative electrode current collector, a negative electrode layer, and a separator are laminated in this order). This laminate retains the non-aqueous electrolyte. The width of the laminate was 20 mm, and the length was 50 mm. This laminate is placed on a support base with the current collector side facing down. Next, a double-sided tape (trade name: Scotch, CAT. No. 665-3-24, manufactured by Sumitomo 3M Co., Ltd.), base material is transparent hard vinyl chloride, and an adhesive is an acrylic resin-based adhesive is formed on the upper surface of the laminate. Is attached. The adhesion area between the laminate and the double-sided tape was set to 20 × 30 mm. The double-sided tape is pulled in a direction parallel to the upper surface of the laminate at a speed of 2 cm per minute to peel off the separator from the negative electrode layer. The force required to peel the separator fluctuates at the beginning of peeling, and the traction force at the time when this force becomes constant is defined as the peel strength between the negative electrode layer and the separator. The results are shown in Table 3 below.

Further, the viscosity of the liquid non-aqueous electrolyte of each secondary battery was measured at 20 ° C., and the results are shown in Table 3 below.

As is clear from Tables 1 to 3, the secondary batteries of Examples 1 to 21 in which the peel strength of the negative electrode layer and the separator is smaller than the peel strength of the negative electrode layer and the negative electrode current collector are the same as those of Comparative Examples 1 to 3. It can be seen that the capacity retention at the time of 3C discharge is higher and the capacity retention at the time of 500 cycles is superior to that of the secondary battery. In addition, the secondary batteries of Examples 1 to 21 were able to suppress swelling of the exterior material when stored at a high temperature to less than 2%.

(Example 22)
The thickness of the laminate film as an exterior material was set to 0.5 mm, and the thickness of the electrode group was adjusted so that the battery dimensions were the same as in Example 3 (thickness was 2.7 mm, width was 32 mm, and height was 55 mm). A thin non-aqueous electrolyte secondary battery was manufactured in the same manner as in Example 3 except that the thickness was reduced. The capacity of the obtained secondary battery was 60% (the capacity of the secondary battery of Example 3 was 100%).

Example 23
<Preparation of positive electrode>
First, 91% by weight of lithium cobalt oxide (Li _x CoO ₂ ; X is 0 ≦ X ≦ 1) powder, 3.5% by weight of acetylene black, 3.5% by weight of graphite, ethylene propylene diene A slurry was prepared by mixing 2% by weight of the monomer powder and toluene. The slurry was applied to both surfaces of a current collector made of a porous aluminum foil (having a thickness of 15 μm) having 0.5 mm diameter holes at a rate of 10 per 10 cm ² . Next, by drying and pressing, a positive electrode having an electrode density of 3.0 g / cm ³ was produced.

<Preparation of negative electrode>
A mesophase pitch-based carbon fiber heat-treated at 3000 ° C. was prepared as a carbonaceous material. This carbon fiber had a fiber diameter of 8 μm, an average fiber length of 20 μm, and an average interplanar spacing (doo ₂ ) of 0.3360 nm. A slurry was prepared by mixing 93% by weight of the carbon fiber powder, 7% by weight of polyvinylidene fluoride (PVdF) as a binder, and an NMP solution. The slurry was applied to both surfaces of a current collector made of a porous copper foil (thickness: 15 μm) having holes of 0.5 mm in diameter at a rate of 10 per 10 cm ² . Subsequently, by drying, and pressing, a negative electrode having an electrode density of 1.3 g / cm ³ was produced.

<Separator>
Two separators made of a polyethylene porous film having a thickness of 25 μm, a heat shrinkage of 20% at 120 ° C. for 1 hour, and a porosity of 50% were prepared. The length of each side of the separator is 2 mm longer than the length of each side of the positive electrode, and 1.5 mm longer than the length of each side of the negative electrode.

<Preparation of non-aqueous electrolyte>
Lithium hexafluorophosphate (LiPF ₆ ) was dissolved in a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (MEC) (mixing volume ratio 1: 2) at a mole ratio of 1 mol / 1 to prepare a non-aqueous electrolyte (liquid non-aqueous electrolyte). Water electrolyte) was prepared.

<Preparation of electrode group>
The obtained positive electrode, negative electrode and separator are laminated in the order of separator, positive electrode, separator and negative electrode, and spirally wound so that the outermost periphery becomes a positive electrode current collector. To obtain a flat electrode group shown in FIG.

The resulting electrode assembly has a thickness T measured by the method described in FIG. 10 described above is 2.9 mm, a length L ₁ along the longitudinal direction 250 mm, a length L ₂ along the short direction 180mm In this case, the length ratio (L ₁ / L ₂ ) calculated by the above equation (1) was 1.39. Further, the laminated structure including the positive electrode, the negative electrode, and the separator was exposed on the side surface on the longitudinal direction side. Further, in this electrode group, the end of the separator extended 1 mm from the end of the positive electrode, and extended 0.75 mm from the end of the negative electrode.

(4) A laminated film having a thickness of 0.1 mm (100 μm) in which both surfaces of an aluminum foil were covered with polypropylene was formed into a bag shape, and the electrode group was housed in the bag so that the layered surface could be seen from the opening of the bag. 0.5% by weight of polyacrylonitrile (PAN), which is an adhesive polymer, was dissolved in dimethylformamide (boiling point: 153 ° C.) which was an organic solvent. The obtained solution was injected into the electrode group in the laminate film so that the amount per battery capacity of 100 mAh was 0.25 ml, and the solution was permeated into the electrode group, and was spread over the entire surface of the electrode group. Attached.

Next, the organic solvent is evaporated by performing vacuum drying at 80 ° C. for 12 hours to the electrode group in the laminate film, and the positive electrode, the negative electrode, The separator was integrated, and a porous adhesive portion was formed on the surface of the electrode group. The total amount of PAN was 1.25 mg per 100 mAh of battery capacity.

The non-aqueous electrolyte was injected into the electrode group in the laminate film so as to have an amount of 4.1 g per 1 Ah of battery capacity, heat-sealed under a reduced pressure of 30 Torr or less, and shown in FIGS. A thin non-aqueous electrolyte secondary battery having a structure was assembled.

Example 24
And the electrode group thickness T to 2.0 mm, and a length L ₁ along the longitudinal direction of the electrode group to 300 mm, the length L ₂ along the widthwise direction to 150 mm, is calculated by the aforementioned equation (1) A thin non-aqueous electrolyte secondary battery was assembled in the same manner as described in Example 23 except that the length ratio (L ₁ / L ₂ ) was set to 2.0.

Example 25
A positive electrode, a negative electrode and a separator similar to those described in Example 23 described above are stacked in the order of a separator, a positive electrode, a separator, and a negative electrode, and after being spirally wound so that the outermost periphery becomes a positive electrode current collector, The flattened electrode group shown in FIG. 11 described above was obtained by pressing the obtained wound product in the radial direction.

The resulting electrode group, with 4.0mm thickness T as measured by the method described above, the length L ₁ along the longitudinal direction 200 mm, a length L ₂ along the short direction at 135mm, the above-described ( The length ratio (L ₁ / L ₂ ) calculated by the expression 1) was 1.48. Further, the laminated structure including the positive electrode, the negative electrode, and the separator was exposed on the side surface on the longitudinal direction side. Further, in this electrode group, the end of the separator extended 1 mm from the end of the positive electrode, and extended 0.75 mm from the end of the negative electrode.

Next, the electrode group was housed in a laminate film similar to that described in Example 23 described above. Subsequently, the positive electrode, the negative electrode, and the separator were integrated by applying a pressure of 15 kg / cm ² along the thickness direction of the electrode group in a vacuum atmosphere at 90 ° C.

Next, the same non-aqueous electrolyte as described in Example 23 was injected into the electrode group in the laminate film, heat-sealed under a reduced pressure of 30 Torr or less, and a thin non-aqueous electrolyte secondary battery was assembled. Was.

Example 26
And the electrode group thickness T to 1.5 mm, and a length L ₁ along the longitudinal direction of the electrode group to 200 mm, the length L ₂ along the widthwise direction to 50 mm, is calculated by the aforementioned equation (1) A thin non-aqueous electrolyte secondary battery was assembled in the same manner as described in Example 25, except that the length ratio (L ₁ / L ₂ ) was set to 4.0.

Example 27
A positive electrode and a negative electrode similar to those described in Example 23 described above are stacked so that the outermost layer becomes a positive electrode current collector with a separator similar to that described in Example 23 described above interposed therebetween. As a result, a flat electrode group was obtained.

The resulting electrode assembly has a thickness T as measured by the method described above is 2.9 mm, a length L ₁ along the longitudinal direction 250 mm, a length L ₂ along the widthwise direction at 180 mm, the above-described ( The length ratio (L ₁ / L ₂ ) calculated by the expression 1) was 1.39. Further, in this electrode group, the end of the separator extended 1 mm from the end of the positive electrode, and extended 0.75 mm from the end of the negative electrode.

Next, the electrode group was housed in a laminate film similar to that described in Example 23 described above. Subsequently, a thin non-aqueous electrolyte secondary battery was obtained by performing injection of a polymer solution having adhesive properties, vacuum drying, injection of a non-aqueous electrolyte, and heat sealing in the same manner as described in Example 23 described above. Assembled.

Example 28
A thin nonaqueous electrolyte secondary battery similar to that described in Example 23 described above was assembled except that a laminated structure including a positive electrode, a negative electrode, and a separator was exposed on the side surface on the short side of the electrode group.

Examples 29 to 31
A thin non-aqueous electrolyte secondary battery similar to that described in Example 23 described above was assembled except that the thickness of the laminate film as the exterior material was changed as shown in Table 4 below.

Example 32
Non-aqueous electrolysis prepared by dissolving lithium tetrafluoroborate (LiBF ₄ ) in a mixed solvent of 34% by volume of ethylene carbonate (EC) and 66% by volume of γ-butyrolactone (BL) at 1.5 mol / 1. A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 23 except that the liquid was used.

Example 33
Non-aqueous electrolysis prepared by dissolving 1.5 mol / 1 lithium tetrafluoroborate (LiBF ₄ ) in a mixed solvent of 25 vol% ethylene carbonate (EC) and 75 vol% γ-butyrolactone (BL) A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 23 except that the liquid was used.

Comparative Example 6
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 23 except that the thickness T of the electrode group was changed to 8.0 mm.

Comparative Example 7
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 23 except that the outermost periphery of the electrode group was a negative electrode current collector.

Comparative Example 8
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 23 except that the outermost periphery of the electrode group was the positive electrode layer.

Comparative Example 9
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as in Example 23 except that the thickness of the exterior material was set to 0.6 mm.

The obtained secondary batteries of Examples 23 to 33 and Comparative Examples 6 to 9 were charged at a charging current value of 0.5 C to 4.2 V for 5 hours, and then discharged at 0.5 C to 2.7 V. A discharge cycle test was performed to determine the discharge capacity at 300 cycles when the discharge capacity at the first cycle was 100%, and this is shown in Table 5 below as the capacity retention rate at 300 cycles.

Further, the secondary batteries of Examples 23 to 33 and Comparative Examples 6 to 9 were left in an oven at 100 ° C., and the temperature of the outer surface of the laminate film was monitored. The results are also shown in Table 5 below. “None” in Table 5 means that the temperature did not rise due to being left in the oven.

Further, for the secondary batteries of Examples 23 to 33 and Comparative Examples 6 to 9, after swelling after being charged to 4.2 V and stored at 80 ° C. for 24 hours, the results are also shown in Table 5 below.

The energy densities per unit volume of the secondary batteries of Examples 23 to 33 and Comparative Examples 6 to 9 were measured, and the results are also shown in Table 5 below.

As is clear from Tables 4 and 5, the secondary batteries of Examples 23 to 33 in which the surface having the maximum area of the electrode group is formed of the positive electrode current collector have a high capacity retention rate at 300 cycles and a high temperature. It can be seen that temperature rise and gas generation when left in an environment can be suppressed.

On the other hand, although the secondary batteries of Comparative Examples 6 to 8 have a high capacity retention rate at 300 cycles, the temperature rise when left in a high-temperature environment is higher than that of Examples 23 to 33, It can be seen that the amount of gas generated when left in an environment is larger than in Examples 23 to 33. Furthermore, the secondary battery of Comparative Example 9 including a packaging material having a thickness of more than 0.5 mm not only has a low energy density per unit volume but also has a surface having the maximum area of the electrode group as a positive electrode current collector. It can also be seen that it is difficult to suppress the temperature rise and gas generation when left in a high temperature environment.

Example 34
The same positive electrode, negative electrode, and separator as described in Example 23 were laminated in the order of separator, positive electrode, separator, and negative electrode, and spirally wound so that the outermost periphery became a separator, and then the obtained winding was obtained. The flat-shaped electrode group shown in FIG. 13 described above was obtained by pressing the object radially.

It consists of an aluminum foil coated on both sides with a polypropylene layer. The thickness of the polypropylene layer on the side (inner side) in contact with the electrode group is 0.015 mm (15 μm) and the total thickness is 0.08 mm (80 μm). A laminate film was prepared. After the laminate film was formed into a bag shape, the electrode group was housed in the bag so that its lamination surface could be seen from the opening of the bag. 0.5% by weight of polyacrylonitrile (PAN), which is an adhesive polymer, was dissolved in dimethylformamide (boiling point: 153 ° C.) which was an organic solvent. The obtained solution was injected into the electrode group in the laminate film so that the amount per battery capacity of 100 mAh was 0.25 ml, and the solution was permeated into the electrode group, and was spread over the entire surface of the electrode group. Attached.

Next, the organic solvent is evaporated by performing vacuum drying at 80 ° C. for 12 hours to the electrode group in the laminate film, and the positive electrode, the negative electrode, The separator was integrated, and a porous adhesive portion was formed on the surface of the electrode group. The total amount of PAN was 1.25 mg per 100 mAh of battery capacity.

The same non-aqueous electrolyte as that described in Example 23 was injected into the electrode group in the laminate film so that the amount per battery capacity 1 Ah was 4.1 g, and the thickness was 3 mm, the width was 40 mm, and the height was 3 mm. A thin non-aqueous electrolyte secondary battery having a thickness of 70 mm was assembled.

Example 35
A positive electrode, a negative electrode and a separator similar to those described in Example 23 described above are stacked in the order of a separator, a positive electrode, a separator, and a negative electrode, and after being spirally wound so that the outermost periphery becomes a positive electrode current collector, The flattened electrode group shown in FIG. 15 described above was obtained by pressing the obtained wound product in the radial direction.

The resulting electrode group has a thickness of 2.5 mm, a length L ₁ along the longitudinal direction at 63 mm, the length L ₂ along the widthwise direction was 36 mm.

(4) A polyimide tape having a width of 40 mm and a thickness of 0.15 mm was prepared as an insulating protective sheet, and the outermost periphery of the electrode group was covered with a protective sheet so that both ends thereof were in contact with each other. Therefore, the distance X between both ends is zero.

Further, a laminate film having a thickness of 0.1 mm (100 μm) made of an aluminum foil coated on both sides with a polypropylene layer was prepared. After this laminate film was formed into a bag shape, the electrode group was housed. Subsequently, the positive electrode, the negative electrode, and the separator were integrated by applying a pressure of 15 kg / cm ² along the thickness direction of the electrode group in a vacuum atmosphere at 90 ° C.

On the other hand, lithium tetrafluoroborate (LiBF ₄ ) was dissolved in a mixed solvent of 25% by volume of ethylene carbonate (EC) and 75% by volume of γ-butyrolactone (BL) at 1.5 mol / 1 to obtain a non-aqueous electrolyte. Was prepared.

Next, a non-aqueous electrolytic solution was injected into the electrode group in the laminate film so that the amount per 4.1 Ah of battery capacity was 4.1 g, and heat-sealed under a reduced pressure of 30 Torr or less, and the thickness was 3 mm, the width was 40 mm, and the height was 3 mm. A 70-mm thin non-aqueous electrolyte secondary battery was assembled.

Examples 36 to 37
A non-aqueous electrolyte secondary battery similar to that described in Example 35 above was assembled except that the thickness of the insulating protective sheet was changed as shown in Table 6 below.

Example 38
The outermost periphery of the flat electrode group similar to that described in Example 35 described above was covered with a protective sheet similar to that described in Example 35 so as to form a gap between both ends. The distance X between both ends is 7 mm, that is, 0.20 × L ₂ .

Next, a non-aqueous electrolyte secondary battery was assembled by carrying out storage in a laminate film, press molding, injection of a liquid non-aqueous electrolyte, and heat sealing in the same manner as described in Example 35 described above.

Example 39
A non-aqueous electrolyte secondary battery similar to that described in Example 38 was assembled except that the distance X between both ends of the protective sheet was set to 14 mm, that is, 0.40 × L ₂ .

Example 40
The outermost periphery of a flat electrode group similar to that described in Example 35 described above was covered with a protective sheet similar to that described in Example 35 so that both ends overlapped by 10 mm.

Next, a non-aqueous electrolyte secondary battery was assembled by carrying out storage in a laminate film, press molding, injection of a liquid non-aqueous electrolyte, and heat sealing in the same manner as described in Example 35 described above.

Example 41
A flat electrode group similar to that described in Example 35 was coated with a protective sheet in the same manner as described in Example 35.

ラ ミ ネ ー ト Also, a laminated film having a thickness of 0.2 mm, which was made of an aluminum foil coated on both sides with a polypropylene layer, was prepared. After this laminate film was formed into a bag shape, the electrode group was housed. Subsequently, after injecting a solution of a polymer having adhesiveness and performing vacuum drying in the same manner as described in Example 34, a liquid non-aqueous electrolyte similar to that described in Example 35 was formed. The mixture was injected, heat-sealed, and a thin nonaqueous electrolyte secondary battery having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm was assembled.

Examples 42 to 43
A thin non-aqueous electrolyte secondary battery was assembled in the same manner as described in Example 41, except that the thickness of the exterior material was changed as shown in Table 6 below.

Example 44
A polypropylene tape having a width of 40 mm and a thickness of 0.2 mm was prepared as an insulative protective sheet, and the outermost periphery of the flat electrode group similar to that described in Example 35 described above was protected with protective sheets at both ends. The parts were covered so that they touched each other. Therefore, the distance X between both ends is zero.

ラ ミ ネ ー ト Also, a laminated film having a thickness of 0.1 mm, which was made of aluminum foil coated on both sides with a polypropylene layer, was prepared. After this laminate film was formed into a bag shape, the electrode group was housed. Subsequently, after injecting a solution of a polymer having adhesiveness and performing vacuum drying in the same manner as described in Example 34, a liquid non-aqueous electrolyte similar to that described in Example 35 was formed. The mixture was injected, heat-sealed, and a thin nonaqueous electrolyte secondary battery having a thickness of 3 mm, a width of 40 mm, and a height of 70 mm was assembled.

Example 45
A thin non-aqueous electrolyte secondary battery having the same configuration as in Example 44 described above except that the material of the protective sheet was changed to polyethylene resin was assembled.

Comparative Example 10
A thin non-aqueous electrolyte secondary battery having the same configuration as that described in Example 34 above was assembled except that the outermost periphery of the electrode group was a negative electrode current collector.

Comparative Example 11
A thin non-aqueous electrolyte secondary battery having the same configuration as that described in Example 34 above except that the outermost periphery of the electrode group is a negative electrode current collector, and the thickness of the exterior material is 0.7 mm. Assembled.

The obtained secondary batteries of Examples 34 to 45 and Comparative Examples 10 to 11 were charged at a charging current value of 0.5 C to 4.2 V for 5 hours, and then discharged at 0.5 C to 2.7 V. A discharge cycle test was performed to determine a discharge capacity at 300 cycles when the discharge capacity at the first cycle was set to 100%, and this is shown in Table 6 below as a capacity retention rate at 300 cycles.

Also, 20 secondary batteries of each of Examples 34 to 45 and Comparative Examples 10 to 11 were prepared and charged to 4.2 V, and then a drop test from 180 cm was performed 5 times. The number of observed batteries was measured, and the results are shown in Table 6 below.

Further, the energy densities per unit volume of the secondary batteries of Examples 34 to 45 and Comparative Examples 10 to 11 were measured, and the results are also shown in Table 6 below.

As is clear from Table 6, the secondary battery of Example 34 including the electrode group in which the two surfaces having the maximum area are the separators has a high capacity retention rate at 300 cycles, and has a low battery performance by a drop test. It can be seen that there is no abnormal battery. In addition, the secondary batteries of Examples 34 to 45 each including the electrode group in which the protective sheet was formed over the two surfaces having the largest areas had a high capacity retention rate at 300 cycles and a battery performance by a drop test. It can be seen that the number of batteries having an abnormality can be reduced.

On the other hand, the secondary battery of Comparative Example 10 including the electrode group whose outermost periphery is the negative electrode current collector has a high capacity retention rate at 300 cycles, but has an abnormal battery performance due to the drop test. It turns out that there are many. On the other hand, the secondary battery of Comparative Example 11 provided with an electrode group whose outermost periphery is a negative electrode current collector and a 0.6 mm-thick outer package has a high capacity retention rate at 300 cycles, and has a battery It can be seen that the energy density per unit volume is low, although there is no battery with abnormal performance.

Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying its components in an implementation stage without departing from the scope of the invention. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, components of different embodiments may be appropriately combined.

FIG. 1 is a schematic diagram for explaining a 180-degree peel strength method. FIG. 2 is a schematic diagram for explaining a 180-degree peel strength method. FIG. 1 is a cross-sectional view showing a thin lithium ion secondary battery as an example of a first nonaqueous electrolyte secondary battery according to the present invention. FIG. 4 is an enlarged sectional view showing a portion A in FIG. 3. FIG. 4 is a perspective view showing still another example of the electrode group incorporated in the thin lithium ion secondary battery of FIG. 3. FIG. 4 is a side view showing still another example of the electrode group incorporated in the thin lithium ion secondary battery of FIG. 3. FIG. 4 is a side view showing another example of the electrode group incorporated in the thin lithium ion secondary battery of FIG. 3. FIG. 4 is a cross-sectional view showing a thin lithium ion secondary battery as an example of a second nonaqueous electrolyte secondary battery according to the present invention. FIG. 9 is an enlarged sectional view showing a portion B in FIG. 8. FIG. 9 is a perspective view showing an electrode group incorporated in the thin lithium ion secondary battery of FIG. 8. FIG. 9 is a perspective view showing another example of the electrode group incorporated in the thin lithium ion secondary battery of FIG. 8. FIG. 9 is a sectional view showing still another example of the electrode group incorporated in the thin lithium ion secondary battery of FIG. 8. The principal part expanded sectional view of the 3rd nonaqueous electrolyte secondary battery which concerns on this invention. FIG. 9 is a perspective view showing another example of the electrode group incorporated in the third nonaqueous electrolyte secondary battery according to the present invention. FIG. 9 is a schematic diagram for explaining an electrode group incorporated in a fourth nonaqueous electrolyte secondary battery according to the present invention. FIG. 16 is an enlarged cross-sectional view showing a part C in FIG. 15.

Explanation of reference numerals

# 4: exterior material, 5: electrode group, 13: adhesive layer, 14: positive electrode lead, 15: negative electrode lead.

Claims (14)

A positive electrode including a positive electrode current collector and a positive electrode layer supported by the positive electrode current collector, a negative electrode, and a flat electrode group including a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, and comprises an exterior material having a thickness of 0.3 mm or less,
A secondary battery, wherein a positive electrode current collector is located on at least one of two surfaces having a maximum area on the surface of the electrode group. A positive electrode including a positive electrode current collector and a positive electrode layer supported by the positive electrode current collector, a negative electrode, and a flat electrode group including a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, comprising a packaging material having a thickness of 0.5 mm or less including a resin layer,
A secondary battery, wherein a positive electrode current collector is located on at least one of two surfaces having a maximum area on the surface of the electrode group. An electrode group having a structure in which a positive electrode and a negative electrode including a positive electrode current collector and a positive electrode layer supported on the positive electrode current collector are wound into a flat shape via a separator,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, comprising a packaging material having a thickness of 0.5 mm or less including a resin layer,
A secondary battery, wherein the outermost periphery of the electrode group is the positive electrode current collector. The thickness of the said electrode group is 4 mm or less, and the length ratio calculated by the following (1) formula in the said electrode group is 1.2 or more, The Claims 1-3 characterized by the above-mentioned. Secondary battery.
L ₁ / L _{2 (1)}
However, in the expression (1), L ₁ indicates a length along the longitudinal direction of the electrode group, and L ₂ indicates a length in a direction orthogonal to the longitudinal direction of the electrode group. The secondary battery according to any one of claims 1 to 3, wherein a laminated structure including the positive electrode, the negative electrode, and the separator is exposed on a side surface on a longitudinal direction side of the electrode group. . The secondary battery according to any one of claims 1 to 3, wherein a length ratio of the electrode group calculated by the following equation (1) is 1.2 or more and 5 or less.
L ₁ / L _{2 (1)}
However, in the expression (1), L ₁ indicates a length along the longitudinal direction of the electrode group, and L ₂ indicates a length in a direction orthogonal to the longitudinal direction of the electrode group. 3. The secondary battery according to claim 1, further comprising an insulating protective sheet disposed so as to straddle the two surfaces of the electrode group having the maximum area. 4. A positive electrode, a negative electrode, a flat electrode group including a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, and comprises an exterior material having a thickness of 0.3 mm or less,
A secondary battery in which separators are located on two surfaces having a maximum area on the surface of the electrode group. A positive electrode, a negative electrode, a flat electrode group including a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, comprising a packaging material having a thickness of 0.5 mm or less including a resin layer,
A secondary battery in which separators are located on two surfaces having a maximum area on the surface of the electrode group. A positive electrode, a negative electrode, and a flat electrode group including a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, and comprises an exterior material having a thickness of 0.3 mm or less,
A secondary battery, wherein an insulating protective sheet is formed so as to straddle two surfaces having a maximum area on the surface of the electrode group. A positive electrode, a negative electrode, and a flat electrode group including a separator disposed between the positive electrode and the negative electrode,
A liquid non-aqueous electrolyte impregnated in the electrode group,
The electrode group is housed, comprising a packaging material having a thickness of 0.5 mm or less including a resin layer,
A secondary battery, wherein an insulating protective sheet is formed so as to straddle two surfaces having a maximum area on the surface of the electrode group. The secondary battery according to any one of claims 7, 10 to 11, wherein the thickness of the insulating protective sheet is in a range of 0.05 to 0.5 mm. 12. The insulating protective sheet according to claim 7, wherein both ends of the insulating protective sheet are in contact with or separated from each other on the surface of the electrode group, and a distance X between both ends satisfies the following expression (2). Rechargeable battery.
0 ≦ X ≦ 0.4 × L ₃ (2)
However, L ₃ represents a circumferential direction and parallel towards the length of the protective sheet of the direction of length perpendicular to the longitudinal direction of the length and the electrode group in the longitudinal direction of the electrode group. The secondary battery according to any one of claims 1, 2, 3, 8, 9, 10, and 11, wherein the negative electrode includes lithium titanium oxide.

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