JP2003077546A - Nonaqueous electrolyte secondary battery and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the safety and cycle performance of a battery. SOLUTION: This nonaqueous electrolyte secondary battery comprises a positive plate, a negative plate and a separator. A porous polymer electrolyte is provided in an electrode of at least one of the positive plate and the negative plate, and fixation is applied at least either between the positive plate and the separator or between the negative plate and the separator.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery and a method for manufacturing the same.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries currently on the market are composed of a positive electrode plate containing a transition metal composite oxide such as lithium cobalt oxide, a negative electrode plate containing a carbon-based active material such as graphite, polyethylene and polypropylene. The separator is composed of an organic electrolytic solution in which a lithium salt such as LiPF ₆ is dissolved in a carbonate ester mixed solvent such as ethylene carbonate.

These non-aqueous electrolyte secondary batteries are mounted on small equipment such as mobile phones and are expected to be used as a power source for electric vehicles or hybrid electric vehicles in the future.

In a non-aqueous electrolyte secondary battery, a battery using only a polyolefin having a melting point of 120 ° C. or less as a material of a porous film used as a separator is stored for a long time at a temperature slightly lower than the melting point of the polyolefin. , The discharge characteristics are significantly reduced. It is considered that this is because some of the pores of the polyolefin film are blocked or the pore structure is changed.

[0005]

When the temperature of the non-aqueous electrolyte secondary battery in the charged state is equal to or higher than the melting point of the separator, the separator contracts and the positive electrode plate and the negative electrode plate come into contact with each other, causing a short circuit. Examples of separators currently used in non-aqueous electrolyte secondary batteries include biaxially stretched porous polyolefin membranes and uniaxially stretched porous polyolefin membranes. When the former is heated above its melting point, it contracts remarkably in both the width direction and the length direction, so that a short circuit occurs when the battery using this film is left under high temperature.

On the other hand, when the latter is heated above its melting point, the contraction direction is only in the stretched direction. Therefore, the frequency of occurrence of short circuit when the battery using this film is left at high temperature. Is expected to decline. However, the direction perpendicular to the stretched direction has a property of low tensile strength. For this reason, when the battery is left at a high temperature and the stretched direction contracts, a short-circuit also occurs because the direction perpendicular to the stretched direction is torn.

When a non-aqueous electrolyte secondary battery is used as a power source for an electric vehicle or a hybrid electric vehicle, it is required to further improve safety and charge / discharge cycle performance. Therefore, an object of the present invention is to further improve the safety and charge / discharge cycle characteristics of the non-aqueous electrolyte secondary battery.

[0008]

According to a first aspect of the present invention, in a non-aqueous electrolyte secondary battery including a positive electrode plate, a negative electrode plate and a separator, a porous polymer is provided inside at least one of the positive electrode plate and the negative electrode plate. An electrolyte is provided, and at least one of the positive electrode plate / separator and the negative electrode plate / separator is fixed.

According to the invention of claim 1, a non-aqueous electrolyte secondary battery having excellent charge-discharge cycle characteristics and safety can be obtained.

According to a second aspect of the present invention, in the non-aqueous electrolyte secondary battery according to the first aspect, the separator has a melting point of T1 ° C.
Of the first polyolefin and the second polyolefin having a melting point of T2 ° C., 90 ≦ T1 ≦ 12
It is characterized in that the relationship of 0, 120 <T2 is satisfied.

According to the second aspect of the invention, the battery is 90 to 1
When left at a high temperature of 20 ° C., the pores of the entire separator are less likely to be blocked, and deterioration of the high rate discharge characteristics of the non-aqueous electrolyte secondary battery can be suppressed.

According to a third aspect of the present invention, in the non-aqueous electrolyte secondary battery according to the first aspect, the separator has a melting point of T1 ° C.
Of a first polyolefin and a second polyolefin having a melting point of T2 ° C., and a porous film made of a second polyolefin having a melting point of T2 ° C.
It is characterized in that the relations 0 ≦ T1 ≦ 120 and 120 <T2 are satisfied.

According to the invention of claim 3, the battery is 90 to 1
When left at a high temperature of 20 ° C., the shape of the pores of the porous film made of the second polyolefin does not change, so that a non-aqueous electrolyte secondary battery having excellent high rate discharge characteristics can be obtained.

According to a fourth aspect of the present invention, in the non-aqueous electrolyte secondary battery according to the first aspect, the separator has a melting point of T2 ° C.
A three-layer film comprising a porous film containing a first polyolefin having a melting point of T1 ° C. and a second polyolefin having a melting point of T2 ° C. on both sides of the porous film made of the second polyolefin of 90 ≦ It is characterized in that the relationship of T1 ≦ 120, 120 <T2 is satisfied.

According to the invention of claim 4, the battery is 90 to 1
When left at a high temperature of 20 ° C., since the shape of the pores of the porous film made of the second polyolefin does not change, it is possible to obtain a non-aqueous electrolyte secondary battery excellent in high rate discharge characteristics. By melting only the first polyolefin, the separator and the electrode can be easily fixed.

The invention of claim 5 relates to the method for producing a non-aqueous electrolyte secondary battery according to claim 1, 2, 3 or 4, wherein the positive electrode is heated at a temperature of T1 ° C. or higher and 120 ° C. or lower. At least one of the plate / separator and the negative electrode plate / separator is fixed.

According to the fifth aspect of the present invention, the separator and the electrode can be easily fixed to each other, the second polyolefin is prevented from melting, the porosity of the separator is maintained, and the non-aqueous electrolyte secondary battery It is possible to suppress deterioration of discharge characteristics.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention relates to a non-aqueous electrolyte secondary battery comprising a positive electrode plate, a negative electrode plate and a separator, wherein a porous polymer electrolyte is provided inside at least one of the positive electrode plate and the negative electrode plate, At least one of the plate / separator and the negative electrode plate / separator is fixed.

According to the present invention, by providing the porous polymer electrolyte inside the electrode, the porous polymer electrolyte provided inside the electrode acts as a binder, and the electrode plate of the active material accompanying repeated charge / discharge cycles. Is prevented from falling off, and further, the porous polymer electrolyte is swollen with the electrolytic solution, so that the electrolytic solution is evenly distributed inside the electrode,
Charge / discharge cycle characteristics are improved.

Further, since at least one of the positive electrode plate / separator and the negative electrode plate / separator is fixed, even if gas is generated inside the battery and the battery case expands, the electrode and the separator are separated from each other. In addition, the distance between the positive electrode and the negative electrode is kept substantially constant, and stable charge / discharge characteristics and cycle performance are obtained. Further, when the porous polymer electrolyte is provided in the space of the electrode surface layer, the porous polymer electrolyte functions as an adhesive that easily fixes the electrode and the separator.

The porous polymer electrolyte is a polymer electrolyte having ion conductivity in which a large number of pores are formed, and an organic electrolyte solution is held in the pores. Both the polymer portion and the pore portion are ion conductive. Is shown. Furthermore, the porous polymer electrolyte preferably has a network structure, and more preferably has a three-dimensional network structure.

The positive and negative electrode plates are provided with a porous mixture layer containing an active material, and the electrode plate provided with a porous polymer electrolyte means that the inside of the pores of the mixture layer or the surface of the mixture layer is porous. By means of the presence of a polar polymer electrolyte.

The porous polymer electrolyte may be present in at least a part of the pores in the mixture layer of the electrode plate, but it is preferable that it is uniformly distributed in these pores. Also, positive
It is sufficient that at least one of the negative electrode plates is provided with the porous polymer electrolyte, but it is preferable that both the positive and negative electrode plates are provided with the porous polymer electrolyte.

In the present invention, "fixed" between the positive electrode plate / separator and between the negative electrode plate / separator means that the electrode plate and the separator are integrated by melting a part of the components of the separator. Means that the battery cannot be disassembled and the electrode plate and the separator cannot be easily separated by a normal method.

Further, the present invention provides the nonaqueous electrolyte secondary battery according to claim 1, wherein the separator includes a first polyolefin having a melting point of T1 ° C. and a second polyolefin having a melting point of T2 ° C. A film, 90 ≦ T1 ≦ 120,
It is characterized in that the relationship of 120 <T2 is satisfied.

When the battery is left at a high temperature of 90 to 120 ° C., the first polyolefin having a melting point of 120 ° C. or less melts and some of the pores of the separator are clogged or the pore structure changes. , The battery characteristics may deteriorate, but the second polyolefin whose melting point is higher than 120 ° C. does not melt,
The pores of the entire separator are less likely to be blocked, the porosity is maintained, and deterioration of the high rate discharge characteristics of the non-aqueous electrolyte secondary battery can be suppressed.

Further, the present invention provides the non-aqueous electrolyte secondary battery according to claim 1, wherein the separator comprises a first polyolefin having a melting point of T1 ° C. and a second polyolefin having a melting point of T2 ° C. And a porous film made of a second polyolefin having a melting point of T2 ° C.
It is characterized in that the relationship of ≦ T1 ≦ 120 and 120 <T2 is satisfied.

According to the present invention, when the battery is left at a high temperature of 90 to 120 ° C., the first polyolefin and the second polyolefin are
In the porous film containing the polyolefin of, the first polyolefin is melted and some of the pores are closed,
Since the shape of the pores of the porous film made of the second polyolefin does not change and the porosity is maintained, it is possible to obtain a non-aqueous electrolyte secondary battery having excellent high rate discharge characteristics. In the two-layer structure separator described here, the direction in which the porous films made of the second polyolefin face each other may be the positive electrode side or the negative electrode side.

The present invention also provides the non-aqueous electrolyte secondary battery according to claim 1, wherein the separator has a first melting point of T1 ° C. and a first melting point of T1 ° C. on both sides of a porous film made of a second polyolefin having a melting point of T2 ° C. And a second polyolefin having a melting point of T2 ° C., which has a three-layer structure and satisfies the relationship of 90 ≦ T1 ≦ 120 and 120 <T2.

According to the present invention, when the battery is left at a high temperature of 90 to 120 ° C., the melting point of the second polyolefin is higher than 120 ° C., so that the pores of the porous membrane made of the second polyolefin are Since no blockage occurs, the shape of the pores does not change, and the porosity is maintained, it is possible to obtain a non-aqueous electrolyte secondary battery having excellent high rate discharge characteristics.

The three-layer structure separator of the present invention comprises a porous membrane containing a first polyolefin and a second polyolefin, a porous membrane composed of a second polyolefin, and a first polyolefin when a battery is assembled. It can be obtained by sequentially stacking a porous film containing a second polyolefin. Further, the laminated materials may be fused to each other by a method such as heating to form an integrated structure. Further, a porous film made of the second polyolefin may be formed in advance, and a porous film containing the first polyolefin and the second polyolefin may be directly formed on both surfaces of the porous film.

Further, since the separator of the present invention has a three-layer structure in which a porous film containing the first polyolefin and the second polyolefin is provided on both surfaces of the porous film made of the second polyolefin, the separator has a three-layer structure. By melting only the first polyolefin contained in the surface layer in contact with the separator, the separator and the electrode can be easily fixed.

Examples of the material of the polyolefin used in the present invention include low density polyethylene, medium density polyethylene, and some high density polyethylene as the first polyolefin. Further, a copolymer containing polyethylene, polypropylene, polybutylene, or the like can be given.
Moreover, you may use these mixtures. Examples of the second polyolefin include some low-density polyethylene, some medium-density polyethylene, high-density polyethylene, polypropylene, and the like, and a mixture thereof may be used.

The molecular weight of polyethylene is 1 ×
Those of 10 ⁴ or more can be used. The melting point of polyolefin can be measured by suggestive scanning calorimetry.

Further, the total thickness of the separator used in the present invention is preferably a thickness capable of preventing a short circuit between the positive electrode and the negative electrode, that is, 5 μm or more. On the other hand, the thickness is 4 to improve the volumetric energy density of the battery.
It is preferably 0 μm or less, more preferably 30 μm or less. When a separator having a multilayer structure is used, the thickness of the porous film containing the first polyolefin and the second polyolefin is preferably 0.1 to 10 μm.

In the separator of the present invention, the first
The amount of the first polyolefin contained in the porous film containing the second polyolefin and the second polyolefin is 0.3 wt.
% Or more and 90 wt% or less, and when the battery is left at a high temperature, in order to easily adhere the porous film containing the first polyolefin and the second polyolefin to the electrode plate, 5w of 1 polyolefin
It is desirable to be t% or more.

In the non-aqueous electrolyte secondary battery, generally, when the amount of the electrolytic solution is reduced, the cycle performance of the battery deteriorates.
This is because the electrolyte is unevenly distributed in the battery element,
This is because precipitation of metallic lithium during charging becomes remarkable.
However, when a porous polymer electrolyte is provided inside the electrode, and the positive electrode plate, the negative electrode plate, and the porous polymer film are fixed to each other,
Since a small amount of electrolytic solution can be uniformly distributed over the battery elements, it is possible to suppress deterioration of charge / discharge cycle performance.

The porous polymer electrolyte provided inside the electrode is, for example, a polymer electrolyte having pores formed by a wet method which is one of phase transition methods, and has a three-dimensional network structure having a large number of pores. is there. When a porous polymer electrolyte is formed in the pores inside the electrode, a part of it becomes a shape in which thread-like polymer is stretched around the pores, etc. May exhibit various forms. Further, the porous polymer electrolyte may be one in which the polymer itself has ion conductivity, or it is one in which the polymer becomes wet or swells when it is immersed in an electrolytic solution to have ion conductivity. May be.

The polymer used for the porous polymer electrolyte is preferably a polymer which becomes ionic conductive when wet or swollen, and examples thereof include polyvinylidene fluoride (PVdF), polyvinyl chloride, polyacrylonitrile and polyethylene oxide. , Polyether such as polypropylene oxide, polyacrylonitrile,
Polyvinylidene chloride, polymethyl methacrylate, polymethyl acrylate, polyvinyl alcohol, polymethacrylonitrile, polyvinyl acetate, polyvinylpyrrolidone, polyethyleneimine, polybutadiene, polystyrene, polyisoprene, or their attractants, alone or in combination. Can be used.

Further, a polymer obtained by copolymerizing various monomers constituting the above polymer, for example, vinylidene fluoride / hexafluoropropylene copolymer (P (V
dF / HFP)) and the like can also be used. In addition, it is preferable that the active material has flexibility capable of changing its shape following the volume expansion and contraction of the active material.

As a method of performing the porous treatment, a through hole forming method by ultraviolet irradiation, a phase transition method, etc. can be used, and among them, a wet method which is one of the phase transition methods is preferable.

The wet method is a method of obtaining a porous polymer by using a first solvent that dissolves the polymer and a second solvent for extraction that extracts the first solvent from the polymer solution. The first solvent of the polymer solution is extracted by immersing the dissolved polymer solution in a second solvent that is insoluble in the polymer and is compatible with the first solvent, and the first solvent is removed. It is said that the formed portions become pores to form a porous polymer. And
With this wet method, a through hole having a circular opening can be formed in the polymer.

As the first solvent for dissolving the polymer,
Depending on the polymer, for example, dimethylformamide,
Propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, carbonic acid esters such as ethyl methyl carbonate, dimethyl ether, diethyl ether, ethyl methyl ether, ethers such as tetrahydrofuran, dimethyl acetamide,
1-Methyl-pyrrolidinone, N-methyl-2-pyrrolidone or a mixture thereof can be used.

As the second solvent, one which is compatible with the first solvent is selected according to the first solvent, and for example, water, alcohol, acetone, or a mixed solution thereof can be used.

The non-aqueous electrolyte secondary battery in which the positive electrode plate / separator is fixed according to the present invention includes, for example, a separator laminated on the positive electrode mixture layer of the positive electrode plate, and a thin plate made of polytetrafluoroethylene on the separator. Can be manufactured by stacking them, sandwiching them between metal heaters, and heating at a temperature of T1 ° C. or higher and 120 ° C. or lower. A non-aqueous electrolyte secondary battery having a fixed negative electrode plate / separator can be manufactured by the same method.

The non-aqueous electrolyte secondary battery in which the positive electrode plate / separator and the negative electrode plate / separator are fixed according to the present invention includes a positive electrode plate / separator / negative electrode plate, a separator / positive electrode mixture layer, and a separator / negative electrode. It can be manufactured in the same manner as above by overlapping so as to contact the mixture layer. Further, the battery can be manufactured by assembling a battery in a state where the positive electrode plate / separator and the negative electrode plate / separator are not fixed, and then heating the battery at a temperature of T1 ° C. or higher and 120 ° C. or lower.

Since heating at a high temperature may affect each element constituting the power generation element, it is particularly preferable to use a material having a melting point T1 ° C. of the first polyolefin of 105 ° C. or less.

If the battery is left above 120 ° C,
The rate of volatilization of the electrolytic solution is remarkably high, and in this case, the battery element is spread before the first polyolefin melts and adheres to the electrode plate. Since the battery element is pressed by the battery case, a force is applied to the positive electrode plate or the negative electrode plate to break the battery element, and a short circuit occurs because the electrode plate penetrates the separator. However, if at least one of the positive electrode plate / separator and the negative electrode plate / separator is fixed in advance, bending of the battery element is suppressed, and a short circuit is less likely to occur. In addition,
In the present invention, it is most preferable that all of the positive electrode plate / separator, the negative electrode plate / separator, and the plurality of porous films constituting the separator are fixed.

According to the present invention, the first polyolefin having a melting point of T1 ° C. acts as a fusing agent for fusing the separator and the positive electrode and the separator and the negative electrode plate, and easily fixes the separator and the electrode. it can. Further, the heating temperature is lower than the melting point T2 ° C. of the second polyolefin, which is 120.
By setting the temperature to be equal to or lower than 0 ° C., it is possible to prevent the second polyolefin from melting and maintain the porosity of the separator, and as a result, it is possible to suppress deterioration of the discharge characteristics of the non-aqueous electrolyte secondary battery.

As a method of heating the battery, there are a method of arranging the battery in a constant temperature bath and a method of immersing the battery in a water bath or an oil bath. Further, the battery may be heated before or after the injection of the electrolytic solution. When performing after injection, it is desirable to carry out preliminary charging.

When the battery after the liquid injection is subjected to the heat treatment, it is preferable to immerse it in a water bath or an oil bath. In this case, the battery can be heated up to a target temperature quickly, so that mass productivity is excellent. Moreover, since the heating is performed for a short time, the volatilization amount of the electrolytic solution is small, and the swelling of the battery case or the like is suppressed. In order to prevent the battery case from swelling, the battery may be heated while being sandwiched between iron plates or the like.
When the battery case swells, the case may be replaced, or the case may be opened once to remove the generated gas, and then sealed again. When graphite or the like is used as the negative electrode active material, it is preferable to heat in a discharged state. This is because it is possible to suppress the reaction between Li _x C ₆ and the electrolytic solution which is accompanied by heat generation.

Positive electrode active material for non-aqueous electrolyte secondary battery of the present invention
As the compound, a compound capable of inserting and extracting lithium is used.
Can be, for example, LiCoO₂, LiNiO₂, Li
Mn ₂O_FourSuch as the composition formula Li_xMO₂, Or Li_yM₂O
_Four(However, M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦ 2)
Complex oxide represented, oxide having tunnel-like pores,
Layered structure metal chalcogenide etc. can be used
It In addition, LiNi_{0. 80}Co_0.2O_TwoAnd so on
In addition, a part of the transition metal M is at least one kind of other element
It is also possible to use an inorganic compound substituted with element. further
Is an organic compound such as polyaniline
You can also It should be noted that the above various active materials should be mixed and used.
You can also

Examples of the negative electrode active material of the non-aqueous electrolyte secondary battery of the present invention include lithium alloys of Li and Al, Si and the like, transition metal composite oxides such as LiFe ₂ O ₃ and WO.
₂ , a transition metal oxide such as MoO ₂ , a carbonaceous material such as graphite, lithium nitride, metallic lithium, or a mixture thereof can be used.

As a method of providing the porous polymer electrolyte inside the electrode, for example, there are the following methods. First, the electrode body before pressing is immersed in the polymer solution, and the polymer solution is allowed to permeate into the voids inside the electrode to provide the polymer solution inside the electrode body. As another method of providing the polymer solution inside the electrode, a method of applying the polymer solution to the electrode surface by a vacuum impregnation method, a screen printing method, a doctor blade method or the like, and allowing it to permeate the inside of the electrode by osmotic pressure may also be used. it can.

Then, the excess polymer solution carried on the electrode surface is removed by passing the electrode through a roller or the like, and thereafter, the polymer solution is dissolved in the above-mentioned second solvent which is a solvent for extraction of the first solvent. By immersing, the pores of the active material particles in the outermost layer of the electrode and the voids existing between the active material particles inside the electrode are occupied by the porous polymer. After that, the electrode may have a predetermined thickness.

The separator of the present invention is produced, for example, by a wet method or a dry method. In the wet method, first, a polymer solution is prepared by dissolving a first polyolefin and a second polyolefin in a first solvent. Next, this polymer solution is formed into a film by the T-die method or the inflation method. Next, the polymer solution processed into a film is immersed in a second solvent that is compatible with the first solvent, and the first solvent is extracted from the polymer solution.
The porous polymer film obtained may be dried and then uniaxially or biaxially stretched at a melting point T1 ° C. or lower of the first polyolefin to control the pore shape, the film thickness and the like. Here, the stretching step may be performed before or after the step of immersing the polymer solution processed into a film in the second solvent.

The first solvent used in the step of preparing the polymer solution may be any solvent which can dissolve the polyolefin, such as xylene, decane, dodecane, liquid paraffin, decanol, o-dichlorobenzene and trichlorobenzene. When the polyolefin is dissolved in these solvents, it may be heated to 70 to 180 ° C.

The second solvent used in the step of extracting the first solvent from the polymer solution may be water, acetone, alcohol or the like as long as it is compatible with the first solvent, and a mixture of these may also be used. Good. This process is the first
It is advisable to carry out at a temperature lower than the melting point T1 ° C. of the polyolefin.

When a porous polymer film is produced by the dry method, for example, first, a polymer solution produced in the same manner as the above-mentioned wet method is formed into a film by the T-die method or the like. Next, the polymer solution processed into a film is solidified without immersing it in the second solvent. Next, the polyolefin film is heat-treated. Finally, the film is made porous by stretching. The stretching temperature is preferably 70 to 140 ° C., but is preferably the melting point T1 ° C. or lower of the first polyolefin.

In the present invention, the positive electrode plate and the negative electrode plate are laminated with a separator interposed therebetween, or these are laminated and wound,
The battery is placed in a battery case such as a prismatic, cylindrical, or aluminum laminated bag, and an electrolyte for a non-aqueous electrolyte secondary battery is injected to obtain a battery.

As the electrolytic solution solvent of the non-aqueous electrolyte secondary battery of the present invention, a polar solvent such as ethylene carbonate, dimethyl carbonate, 1,2-dimethoxyethane, or a mixture thereof can be used. Further, as the salt to be contained in the electrolytic solution, a lithium salt such as LiPF ₆ or LiBF ₄ , or a mixture thereof can be used.

The injection amount of the electrolytic solution is 1 of the total pore volume (excluding the porous polymer electrolyte component) of the positive electrode, the negative electrode and the separator.
The amount is preferably 40% or less and 80% or more, and at least an amount that can follow the expansion and contraction of the electrode volume according to the electrode material.

[0063]

EXAMPLES The present invention will be further described below with reference to examples. In the non-aqueous electrolyte secondary batteries of Examples and Comparative Examples, the same positive electrode plate, negative electrode plate, electrolytic solution and battery shape were used as shown below.

The positive electrode plate was made of LiNi _0.83 C as an active material.
o _0.17 O ₂ 48.7 wt%, acetylene black 2.7 wt% as a conductive agent, PVdF 3.3 as an adhesive agent
A mixture of wt% and NMP 45.3 wt% as a paste solvent is applied to both sides of the aluminum foil, and 90%
The positive electrode main body was prepared by drying at C and evaporating NMP.
After that, the positive electrode plate was pressed to have a thickness of 160 μm. The porosity of the positive electrode material mixture layer was 33%, and the weight of the active material filled in per unit area was 20 mg / cm ² . The positive electrode plate P was used as the positive electrode plate P. The porosity of the electrode was calculated from the respective densities of the active material, the binder, and the conductive auxiliary agent, and the electrode mixture density and the outer shape (length, width, thickness) of the electrode. It is calculated from the apparent volume calculated from the above and the weight of the electrode. The same applies to the following.

Next, a positive electrode plate having a porous polymer electrolyte inside the positive electrode plate (inside the pores of the positive electrode mixture layer) was produced. First, in NMP, 8 wt% P (VdF / HFP)
A polymer solution in which the molecular weight was about 250,000 and HFP was 5 mol% was prepared, and the unpressed positive electrode plate main body was immersed in this to support the polymer solution on the positive electrode plate. And
After the excess polymer solution attached to the positive electrode surface is removed by passing it through a roller, the positive electrode plate is immersed in deionized water to perform NMP.
Was extracted. This electrode was taken out, dried at 130 ° C., and then pressed to obtain a positive electrode plate having a thickness of 160 μm and having a porous polymer inside. The porosity of the electrode excluding the porous polymer was 33%, and the weight of the active material charged per unit area was 20 mg / cm ^2.
Met. This was used as the positive electrode plate P1.

As the negative electrode plate, a mixture of 81 wt% graphite as a negative electrode active material, 9 wt% PVdF as a binder, and 10 wt% NMP as a paste solvent was applied to both sides of a copper foil having a thickness of 14 μm, and at 90 ° C. Dry and N
MP was evaporated to prepare the negative electrode body. After that, the negative electrode was pressed to have a thickness of 208 μm. The porosity of the negative electrode is 3
It was 5%. The weight of the active material charged per unit area was 14 mg / cm ² . This was used as the negative electrode plate N.

Next, 6 wt% P (VdF / H
FP) (molecular weight is about 250,000, HFP is 5 mol%) is prepared, and the unpressed negative electrode plate body is immersed in the polymer solution, and the porosity is formed inside the negative electrode in the same manner as the positive electrode plate. A negative electrode plate provided with a polymer was obtained. The thickness of the negative electrode was 208 μm, the porosity of the negative electrode excluding the porous polymer was 33%, and the weight of the active material charged per unit area was 14 mg / cm ² . This was made into the negative electrode N1.

The porous polymer provided inside the electrodes of the positive electrode plate P1 and the negative electrode plate N1 is a porous polymer prepared by assembling these electrodes into a battery, injecting an electrolytic solution, and then absorbing or swelling the electrolytic solution. It becomes an electrolyte.

The positive electrode plate and the negative electrode plate separator thus produced were combined and wound to form a wound type electrode plate group,
The battery was assembled by inserting this into an aluminum laminate case whose surface was resin-processed. Then, an electrolytic solution containing 1M LiPF ₆ was added to a mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1: 1), and the mixture was sealed. The injection amount of the electrolytic solution was set to an amount that satisfied 120% of the total pore volume of the positive electrode, the negative electrode, and the porous polymer film. Then, the battery was quickly preliminarily charged at a current of 120 mA for 2 hours to produce a non-aqueous electrolyte battery having a designed capacity of 600 mAh.

[Experiment 1] A separator was manufactured as follows. First, melting point (T1) 103 ° C., density 0.924
Low density polyethylene of g / cm ² was dissolved in xylene. Next, this solution was formed into a film by the T-die method and dipped in methanol to extract xylene. Next, the solvent remaining in the film was removed by drying, and the film was uniaxially stretched using a high temperature tensile tester heated to 90 ° C. The thickness of the obtained separator was 25 μm. This is designated as a separator SP1.

Using this separator SP1, the positive electrode plate P
Alternatively, 16 types of batteries were prepared by combining P1 and the negative electrode plate N or N1, and the influence of the presence of the porous polymer electrolyte inside the electrodes and the adhesion between the electrodes and the separator on the battery characteristics was examined.

The adhesion between the positive electrode plate and the separator is determined by the positive electrode plate P.
Alternatively, a separator is overlaid on the P1 positive electrode mixture layer, and a 0.2 mm-thick polytetrafluoroethylene thin plate is overlaid on the separator, which are sandwiched between stainless steel heaters and heated at 110 ° C. for 30 minutes. I went by. Fixing between the negative electrode plate N or N1 and the separator was also performed by the same method.

Further, the fixing between the positive electrode plate / separator and between the negative electrode plate / separator is performed by stacking the positive electrode plate / separator / negative electrode plate so that the separator is in contact with the positive electrode mixture layer and the separator is in contact with the negative electrode mixture layer. These were sandwiched between stainless steel heaters and heated at 110 ° C. for 30 minutes. The contents of the 16 types of batteries produced here are summarized in Table 1.

[0074]

[Table 1]

Next, an oven test was conducted on each of these batteries. The conditions of the oven test were that each battery was charged to 4.2 V at a constant current of 600 mA, and then charged to a constant voltage of 4.2 V for 5 hours. After that, these batteries were left in a constant temperature bath set at 150 ° C., and the state of the batteries after 3 hours was observed.

Further, a charge / discharge cycle test was conducted. Each of the 10 batteries was charged at room temperature to a constant current of 300 mA up to 4.2 V, and further charged to a constant voltage of 4.2 V for 5 hours. Then, at room temperature and a constant current of 600 mA, 2.7.
It was discharged to 5V. This charge / discharge cycle was performed 300 times. And 30 against the discharge capacity of the first cycle
The discharge capacity retention ratio (%) was defined as the ratio of the discharge capacity at the 0th cycle.

The above test results are summarized in Table 2. In addition,
In Table 2, with respect to the discharge capacity and the discharge capacity retention rate after leaving it at 80 ° C., the average value of 10 batteries was shown.

[0078]

[Table 2] Oven test results

From Table 2, the following was found.
In the oven test result, the battery A in which neither the positive electrode plate / separator nor the negative electrode plate / separator is fixed,
In E, I, and M, the battery element was significantly bent (buckled), and the battery case was completely opened, and a strange odor was drifting in the thermostat. It was also found that the separator contracted significantly and the positive electrode plate and the negative electrode plate were short-circuited.

Batteries B and C having no porous polymer electrolyte inside the electrodes and fixed at least one of the positive electrode / separator and the negative electrode / separator
Also in D and D, buckling of the battery element and opening of the battery case were confirmed. Since no porous polymer electrolyte was provided inside the battery, metallic lithium was deposited by high-rate charging, and it is considered that this reacted.

Batteries F, G, J having a porous polymer electrolyte inside either one of the positive electrode plate and the negative electrode plate and having either the positive electrode plate / separator or the negative electrode plate / separator fixed thereto are fixed. , K, N and O, no buckling of the battery element was observed, and the battery case was not opened, but the battery case was swollen.

Further, a battery H having a porous polymer electrolyte inside both the positive electrode plate and the negative electrode plate, and fixing both the positive electrode plate / separator and the negative electrode plate / separator.
In L and P, the buckling of the battery element was not observed, the battery case was not opened, and the battery case was not swollen.

Further, the batteries F, G, H, J, K, L,
In N, O, and P, the discharge capacity retention rate after the cycle was a large value of 70% or more.

As described above, the porous polymer electrolyte is provided in the electrode of at least one of the positive electrode plate and the negative electrode plate of the present invention, and at least one of the positive electrode plate / separator and the negative electrode plate / separator is fixed. The non-aqueous electrolyte secondary battery of the present invention was shown to be extremely excellent in both the oven test and the discharge capacity retention rate after 300 cycles.

[Experiment 2] Next, a positive electrode plate P1 having a porous polymer electrolyte inside the positive electrode plate and a negative electrode plate N1 having a porous polymer electrolyte inside the negative electrode plate were used. The characteristics of the non-aqueous electrolyte secondary battery in which both the separator and the negative electrode plate / separator were fixed were compared when the type of the separator was changed. The following was used as the type of separator.

Separator SP1: melting point 1 having a thickness of 25 μm
Low density polyethylene at 03 ° C. (same as used in Experiment 1) Separator SP2: Density as first polyolefin 0.924 g / cm ³ , melting point (T1) 103 ° C.
30:70 (wt%) mixture of low density polyethylene of No. 2 and high density polyethylene having a density of 0.960 g / cm ³ as the second polyolefin and a melting point (T2) of 141 ° C. was dissolved in xylene at 120 ° C. Next, this solution was formed into a film by the T-die method and dipped in methanol to extract xylene. Next, it was dried to remove the solvent contained in the film, and uniaxially stretched using a high temperature tensile tester heated to 90 ° C. The obtained separator thickness is 2
It was 5 μm.

Separator SP3: First, the second polyolefin was dissolved in xylene at 120 ° C. Next, this solution was formed into a film by the T-die method and dipped in methanol to extract xylene. Next, it was dried to remove the solvent contained in the film, and uniaxially stretched using a high temperature tensile tester heated to 90 ° C. The obtained separator thickness was 10 μm. This was used as a separator X.

Next, a low density polyethylene having a density of 0.924 g / cm ³ and a melting point (T1) of 103 ° C. as a first polyolefin, and a density of 0.960 g / cm ³ and a melting point (T2) as a second polyolefin. 120: 30:70 (wt%) mixture with high density polyethylene at 141 ° C
It was dissolved in xylene at ℃. Next, this solution was formed into a film by the T-die method and dipped in methanol to extract xylene. Next, it was dried to remove the solvent contained in the film, and uniaxially stretched using a high temperature tensile tester heated to 90 ° C. The obtained separator thickness was 8 μm. This was used as a separator Y. Then, one separator X and one separator Y were laminated to form a two-layer structure, which was referred to as a separator SP3.

Separator SP4: The separator X1 used in the separator SP3 and the separator Y2 are used,
A separator SP4 has a three-layer structure in which both sides of the separator X are sandwiched by the separators Y.

Further, the fixing of the separator and the electrode was carried out by the following method. After assembling the battery and performing preliminary charging, the battery was charged to a constant current of 120 mA to 4.2 V, and further charged to a constant voltage of 4.2 V for 3 hours. Next, 60m
A constant current was discharged to 2.75V. Then, the battery was sandwiched between iron plates and immersed in an oil bath at 110 ° C. for 10 minutes.

Then, a battery using these four kinds of separators was tested under the same conditions as in Experiment 1. Further, the high rate discharge capacity after leaving these batteries at 80 ° C. was measured. Ten of each battery was stored for 2 weeks in a thermostat set at 80 ° C. Then place the batteries at room temperature for 24 hours.
Saved for hours. Next, the battery was charged at room temperature with a constant current of 120 mA to 4.2 V, and then with a constant voltage of 4.2 V for 5 hours. Then, the battery was discharged at a constant current of 1200 mA to 2.75 V at room temperature, and the discharge capacity at that time was obtained. These results are summarized in Table 3.

[0092]

[Table 3]

From Table 3, the first melting point of the present invention is T1 ° C.
Is a porous film containing the second polyolefin having a melting point of T2 ° C. and 90 ≦ T1 ≦ 120, 12
Battery Q using a separator satisfying the relationship of 0 <T2, 2
In the battery R using the layered separator and the battery S using the three-layered separator, the battery did not swell even in the oven test, and the discharge capacity after standing at 80 ° C. or 3
It was also shown that the discharge capacity retention rate after 00 cycles was also superior to that of the battery P.

[0094]

INDUSTRIAL APPLICABILITY The present invention provides a non-aqueous electrolyte secondary battery comprising a positive electrode plate, a negative electrode plate and a separator, which comprises a porous polymer electrolyte inside at least one electrode of the positive electrode plate and the negative electrode plate. At least one of the separator and the negative electrode plate / separator is fixed.

According to the present invention, by providing the porous polymer electrolyte inside the electrode, the porous polymer electrolyte provided inside the electrode acts as a binder, and the electrode plate of the active material accompanying the charge / discharge cycle is formed. Of the porous polymer electrolyte is suppressed, and the porous polymer electrolyte is swollen with the electrolytic solution, so that the electrolytic solution is uniformly distributed inside the electrode, and the charge / discharge cycle characteristics are improved.

Further, since at least one of the positive electrode plate / separator and the negative electrode plate / separator is fixed, even if gas is generated inside the battery and the battery expands, the electrode and the separator do not separate. The distance between the positive electrode and the negative electrode is always kept constant, and safety is excellent and stable charge / discharge characteristics are obtained. Further, by providing the porous polymer electrolyte in the electrode, the electrode and the separator can be easily fixed.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 4/62 H01M 4/62 Z F term (reference) 5H021 BB01 BB11 EE04 HH06 5H029 AJ05 AJ12 AK02 AK03 AK05 AK16 AL01 AL02 AL06 AL07 AL11 AL12 AM03 AM04 AM05 AM07 AM16 CJ02 CJ05 DJ04 DJ13 EJ12 HJ14 5H050 AA07 AA15 BA17 CA02 CA07 CA11 CA21 CB01 CB02 CB07 CB08 CB11 CB12 CB29 DA13 DA19 FA13 GA02 GA07 HA14

Claims (5)

[Claims] 1. A non-aqueous electrolyte secondary battery including a positive electrode plate, a negative electrode plate, and a separator, wherein a porous polymer electrolyte is provided inside at least one of the positive electrode plate and the negative electrode plate, and a positive electrode plate / separator and a negative electrode are provided. A non-aqueous electrolyte secondary battery characterized in that at least one of the plate and the separator is fixed. 2. The separator is a porous film containing a first polyolefin having a melting point of T1 ° C. and a second polyolefin having a melting point of T2 ° C., and 90 ≦ T1 ≦ 120, 120 <
The nonaqueous electrolyte secondary battery according to claim 1, wherein the relationship of T2 is satisfied. 3. A separator comprising: a porous film containing a first polyolefin having a melting point of T1 ° C. and a second polyolefin having a melting point of T2 ° C .; and a porous film composed of a second polyolefin having a melting point of T2 ° C. Consisting of a two-layer film of 90 ≦ T1 ≦
The non-aqueous electrolyte secondary battery according to claim 1, wherein the relationship of 120, 120 <T2 is satisfied. 4. The separator has a melting point of T1 ° C. on both sides of a porous film made of a second polyolefin having a melting point of T2 ° C.
Consisting of a first polyolefin and a second polyolefin having a melting point of T2 ° C.
The non-aqueous electrolyte secondary battery according to claim 1, wherein the relations 0 ≦ T1 ≦ 120 and 120 <T2 are satisfied. 5. The heating method according to claim 1, wherein at least one of the positive electrode plate / separator and the negative electrode plate / separator is fixed by heating at a temperature of T1 ° C. or higher and 120 ° C. or lower. 4. The method for producing a non-aqueous electrolyte secondary battery described in 4.