JPH11329448A - Nonaqueous secondary battery positive electrode current collector and nonaqueous secondary battery having this current collector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the charge and discharge cycle durability with good retainability of electrolyte and stability by integrating an aluminum foil having a roughed surface layer having a specified thickness on the surface and having a specified breaking energy to an electrode consisting of a positive electrode active material and a binder to form a positive electrode body. SOLUTION: An aluminum foil having a roughed surface layer 1-5 μm thick in average, desirably 2-4 μm thick on the surface and having a breaking energy for No.1 dumbbell-like test piece regulated in JIS-K6301 of 3 kg.mm or more, desirably, 4-10 kg.mm is used. Further, this aluminum foil consists of an etched foil, and it has a loss by etching of a 1-8 g/m<2> , desirably, 3-5 g/m<2> . A positive electrode consisting of a positive electrode material and a binder is integrated with a current collector consisting of the aluminum foil to form a positive electrode body, and it is housed in a case together with a negative electrode body and a solution consisting of a lithium salt of solute and a nonaqueous solvent capable of dissolving the lithium salt to form a nonaqueous secondary battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous secondary battery, and more particularly to a non-aqueous secondary battery having excellent operation reliability.

[0002]

2. Description of the Related Art A battery using a material capable of occluding and releasing an alkali metal or an alkali metal ion as an electrode active material has attracted attention as having a high energy density. Among them, a lithium secondary battery has a particularly high energy density. For,
It is being widely used as a power source for electronic devices.

[0003] A secondary battery using a liquid electrolyte is prepared, for example, by applying a slurry obtained by adding a solvent to a positive electrode active material, a conductive material and a binder on a surface of a current collector made of a metal foil. An electrode layer having a thickness of 50 to 100 μm is formed and dried to obtain a sheet-like positive electrode body integrated with the current collector. After the negative electrode body is obtained in the same manner, the positive electrode body and the negative electrode body are cut into required dimensions, and a separator film is sandwiched therebetween and wound to form an element, or the positive electrode body and the negative electrode body are separated from each other by a separator. A plurality of elements are alternately laminated with a film interposed therebetween to form an element. The element is housed in a container, impregnated with an electrolytic solution, and sealed to form a battery. A secondary battery using such a liquid electrolyte is desired to have improved charge / discharge cycle durability.

In recent years, measures have been taken to prevent liquid leakage caused by using a liquid electrolyte for a primary battery and a secondary battery.
Various polymer electrolytes have been proposed from the standpoints of measures to reduce the ignitability of the flammable electrolyte, improvement of incorporation into electronic devices by making the battery into a film, and effective use of space (Japanese Patent Application Laid-Open No. 8-507407). ).

[0005] Among them, polyethylene oxide-based polymer electrolytes are electrochemically stable, but have a drawback that the solvent retention of the organic electrolyte is low. The polyacrylate-based polymer electrolyte having a three-dimensional structure has good solvent retention, but is electrochemically unstable and is not suitable for a high-potential battery.

[0006] A polymer electrolyte made of polyvinylidene fluoride is electrochemically stable and has high heat resistance because of containing fluorine atoms. However, when the temperature of the polymer electrolyte is increased, the electrolyte oozes out of the polymer. On the other hand, there is an attempt to solve this problem by using a copolymer of vinylidene fluoride and hexafluoropropylene. However, a conventional lithium secondary battery using a polymer electrolyte has a drawback that it is difficult to perform charging / discharging at a large current, and the charge / discharge cycle durability is inferior to a lithium secondary battery using a liquid electrolyte.

On the other hand, as for the current collector, an aluminum electrolytic foil for an electrode of an aluminum electrolytic capacitor is preferably used as a positive electrode current collector in order to improve the adhesion to a conductive polymer active material having a redox property. It has been proposed (JP-A-8-298137).

[0008]

For example, an aluminum electrolytic foil for an electrode of the above aluminum electrolytic capacitor is used as a positive electrode current collector, and a polymer electrolyte containing a polymer containing polymerized units based on fluoroolefin as a matrix and a positive electrode active material. When the positive electrode body is formed integrally with the positive electrode made of the mixture, the adhesion is improved as compared with the case where the current collector is made of a smooth aluminum foil or an aluminum foil whose surface is roughened by sandblasting or the like.

However, the strength of the obtained positive electrode body is low, and breakage is likely to occur in the process of manufacturing the positive electrode body or in the step of manufacturing an element using the positive electrode body, the separator and the negative electrode body. In order to ensure the strength of the positive electrode body, the thickness of the aluminum electrolytic foil may be increased, but there is a problem in that the weight and size of the battery are impaired, and the use of the aluminum electrolytic foil increases to increase the cost. is there.

In addition, the number of pores having an average pore diameter of 10 to 100 μm is 2
It has also been proposed to use an aluminum foil having 5 to 50000 pieces / cm ² and an aperture ratio of less than 5% as a positive electrode current collector (Japanese Patent Application Laid-Open No. 9-22699), but the density of holes is insufficient. For this reason, the adhesion of the polymer electrolyte to the current collector is insufficient, and it is difficult to balance the strength of the current collector with the bonding force of the polymer electrolyte to the current collector, and further improvement has been desired.

Accordingly, the present invention solves the above-mentioned problems, and has a low internal resistance, the positive electrode material does not fall off from the positive electrode body even after repeated charge / discharge cycles, and there is no decrease in battery capacity or increase in internal resistance. It is another object of the present invention to provide a positive electrode current collector for a non-aqueous secondary battery having excellent charge / discharge cycle durability and a non-aqueous secondary battery having the current collector.

Further, by using the above-mentioned positive electrode current collector in combination with a polymer electrolyte having a specific polymer as a matrix, the use of a polymer electrolyte having good electrolyte retention, stability, and excellent charge / discharge cycle durability can be achieved. An object is to provide an aqueous secondary battery.

[0013]

According to the present invention, a positive electrode body is formed integrally with an electrode comprising a positive electrode active material and a binder.
In the positive electrode current collector for a non-aqueous secondary battery made of an aluminum foil, the aluminum foil has an average surface of 1 to 5 μm on its surface.
A positive electrode for a non-aqueous secondary battery, characterized by having a roughened layer having a thickness of 3 mm and having a breaking energy of 3 kg · mm or more in a No. 1 dumbbell-shaped test piece specified in JIS-K6301. Provided is a current collector and a non-aqueous secondary battery including the current collector.

In the present specification, a positive electrode body in which a positive electrode comprising a positive electrode active material, a binder, and a conductive material added as necessary is integrated with a positive electrode current collector. The same definition applies to the negative electrode body.

The aluminum foil of the present invention has a surface roughened layer having an average thickness of 1 to 5 μm. If it is less than 1 μm, the bonding strength between the positive electrode comprising the positive electrode active material and the binder and the current collector is weak. In particular, when the positive electrode is previously formed into a sheet and then joined to the current collector, the joining force is weak because the positive electrode sheet and the current collector are joined almost only on the surface of the current collector.
On the other hand, if it exceeds 5 μm, no further improvement in bonding strength is observed, and the strength of the aluminum foil decreases as the thickness of the roughened layer increases. In particular, the thickness is preferably 2 to 4 μm.

In the present invention, when the positive electrode is formed on only one surface of the positive electrode current collector, the roughened layer of the aluminum foil may be formed only on one surface of the aluminum foil to be joined to the positive electrode. However, in order to form the roughened layer continuously and inexpensively on the aluminum foil, it may be provided on both sides of the foil.

In the present invention, the aluminum foil serving as the positive electrode current collector is punched out in the form of a No. 1 dumbbell-shaped test piece specified in JIS-K6301, and the tensile strength is measured by a tensile tester using the test piece. Is measured, 3
It has a breaking energy of not less than kg · mm. Incidentally, the breaking energy in the present invention, by measuring the relationship between the tensile load and elongation of the test piece by a tensile tester,
It is determined as an integral value of the obtained elongation (mm) / tensile load (kg) curve. However, the measurement condition at this time is that the measurement temperature is room temperature (20 to 25 ° C.)
The pulling speed is 5 mm / min, and the initial distance between the specimen grips is 70 mm.

The breaking energy of the aluminum foil is 3 kg ·
If less than mm, when joining the active material and the current collector,
When the battery element is assembled by laminating or winding the positive electrode body and the negative electrode body, or when the lead is welded to the positive electrode body, the positive electrode body is easily damaged by external stress. In particular, in applications where the battery is exposed to severe external vibration, the breaking energy of the positive electrode current collector aluminum foil is preferably 4 kg · mm or more.

Further, it is preferable that the breaking energy is large in terms of strength. However, in order to increase the breaking energy, the non-roughened part of the aluminum foil must be thickened. The proportion occupied by the conductor increases, and the capacity per unit volume of the battery (hereinafter referred to as capacity density) decreases. Therefore, the breaking energy is preferably 15 kg · mm or less, particularly preferably 10 kg · mm or less.

It is a basic proposition of commercial products that a conventional foil for an aluminum electrolytic capacitor develops a high capacity while maintaining strength. On the other hand, the current collector for a battery is required to have a strong bonding force between the active material and the current collector and to have a strong electrode body integrated with the current collector. It is different from the basic proposition. Therefore, even if the foil for an aluminum electrolytic capacitor is applied to a battery current collector, good characteristics as a battery cannot be obtained. Therefore, the present inventors diligently studied an aluminum foil having a new structure separately from the foil for an aluminum electrolytic capacitor, and reached the present invention.

The aluminum foil in the present invention is preferably an etched foil, and the etching preferably reduces the weight by 1 to 8 g / m ² . If the weight loss due to etching is less than 1 g / m ² , the bonding strength between the polarizable electrode and the current collector tends to be weak. If the weight loss due to etching exceeds 8 g / m ² , the bonding strength between the electrode layer and the current collector will no longer be improved, and the etching cost will increase, resulting in poor production efficiency. Furthermore, since the porosity of the roughened layer due to etching becomes too high, the mechanical strength of the roughened layer itself decreases, and current is collected when the electrode layer and the current collector are joined to form the electrode body. In some cases, it is easy to peel off at the interface between the roughened layer and the non-roughened part of the body. The loss on etching is more preferably ² to 6 g / m ² , particularly preferably 3 to 5 g / m ² .

As the method for etching the aluminum foil in the present invention, there are three methods: AC etching, DC etching, and chemical etching. Then, by appropriately selecting the composition of the etching solution, the temperature, the time, the frequency, the current density, the multi-stage etching method, etc., the thickness of the roughened layer,
It is possible to industrially continuously produce foils having various roughened structures having different etching pit densities of the aluminum foil and different capacitances of the roughened layer.

In the case of AC etching, for example, S. A
J. lwitt et al. Electrochem. So
c. , 128, 300-305 (1981) or Sumitomo Light Metal Technical Report 205-212 (1993) by Fukuoka et al. Can form a spongy surface structure. In the AC etching, when the frequency or the etching temperature is increased, the diameter of the etching hole on the surface of the aluminum foil can be reduced.

DC etching is performed using a roughened layer having a spongy porous structure formed by AC etching and a foil in which the (100) plane is oriented and occupies most of the aluminum foil surface. A layer having a so-called pit foil structure in which holes are formed perpendicular to the thickness direction is a typical structure of the surface roughening layer of the positive electrode current collector aluminum foil in the present invention.

The capacitance of the aluminum foil as the positive electrode current collector of the present invention is preferably 5 to 40 μF / cm ² . If it is less than 5 μF / cm ² , the adhesion strength of the mixture of the positive electrode active material and the polymer electrolyte to the current collector decreases.

If it exceeds 40 μF / cm ² , the adhesion strength of the binder or the mixture of the polymer electrolyte and the positive electrode active material to the current collector is no longer improved even if the capacitance is further increased. Conversely, the mechanical strength of the current collector itself decreases,
When forming a roughened layer by continuous etching, the etching rate must be reduced. Therefore, the efficiency of etching is low, and the amount of by-product aluminum chloride increases due to an increase in the amount of etching solution used. From the viewpoint of bonding strength, foil strength and cost, in particular, 10 to 30 μF / cm
² is preferred.

The surface of the aluminum foil in the present invention is:
When projected at a magnification of 20,000 with an electron microscope, it is preferable that the hole diameter of the opening is substantially 0.05 to 0.5 μm. Further, it is preferable to have 5 × 10 ^{7 to} 3 × 10 ¹⁰ holes having a hole diameter of 0.05 to 0.5 μm per 1 cm ² .
In particular, a cubic, spherical or intermediate shape is preferably used as the basic etching shape, and a spongy roughened structure is preferable. The total surface area of the fine holes formed by etching reflects the capacitance, but the hole diameter is 0.1 mm.
When the thickness is less than 05 μm, the binder hardly enters the inside of the pores, and the bonding strength between the current collector and the positive electrode active material is reduced. In particular, when a polymer electrolyte is used to give the polymer electrolyte the function of a binder, the decrease is remarkable.

If the pore size is more than 0.5 μm, the strength of the aluminum foil is reduced, and it is necessary to reduce the number of holes in order to secure the strength. In particular, the pore size is preferably from 0.08 to 0.3 μm. However, the pore size in the present specification,
It indicates the longest diameter of the hole having the basic etching structure when observed at a magnification of 20,000 with a microscope.

The spongy etching holes of the aluminum foil are fine as described above, and the density of the holes is 2 μm by an electron microscope, assuming that the etching holes are not united.
When observed at 10,000 times, the aperture ratio due to the surface holes is 20%
It is preferable that it is above. If the aperture ratio due to the holes is less than 20%, a desired bonding force cannot be obtained because the bonding area between the binder and the current collector foil is reduced. In particular, when a polymer electrolyte is used to give the polymer electrolyte the function of a binder, the bonding strength is very weak.

The bonding strength of the above holes having a diameter of 0.05 to 0.5 μm is insufficient if the number is less than 5 × 10 ⁷ per 1 cm ² of the projected area of the foil surface. If the number is more than 3 × 10 ^10, the strength of the roughened layer itself is reduced, and particularly when a polymer electrolyte is used, the polymer electrolyte penetrates into the concave portions of the roughened layer and is integrated with the roughened layer. It is not preferable because it is easy to peel off at the interface between the formed composite layer and the non-roughened portion of the aluminum foil. More preferably 5 × 10
^{8 to} 1.5 × 10 ¹⁰ .

In the present invention, the thickness of the non-roughened portion of the aluminum current collector foil is preferably 8 to 40 μm. If the thickness of the non-roughened part is less than 8 μm, the strength of the foil is insufficient, and the bonding of the positive electrode active material and the current collector or the step of continuously laminating the positive electrode body, the separator, and the negative electrode body It is easy to break. If it exceeds 40 μm, the weight and volume of the electrode body will increase, and it will be difficult to meet the demands for lighter and smaller batteries.

In the non-aqueous secondary battery having the positive electrode current collector of the present invention and having a liquid electrolyte, the binder used for bonding the positive electrode active material to the current collector is strongly bonded to the current collector. By adhering to, it is excellent in charge / discharge cycle durability. Examples of the binder include polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / perfluoro (alkyl vinyl ether) copolymer, vinylidene fluoride / hexafluoropropylene copolymer, from the viewpoint of bonding strength with the current collector. One or more selected from the group consisting of chlorotrifluoroethylene / vinylene carbonate copolymer is preferred.

The positive electrode current collector of the present invention, when applied to a non-aqueous secondary battery having a polymer electrolyte, has a great effect of improving the charge / discharge cycle durability. In the case of a non-aqueous secondary battery having a polymer electrolyte, the polymer electrolyte is contained in the electrode and has a function of a binder at the same time as the function of the electrolyte.However, the polymer electrolyte contains a solvent and swells. Adhesion to the current collector is weaker than the binder contained in the liquid electrode. However, in the case of the positive electrode body of the present invention, the positive electrode active material and the polymer electrolyte can be strongly adhered to the current collector by entering the polymer electrolyte into the concave portion on the surface of the aluminum current collector foil.

In the present invention, when the positive electrode for a non-aqueous secondary battery has a polymer electrolyte, the polymer electrolyte contains an organic polymer as a matrix and contains a solution comprising a solute of a lithium salt and a non-aqueous solvent capable of dissolving the lithium salt. .
The organic polymer as the polymer matrix is a copolymer containing polymerized units based on two or more monomers, and one or more of the polymerized units based on the monomers are polymerized units based on a fluoroolefin. Is preferable because a secondary battery having high electrochemical stability and stable operation at a high voltage can be obtained. In this case, the copolymer is preferably contained in the positive electrode together with the solution as a binder for the positive electrode.

Various fluoroolefins can be used as raw materials for obtaining a copolymer containing polymerized units based on a fluoroolefin by polymerization, but are excellent in copolymerizability with other monomers and have a high polymer strength. Chlorotrifluoroethylene, tetrafluoroethylene,
Vinylidene fluoride or hexafluoropropylene is preferred. In the present invention, the copolymer of the matrix of the polymer electrolyte is 2 of the above four kinds of fluoroolefins.
A copolymer obtained by copolymerizing at least one kind or a copolymer obtained by copolymerizing at least one of the above four kinds of fluoroolefins with another monomer can be preferably used.

Other monomers to be copolymerized with the above four kinds of fluoroolefins include, for example, hexafluoroacetone, perfluoro (methyl vinyl ether), perfluoro (propyl vinyl ether), ethylene, propylene, isobutylene, and pivalic acid. Vinyl, vinyl acetate, vinyl benzoate, ethyl vinyl ether, butyl vinyl ether, cyclohexyl vinyl ether, ethyl allyl ether, cyclohexyl allyl ether, norbornadiene, crotonic acid and its ester, acrylic acid and its alkyl ester, methacrylic acid and its alkyl ester, vinylene carbonate And the like.

It is also preferable to use a fluoroolefin such as trifluoroethylene, vinyl fluoride, (perfluorobutyl) ethylene and (perfluorooctyl) propylene together with the above four kinds of fluoroolefins.

The matrix of the polymer electrolyte is specifically made of vinylidene fluoride / perfluoro (E) from the viewpoints of electrochemical stability, electric conductivity when a polymer electrolyte is used, adhesion to a current collector, and strength. Alkyl vinyl ether) copolymers, vinylidene fluoride / chlorotrifluoroethylene copolymers, vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene copolymers, and vinylidene fluoride / hexafluoropropylene copolymers are preferred. Particularly, vinylidene fluoride / perfluoro (alkyl vinyl ether copolymer) is preferable because of the excellent properties described above. However, in this specification, the A / B copolymer means a copolymer composed of a polymer unit based on A and a polymer unit based on B.

In the present invention, the content of the polymerized unit based on fluoroolefin in the polymer forming the matrix of the polymer electrolyte is preferably 10% by weight or more. If the amount is less than 10% by weight, the flexibility of the polymer electrolyte becomes too high, and the strength tends to decrease. In order to obtain a polymer electrolyte having particularly high strength, the content is more preferably 60% by weight or more.

Further, the polymerization unit based on one kind of fluoroolefin is preferably 97% by weight or less,
It is more preferably at most 95% by weight. If the content is more than 97% by weight, the crystallinity of the polymer will be high, the flexibility will be low, the molding processability will be low, the lithium salt solution will not easily penetrate into the matrix, and the electric conductivity of the polymer electrolyte will be low. .

The organic polymer forming the matrix of the polymer electrolyte is preferably crosslinked as necessary from the viewpoint of preventing a change in volume during charge and discharge of the polymer electrolyte and improving mechanical strength.

The molecular weight of the organic polymer forming the matrix of the polymer electrolyte is preferably 10,000 to 1,000,000. If the molecular weight exceeds 1,000,000, the dissolution viscosity is extremely high, and it is difficult to uniformly mix with the lithium salt solution, or the holding amount of the lithium salt solution is reduced, and the electric conductivity of the polymer electrolyte is undesirably reduced. On the other hand, if it is less than 10,000, the mechanical strength of the polymer electrolyte is significantly reduced, which is not preferable. Particularly preferably, 30,000 to 500,000 is employed.

When a polymer electrolyte is used, the positive electrode preferably contains a polymer electrolyte. in this case,
Since the organic polymer which is the matrix of the polymer electrolyte has the function of the binder, another binder different from the organic polymer is not particularly required. At this time, it is preferable that the weight ratio of the positive electrode active material / polymer electrolyte in the positive electrode is 1/2 to 2/1. When the weight ratio is less than 1/2, the capacity of the battery decreases. If the ratio exceeds 2/1, the bonding strength to the current collector decreases and the bonding strength between the active materials decreases. More preferably, it is 2/3 to 3/2.

In the present invention, the content ratio of the polymerized unit based on the fluoroolefin in the organic polymer, the content ratio of other components, the molecular weight of the polymer and the like are determined by the solubility or dispersion of the matrix in an organic solvent for forming a film. sex,
The matrix can be appropriately selected depending on the miscibility with the lithium salt solution, the retention of the lithium salt solution, the adhesion of the polymer electrolyte to the current collector metal, the strength, the moldability, the handleability, the availability of the matrix, and the like.

The non-aqueous solvent capable of dissolving the lithium salt of the non-aqueous secondary battery of the present invention is preferably a carbonate ester. Carbonate can be used either cyclic or chain. Examples of the cyclic carbonate include propylene carbonate and ethylene carbonate. Dimethyl carbonate, diethyl carbonate,
Ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate and the like are exemplified.

In the present invention, the above-mentioned carbonates can be used alone or in combination of two or more. It may be used by mixing with other solvents. Further, depending on the material of the negative electrode active material, the combined use of a chain carbonate and a cyclic carbonate may improve the discharge characteristics, cycle durability, and charge / discharge efficiency.

The lithium salt used in the present invention includes:
ClO ₄ ⁻ , CF ₃ SO ₃ ⁻ , BF ₄ ⁻ , PF ₆ ⁻ , As
F ₆ ⁻ , SbF ₆ ⁻ , CF ₃ CO ₂ ⁻ , (CF ₃ SO ₂ ) ₂ N
^- that is preferable to use any one or more of lithium salt having an anion.

The lithium salt solution in the present invention is preferably a solution in which the lithium salt is dissolved in the non-aqueous solvent at a concentration of 0.2 to 2.0 mol / l. Outside of this range, the ionic conductivity decreases, and the electrical conductivity of the electrolytic solution or polymer electrolyte decreases. More preferably, 0.
5 to 1.5 mol / l is selected.

In the present invention, when a polymer electrolyte is used, a mixture of the polymer electrolyte and the positive electrode active material in which the lithium salt solution is uniformly distributed in a matrix is integrated with a positive electrode current collector and used as a positive electrode body. However, the content of the lithium salt solution in the polymer electrolyte is preferably 30 to 90% by weight. If the content is less than 30% by weight, the electric conductivity is undesirably low. If the content exceeds 90% by weight, the polymer electrolyte cannot maintain a solid state, which is not preferable. Particularly preferably, 40 to 80% by weight is employed.

The cathode body of the present invention can be manufactured by various methods. When applied to an electrolyte-based nonaqueous secondary battery, for example, a binder is dissolved or uniformly dispersed in an organic solvent, and a positive electrode active material is further dispersed to form a slurry. The slurry is applied, cast or spin-coated on the current collector with a bar coater or a doctor blade, and then dried to remove the organic solvent to obtain a positive electrode body.

In the case of a non-aqueous secondary battery having a polymer electrolyte, for example, a polymer forming a matrix of the polymer electrolyte is dissolved or uniformly dispersed in an organic solvent, and mixed with a solution in which a lithium salt is dissolved in the solvent. (Hereinafter, this mixed liquid is also referred to as a mixed liquid for forming a polymer electrolyte). The mixed solution is further mixed with a positive electrode active material to form a slurry, which is then coated on a current collector with a bar coater or a doctor blade, cast or spin-coated, and then dried to remove an organic solvent mainly dissolving or dispersing the polymer. Then, a positive electrode film obtained by integrating a mixture comprising a polymer electrolyte and a positive electrode active material with a positive electrode current collector is obtained. If the solvent used in the lithium salt solution partially evaporates during drying, the film is newly impregnated with the solvent or the film is exposed to the solvent vapor to obtain a desired composition.

As an organic solvent for dissolving or dispersing the polymer, tetrahydrofuran (hereinafter referred to as THF), methyl ethyl ketone, methyl isobutyl ketone,
Toluene, xylene, N-methylpyrrolidone, acetone, acetonitrile, dimethyl carbonate, ethyl acetate, butyl acetate and the like can be used, but in order to selectively remove this organic solvent by drying, the boiling point of THF, acetone or the like is 100 ° C or less. Volatile organic solvents are preferred.

The positive electrode active material in the present invention is a material capable of inserting and extracting lithium ions. For example, Ti, Zr, Hf of group 4 of the periodic table, V, Nb, Ta of group 5 and C of group 6
r, Mo, W, Group 7 Mn, Group 8 Fe, Ru, Group 9 Co, Group 10 Ni, Group 11 Cu, Group 12 Zn, C
d, Al, Ga, In of group 13; Sn, Pb of group 14;
Oxides and composite oxides containing a metal such as Sb and Bi of Group 15 and Te of Group 16 as main components, chalcogenides such as sulfides, oxyhalides, and composite oxides of the above metals and lithium can be used. .

As the lithium-containing compound used for the positive electrode active material, a composite oxide of lithium and manganese, a composite oxide of lithium and cobalt, and a composite oxide of lithium and nickel are particularly preferable. The particle size of these positive electrode active materials is preferably 30 μm or less in order to stabilize the slurry for producing the positive electrode and to develop the strength of the electrode layer itself.

When the conductivity of the positive electrode active material itself is insufficient, a conductive material may be added to the positive electrode active material. As the conductive material, natural graphite having good conductivity or artificial graphite which is highly graphitized is preferably used. Further, in order to improve the absorbency of the electrolyte while maintaining the conductivity, 1 to 5% by weight
Can also be added. The particle size of these conductive materials is preferably 5 μm or less.

Further, a conductive polymer material such as a polyaniline derivative, a polypyrrole derivative, a polythiophene derivative, a polyacene derivative, a polyparaphenylene derivative, or a copolymer thereof may be used in combination.

In the non-aqueous secondary battery of the present invention, the negative electrode and / or the positive electrode contain lithium. Generally, a lithium-containing compound is used as the positive electrode active material when synthesizing the positive electrode active material. In addition, lithium can be contained in the negative electrode by a chemical or electrochemical method before the battery is assembled, or lithium can be contained by bringing lithium metal into contact with the negative electrode and / or the positive electrode when the battery is assembled.

The negative electrode active material in the non-aqueous secondary battery of the present invention is a material capable of inserting and extracting lithium ions.
The material forming these negative electrode active materials is not particularly limited. For example, lithium metals, lithium alloys, carbon materials, oxides mainly composed of metals of Groups 14 and 15 of the periodic table, carbon compounds, silicon carbide compounds, silicon oxide compounds , Titanium sulfide, boron carbide compounds and the like.

As the carbon material, those obtained by thermally decomposing organic substances under various thermal decomposition conditions, artificial graphite, natural graphite, soil graphite, expanded graphite, flaky graphite, and the like can be used. As the oxide, a compound mainly composed of tin oxide can be used. The particle size of these negative electrode active materials is 3 to stabilize the slurry for producing the negative electrode and to develop the strength of the electrode itself.
It is preferably 0 μm or less.

When the negative electrode active material is used, the negative electrode body can be manufactured in the same manner as the positive electrode body using the negative electrode current collector.

When the nonaqueous secondary battery of the present invention has a polymer electrolyte, the polymer electrolyte interposed between the positive electrode and the negative electrode is formed, for example, as follows. That is, the mixed solution for forming a polymer electrolyte is made into a slurry form, and coated on a glass plate by a bar coater or a doctor blade,
After casting or spin-coating, drying is performed to remove mainly the organic solvent in which the polymer is dissolved or dispersed, and this is peeled off from the glass plate to obtain a film made of a polymer electrolyte to obtain a separator. When the solvent of the lithium salt solution partially evaporates during drying, the separator film is newly impregnated with the solvent or the separator film is exposed to the solvent vapor to obtain a desired composition.

It is preferable to use a porous polypropylene, a porous polytetrafluoroethylene, a nonwoven fabric, a polymer woven fabric, a net, or the like as a reinforcing body and carry a polymer electrolyte as a separator because the strength can be improved.

The matrix of the polymer electrolyte used for the positive electrode, the separator or the negative electrode may have the same composition. However, the composition may be varied as necessary in consideration of the oxidation resistance and reduction resistance of the polymer.

The shape of the non-aqueous secondary battery of the present invention is not particularly limited. A sheet shape (a so-called film shape), a folded shape, a rolled bottomed cylindrical shape, a button shape, and the like are selected according to the application.

[0065]

EXAMPLES The present invention will be specifically described below with reference to Examples (Examples 1 to 4) and Comparative Examples (Examples 5 and 6), but the present invention is not limited thereto.

Example 1 A stainless steel autoclave with a stirrer having an inner volume of 1 L was used, and 540 g of ion-exchanged water was used.
tert-butanol 59.4 g, sec-butanol 0.6 g, C ₈ F ₁₇ CO ₂ NH ₄ 6 g, Na ₂ H
12 g of PO ₄ .12H ₂ O and 6 g of ammonium persulfate
g, the _{FeSO 4 · 7H 2 O 0.009g,} EDTA ·
11 g of 2H ₂ O (ethylenediaminetetraacetic acid dihydrate),
After adding 40.5 g of CF ₂ = CFOCF ₂ CF ₂ CF ₃ and replacing the gas phase with nitrogen, 99.8 g of vinylidene fluoride
Was charged. After the temperature was raised to 25 ° C., CH ₂ OHSO ₂ N
a. A 1% by weight aqueous solution of 2H ₂ O (Rongalit) was added to 21
The polymerization reaction was performed by adding at a rate of ml / hr. Since the pressure decreased with the progress of the reaction, vinylidene fluoride was added so that the pressure in the system was maintained at 23 atm. After 5 hours, the polymerization was stopped by purging the gas phase to obtain an emulsion having a concentration of 30% by weight.

This emulsion is coagulated, washed and dried,
Vinylidene fluoride / CF ₂ = CFOCF ₂ CF ₂ CF ₃
The copolymer was recovered. The composition of the copolymer is vinylidene fluoride / CF ₂ ＣＦCFOCF ₂ CF ₂ CF ₃ = 89 /
11 (weight ratio), the intrinsic viscosity using THF as a solvent was 1.
It was 4 dl / g.

In an argon atmosphere, 10 parts by weight of this copolymer was dissolved in 32 parts by weight of THF while stirring. This is designated as solution 1. Next, LiPF ₆ was dissolved at a concentration of 1 mol / l in an argon atmosphere in a solvent in which ethylene carbonate and propylene carbonate were mixed at a volume ratio of 1/1. This is designated as solution 2.

5 parts by weight of solution 2 was added to 21 parts by weight of solution 1 and heated to 60 ° C. with stirring. This solution was applied on a glass plate using a bar coater, and dried at 40 ° C. for 1 hour to remove acetone to obtain a 100 μm thick transparent polymer electrolyte film. The composition of this film was 48/46/6 by weight of the copolymer, ethylene carbonate / propylene carbonate mixed solvent, and LiPF ₆ .

This film was peeled from the glass substrate, and the electric conductivity was measured by an alternating current impedance method at 25 ° C. in an argon atmosphere. Electric conductivity is 4 × 10 ^-4 S / c
m.

Next, a positive electrode current collector was produced as follows. A mixture of hydrochloric acid / phosphoric acid / sulfuric acid using a hard aluminum foil having an aluminum purity of 99.9% by weight or more and a copper content of less than 0.05% by weight, a thickness of 30 μm, a width of 7 cm and a length of 10 cm. Using an aqueous solution as an etching electrolyte, alternating current two-stage etching was performed to obtain an aluminum foil having both surfaces roughened.

The obtained foil had a thickness of 30 μm, the thickness of the roughened layer was the same on both sides, each averaged 3 μm, and the thickness of the unroughened portion was 24 μm. The weight loss of the etching foil due to etching was 5.5 g / m ² . When the surface of the aluminum foil was observed with a scanning electron microscope at a magnification of 20,000 times, the surface was spongy, and the etching holes had an average pore diameter of 0,0.
It was 1 μm. JIS-K6 from the above aluminum foil
A No. 1 dumbbell-shaped test piece specified in 301 was punched out and subjected to a tensile test to measure the breaking energy, which was 4.50 kg · mm.

LiCoO having a particle size of 5 μm as a positive electrode active material
₍₂₎ 11 parts by weight of powder, 1.5 parts by weight of acetylene black having a particle size of 0.01 μm or less as a conductive material, 6 parts by weight of the above copolymer, 11 parts by weight of solution 2 and 70 parts by weight of THF in an argon atmosphere. The mixture was mixed and heated with stirring to obtain a slurry. This slurry was applied to the above aluminum foil with a bar coater and dried to obtain a positive electrode. The positive electrode body composed of the positive electrode current collector, the positive electrode active material, and the polymer electrolyte is 18
No abnormalities such as peeling were observed even when bent at 0 °.

The mesophase carbon fiber powder (average diameter 8 μm, average length 50 μm, (0
02) 12 parts by weight of the spacing 0.336 nm), 6 parts by weight of the above copolymer, 11 parts by weight of solution 2 and 70 parts by weight of THF were mixed in an argon atmosphere and heated with stirring to obtain a slurry. . The slurry was applied to a copper foil having a thickness of 20 μm and the surface of which was sand blasted by a bar coater and dried to obtain a negative electrode body.

The above-mentioned polymer electrolyte film was set to 1.5 cm
Formed into corners, through which the effective electrode area 1 cm x 1 cm
The positive electrode body and the negative electrode body are opposed to each other.
A lithium ion secondary battery was assembled by sandwiching and clamping the two corners of the polytetrafluoroethylene back plate, and covering the outside with an exterior film and further housing in a polypropylene case. This operation was all performed in an argon atmosphere.

The charge / discharge cycle test was performed under the conditions of a constant current of 0.5 C, a charge voltage of up to 4.2 V, and a discharge voltage of up to 2.5 V. As a result, the capacity retention after 500 cycles was 94%.

Example 2 A lithium secondary battery was assembled in the same manner as in Example 1 except that a lithium / aluminum alloy foil having a thickness of 100 μm was used as a negative electrode, and a charge / discharge cycle test was performed as in Example 1. The capacity retention after 500 cycles was 90%.

Example 3 Using a soft aluminum foil having a thickness of 40 μm and a purity of 99.9% by weight, the conditions for AC etching of the aluminum foil in Example 1 were changed, ie, the frequency, current density, temperature and electrolysis time were changed. In the same manner as in Example 1, an aluminum foil having both surfaces roughened was obtained. The obtained foil had a thickness of 40 μm, the average thickness per side of the roughened layer was 4 μm, and the thickness of the non-roughened portion was 32 μm. The weight loss due to etching of this foil was 4.2 g / m ^2.
Met.

When the foil was observed with a scanning electron microscope at a magnification of 20,000 times, the surface was spongy, and the etching holes had an average hole diameter of 0.1 μm. When the breaking energy was measured in the same manner as in Example 1, it was 8.60 kg · mm. Example 1 except that this aluminum foil was used as the current collector of the positive electrode
A lithium ion secondary battery was assembled in the same manner as in Example 1, and a charge / discharge cycle test was performed in the same manner as in Example 1. As a result, the capacity retention after 500 cycles was 95%.

Example 4 Using the same aluminum-etched foil as in Example 1, LiCo having a particle size of 5 μm was used as a positive electrode active material.
11 parts by weight of O ₂ powder, particle size 0.01 μm as conductive material
1.5 parts by weight of the following acetylene black and 7 parts by weight of an aqueous dispersion containing 20% by weight of polytetrafluoroethylene were added, water was further added, and the mixture was mixed by a ball mill to obtain a slurry. This slurry was applied to the above aluminum foil with a bar coater, heated and dried, and then roll pressed to obtain a positive electrode body. The positive electrode body including the positive electrode current collector, the positive electrode active material, and the binder did not show any abnormality such as peeling even when bent at 180 degrees.

As the negative electrode active material, mesophase carbon fiber powder (average diameter 8 μm, average length 50 μm, (0
02) N-methyl-2-pyrrolidone was added as a solvent to 10 parts by weight of the spacing 0.336 nm) and 1 part by weight of polyvinylidene fluoride, and mixed with a ball mill to obtain a slurry. This slurry was applied to a copper foil having a thickness of 20 μm and the surface of which was sand blasted by a bar coater, heated and dried, and then roll-pressed to obtain a negative electrode body. Next, the positive electrode body and the negative electrode body were vacuum-dried at 180 ° C.

A positive electrode body having an effective electrode area of 1 cm × 1 cm and a negative electrode body were opposed to each other through a 1.5 cm square porous polypropylene separator having a thickness of 25 μm in an argon box. The sheet was clamped and clamped between two polytetrafluoroethylene back plates, and the outside thereof was covered with an exterior film, and further housed in a polypropylene case.
Next, 1 mol / L of LiPF ₆ was mixed with a mixed solvent of ethylene carbonate and diethyl carbonate (volume ratio 1: 1).
By vacuum impregnating the solution dissolved in 1), a lithium ion secondary battery was assembled. This operation was all performed in an argon atmosphere.

A charge / discharge cycle test was conducted in the same manner as in Example 1. As a result, the capacity retention after 500 cycles was 97%.

Example 5 An aluminum foil having both surfaces roughened was obtained in the same manner as in Example 1 except that the conditions for AC etching of the aluminum foil in Example 1 were changed, that is, the frequency, current density, temperature and electrolysis time were changed. . The resulting foil is 30μ thick
m, the average thickness per side of the roughened layer is 7 μm,
The thickness of the unroughened portion was 16 μm. The weight loss due to etching of this foil was 11.5 g / m ² . Observation with a scanning electron microscope at a magnification of 20,000 times revealed that the surface was spongy and the etching holes had an average pore size of 0.0
It was 8 μm. When the breaking energy was measured in the same manner as in Example 1, it was 2.58 kg · mm.

When a positive electrode body was prepared in the same manner as in Example 1, the positive electrode body was cut during press rolling of the positive electrode body, and was not usable.

Example 6 The same as Example 1 except that the same aluminum foil having a thickness of 30 μm as in Example 1 was mechanically roughened with sandpaper # 600 and used as a positive electrode current collector. To produce a positive electrode body. On the surface of the roughened current collector, a linear groove having a depth of 7 μm and a width of 4 to 15 μm was formed. The positive electrode body did not have any abnormality when laid flat, but peeled off from the current collector when bent at 90 degrees.
Using this positive electrode body, a polymer battery was prepared in the same manner as in Example 1, and a charge / discharge cycle test was performed. As a result, the capacity retention after 50 cycles was 50%.

Further, a linear groove having a depth of 7 μm and a width of 4 to 15 μm was similarly formed in an aluminum foil having a thickness of 30 μm, and a positive electrode body was manufactured in the same manner as in Example 1. And a battery could not be produced.

[0088]

The positive electrode current collector for a non-aqueous secondary battery of the present invention has excellent charge-discharge cycle characteristics due to the strong adhesion between the positive electrode active material and the binder and the current collector, and the current collector breaks. Since the energy is high, the positive electrode body can be easily formed. In particular, in the case of a non-aqueous secondary battery having a polymer electrolyte, the adhesive strength between the positive electrode active material and the current collector is higher than that of an electrolyte battery because the swollen polymer electrolyte containing a solvent also functions as a binder. Although weakness has conventionally been a problem, the use of the positive electrode current collector of the present invention has a strong adhesion between the positive electrode active material and the polymer electrolyte and the current collector, and has excellent cycle characteristics in a secondary battery using a polymer electrolyte. Is obtained.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Ken Kawari, Asahi Glass Co., Ltd., 1150 Hazawa-cho, Kanagawa-ku, Yokohama, Kanagawa Prefecture (72) Inventor Yoshiaki Higuchi 1150 Hazawa-cho, Kanagawa-ku, Yokohama, Kanagawa, Japan

Claims (7)

[Claims] 1. A positive electrode current collector for a non-aqueous secondary battery comprising an aluminum foil, which is integrated with an electrode comprising a positive electrode active material and a binder to form a positive electrode body, wherein the aluminum foil has an average surface area of 1%. For a non-aqueous secondary battery, characterized in that it has a roughened layer having a thickness of about 5 μm and a breaking energy of 3 kg · mm or more in a No. 1 dumbbell-shaped test piece specified in JIS-K6301. Positive electrode current collector. 2. An aluminum foil is an etched foil, and a weight loss by etching of the aluminum foil is 1 to 2.
Positive electrode current collector for a nonaqueous secondary battery of claim 1 wherein the 8 g / m ^2. 3. A positive electrode body obtained by integrating a positive electrode comprising a positive electrode active material and a binder and a current collector comprising an aluminum foil; a negative electrode body; and a non-aqueous solvent capable of dissolving a solute of a lithium salt and a lithium salt. A nonaqueous secondary battery containing a solution comprising a roughened layer having an average thickness of 1 to 5 μm on the surface and JIS-
A non-aqueous secondary battery characterized in that the breaking energy of a No. 1 dumbbell-shaped test piece specified in K6301 is 3 kg · mm or more. 4. The binder according to claim 1, wherein the binder is polytetrafluoroethylene, polyvinylidene fluoride, vinylidene fluoride / perfluoro (alkyl vinyl ether) copolymer, vinylidene fluoride / hexafluoropropylene copolymer, and chlorotrifluoroethylene / vinylene. The non-aqueous secondary battery according to claim 3, which is at least one member selected from the group consisting of a carbonate copolymer. 5. The non-aqueous secondary battery according to claim 3, wherein said solution forms a polymer electrolyte with a matrix comprising an organic polymer. 6. The binder according to claim 5, wherein the binder is a polymer electrolyte matrix and is a copolymer composed of polymerized units based on two or more monomers containing at least one polymerized unit based on fluoroolefin. Non-aqueous secondary batteries. 7. The copolymer includes vinylidene fluoride / perfluoro (alkyl vinyl ether) copolymer, vinylidene fluoride / chlorotrifluoroethylene copolymer, vinylidene fluoride / hexafluoropropylene / tetrafluoroethylene copolymer. 7. The non-aqueous secondary battery according to claim 6, which is a unified or vinylidene fluoride / hexafluoropropylene copolymer.