JP2003346786A - Non-aqueous electrolyte battery and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery which is superior in any of current characteristics, low temperature discharge characteristics, cycle characteristics, safety, and high temperature preservation characteristics and realizes high energy density. <P>SOLUTION: The battery comprises a negative electrode 2, a positive electrode 3, and a non-aqueous electrolyte 4, and the negative electrode 2 contains natural graphite and styrene-butadiene rubber, and the electrode density of the above negative electrode 2 is 1.68 g/cc or more and 1.85 g/cc or less. It is desirable that the above natural graphite has an amorphous layer on the surface and the thickness of the amorphous layer is 5 μm or more and 10 μm or less. It is desirable that the above negative electrode contains carboxymethylcellulose 100 ppm or less. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous electrolyte battery having a negative electrode, a positive electrode, and a non-aqueous electrolyte, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, nickel-cadmium batteries and lead batteries have been used as secondary batteries for electronic equipment. 2. Description of the Related Art In recent years, as electronic devices have become smaller and more portable with advances in electronic technology, it has become necessary to increase the energy density of secondary batteries for electronic devices. However, in nickel-cadmium batteries and lead batteries, the discharge voltage is low, and the energy density cannot be sufficiently increased.

[0003] Under such circumstances, a so-called non-aqueous electrolyte battery using a non-aqueous electrolyte as an electrolyte has recently been proposed. Above all, a non-aqueous electrolyte battery called a so-called lithium ion secondary battery has a high discharge voltage and a high energy density, and has already been put to practical use and widely used.

[0004] A lithium ion secondary battery is composed of a positive electrode and a negative electrode having an active material capable of reversibly inserting and removing lithium ions, and a non-aqueous electrolyte. Deintercalation occurs in the electrolytic solution, and progresses in the negative electrode by intercalation of lithium ions in the negative electrode active material. Conversely, when discharging, the above-described reverse reaction proceeds, and lithium ions intercalate at the positive electrode. That is, charge and discharge can be repeated by repeating a reaction in which lithium ions from the positive electrode enter and exit the negative electrode active material.

Further, research and development are still being actively conducted to further enhance the performance of this nonaqueous electrolyte battery.

[0006] A negative electrode constituting a normal non-aqueous electrolyte battery includes:
As a negative electrode active material, a carbon material capable of doping and undoping lithium ions such as graphite, and polyvinylidene fluoride as a binder are mixed to prepare a negative electrode mixture, dispersed in a solvent to form a slurry, It is applied on a negative electrode current collector made of a metal foil, and is produced through a drying / compression step.

[0007]

In recent years, power consumption has tended to increase further with the rapid increase in performance of portable electronic devices and the like. For this reason, it is urgently necessary to further increase the energy density of the nonaqueous electrolyte battery in order to satisfy the demand for long-time operation.

However, when polyvinylidene fluoride is used as a binder for the negative electrode in such a battery aimed at increasing the energy density, all of the current characteristics, low-temperature discharge characteristics, cycle characteristics, safety and high-temperature storage characteristics are reduced. It is difficult to obtain excellent effects.

Accordingly, the present invention has been proposed in view of such a conventional situation, and has a current characteristic, a low-temperature discharge characteristic,
An object of the present invention is to provide a non-aqueous electrolyte battery which is excellent in all of cycle characteristics, safety and high-temperature storage characteristics, and can realize a high energy density, and a method for manufacturing the same.

[0010]

In order to achieve the above-mentioned object, a non-aqueous electrolyte battery according to the present invention comprises a negative electrode, a positive electrode and a non-aqueous electrolyte, and the negative electrode comprises natural graphite and styrene-butadiene rubber. And the electrode density of the negative electrode is 1.68 g / cc or more and 1.85 g / cc or less.

In the non-aqueous electrolyte battery constructed as described above, since natural graphite is used for the negative electrode and styrene-butadiene rubber is used, current characteristics, low-temperature discharge characteristics, charge / discharge cycle characteristics, safety and high-temperature storage characteristics are improved. I do. Further, the electrode density of the negative electrode is 1.68 g / cc or more and 1.8 or more.
Since it is specified to be 5 g / cc or less, the volume energy density can be improved.

Further, a method for manufacturing a non-aqueous electrolyte battery according to the present invention is a method for manufacturing a non-aqueous electrolyte battery including a negative electrode, a positive electrode, and a non-aqueous electrolyte.
A mixing step of mixing natural graphite and styrene-butadiene rubber to obtain a negative electrode mixture, a coating step of coating the negative electrode mixture on a negative electrode final body to obtain a negative electrode raw material, and compressing the negative electrode raw material The electrode density of the negative electrode is 1.68 g / cc or more,
g / cc or less.

In the method for manufacturing a nonaqueous electrolyte battery as described above, by using a negative electrode prepared by defining the negative electrode material and the electrode density of the negative electrode, current characteristics, low-temperature discharge characteristics, charge / discharge cycle characteristics, safety, A nonaqueous electrolyte battery excellent in high-temperature storage characteristics and volume energy density can be manufactured.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a non-aqueous electrolyte battery to which the present invention is applied and a method for manufacturing the same will be described in detail with reference to the drawings. Hereinafter, as a non-aqueous electrolyte battery, a so-called lithium polymer secondary battery in which a negative electrode, a positive electrode, and a gel electrolyte are hermetically sealed in an outer package made of a laminate film will be described as an example.

As shown in FIGS. 1 and 2, the non-aqueous electrolyte battery 1 has a battery element 5 in which a negative electrode 2 and a positive electrode 3 are laminated via a gel electrolyte layer 4 inside an exterior film 6. It is housed and thin. The negative electrode 2 is connected to the negative electrode lead 7, and the positive electrode 3 is connected to the negative electrode lead 7. These negative electrode lead 7 and positive electrode lead 8
Exterior film 6 via resin film 9 made of resin or the like
And is drawn out of the exterior film 6.

The negative electrode 2 is manufactured by applying a negative electrode mixture containing a negative electrode active material and a binder on a negative electrode current collector and drying. As the negative electrode current collector, for example, a metal foil such as a copper foil is used.

The negative electrode 2 of the present invention has a particulate natural graphite as the negative electrode active material and styrene butadiene rubber (Styrene Butadiene Rubber: hereinafter referred to as SBR) as a binder.
And the electrode density of the negative electrode 2 is 1.68 g.
/ Cc or more and 1.85 g / cc or less. By using natural graphite as the negative electrode active material, when the negative electrode is compressed as described later, it is not less than 1/68 g / cc and 1.85 g.
/ Cc or less, an unprecedentedly high electrode density, high energy density, and improved current characteristics and low-temperature discharge characteristics. For example, when the electrode density of the negative electrode is less than 1.68 g / cc, the effect of improving the energy density, current characteristics, and low-temperature discharge characteristics is insufficient. Conversely, the electrode density of the negative electrode is 1.85
If it exceeds g / cc, the discharge capacity may decrease.

SBR used as a binder is
The reactivity with the nonaqueous electrolyte solution and the like contained in the gel electrolyte layer 4 is lower than that of polyvinylidene fluoride and the like generally used in a normal nonaqueous electrolyte battery, and gas generation is suppressed. Therefore, the nonaqueous electrolyte battery 1 has excellent current characteristics, low-temperature discharge characteristics, charge / discharge cycle characteristics, high-temperature storage characteristics, and safety.

Therefore, the non-aqueous electrolyte battery 1 of the present invention realizes a high energy density and has excellent current characteristics, low-temperature discharge characteristics, cycle characteristics, safety and high-temperature storage characteristics.

The natural graphite used here has a (002) plane spacing (d002) of 0.34 n according to the X-ray wide-angle diffraction method.
Preferably, it is less than m. By using natural graphite having high crystallinity as the negative electrode active material, high capacity is realized. For example, natural graphite having a (002) plane spacing (d002) of 0.34 nm or more measured by the X-ray wide-angle diffraction method has a large change in potential due to the release of lithium ions, and a decrease in effective capacity usable as a battery. May be caused. In addition, from the viewpoint of realizing a high capacity, the plane spacing (d00) of the (002) plane of natural graphite obtained by the X-ray
2) is more preferably 0.3354 nm or more and 0.3380 nm or less, and more preferably 0.3354 nm or more and 0.3.
More preferably, it is 3360 nm or less.

Since the above-mentioned natural graphite has very good crystallinity, it has an extremely high activity, and causes inconvenience such as generation of gas by reacting with the non-aqueous electrolyte contained in the gel electrolyte layer 4. Sometimes. So, natural graphite,
It is preferable to have a double structure having an amorphous layer composed of amorphous carbon on the surface. By covering natural graphite with high crystallinity with an amorphous layer with low crystallinity, direct contact between natural graphite and non-aqueous electrolyte is prevented, and decomposition of non-aqueous electrolyte etc. on the surface of natural graphite is prevented. Can be suppressed. As a result, generation of gas due to decomposition of the electrolytic solution and the like is suppressed,
An increase in battery internal pressure can be prevented. That is, even if the nonaqueous electrolyte battery 1 of the present invention is covered with the exterior film 6 that is easily affected by the increase in battery internal pressure, the expansion of the exterior film 6 can be suppressed.

The carbon material constituting the amorphous layer has a (002) plane spacing (d002) of 0. 0 by X-ray wide-angle diffraction.
It is preferably from 34 nm to 0.38 nm. By using such a low-crystalline carbon material for the amorphous layer, the reactivity with the non-aqueous electrolyte can be sufficiently suppressed.
X-ray wide angle diffraction method (002) plane spacing (d00)
When a carbon material having 2) less than 0.34 nm is used for the amorphous layer, the crystallinity is too high to cause a decrease in charging efficiency presumed to be caused by decomposition of the electrolytic solution, and the charge and discharge are repeatedly performed. There is a possibility that the carbon material is destroyed due to the expansion and contraction of the crystal plane spacing. Conversely, the spacing (d002) of the (002) plane determined by the X-ray wide-angle diffraction method is 0.3.
If the carbon material has a thickness of more than 8 nm, the movement of lithium ions becomes difficult, and the effective capacity usable as a battery may be reduced. From such a viewpoint, it is more preferable that the plane distance (d002) of the (002) plane of the carbon material used for the amorphous layer by X-ray wide-angle diffraction is from 0.34 nm to 0.36 nm.

The thickness of the amorphous layer is, for example, preferably from 3 μm to 20 μm, and more preferably from 5 μm to 10 μm.
m is more preferable.

Specific examples of the carbon material for the amorphous layer include an organic fired body. The amorphous layer having an organic fired body covers the surface of the natural graphite particles with a liquid organic material (for example, pitches such as a molten pitch, polymers, etc.),
It is obtained by firing at a temperature of about 500 ° C. or more and 2000 ° C. or less and carbonizing. The amorphous layer is not limited to the one formed in such a liquid phase, but may be one formed in a gas phase.

The natural graphite used for the negative electrode 2 is as follows:
In order to realize an unprecedentedly high electrode density of 1.68 g / cc or more and 1.85 g / cc or less, it is preferable that the particle size and the like are defined as follows. That is, the natural graphite preferably has a minimum particle size Dmin of 10 μm or more and a maximum particle size Dmax of 80 μm or less. The cumulative 50% particle size D50 of natural graphite is:
It is preferably 15 μm or more and 35 μm or less. If the rule regarding the particle size distribution of natural graphite is outside the above range, the energy density may be reduced. In addition, when the regulation on the particle size of natural graphite is out of the above range, particularly when it exceeds, the above-described double structure is broken when the negative electrode 2 is subjected to a compression treatment to produce the nonaqueous electrolyte battery 1. In a thin nonaqueous electrolyte battery, a high electrode density of 1.68 g / cc or more and 1.85 g / cc or less cannot be obtained.

When a negative electrode mixture for preparing the negative electrode 2 is prepared, carboxymethyl cellulose (carboxymethyl cellulose) is used as a thickening agent together with the above-mentioned natural graphite as the negative electrode active material and SBR as a binder. Hereinafter referred to as CMC) and / or CM such as CMC-Na
A C metal compound is added, and after mixing, these are mixed. When using SBR as a binder, the above-mentioned addition of CMC to the negative electrode mixture is indispensable. However, if a large amount of CMC remains in the completed negative electrode 2, battery characteristics may be impaired. Therefore, the CM in the negative electrode 2
By setting the residual amount of C to 100 ppm or less, it is possible to prevent deterioration in battery characteristics such as initial charge / discharge efficiency, current characteristics, low-temperature discharge characteristics, and charge / discharge cycle characteristics. Negative electrode 2
As a method for removing CMC from carbon, it is preferable to adopt a method of carbonizing CMC by heat treatment as described later.

Next, the configuration of the nonaqueous electrolyte battery 1 other than the negative electrode 2 will be described.

The positive electrode 3 is manufactured by applying a positive electrode mixture containing a positive electrode active material and a binder on a positive electrode current collector and drying. As the positive electrode current collector, for example, a metal foil such as an aluminum foil is used.

As the positive electrode active material, a chalcogen compound of a transition metal containing an alkali metal, among which an oxide of the alkali metal and the transition metal can be used. The crystal structure of the compound is generally a layered compound or a spinel type compound. Specifically, a general formula A as a positive electrode active material
_{x MyO 2} (where A is one selected from Li, Na and K. Also, 0.5 ≦ x ≦ 1.1. M is Fe, Co, Ni, Mn, Cu , Zn, Cr, V, T
It is at least one selected from the group consisting of i, Al, Sn, B, Ga, Mg, Ca, and Sr. It is preferable to use the compound represented by the formula: In addition, the positive electrode active material is not limited to the above example, and any known materials used for this type of nonaqueous electrolyte battery can be used.

As the binder in the positive electrode 3, for example, polyvinylidene fluoride or the like can be used. The positive electrode 3
May contain a conductive material, an additive, and the like, if necessary, in addition to the above-described positive electrode active material and binder.

Next, the gel electrolyte layer 4 will be described. The gel electrolyte has a role as an ion conductor between the negative electrode 2 and the positive electrode 3. The gel electrolyte layer 4 contains an electrolyte salt, a matrix polymer, and a swelling solvent as a plasticizer.

As the electrolyte salt, LiPF ₆ , LiBF
₄ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO
₂ ) Lithium compounds such as ₂ and LiCF ₃ SO ₃ can be used alone or in combination. Among them, it is preferable to use LiPF ₆ from the viewpoint of ion conductivity.

The matrix polymer refers to a polymer alone or a gel electrolyte using the same at room temperature of 1 mS / cm.
The chemical structure is not particularly limited as long as it has the above ionic conductivity. As a specific matrix polymer, a compound containing at least one of vinylidene fluoride, acrylonitrile, ethylene oxide, propylene oxide, and methacrylonitrile as a repeating unit is used. Specifically, polyvinylidene fluoride,
Examples thereof include polyacrylonitrile, polyethylene oxide, polypropylene oxide, and polymethacrylonitrile.

Examples of the swelling solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, γ-butyrolactone, ethyl propyl carbonate, dipropyl carbonate, butyl propyl carbonate, dibutyl carbonate and 1,2-dimethoxy carbonate. Non-aqueous solvents such as ethane and 1,2-diethoxyethane can be used alone or in combination.

The exterior film 6 includes, for example, an exterior protection layer,
It is formed of a laminate film composed of a metal layer and a heat welding layer (sealant layer). Exterior protective layer and / or
Or, as a plastic material usable for the sealant layer, polyethylene terephthalate (Poly Ethylene Tere
phthalate: PET), molten polypropylene (Polypropy)
lene: PP), undrawn polypropylene (Cast Polypropy)
lene: CPP), polyethylene: P
E), Low Density Polyethylen
e: LDPE), high density polyethylene (High Density Po)
lyethylene: HDPE), Linear Low Density Polyethylene (LLDPE),
Polyamide (Ny) is exemplified. Also. Aluminum (hereinafter, AL) is preferably used for the metal layer, but it is of course possible to use another metal that has moisture resistance and can function as a barrier film.

The most general configuration of the exterior film 6 is as follows: exterior protective layer / metal layer / sealant layer = PET / AL / PE
It is. In addition, the present invention is not limited to this combination, and may have the following configuration or the like. That is, Ny / AL /
CPP, PET / AL / CPP, PET / AL / PET
/ CPP, PET / Ny / AL / CPP, PET / Ny
/ AL / Ny / CPP, PET / Ny / AL / Ny / P
E, Ny / PE / AL / LLDPE, PET / PE / A
L / PET / LDPE, PET / Ny / AL / LLDP
E and the like.

As the negative electrode lead 7, for example, a metal foil such as nickel can be used. Further, as the positive electrode lead 8, for example, a metal foil such as aluminum can be used.

The non-aqueous electrolyte battery 1 as described above
Is manufactured as follows.

First, when producing the negative electrode 2, natural graphite as a negative electrode active material, SBR as a binder, and CMC or a metal compound of CMC as a thickener were sufficiently mixed. Is prepared. Known additives and the like may be added to the negative electrode mixture. The obtained negative electrode mixture is uniformly applied onto a metal foil such as a copper foil, for example, serving as a negative electrode current collector, and dried to prepare a negative electrode material.

Next, the negative electrode raw material is compressed at a predetermined pressure so that the electrode density after compression is 1.68 g / cc or more and 1.8 or more.
It should be 5 g / cc or less. At this time, a commonly known negative electrode active material (for example, mesocarbon microbeads:
It is necessary to set compression conditions more carefully than in the case where MCMB is used, and take care not to break the double structure of the double structure graphite described above, for example. For example, when the negative electrode raw material is compressed by a roller, attention should be paid to conditions such as a pressing speed, a roller curvature, a tension, a dried state of the negative electrode raw material before compression (solvent remaining amount), and a pressing temperature. .

Next, a gel electrolyte layer 4 is formed on the negative electrode active material layer.
To form To form the gel electrolyte layer 4, first,
A non-aqueous electrolyte is prepared by dissolving an electrolyte salt in a non-aqueous solvent. Then, a matrix polymer is added to the non-aqueous electrolyte, and the mixture is stirred well to dissolve the matrix polymer to obtain a sol electrolyte solution.

Next, a predetermined amount of this electrolyte solution is applied on the negative electrode active material. Subsequently, the matrix polymer is gelled by cooling at room temperature, and the gel electrolyte layer 4 is formed on the negative electrode active material.

Here, a heat treatment was performed on the negative electrode raw material to carbonize the CMC, and the residual amount of CMC in the negative electrode was 100 pp.
The CMC is removed so as to be not more than m. The heat treatment temperature at the time of carbonizing CMC is preferably 200 ° C. or higher.
The temperature is preferably 250 ° C. or higher from the viewpoint of carbonizing C surely. However, from the viewpoint of sufficiently maintaining the binding property of the SBR, the heat treatment temperature at the time of carbonizing the CMC is preferably equal to or lower than an extent not damaging the SBR used as the binder. The heat treatment time is not particularly limited as long as the carbonization of the CMC is sufficiently advanced, but it requires several hours to about one day. Also,
If oxygen is present during the heat treatment, the SBR may be oxidized at a low temperature before the carbonization of the CMC. Therefore, it is preferable to carbonize the CMC in a vacuum or an inert atmosphere.

Next, the negative electrode raw material is cut into a rectangular shape. Then, the negative electrode lead 7 is welded to a portion of the negative electrode current collector where the negative electrode active material layer is not formed, to obtain the negative electrode 2.

In preparing the positive electrode 3, a positive electrode mixture is prepared by mixing a positive electrode active material and a binder. The obtained negative electrode mixture is uniformly coated on a metal foil such as an aluminum foil serving as a positive electrode current collector and dried to form a positive electrode active material layer, thereby preparing a positive electrode raw material. As the binder of the positive electrode mixture, in addition to known binders,
Known additives and the like can be added to the positive electrode mixture.

Next, a gel electrolyte layer 4 is formed on the positive electrode active material layer.
To form To form the gel electrolyte layer 4, first,
A non-aqueous electrolyte is prepared by dissolving an electrolyte salt in a non-aqueous solvent. Then, a matrix polymer is added to the non-aqueous electrolyte, and the mixture is stirred well to dissolve the matrix polymer to obtain a sol electrolyte solution.

Next, a predetermined amount of the electrolyte solution is applied on the positive electrode active material. Subsequently, the matrix polymer is gelled by cooling at room temperature, and the gel electrolyte layer 4 is formed on the positive electrode active material.

Next, the positive electrode raw material is cut into a rectangular shape. Then, the positive electrode lead 8 is welded to a portion where the positive electrode active material layer is not formed. Thus, the positive electrode 3 is obtained.

Then, the rectangular negative electrode 2 and the positive electrode 3 produced as described above are bonded together with the gel electrolyte layer 4 interposed therebetween and pressed to obtain a battery element 5.

Finally, the battery element 5 is sandwiched between the outer films 6 made of an insulating material, the outer peripheral edge of the outer film 6 is sealed, and the negative electrode lead 8 and the positive electrode lead 9 are interposed via the resin film 9. The battery element 5 is sealed in the exterior film 6 while being sandwiched between the sealing portions of the exterior film 6.
Furthermore, in the state packed by the exterior film 6,
Heat treatment is performed on the battery element 5. As described above, the nonaqueous electrolyte battery 1 is completed.

In the above-described embodiment, the case where the negative electrode 2 and the positive electrode 3 cut into a rectangular shape are stacked to form the battery element 5 has been described as an example, but the present invention is not limited to this. Instead, the present invention is also applicable to a case where the negative electrode 2 and the positive electrode 3 cut out in a band shape are laminated and wound in the longitudinal direction to form a battery element, or a case where the battery element is alternately folded.

In the above-described embodiment, a so-called lithium polymer secondary battery using a gel electrolyte as the non-aqueous electrolyte has been described as an example. However, for example, lithium ion conductivity such as lithium nitride and lithium iodide can be improved. Any known solid electrolyte such as an inorganic solid electrolyte having the same can be used. Further, the present invention can of course be applied to a non-aqueous electrolyte battery using a non-aqueous electrolyte as a non-aqueous electrolyte.

Further, in FIGS. 1 and 2, a flat and thin non-aqueous electrolyte battery in which a battery element is sealed in a laminate film is described as an example, but the non-aqueous electrolyte battery of the present invention is not limited to this. For example, it may be a square type, a cylindrical type, a coin type, a button type, or the like in a state where an electric element is sealed in a battery can. In addition, the shape is not limited, and it can be any size such as large or small. However, in order to obtain the maximum effect of the present invention, as shown in FIGS. 1 and 2, a non-aqueous electrolyte having a structure in which a thin battery element is sealed with a flexible outer material such as a laminate film or the like. Preferably, it is a battery.

The non-aqueous electrolyte battery may be a primary battery or a secondary battery.

[0055]

EXAMPLES Specific examples to which the present invention is applied will be described below based on experimental results.

[Experiment 1] First, the effects of the negative electrode active material and the binder used for the negative electrode were evaluated.

[0057]Comparative Example 1 The negative electrode can be manufactured as follows. First, the following composition
The suspension was mixed with a disper for 4 hours,
Was prepared. This is used as a negative electrode current collector and has a thickness of 10 μm.
Was uniformly applied to both surfaces of the copper foil to obtain a negative electrode raw material. Further
Then, the negative electrode material was pressed at a linear pressure of 300 kg / cm
And the electrode density is 1.6 g / c.
c.

Anode mix slurry composition Mesocarbon microbeads: 100 parts by weight Polyvinylidene fluoride (average molecular weight 300,000): 6 parts by weight N-methyl-2-pyrrolidone: 100 parts by weight

The positive electrode was manufactured as follows.
First, a suspension of the following composition was mixed with a disper for 4 hours.
Thus, a positive electrode mixture slurry was prepared. This is called the positive electrode current collector.
And apply a pattern coating on both sides of a 20 μm thick aluminum foil
Then, a raw material for a positive electrode was obtained. The coating pattern should be
With a cloth length of 160 mm and an uncoated portion length of 30 mm
And the start and end positions of both sides match
Control was performed. Furthermore, the positive electrode raw material is subjected to a linear pressure of 30.
Press at 0kg / cm and make the thickness after pressing 120μm
And the electrode density was 3.4 g / cc. Here,
LiCoO used ₂Has an average particle size of 10 μm,
Small particle size is 5μm, maximum particle size is 18μm, ratio
0.25m surface area²/ G.

Positive electrode mixture slurry composition LiCoO ₂ : 100 parts by weight Polyvinylidene fluoride (average molecular weight 300,000): 5 parts by weight ECP (Ketjen black): 10 parts by weight N-methyl-2-pyrrolidone: 100 parts by weight

A gel electrolyte layer was formed on the negative electrode raw material and the positive electrode raw material as described above. First, a composition for a gel electrolyte layer containing an electrolytic solution having the following composition was mixed for 1 hour by a disper under heating at 70 ° C. Next, this composition was pattern-coated on both surfaces of the negative electrode raw material so as to have a layer thickness of 20 μm, and dried with a dryer. Similarly to the negative electrode raw material, this composition was pattern-coated on both surfaces of the positive electrode raw material so as to have a layer thickness of 20 μm, and dried with a dryer. In the dryer, the electrode preheating device was set at a predetermined temperature (for example, 60 ° C.) and adjusted so that substantially only dimethyl carbonate was evaporated.

Composition for Gel Electrolyte Layer Containing Electrolyte Poly (hexafluoropropylene-vinylidene fluoride)
Copolymer: 5 parts by weight Dimethyl carbonate: 75 parts by weight Electrolyte (LiPF ₆ : 1 mol / l): 20 parts by weight. Poly (hexafluoropropylene-vinylidene fluoride)
The content of hexafluoropropylene in the copolymer is 6 parts by weight. The solvent used for the electrolytic solution was ethylene carbonate: propylene carbonate = 4: 1.

Next, the negative electrode raw material on which the gel electrolyte layer was formed was cut into a width of 51.5 mm, and the strip-shaped negative electrode was wound around the hub many times to produce a pancake of the negative electrode. In addition, the positive electrode raw material on which the gel electrolyte layer was formed was cut into a width of 50 mm, and the band-shaped positive electrode was wound around the hub many times to produce a positive electrode pancake.

Next, the strip-shaped negative electrode was rewound from the negative electrode pancake, cut into a predetermined length to obtain a rectangular negative electrode, and the negative electrode lead was welded. Further, the strip-shaped positive electrode was rewound from the positive electrode pancake, cut into a predetermined length to obtain a rectangular positive electrode, and the positive electrode lead was welded.

Next, the cut negative electrode and positive electrode were bonded together with their gel electrolyte layers facing each other, and then pressed to produce a battery element.

The battery element was covered with a laminate film and the periphery thereof was thermally welded to obtain a flat nonaqueous electrolyte battery as shown in FIGS. The laminate film has a laminated structure of nylon / aluminum / unstretched polypropylene and has a nylon film thickness of 3
One having a thickness of 0 μm, a thickness of aluminum of 40 μm, and a thickness of unstretched polypropylene of 30 μm was used.

[0067]Comparative Example 2 Use the negative electrode mixture slurry of the following composition to
Except for producing the pole, the same as in Comparative Example 1 described above
A non-aqueous electrolyte battery was manufactured. The natural black used here
Lead a has a minimum particle size Dmin of 11 μm and a maximum particle size of
Dmax is 78 μm, and cumulative 10% particle size D10 is 1
5 μm, and the cumulative 50% particle size D50 is 25 μm.
The cumulative 90% particle size is 34 μm. Also here for
Natural graphite a was (002) plane by X-ray wide-angle diffraction
With a plane spacing (d002) of 0.3358 nm
Low crystallinity formed in the gas phase on a highly graphite surface
It has a double structure with an amorphous layer. In addition, this amorphous
The layer is 6 μm thick.

Anode mix slurry composition Natural graphite a: 100 parts by weight Polyvinylidene fluoride (average molecular weight 300,000): 6 parts by weight N-methyl-2-pyrrolidone: 100 parts by weight

[0069]Example 1 Use the negative electrode mixture slurry of the following composition to
The pole was made. The thickness after pressing is 103 μm.
And the negative electrode substrate so that the electrode density becomes 1.67 g / cc.
Was pressed. Furthermore, the negative electrode substrate is cut and the negative electrode pan is cut.
After making the cake, the pancake is heat-treated
To carbonize the CMC. Specifically, the pancake is vacuumed
After installing in the oven, the inside of the vacuum oven is 13.3Pa
The temperature was raised from room temperature to 120 ° C.
After holding for 5 hours, it is cooled to 80 ° C. or less in a vacuum,
I took it out. As a result, the residual amount of CMC in the negative electrode is
It became 1000 ppm. Except for these differences,
A non-aqueous electrolyte battery was produced in the same manner as in Comparative Example 1.

Anode mix slurry composition Natural graphite a: 100 parts by weight SBR: 3 parts by weight CMC-Na: 3 parts by weight H ₂ O: 100 parts by weight

[0071]Example 2 When manufacturing the negative electrode, the thickness after pressing is 103 μm.
And the negative electrode substrate so that the electrode density becomes 1.68 g / cc.
Was pressed. Furthermore, the negative electrode substrate is cut and the negative electrode pan is cut.
After making the cake, the pancake is heat-treated
To carbonize the CMC. Specifically, the pancake is vacuumed
After installing in the oven, the inside of the vacuum oven is 13.3Pa
The temperature was raised from room temperature to 180 ° C.
After holding for 5 hours, it is cooled to 80 ° C. or less in a vacuum,
I took it out. As a result, the residual amount of CMC in the negative electrode is
It became 200 ppm. Except for these differences,
A non-aqueous electrolyte battery was produced in the same manner as in Example 1.

[0072]Example 3 When manufacturing the negative electrode, the thickness after pressing is 106 μm.
And the negative electrode substrate so that the electrode density becomes 1.63 g / cc.
Was pressed. Furthermore, the negative electrode substrate is cut and the negative electrode pan is cut.
After making the cake, the pancake is heat-treated
To carbonize the CMC. Specifically, the pancake is vacuumed
After installing in the oven, the inside of the vacuum oven is 13.3Pa
The temperature was raised from room temperature to 200 ° C.
After holding for 5 hours, it is cooled to 80 ° C. or less in a vacuum,
I took it out. As a result, the residual amount of CMC in the negative electrode is
It became 100 ppm. Except for these differences,
A non-aqueous electrolyte battery was produced in the same manner as in Example 1.

[0073]Example 4 When manufacturing the negative electrode, the thickness after pressing is 104 μm.
And the negative electrode substrate so that the electrode density becomes 1.68 g / cc.
Was pressed. Furthermore, the negative electrode substrate is cut and the negative electrode pan is cut.
After making the cake, the pancake is heat-treated
To carbonize the CMC. Specifically, the pancake is vacuumed
After installing in the oven, the inside of the vacuum oven is 13.3Pa
The temperature was raised from room temperature to 200 ° C.
After holding for 5 hours, it is cooled to 80 ° C. or less in a vacuum,
I took it out. As a result, the residual amount of CMC in the negative electrode is
It became 100 ppm. Except for these differences,
A non-aqueous electrolyte battery was produced in the same manner as in Example 1.

[0074]Example 5 When manufacturing the negative electrode, the thickness after pressing is 94 μm.
And the negative electrode substrate so that the electrode density becomes 1.85 g / cc.
Was pressed. Furthermore, the negative electrode substrate is cut and the negative electrode pan is cut.
After making the cake, the pancake is heat-treated
To carbonize the CMC. Specifically, the pancake is vacuumed
After installing in the oven, the inside of the vacuum oven is 13.3Pa
The temperature was raised from room temperature to 200 ° C.
After holding for 5 hours, it is cooled to 80 ° C. or less in a vacuum,
I took it out. As a result, the residual amount of CMC in the negative electrode is
It became 100 ppm. Except for these differences,
A non-aqueous electrolyte battery was produced in the same manner as in Example 1.

[0075]Example 6 When manufacturing the negative electrode, the thickness after pressing is 90 μm.
And the negative electrode substrate so that the electrode density becomes 1.95 g / cc.
Was pressed. Furthermore, the negative electrode substrate is cut and the negative electrode pan is cut.
After making the cake, the pancake is heat-treated
To carbonize the CMC. Specifically, the pancake is vacuumed
After installing in the oven, the inside of the vacuum oven is 13.3Pa
The temperature was raised from room temperature to 200 ° C.
After holding for 5 hours, it is cooled to 80 ° C. or less in a vacuum,
I took it out. As a result, the residual amount of CMC in the negative electrode is
It became 100 ppm. Except for these differences,
A non-aqueous electrolyte battery was produced in the same manner as in Example 1.

The following table shows the thickness of the negative electrode, the electrode density of the negative electrode, and the amount of CMC remaining in the negative electrode of the non-aqueous electrolyte batteries of Comparative Examples 1 and 2 and Examples 1 to 6 prepared as described above. It is shown in FIG.

[0077]

[Table 1]

Of the non-aqueous electrolyte batteries thus produced, the current characteristics of Comparative Example 2 using polyvinylidene fluoride as a binder and Example 3 using SBR as a binder were as follows.
The low-temperature discharge characteristics, charge-discharge cycle characteristics, safety, and high-temperature storage characteristics were each tested and evaluated.

(1) Current Characteristics The nonaqueous electrolyte batteries of Comparative Example 2 and Example 3 were charged at a constant current and a constant voltage at a test temperature of 23 ° C. That is,
First, constant-current charging was performed at 1 C = 0.8 A up to a maximum voltage of 4.2 V, and thereafter, the battery was held at 4.2 V for 2.5 hours to be fully charged.

Next, 0.2C = 0.16A, 2C = 1.
Constant current discharge was performed at 6A and 3C = 2.4A, and the respective discharge capacities were measured. Further, the ratio of the discharge capacity at the 3C discharge to the discharge capacity at the 0.2C discharge was expressed as a maintenance ratio. Table 2 below shows the discharge capacities and the retention rates at 0.2 C discharge, 2 C discharge, and 3 C discharge measured as described above.

[0081]

[Table 2]

From Table 2 above, it was found that SB was used as the binder for the negative electrode.
It was found that by using R, a high discharge capacity can be maintained even under heavy load discharge conditions such as 3C discharge.

(2) Low-Temperature Discharge Characteristics Comparative Example 2 was performed in the same manner as in the evaluation of the current characteristics described above.
And the nonaqueous electrolyte battery of Example 3 was fully charged.

Next, discharge was performed at 1 C = 0.8 A up to 3.0 V at each environmental temperature of 23 ° C., 0 ° C., and −20 ° C., and the discharge capacity at this time was measured. The ratio of the discharge capacity at −20 ° C. to the discharge capacity at an environmental temperature of 23 ° C. was expressed as a maintenance rate. 23 measured as above
Table 3 below shows the discharge capacity and the maintenance rate at each environmental temperature of 0 ° C, 0 ° C, and -20 ° C.

[0085]

[Table 3]

From Table 3 above, it was found that SB was used as the binder for the negative electrode.
It has been found that the use of R can maintain a higher discharge capacity in a low-temperature environment such as -20 ° C. than in Comparative Example 2 using polyvinylidene fluoride as a binder.

(3) Charge / Discharge Cycle Characteristics First, Comparative Example 2 was performed in the same manner as in the evaluation of the current characteristics described above.
And the nonaqueous electrolyte battery of Example 3 was fully charged. Next, at an ambient temperature of 23 ° C., 1 C = 0.8 A up to 3.0 V.
Was discharged. This charge and discharge is one cycle,
The discharge capacities at the first cycle, the 100th cycle, and the 400th cycle were measured, respectively. Further, the ratio of the discharge capacity at the 400th cycle to the discharge capacity at the first cycle was represented as a retention ratio. Table 4 below shows the discharge capacity and the retention rate at the first cycle, the 100th cycle, and the 400th cycle measured as described above.

[0088]

[Table 4]

From Table 4 above, it was found that SB was used as the binder for the negative electrode.
It has been found that the use of R can suppress the deterioration of the discharge capacity due to the charge / discharge cycle.

(4) Safety First, a comparative example 2 was made in the same manner as in the evaluation of the current characteristics described above.
And the nonaqueous electrolyte battery of Example 3 was fully charged.

Next, the nonaqueous electrolyte battery and the test jig were held at the test temperatures of 23 ° C. and 55 ° C. for 1 hour within 2 hours after the completion of the charging. Next, a 2.5 mm diameter stainless steel nail with a sharply polished tip was vertically pierced into the center of the battery and penetrated, and the maximum temperature of the battery was measured with a K thermocouple attached to the battery surface. The maximum temperatures of the battery at 23 ° C. and 55 ° C. measured as described above are shown in Table 5 below.

[0092]

[Table 5]

From Table 5 above, it was found that SB was used as the binder for the negative electrode.
It has been found that by using R, even when the environmental temperature is high, heat generation of the battery at the time of abnormality can be minimized.

(5) High-Temperature Storage Characteristics First, the non-aqueous electrolyte batteries of Comparative Examples 1, 2 and 3 were fully charged in the same manner as in the evaluation of the current characteristics described above. Next, discharge was performed to 3.0 V at 0.2 C = 0.8 A, and the discharge capacity at this time was defined as the discharge capacity before the storage test. At this time, the thickness of the battery was measured.

Next, the battery after the above-mentioned measurement of the discharge capacity and the battery thickness was stored in a constant temperature bath at 60 ° C. for one week. After the storage was completed, the nonaqueous electrolyte battery was taken out of the thermostat, and after 3 hours, the battery thickness was measured with the battery temperature returned to room temperature (23 ° C.).

Next, these non-aqueous electrolyte batteries were discharged at 3.0 C = 0.8 A down to 3.0 V. Further, at a test temperature of 23 ° C., a maximum voltage of 4.2 V is set to 0.8 V.
A constant-current charging at A, followed by a 2.5-hour hold at 4.2 V and a discharge to 3.0 V at 0.2 C = 0.8 A, where 5 cycles of charging and discharging The discharge capacity in each cycle was measured repeatedly, and the maximum discharge capacity among these discharge capacities was defined as the recovery capacity. Table 6 below shows the battery thickness and discharge capacity before storage test, and the battery thickness and recovery capacity after storage at 60 ° C. for one week, measured as described above.

[0097]

[Table 6]

[0098] From Table 6 above, in Example 3 using SBR as the binder and natural graphite as the negative electrode active material, the expansion of the battery after high temperature storage was suppressed, and
High discharge capacity could be maintained. On the other hand, in Comparative Example 1 in which MCBR was used as the negative electrode active material but SBR was used as the binder, and Comparative Example 2 in which natural graphite was used as the negative electrode active material and polyvinylidene fluoride was used as the binder, And the capacity was remarkably deteriorated.

Therefore, from Experiment 1, the use of natural graphite as the negative electrode active material and SBR as the binder provided current characteristics, low-temperature discharge characteristics, charge / discharge cycle characteristics,
It has been found that safety and high-temperature storage characteristics can be improved.

[Experiment 2] In Experiment 2, in order to examine the optimum range of the electrode density of the negative electrode, the following Examples 3 to 6 were used.
The non-aqueous electrolyte battery was tested for volume energy density, current characteristics and low-temperature discharge characteristics.

(6) Volume Energy Density First, the non-aqueous electrolyte batteries of Examples 3 to 6 were fully charged in the same manner as in (1) Evaluation of current characteristics described above.

Next, the battery was discharged at 3.0 V at 0.2 C = 0.16 A, the discharge capacity at this time was measured, and the volume energy density was calculated. After the measurement, the battery thickness was measured. The results are shown in Table 7 below. Also,
FIG. 3 is a diagram in which the horizontal axis represents the electrode density of the negative electrode and the vertical axis represents the volume energy density.

[0103]

[Table 7]

From the results shown in Table 7 and FIG.
And Example 5 showed a high volume energy density, while Examples 3 and 6 showed a remarkable decrease in volume energy density.

In Experiment 1, (1) current characteristics and (2)
Under the same test conditions as the low-temperature discharge characteristics, current characteristics and low-temperature discharge characteristics were evaluated. The results of the current characteristics are shown in Table 8 below and FIG. The results of the low temperature characteristics are shown in Table 9 below and FIG.

[0106]

[Table 8]

[0107]

[Table 9]

From the above Table 8 and FIG. 4, it was found that Examples 3 to 6 can maintain a high discharge capacity even under heavy load discharge conditions. Further, from Table 9 and FIG. 5, it was found that in Examples 3 to 6, a high discharge capacity could be maintained even in a low temperature environment of −20 ° C.

Therefore, from the results of Experiment 2, by setting the electrode density of the negative electrode within the range of 1.68 g / cc or more and 1.85 g / cc or less, all of the volume energy density, current characteristics, and low-temperature discharge characteristics were obtained. It was found that it could be improved.

[Experiment 3] In Experiment 3, in order to examine the residual amount of CMC, Examples 1, 2 and 4 were used.
The first charge / discharge efficiency, current characteristics, low-temperature discharge characteristics, charge / discharge cycle characteristics, and battery thickness of the nonaqueous electrolyte battery of Example 1 were tested.

(7) Initial Charge / Discharge Efficiency First, the non-aqueous electrolyte batteries of Examples 1, 2 and 4 were subjected to constant current constant voltage charging at a test temperature of 23 ° C. That is, first, 5C =
Constant current charging was performed at 0.8 A, and thereafter, the battery was held at 4.2 V for 10 hours, and the charging capacity at this time was measured. Next, these non-aqueous electrolyte batteries were discharged at 0.2 C = 0.16 A, and the discharge capacity at this time was measured. The ratio of the discharge capacity to the charge capacity was calculated as the charge / discharge efficiency. The above results are shown in Table 10 below.

[0112]

[Table 10]

From the results shown in Table 10 above, it was found that the charge / discharge efficiency tended to increase as the residual amount of CMC decreased.

The current characteristics were evaluated under the same test conditions as (1) Current Characteristics in Experiment 1. The results are shown in Table 11 below.
Shown in

[0115]

[Table 11]

From the results shown in Table 11, it was found that in Example 4 in which the residual amount of CMC was 100 ppm or less, the current characteristics were remarkably improved.

Further, the low-temperature discharge characteristics were evaluated under the same test conditions as (2) the low-temperature discharge characteristics in Experiment 1. The results are shown in Table 12 below.

[0118]

[Table 12]

From the results in Table 12 above, it was found that the discharge capacity at low temperatures tends to improve as the residual amount of CMC decreases.

Further, the charge / discharge cycle characteristics were evaluated under the same conditions as (3) charge / discharge cycle characteristics in Experiment 1. The results are shown in Table 13 below.

[0121]

[Table 13]

From the results in Table 13 above, it was found that in Example 4 in which the residual amount of CMC was 100 ppm or less, the charge / discharge cycle characteristics were significantly improved.

(8) Battery Thickness First, Examples 1 and 2 in an uncharged state immediately after assembly
And the battery thickness of the nonaqueous electrolyte battery of Example 4 was measured.
Next, these non-aqueous electrolyte batteries were subjected to constant current and constant voltage charging at a test temperature of 23 ° C. That is, first, constant current charging was performed at 0.2 C = 0.16 A up to a maximum voltage of 4.2 V, and thereafter, the battery was held at 4.2 V for 10 hours to be in a fully charged state. The battery thickness at this time was measured. Next, with respect to these nonaqueous electrolyte batteries, 3.0 at 0.2C = 0.16A was used.
The battery was discharged to V (complete discharge), and the battery thickness at this time was measured. Further, these non-aqueous electrolyte batteries were aged, and were discharged (semi-discharged) at 1 C = 0.1 A for 0.5 hour. Table 14 below shows the measurement results of the battery thickness in the uncharged state, the fully charged state after the initial charge, the completely discharged state, and the half-discharged state after aging, which were measured as described above.

[0124]

[Table 14]

From the results shown in Table 14, it was found that the expansion and shrinkage due to the charge and discharge of the battery was suppressed with the decrease in the residual amount of CMC.

Therefore, from the results of Experiment 3, from the viewpoint of satisfying all of the initial charge / discharge efficiency, current characteristics, low temperature discharge characteristics, charge / discharge cycle characteristics and battery thickness, the residual amount of CMC in the negative electrode was 100 ppm or less. Was found to be preferable.

[Experiment 4] In Experiment 4, the optimum range of the particle size distribution of natural graphite and the provisions regarding the amorphous layer were examined.

In addition to the natural graphite a used in Experiments 1 to 3 above, natural graphite b to natural graphite g as shown in Table 15 below were prepared and used as the negative electrode active material. A flat nonaqueous electrolyte battery was produced in the same manner as in the example. The method for producing the graphite serving as the nucleus of the natural graphite b to the natural graphite g and the amorphous layer of the natural graphite b to the natural graphite f are the same as those of the natural graphite a.

Here, the press output was increased in the negative electrode compression step at the time of the production of the negative electrode, and the thickness of the negative electrode at the limit at which cracks occurred in the negative electrode current collector was measured. Further, the electrode density of the negative electrode at the limit at which the crack was formed and the energy density of the nonaqueous electrolyte battery assembled using the negative electrode were obtained. Further, the thickness, electrode density, and energy density of the negative electrode were determined in the same manner, except that the copper foil having a thickness of 20 μm was replaced with a copper foil having a thickness of 20 μm as a negative electrode current collector. The results are shown in Table 16 below.

[0130]

[Table 15]

[0131]

[Table 16]

From the above results of Tables 15 and 16, when the natural graphite serving as a nucleus is a non-double-structured natural graphite g of graphite having high crystallinity and amorphous on its surface, the energy density of This resulted in a significant drop. The cause is considered to be that gas was generated due to decomposition of the solvent during charging, and the battery thickness became extremely large. However, in the case of natural graphite e and natural graphite f in which the film thickness of the amorphous layer was too small, the energy density was conversely reduced. From this, there is an optimum range for the thickness of the amorphous layer, which is more than 4 μm and 12 μm.
It has been found that it is preferably less than m. Note that a particularly preferable range of the thickness of the amorphous layer is 5 μm or more,
μm or less.

When natural graphite having a large particle size such as natural graphite d was used, a high electrode density was not obtained when the thickness of the active material layer was relatively reduced, and the energy density was lowered. Natural graphite c having a cumulative 50% particle size D50 of 12 μm and natural graphite d having a cumulative 50% particle size D50 of 40 μm have an insufficient effect of improving the energy density as compared with natural graphite a and natural graphite b. there were. Therefore, it was found that the optimum range of the cumulative 50% particle size D50 is preferably more than 12 μm and less than 40 μm. Note that a particularly preferred 50% cumulative particle size D50 is 15%.
It is not less than μm and not more than 35 μm.

[0134]

As is clear from the above description, according to the present invention, the current characteristics, low-temperature discharge characteristics, charge / discharge cycle characteristics,
It is possible to realize a nonaqueous electrolyte battery excellent in all of safety, high-temperature storage characteristics, and volume energy density.

Further, according to the present invention, by selecting an optimum negative electrode material and setting the electrode density of the negative electrode within a predetermined range, current characteristics, low temperature discharge characteristics, charge / discharge cycle characteristics, safety, high temperature A non-aqueous electrolyte battery excellent in all of storage characteristics and volume energy density can be manufactured.

[Brief description of the drawings]

FIG. 1 is a plan view of a nonaqueous electrolyte battery to which the present invention is applied.

FIG. 2 is a schematic sectional view of the nonaqueous electrolyte battery shown in FIG.

FIG. 3 is a characteristic diagram showing a relationship between an electrode density and a volume energy density of a negative electrode.

FIG. 4 is a characteristic diagram showing a relationship between an electrode density of a negative electrode and current characteristics.

FIG. 5 is a characteristic diagram showing a relationship between an electrode density of a negative electrode and low-temperature discharge characteristics.

[Explanation of symbols]

1 Non-aqueous electrolyte battery 2 Negative electrode 3 Positive electrode 4 Gel electrolyte layer 5 Battery element 6 Exterior film 7 Negative electrode lead 8 Positive electrode lead 9 Resin film

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) H01M 10/40 H01M 10/40 Z F Term (Reference) 5H011 AA03 AA13 CC02 CC06 CC10 DD13 5H029 AJ02 AJ03 AJ04 AJ05 AJ12 AK03 AL07 AM03 AM04 AM05 AM07 AM16 BJ04 BJ12 CJ02 CJ03 CJ05 CJ08 CJ22 DJ02 DJ08 DJ18 EJ04 EJ12 HJ02 HJ04 HJ05 HJ08 HJ13 HJ14 5H050 AA06 AA07 AA08 AA10 AA15 BA17 BA18 CA07 CB08 DA03 DA09 FA11 GA02 FA03 HA13 HA14

Claims (14)

[Claims] 1. A negative electrode comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte, wherein the negative electrode contains natural graphite and styrene-butadiene rubber, and has an electrode density of 1.68 g / cc.
As described above, the non-aqueous electrolyte battery is not more than 1.85 g / cc. 2. The non-aqueous electrolyte battery according to claim 1, wherein said natural graphite has an amorphous layer on the surface. 3. The film thickness of the amorphous layer is 5 μm or more.
3. The non-aqueous electrolyte battery according to claim 2, wherein the thickness is 0 μm or less. 4. The nonaqueous electrolyte battery according to claim 1, wherein the natural graphite has a (002) plane spacing (d002) of less than 0.34 nm according to an X-ray wide-angle diffraction method. 5. The non-aqueous electrolyte battery according to claim 1, wherein said natural graphite has a minimum particle size of 10 μm or more and a maximum particle size of 80 μm or less. 6. The method according to claim 1, wherein the negative electrode contains 100 ppm or less of carboxymethylcellulose.
The nonaqueous electrolyte battery according to any one of the preceding claims. 7. The non-aqueous electrolyte battery according to claim 1, wherein the negative electrode, the positive electrode, and the non-aqueous electrolyte are hermetically sealed in a flexible exterior material. 8. The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte is a non-aqueous electrolyte obtained by dissolving an electrolyte in a non-aqueous solvent. 9. The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte is a gel electrolyte. 10. A method for producing a non-aqueous electrolyte battery comprising a negative electrode, a positive electrode, and a non-aqueous electrolyte, wherein in producing the negative electrode, natural graphite and styrene-butadiene rubber are mixed to obtain a negative electrode mixture. A step of coating the negative electrode mixture on a negative electrode current collector to obtain a negative electrode raw material, and compressing the negative electrode raw material to reduce the electrode density of the negative electrode to 1.68 g /
a compression step of at least cc and not more than 1/85 g / cc. 11. In the mixing step, carboxymethylcellulose is further added to obtain a negative electrode mixture, and after the compression step, the negative electrode is subjected to a heat treatment to reduce the content of the carboxymethylcellulose to 100 ppm or less. A method for manufacturing a nonaqueous electrolyte battery according to claim 10. 12. The method according to claim 11, wherein the heat treatment is performed at 200 ° C. or higher. 13. The non-aqueous electrolyte battery according to claim 10, wherein an amorphous layer is formed on the surface of the natural graphite in a liquid phase. 14. The method according to claim 10, wherein an amorphous layer is formed on the surface of the natural graphite in a gas phase.