JP2002252038A - Non-aqueous electrolytic solution battery and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress self-discharge of electricity in preservation of extended periods of time. SOLUTION: It consists a positive electrode, which contains a transition metal complex oxide containing lithium as a positive-electrode active material, a negative electrode, which contains carbon, metal, or a material that can be made to an alloy, which can dope/de-dope of lithium, as a negative-electrode active material, and non-aqueous electrolysis liquid. There, a quantity of N- methyl-2-pyrrolidone(NMP), which remains to the positive electrode and the negative electrode, is made to be 70 μl/m<2> or less with the average of the positive electrode and the negative electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a positive electrode containing a transition metal composite oxide containing lithium as a positive electrode active material,
Non-aqueous electrolyte comprising a negative electrode containing a lithium-doped / dedopable carbon, metal or alloyable material as a negative electrode active material, and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode The present invention relates to a battery and a method for manufacturing the battery.

[0002]

2. Description of the Related Art In recent years, portable information devices such as laptop computers and word processors, camera-integrated VTRs, liquid crystal TVs
AV devices such as mobile phones and mobile communication devices such as mobile phones have been remarkably developed, and batteries used as power sources are required to have small size, light weight, and high energy density secondary batteries.
Until now, aqueous secondary batteries such as lead batteries and nickel cadmium batteries have been used, but they are not sufficient for requirements such as weight reduction, high energy density and low self-discharge.

Recently, it has a high energy density,
There is great interest and hope for lithium secondary batteries as clean batteries.

In recent years, the development of lithium ion batteries using a carbon material capable of doping / dedoping lithium as a negative electrode and a lithium composite oxide such as lithium cobalt oxide or lithium nickel oxide as a positive electrode has been actively carried out in recent years. ing.
By optimizing the design capacity of the positive electrode / negative electrode, these batteries do not have lithium dendrite formation as seen in battery systems using lithium metal. In addition, these batteries have low self-discharge, excellent cycle characteristics and safety, and are also excellent in low temperature characteristics, load characteristics, or rapid charging characteristics, and are highly expected, as well as laptop computers, word processors, It has been put to practical use as a power supply for portable devices such as a camera-integrated VTR and a mobile phone.

[0005]

However, lithium ion batteries, when stored at full charge,
It will self-discharge. Part of the cause of this self-discharge is due to N-methyl-2-pyrrolidone (NMP) remaining in the battery.
Is considered to be the amount of electricity consumed by the electrolysis of a carbamate compound, chain amide compound or cyclic amide compound. NMP remaining in the lithium ion battery is contained in the positive and negative electrodes.

However, NMP contained in the positive and negative electrodes
Since it is impossible to completely remove NMP, it was necessary to control the amount of NMP remaining in the positive and negative electrodes in order to provide a user with a lithium ion battery with less self-discharge.

The present invention has been proposed in view of such conventional circumstances, and an object of the present invention is to provide a non-aqueous electrolyte battery which is a lithium ion battery and has less self-discharge, and a method of manufacturing the same.

[0008]

A nonaqueous electrolyte battery according to the present invention comprises a positive electrode containing a transition metal composite oxide containing lithium as a positive electrode active material, and a carbon, metal or alloy capable of doping / dedoping lithium. In a non-aqueous electrolyte battery including a negative electrode containing a possible material as a negative electrode active material and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode, N-methyl remaining on the positive electrode and the negative electrode -2-pyrrolidone (N
MP) in an amount of 70 μl / m ² or less on average between the positive electrode and the negative electrode.

In the nonaqueous electrolyte battery according to the present invention as described above, the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is set to 70 μl / m ² or less on average between the positive electrode and the negative electrode. Therefore, the decomposition of NMP is reduced, and the potential drop and self-discharge during long-term storage are reduced.

Further, the method for producing a non-aqueous electrolyte battery according to the present invention is characterized in that a positive electrode containing a transition metal composite oxide containing lithium as a positive electrode active material is formed of carbon, metal or alloy capable of doping / dedoping lithium. A non-aqueous electrolyte battery including a negative electrode containing a non-aqueous material as a negative electrode active material, and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode. A positive electrode mixture application step of applying a positive electrode mixture slurried with N-methyl-2-pyrrolidone on a belt-shaped positive electrode current collector, containing a transition metal composite oxide containing: The positive electrode mixture applied on the positive electrode current collector in the coating step is dried to remove a part of N-methyl-2-pyrrolidone to form a positive electrode active material layer on the positive electrode current collector and form a positive electrode. Positive electrode drying process and negative electrode active material Negative electrode comprising a negative electrode mixture containing carbon, metal or alloyable material capable of doping / dedoping lithium and being slurried with N-methyl-2-pyrrolidone on a strip-shaped negative electrode current collector On the negative electrode current collector by drying the negative electrode mixture applied on the negative electrode current collector in the negative electrode current applying step and removing a portion of N-methyl-2-pyrrolidone Forming a negative electrode active material layer to form a negative electrode.

[0011] The present invention is directed to a method for drying N-methyl-2-pyrrolidone (NMP) remaining in the positive electrode active material layer and the negative electrode active material layer in the positive electrode drying step and the negative electrode drying step.
Is characterized in that the average amount of the positive electrode and the negative electrode is 70 μl / m ² or less.

In the method for manufacturing a nonaqueous electrolyte battery according to the present invention as described above, in the positive electrode drying step and the negative electrode drying step, the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is: Since the average of the positive electrode and the negative electrode is 70 μl / m ² or less, the decomposition of NMP is small, and the potential drop and self-discharge during long-term storage are reduced.

[0013]

Embodiments of the present invention will be described below.

FIG. 1 is a longitudinal sectional view showing one structural example of the nonaqueous electrolyte battery of the present invention. The non-aqueous electrolyte battery 1 is formed by loading a wound body in which a film-shaped positive electrode 2 and a film-shaped negative electrode 3 are wound in close contact with a separator 4 inside a battery can 5. .

The positive electrode 2 is manufactured by applying a positive electrode mixture containing a positive electrode active material and a binder on a current collector and drying the mixture. A metal foil such as an aluminum foil is used for the current collector.

As the positive electrode active material, a metal oxide, a metal sulfide, or a specific polymer can be used depending on the type of the intended battery.

For example, when a lithium primary battery is constructed,
In this case, as the positive electrode active material, TiS₂, MnO₂,graphite,
FeS₂Etc. can be used. In addition, lithium
When constructing a secondary battery, Ti is used as the positive electrode active material.
S₂, MoS₂, NbSe₂, V₂O₅And other metal sulfides
Alternatively, an oxide can be used. Also, Li_x
MO ₂(Where M represents one or more transition metals, and x represents a battery
, Usually 0.05 or more,
10 or less. ) -Based lithium composite oxides
Can be used. This lithium composite oxide is
As the transition metal M to be formed, Co, Ni, Mn and the like are preferable.
New As a specific example of such a lithium composite oxide,
LiCoO₂, LiNiO₂, LiNi_yCo_1-yO
₂(Where 0 <y <1), LiMn₂O₄Etc.
Can be mentioned. These lithium composite oxides
Positive electrode active material that can generate high voltage and has excellent energy density
Quality. The positive electrode 2 contains a plurality of these positive electrode active materials.
You may use it together.

As the binder of the above-mentioned positive electrode mixture, a known binder which is usually used for a positive electrode mixture of a battery can be used. Can be added.

As will be described later, the positive electrode contains a positive electrode active material and a binder, and contains N-methyl-2-pyrrolidone (N
The positive electrode mixture diluted by MP) is uniformly applied to a positive electrode current collector, for example, a metal foil such as an aluminum foil, and dried to form a positive electrode active material layer. The NMP is partially vaporized and removed by drying.

Here, the non-aqueous electrolyte battery 1 according to the present invention
Then, the N remaining in the positive electrode active material layer and the negative electrode active material layer
The amount of MP is set to 70 μl / m ² or less on average between the positive electrode and the negative electrode. By setting the average amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer to 70 μl / m ² or less, it is possible to suppress a decrease in potential caused by decomposition of NMP when the battery is stored for a long period of time. be able to. In addition, by suppressing the decomposition of NMP, self-discharge of the nonaqueous electrolyte battery 1 can be suppressed.

When the average amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer exceeds 70 μl / m ² ,
As described above, the potential drop and the self-discharge due to the decomposition of NMP increase. Therefore, when the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is specified to be 70 μl / m ² or less on average, an excellent non-potential reduction in potential reduction and self-discharge during long-term storage is achieved. The water electrolyte battery 1 can be obtained.

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

In forming a lithium primary battery or a lithium secondary battery, it is preferable to use lithium, a lithium alloy, or a material capable of doping or undoping lithium as a negative electrode material. As a material that can be doped and de-doped with lithium, for example, a carbon material such as a non-graphitizable carbon-based material and a graphite-based material can be used. Specifically, carbon materials such as pyrolytic carbons, cokes, graphites, glassy carbon fibers, fired organic polymer compounds, carbon fibers, and activated carbon can be used. Examples of the coke include pitch coke, needle coke, and petroleum coke. The fired organic polymer compound is obtained by firing a phenol resin, a furan resin or the like at an appropriate temperature and carbonizing the same.

In addition to the above-described carbon materials, polymers such as polyacetylene and polypyrrole and oxides such as SnO ₂ can also be used as materials capable of doping and undoping lithium. Further, as the lithium alloy, a lithium-aluminum alloy or the like can be used.

As the binder of the above-mentioned negative electrode mixture, a known binder which is usually used for a negative electrode mixture of a lithium ion battery can be used, and a known additive of the above-mentioned negative electrode mixture can be used. Etc. can be added.

As will be described later, the negative electrode contains a negative electrode active material and a binder, and contains N-methyl-2-pyrrolidone (N
The negative electrode mixture diluted by MP) is uniformly applied on a metal foil, such as a copper foil, serving as a negative electrode current collector, and dried to form a negative electrode active material layer. N above
Part of the MP is vaporized and removed by drying.

Here, the non-aqueous electrolyte battery 1 according to the present invention
Then, the N remaining in the positive electrode active material layer and the negative electrode active material layer
The amount of MP is set to 70 μl / m ² or less on average between the positive electrode and the negative electrode. By setting the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer to an average of 70 μl / m ² or less, a decrease in potential due to decomposition of NMP when the battery is stored for a long period of time is suppressed. be able to. In addition, by suppressing the decomposition of NMP, self-discharge of the nonaqueous electrolyte battery 1 can be suppressed.

When the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer exceeds 70 μl / m ² on average,
As described above, the potential drop and the self-discharge due to the decomposition of NMP increase. Therefore, when the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is specified to be 70 μl / m ² or less on average, an excellent non-potential reduction in potential reduction and self-discharge during long-term storage is achieved. The water electrolyte battery 1 can be obtained.

The non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent.

As the electrolyte, it is usually used in a battery electrolyte.
Known electrolytes can be used. Concrete
Typically, LiPF₆, LiBF₄, LiAsF₆, Li
CF ₃SO₃, LiN (SO₂CF₃)₂, Etc.
Salt.

Such an electrolyte is contained in a non-aqueous solvent at a concentration of 0.1%.
Preferably, it is dissolved at a concentration of from mol / L to 3.0 mol / L. More preferably, 0.5 mol / L
２．０2.0 mol / L.

As the non-aqueous solvent, various non-aqueous solvents conventionally used for non-aqueous electrolytes can be used. For example, cyclic carbonates such as propylene carbonate and ethylene carbonate, and chain carbonates such as diethyl carbonate and dimethyl carbonate can be used. These non-aqueous solvents may be used alone or in combination of two or more.

In the non-aqueous electrolyte battery 1 according to the present invention as described above, the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is 70 μl / m ^{2 on} average between the positive electrode and the negative electrode.
Because of the following, the decomposition of NMP is small, and the potential is low and the self-discharge during storage for a long time is small, and the product is excellent.

Then, such a non-aqueous electrolyte battery 1 is
It is manufactured as follows.

The positive electrode 2 contains a positive electrode active material and a binder, and is mixed with a positive electrode mixture diluted with N-methyl-2-pyrrolidone (NMP). It is produced by uniformly coating and drying on a metal foil to form a positive electrode active material layer. Known binders can be used as the binder of the positive electrode mixture, and known additives and the like can be added to the positive electrode mixture.

The NMP is partially vaporized and removed by drying. In the present invention, the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is reduced by 70 μl on average between the positive electrode and the negative electrode. / M ² or less.

By setting the average amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer to 70 μl / m ² or less, the potential caused by the decomposition of NMP when the battery is stored for a long period of time. Reduction can be suppressed. In addition, by suppressing the decomposition of NMP, self-discharge of the nonaqueous electrolyte battery 1 can be suppressed.

When the average amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer exceeds 70 μl / m ² ,
As described above, the potential drop and the self-discharge due to the decomposition of NMP increase. Therefore, when the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is specified to be 70 μl / m ² or less on average, an excellent non-potential reduction in potential reduction and self-discharge during long-term storage is achieved. The water electrolyte battery 1 can be obtained.

The negative electrode 3 contains a negative electrode active material and a binder, and mixes a negative electrode mixture diluted with N-methyl-2-pyrrolidone (NMP) with a negative electrode current collector such as copper foil. It is produced by uniformly applying and drying on a metal foil to form a negative electrode active material layer. As the binder of the negative electrode mixture, a known binder can be used, and a known additive or the like can be added to the negative electrode mixture.

The NMP is partially vaporized and removed by drying. In the present invention, the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is reduced by 70 μl on average between the positive electrode and the negative electrode. / M ² or less.

By setting the average amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer to 70 μl / m ² or less, the potential caused by the decomposition of NMP when the battery is stored for a long period of time. Reduction can be suppressed. In addition, by suppressing the decomposition of NMP, self-discharge of the nonaqueous electrolyte battery 1 can be suppressed.

When the average amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer exceeds 70 μl / m ² ,
As described above, the potential drop and the self-discharge due to the decomposition of NMP increase. Therefore, when the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is specified to be 70 μl / m ² or less on average, an excellent non-potential reduction in potential reduction and self-discharge during long-term storage is achieved. The water electrolyte battery 1 can be obtained.

The positive electrode 2 and the negative electrode 3 obtained as described above are brought into close contact with each other via a separator 4 made of, for example, a microporous polypropylene film, and wound in a spiral form many times to form a wound layer body. Is done.

Next, the insulating plate 6 is inserted into the bottom of the nickel-plated iron battery can 5 and the wound body is further housed. Then, in order to collect the current of the negative electrode, one end of a negative electrode lead 7 made of, for example, nickel is pressed against the negative electrode 3 and the other end is welded to the battery can 5. Thereby, the battery can 5
Has conductivity with the negative electrode 3 and becomes an external negative electrode of the nonaqueous electrolyte battery 1. In order to collect the current of the positive electrode 2, one end of a positive electrode lead 8 made of, for example, aluminum is connected to the positive electrode 2.
To the battery cover 1 at the other end via a current interrupting thin plate 9.
0 is electrically connected. The current interrupting thin plate 9 interrupts the current in accordance with the internal pressure of the battery. This allows
The battery lid 10 has conductivity with the positive electrode 2, and serves as an external positive electrode of the nonaqueous electrolyte battery 1.

Next, a non-aqueous electrolyte is injected into the battery can 5. This non-aqueous electrolyte is prepared by dissolving an electrolyte in a non-aqueous solvent.

Next, the battery lid 5 is fixed by caulking the battery can 5 via the insulating sealing gasket 11 coated with asphalt, and the cylindrical nonaqueous electrolyte battery 1 is manufactured.

In this non-aqueous electrolyte battery 1,
As shown in FIG. 1, a center pin 12 connected to the negative electrode lead 7 and the positive electrode lead 8 is provided, and a safety valve device for bleeding gas when the pressure inside the battery becomes higher than a predetermined value. 13 and a PTC element 14 for preventing a rise in temperature inside the battery.

The non-aqueous electrolyte battery 1 thus obtained
Is the NM remaining in the positive electrode active material layer and the negative electrode active material layer.
Since the amount of P is set to 70 μl / m ² or less on average for the positive electrode and the negative electrode, the decomposition of NMP is reduced, and the potential lowers and the self-discharge during long-term storage are reduced, resulting in excellent properties.

In the above-described embodiment, the description has been given by taking the secondary battery as an example. However, the present invention is not limited to this, and is applicable to a primary battery. Further, the shape of the battery of the present invention is not particularly limited, such as a cylindrical shape and a square shape, and the battery can be formed in various sizes such as a large size.

[0050]

EXAMPLES In the following Examples and Comparative Examples, in order to confirm the effects of the present invention, the above-mentioned non-aqueous electrolyte battery was manufactured and its characteristics were evaluated.

<Sample 1> First, a negative electrode was prepared as follows.

A negative electrode mixture was prepared by mixing 90 parts by weight of graphite as a negative electrode active material and 10 parts by weight of polyvinylidene fluoride as a binder. Next, the negative electrode mixture was dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry. Then, this slurry is applied to a negative electrode current collector having a thickness of 1.
0 μm strip of copper foil is uniformly applied on both sides, then
After drying at 20 ° C. for 10 minutes to form a negative electrode active material layer,
A negative electrode was produced by compression molding with a roll press.

The negative electrode active material layer of the obtained negative electrode had an area density of 20 mg / cm ² and a residual NMP amount of 40 μl / m 2.
It was ² .

Next, a positive electrode was prepared as follows.

A positive electrode mixture was prepared by mixing 85 parts by weight of LiCoO ₂ as a positive electrode active material, 5 parts by weight of flake graphite as a conductive agent, and 10 parts by weight of polyvinylidene fluoride as a binder.

Next, the positive electrode mixture was dispersed in N-methyl-2-pyrrolidone (NMP) to form a slurry. Then, this slurry is uniformly applied to both sides of a 20 μm-thick aluminum foil serving as a positive electrode current collector, then dried at 120 ° C. for 5 minutes to form a positive electrode active material layer, and then compression-molded by a roll press. Thus, a positive electrode was produced.

The positive electrode active material layer of the obtained positive electrode had an area density of 50 mg / cm ² and a residual NMP amount of 181 μl / cm ^2.
It was m ^2.

The positive electrode and the negative electrode obtained as described above are brought into close contact with each other via a separator made of a microporous polypropylene film having a thickness of 25 μm, and are wound in a spiral form many times to form a wound layer body. did.

Next, an insulating plate was inserted into the bottom of a nickel-plated iron battery can, and the wound body was further housed. Then, in order to collect the current of the negative electrode, one end of a nickel negative electrode lead was pressed against the negative electrode, and the other end was welded to the battery can. Further, in order to collect the current of the positive electrode, one end of an aluminum positive electrode lead was attached to the positive electrode, and the other end was electrically connected to the battery lid via a current interrupting thin plate. The current interrupting thin plate interrupts the current according to the internal pressure of the battery.

Then, a non-aqueous electrolyte was injected into the battery can. This non-aqueous electrolyte was prepared by dissolving LiPF ₆ as an electrolyte at a concentration of 1.0 mol / L in an equivalent volume mixed solvent of ethylene carbonate and dimethyl carbonate.

Finally, the battery lid is fixed by caulking the battery can through an insulating sealing gasket coated with asphalt, and a cylindrical non-aqueous electrolyte battery having a diameter of about 18 mm and a height of about 65 mm is obtained. Produced.

<Sample 2> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 6 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 178 μl / m ² .

<Sample 3> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 7 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 156 μl / m ² .

<Sample 4> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 8 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 135 μl / m ² .

<Sample 5> A non-aqueous electrolyte battery was manufactured in the same manner as in Sample 1, except that the drying time was changed to 9 minutes when manufacturing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 125 μl / m ² .

<Sample 6> A non-aqueous electrolyte battery was manufactured in the same manner as in Sample 1, except that the drying time was changed to 10 minutes when manufacturing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 110 μl / m ² .

<Sample 7> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 11 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 97 μl / m ² .

<Sample 8> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 12 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 90 μl / m ² .

<Sample 9> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 13 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 84 μl / m ² .

<Sample 10> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 14 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 75 μl / m ² .

<Sample 11> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 15 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 66 μl / m ² .

<Sample 12> A non-aqueous electrolyte battery was manufactured in the same manner as in Sample 1, except that the drying time was changed to 16 minutes when manufacturing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 52 μl / m ² .

<Sample 13> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 17 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 44 μl / m ² .

<Sample 14> A non-aqueous electrolyte battery was produced in the same manner as in Sample 1, except that the drying time was 18 minutes when producing the positive electrode.

The amount of residual NMP in the positive electrode active material layer of the obtained positive electrode was 32 μl / m ² .

Samples 1 to 5 produced as described above
The storage characteristics of the cylindrical nonaqueous electrolyte battery of Sample 14 were evaluated.

First, 4.2 V was applied to each of the obtained batteries.
Constant voltage and constant current charging was performed under charging conditions of 1 A and 3 hours.
Thereafter, a constant current discharge was performed up to 2.5 V with a discharge current of 0.7 A, and the discharge capacity before storage was measured.

Thereafter, the battery was charged under the same charging conditions as described above, and stored for one week in an environment of 45 ° C. in a fully charged state of 4.2 V.

After storage for one week, a discharge test was performed under the same discharge conditions as described above, and the amount of potential drop and the self-discharge rate of the battery were determined from the results.

Further, the battery was disassembled, and the amount of residual NMP remaining in the electrode was measured by gas chromatography. The measurement conditions for gas chromatography were as follows: the temperature of the column thermostat was 60 ° C., and the temperature of the detector was 280 ° C. Also,
The measurement sample size was a square having a side of 50 mm square for both the positive electrode and the negative electrode.

Table 1 shows the potential decrease and the self-discharge rate after storage at 45 ° C. for one week, together with the positive electrode drying time and the residual NMP amount. Further, N remaining in the positive electrode active material
FIG. 2 shows the relationship between the MP amount and the self-discharge rate.

[0094]

[Table 1]

From Table 1 and FIG. 2, it can be seen that the longer the drying time of the positive electrode active material, the smaller the amount of residual NMP. Then, it was confirmed that when the residual NMP amount was 100 μl / m ² or more, the potential sharply decreased and the self-discharge rate increased. Therefore, it was confirmed that the smaller the amount of residual NMP in the electrode, the smaller the self-discharge during long-term storage and the lower the voltage of the battery.

From the above results, when the average residual NMP in the positive electrode active material and the negative electrode active material is 70 μl / m ² or less, self-discharge during storage for a long time is small, and voltage drop is suppressed, which is particularly preferable. Was confirmed.

[0097]

According to the present invention, the amount of NMP remaining in the positive electrode active material layer and the negative electrode active material layer is 70 μl / m ² or less on average between the positive electrode and the negative electrode. As a result, an excellent non-aqueous electrolyte battery with less potential lowering and self-discharge during long-term storage can be realized.

Further, in the present invention, since the self-discharge rate is lowered as a whole, it becomes easy to discriminate a potential drop caused by a minute short-circuit and a potential drop caused by natural self-discharge. The detection period can be shortened.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing one configuration example of a nonaqueous electrolyte battery according to the present invention.

FIG. 2 is a diagram showing the relationship between the amount of NMP remaining in a positive electrode active material and the self-discharge rate for the batteries manufactured in Examples.

[Explanation of symbols]

1 Non-aqueous electrolyte battery, 2 Positive electrode, 3 Negative electrode, 4
Separator, 5 Battery can, 10 Battery lid

Claims (7)

[Claims] 1. A positive electrode containing a transition metal composite oxide containing lithium as a positive electrode active material, a negative electrode containing a carbon, metal or alloyable material capable of doping / dedoping lithium as a negative electrode active material, In a non-aqueous electrolyte battery including a non-aqueous electrolyte interposed between a positive electrode and the negative electrode, the amount of N-methyl-2-pyrrolidone remaining in the positive electrode and the negative electrode is an average of the positive electrode and the negative electrode. A non-aqueous electrolyte battery having a volume of 70 μl / m ² or less. 2. The method according to claim 1, wherein the non-aqueous electrolyte is LiPF ₆ , LiB
F ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF
_3. The nonaqueous electrolyte battery according to claim 1, further comprising one or more compounds selected from ₃ SO ₃ ) ₂ as an electrolyte salt. 3. The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte contains a cyclic carbonate or a chain carbonate alone or as a mixture as a non-aqueous solvent. 4. The nonaqueous electrolyte battery according to claim 1, wherein each of the positive electrode and the negative electrode is formed by forming an active material layer containing an active material on a belt-shaped current collector. 5. A positive electrode containing a transition metal composite oxide containing lithium as a positive electrode active material, a negative electrode containing carbon, metal or alloyable material as a negative electrode active material capable of doping / dedoping lithium, A method for producing a non-aqueous electrolyte battery including a non-aqueous electrolyte interposed between a positive electrode and the negative electrode, comprising a transition metal composite oxide containing lithium serving as a positive electrode active material; A positive electrode mixture applying step of applying a positive electrode mixture formed into a slurry with methyl-2-pyrrolidone on a belt-shaped positive electrode current collector; and a positive electrode applied on the positive electrode current collector in the positive electrode mixture applying step. Drying the mixture to remove a portion of N-methyl-2-pyrrolidone to form a positive electrode active material layer on the positive electrode current collector to form a positive electrode; Carbon that can be doped and undoped , Containing a metal or alloyable material, N-methyl-2
-A negative electrode mixture application step of applying a negative electrode mixture formed into a slurry with pyrrolidone on a strip-shaped negative electrode current collector, and the negative electrode mixture applied on the negative electrode current collector in the negative electrode mixture application step. A negative electrode drying step of forming a negative electrode active material layer on the negative electrode current collector by drying to remove a portion of N-methyl-2-pyrrolidone to form a negative electrode; In the step, N-methyl-2-residue remaining in the positive electrode active material layer and the negative electrode active material layer
The amount of pyrrolidone is 70 μl / m ^{2 on} average for the positive electrode and the negative electrode.
A method for producing a non-aqueous electrolyte battery, characterized in that: 6. The non-aqueous electrolyte comprises LiPF ₆ , LiB
F ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiN (CF
₃ SO ₃₎ method of manufacturing a non-aqueous electrolyte battery according to claim 5, wherein the one or more compounds selected from _2, characterized by containing as an electrolyte salt. 7. The method for producing a non-aqueous electrolyte battery according to claim 5, wherein the non-aqueous electrolyte contains a cyclic carbonate or a chain carbonate alone or as a mixture as a non-aqueous solvent.