JP2001273902A - Non-aqueous secondary battery - Google Patents

Abstract

(57) [Problem] To provide a non-aqueous secondary battery having excellent high-rate discharge characteristics and high safety at the time of short circuit. SOLUTION: A positive electrode formed by forming a positive electrode mixture layer containing a positive electrode active material on at least a part of a positive electrode current collector, and a negative electrode mixture layer containing a negative electrode active material on at least a part of a negative electrode current collector In a non-aqueous secondary battery in which an electrode group consisting of a negative electrode formed with a separator and a separator interposed between the positive electrode and the negative electrode is packaged with a package, the positive electrode mixture layer or the negative electrode mixture layer A non-aqueous secondary battery is formed by including at least one of flake-shaped metals. As the flake-like metal, aluminum, nickel, cobalt, copper, chromium,
Those composed of at least one metal selected from the group consisting of iron, titanium and stainless steel are preferred.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous secondary battery, and more particularly, to a non-aqueous secondary battery having excellent high rate discharge characteristics and high safety in a short circuit.

[0002]

2. Description of the Related Art In recent years, with the development and miniaturization of portable electronic devices using a secondary battery such as a mobile phone or a notebook computer as a main power source, a demand for a lightweight and high energy density secondary battery has been increased. Is coming.

At present, a lithium ion secondary battery using LiCoO ₂ (lithium cobaltate) as a positive electrode active material and a carbon-based material as a negative electrode active material has been commercialized as a secondary battery that meets this demand. . In the charge / discharge reaction of this battery, lithium ions are desorbed from crystals of the positive electrode active material LiCoO ₂ at the time of charging, and the desorbed lithium ions are inserted into the carbon-based material of the negative electrode active material. Lithium ions inserted into the anode are desorbed, and the desorbed lithium ions are used as the positive electrode active material LiC.
It is based on a reaction utilizing the intercalation and deintercalation of lithium ions, which is reinserted into the oO ₂ crystal. This battery is different from a conventional non-aqueous secondary battery using lithium metal as a negative electrode in order to increase the capacity, and the active material is dispersed in an organic solvent together with a binder or the like to form a paste. It is applied to a current collector or a negative electrode current collector, and dried to form an electrode mixture layer containing an active material in the form of a film, which is used as a positive electrode and a negative electrode, respectively. A spirally wound electrode group produced by spirally winding the electrode group through the electrode is housed in a cylindrical battery can to constitute a battery.

[0004]

However, the electrolyte used in the non-aqueous secondary battery is a solution in which a lithium salt is dissolved in an organic solvent, and the conductivity of the electrolyte is the same as that used in alkaline batteries. 40 compared to the aqueous electrolyte solution
There is a problem that the high-rate discharge characteristics have to be low, and sufficient heavy load characteristics cannot be obtained. In addition, since intercalation of lithium ions having high reactivity with moisture in the air is used, it is required to ensure safety during a short circuit.

The present invention has been made in view of the above circumstances of conventional non-aqueous secondary batteries, and has as its object to provide a non-aqueous secondary battery having excellent high-rate discharge characteristics and high safety in the event of a short circuit. I do.

[0006]

According to the present invention, there is provided a positive electrode having a positive electrode mixture layer containing a positive electrode active material formed on at least a part of a positive electrode current collector, and a negative electrode formed on at least a part of a negative electrode current collector. In a nonaqueous secondary battery in which a negative electrode formed with a negative electrode mixture layer containing an active material and an electrode group including a separator interposed between the positive electrode and the negative electrode are packaged with a package, the positive electrode By including a flake-shaped metal in at least one of the mixture layer or the negative electrode mixture layer, the electron conductivity in the electrode mixture layer is improved, the internal resistance is reduced, and excellent high-rate discharge characteristics are obtained. In addition, when a large current is about to flow to the battery at the time of short circuit, the flake-like metal is uniformly dispersed between the active material particles, thereby preventing ion conduction and suppressing the reaction of the active material. Increase the short-circuit current Technique, to prevent the battery generates heat to a high temperature, as the non-aqueous secondary battery having high safety is obtained, is obtained by solving the above problems.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The main components of a non-aqueous secondary battery according to the present invention will be described in detail. First, a positive electrode is formed by forming a positive electrode mixture layer containing a positive electrode active material on at least a part of a positive electrode current collector. It is produced by doing.

As the above-mentioned positive electrode active material, various materials can be used without particular limitation, and transition metal oxides containing lithium are preferable because of their high energy density and excellent reversibility. Is, for example, LiCoO
₂ , lithium manganese oxides such as LiMn ₂ O ₄ , lithium nickel oxides such as LiNiO ₂ , mixtures thereof, and even LiNi
O ₂ in which a part of Ni is substituted by Co or Mn is preferably used. However, the positive electrode active material is not limited to those described above, for example, a one-dimensional chain structure,
Appropriate among lithium-containing oxides such as cobalt, nickel, vanadium, manganese and iron oxide having a two-dimensional layered structure, three-dimensional channel structure, amorphous structure, etc., or lithium-containing materials such as chalcogen or conductive polymer Just choose.

In the present invention, the flake-form metal is contained in at least one of the positive electrode mixture layer and the negative electrode mixture layer. For example, the above-mentioned positive electrode active material, a flake-shaped metal, and a positive electrode mixture-containing paste made into a paste with an organic solvent containing a conductive aid such as carbon black or a binder such as polyvinylidene fluoride, for example. It is formed by applying it to at least a part of the body and drying it, and pressing and adjusting the thickness as necessary.

The flake-like metal contained in the positive electrode mixture layer is composed of at least one metal selected from the group consisting of aluminum, titanium and stainless steel.
In particular, those containing aluminum are suitable. The content of the flaky metal positive electrode material mixture layer is 0 parts by weight with respect to 100 parts by weight of the positive electrode material mixture components (for example, the positive electrode active material, the conductive auxiliary agent and the binder) excluding the flake metal. It is preferably at least 0.5 part by weight, particularly preferably at least 2 parts by weight, more preferably at most 10 parts by weight, particularly preferably at most 5 parts by weight. That is, by increasing the amount of the flaky metal to 0.5 parts by weight or more with respect to 100 parts by weight of the positive electrode mixture component, it is possible to achieve an improvement in the high rate discharge characteristics. By setting the content to 10 parts by weight or less with respect to 100 parts by weight of the component, it is possible to prevent a decrease in the filling amount of the active material and to secure a necessary capacity. In addition,
By adding the flake-like metal, the carbon-based conductive additive can be reduced or eliminated.

The average particle size of the flake-shaped metal is preferably 0.1 to 1 times, more preferably 0.3 to 0.5 times the average particle size of the positive electrode active material. In general, as the positive electrode active material, those having an average particle diameter of about 0.1 to 30 μm are often used. For example, when the average particle diameter of the positive electrode active material is 10 μm, The diameter is preferably 1 to 10 μm, and 3 to 5 μm.
m is more preferred. Since the average particle diameter of the flaky metal is 0.1 times or more the average particle diameter of the positive electrode active material, the flaky metal can be uniformly dispersed between the active material particles without agglomeration, When the average particle diameter of the flaky metal is not more than one time the average particle diameter of the positive electrode active material, it is possible to effectively suppress a large current from flowing between the active materials. In the present invention, the average particle diameter of the flaky metal is measured by observing the lengths of the minor axis and the major axis of 100 flaky metals under a microscope to determine the average particle diameter of each flaky metal. 100
It is determined by averaging individual flake-like metals.

The flake shape of the flake-like metal used in the present invention is synonymous with what is generally called a flake shape, and refers to a thin flake shape such as a thin scale or foil shape.

In the present invention, as the positive electrode current collector, for example, a foil of aluminum, nickel, stainless steel, or the like, a punching metal, a net, an expanded metal, or the like can be used, and an aluminum foil is particularly preferable. The thickness of the positive electrode current collector is preferably 30 μm or less in order to reduce the thickness of the entire positive electrode. However, if it is too thin, wrinkles may occur when the positive electrode mixture-containing paste is applied during the production of the positive electrode, or the film may be broken by pulling, so that the thickness is 30 μm or less and 10 μm or less as described above. The above is preferred. The mounting portion of the lead body on the positive electrode side is usually provided by leaving an exposed portion of the positive electrode current collector without forming a positive electrode mixture layer on a part of the positive electrode current collector at the time of manufacturing the positive electrode. Alternatively, the positive electrode mixture layer may be provided by peeling the positive electrode mixture layer from the positive electrode current collector.

Further, the negative electrode is manufactured by forming a negative electrode mixture layer containing a negative electrode active material on at least a part of a negative electrode current collector.

The negative electrode active material is not particularly limited as long as it is capable of doping and undoping lithium ions, and various materials can be used. Particularly, a carbon-based material is preferable. Graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, carbon fibers, activated carbon,
Graphite or the like is suitably used, and graphite is particularly preferable.

In the present invention, when the flake-shaped metal is contained in the negative electrode mixture layer, the negative electrode mixture layer contains, for example, the above-mentioned negative electrode active material, the flake-shaped metal, and a binder such as polyvinylidene fluoride. The negative electrode mixture-containing paste prepared in the form of a paste with an organic solvent is also applied to at least a part of the negative electrode current collector and dried, and is pressed and adjusted as necessary.

When the flaky metal is contained in the negative electrode mixture layer, the flaky metal is at least one metal selected from the group consisting of nickel, cobalt, copper, chromium, iron, titanium and stainless steel. , But is particularly preferably made of nickel, copper, stainless steel, or the like. The content of the flaky metal in the negative electrode material mixture layer is 0.5 parts by weight or more based on the negative electrode material mixture component (for example, the negative electrode active material and the binder) excluding the flake metal. It is particularly preferably at least 2 parts by weight, more preferably at most 10 parts by weight, particularly preferably at most 5 parts by weight. That is, by making the flake-form metal 0.5 parts by weight or more based on the above-mentioned negative electrode mixture component, it is possible to achieve an improvement in high-rate discharge characteristics and an improvement in safety at the time of short-circuit. To the negative electrode mixture component
By setting the amount to be 0 part by weight or less, it is possible to suppress a decrease in the amount of the negative electrode active material and secure a necessary capacity.

The average particle size of the flake-like metal contained in the negative electrode mixture layer is 0.1% of the average particle size of the negative electrode active material.
It is preferably from 1 to 1, more preferably from 0.3 to 0.5. In general, the average particle diameter of the negative electrode active material is 0.1.
A material having a particle size of about 1 to 30 μm is often used. For example, when the average particle diameter of the negative electrode active material is 7 μm, the average particle diameter of the flaky metal is preferably 0.7 to 7 μm, and 1 to 3.5 μm is more preferred. The reason that the average particle diameter of the flake-shaped metal is preferably 0.1 to 1 times the average particle diameter of the negative electrode active material is the same as that for the positive electrode active material. In the present invention, the flake-shaped metal may be contained in at least one of the positive electrode mixture layer and the negative electrode mixture layer, but the flake-shaped metal is contained in both the positive electrode mixture layer and the negative electrode mixture layer. Needless to say, this may be done.

In the present invention, as the negative electrode current collector, for example, foils such as copper and nickel, punched metal, mesh,
An expanded metal or the like can be used, but usually, a copper foil or a nickel foil is used. The thickness of the negative electrode current collector is preferably 30 μm or less in order to reduce the thickness of the entire negative electrode. However, if it is too thin, wrinkles may occur when the negative electrode mixture-containing paste is applied, or the film may be broken by pulling in the preparation of the negative electrode. Therefore, the thickness is 30 μm or less and 5 μm or less as described above.
The above is preferred. The mounting portion of the lead body on the negative electrode side is usually provided by leaving the exposed portion of the negative electrode current collector without forming the negative electrode mixture layer on a part of the negative electrode current collector at the time of producing the negative electrode. Alternatively, the negative electrode mixture layer may be provided by peeling the negative electrode mixture layer from the negative electrode current collector.

The positive electrode and the negative electrode having the above-described configuration are overlapped with a separator interposed therebetween, and are formed into an electrode group by an appropriate means such as spirally winding, bending, or laminating a plurality of layers. The electrode group is housed in a battery can made of aluminum or stainless steel, and its opening is sealed with a sealing plate or the like, or sealed in a space formed by a laminated film with aluminum foil as the core material and packaged. By doing so, a non-aqueous secondary battery is manufactured.

In the present invention, the exterior body may be any as long as it can externally enclose a power generation element composed of the above-mentioned electrode group and the like in a sealed state, such as a battery can and a sealing plate or a gasket as exemplified above. And may be constituted by the above-mentioned laminated film. In addition, when the exterior body is composed of the laminate film, usually, two laminate films are used,
According to the thickness of the electrode group, one or both of them may be formed in advance into a flanged container shape.

As the electrolyte constituting the power generating element together with the above-mentioned electrode group, a non-aqueous liquid electrolyte in which a lithium salt is dissolved in an organic solvent (referred to as "electrolytic solution") is usually used. The solvent of the electrolyte is not particularly limited,
Suitably, chain esters are used as the main solvent.
Examples of such a chain ester include diethyl carbonate (DEC) and dimethyl carbonate (DM
Organic solvents having a chain-like COO-bond such as C), ethyl methyl carbonate (EMC), ethyl acetate (EA), and methyl propionate (MP). The fact that the chain ester is the main solvent of the electrolytic solution means that the chain ester occupies more than 50% by volume of the total solvent component, and in particular, the chain ester is the solvent component of the total solvent component. Preferably, the chain ester accounts for at least 70% by volume of the total solvent component, especially the chain ester accounts for 75% by volume of the total solvent component.
It is preferable to occupy the above.

It is preferred that the chain ester be used as the main solvent as the solvent for the electrolytic solution because the chain ester exceeds 50% by volume of the total solvent component, and the battery characteristics, especially at low temperature, This is because battery characteristics are improved.

However, in order to improve the battery capacity, an ester having a higher dielectric constant (an ester having a dielectric constant of 30 or more) is added to the chain ester rather than the solvent component of the electrolytic solution consisting of the chain ester alone. Are preferably used in combination. The amount of the ester having a high dielectric constant in the total solvent component is preferably at least 10% by volume, particularly preferably at least 20% by volume. That is, when the ester having a high dielectric constant is 10% by volume or more in all the solvent components, the capacity is clearly improved, and when the ester having a high dielectric constant is 20% by volume or more in all the solvent components, the capacity is increased. The improvement comes to appear more clearly. However, if the volume of the ester having a high dielectric constant in the total solvent component is too large, the discharge characteristics of the battery tend to decrease, so the amount of the ester having a high dielectric constant in the total solvent component is as described above. As described above, the content is preferably 10% by volume or more, more preferably 20% by volume or more, preferably 40% by volume or less, more preferably 30% by volume or less, and still more preferably 25% by volume or less.

Examples of the ester having a high dielectric constant include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), and γ-
Butyrolactone (γ-BL), ethylene glycol sulphite (EGS) and the like are preferable, and those having a cyclic structure such as ethylene carbonate and propylene carbonate are preferable, and cyclic carbonate is particularly preferable. Specifically, ethylene carbonate (EC) is preferable. Is preferred.

Examples of the solvent which can be used in combination with the ester having a high dielectric constant include, for example, 1,2-dimethoxyethane (1,2-DME) and 1,3-dioxolan (1,1).
3-DO), tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (2-Me-THF), diethyl ether (DEE) and the like. In addition, an amine-based or imide-based organic solvent, a sulfur-containing or fluorine-containing organic solvent, and the like can also be used.

When preparing an electrolytic solution, dissolve it in a solvent.
As an electrolyte salt such as a lithium salt, for example, LiCl
O_Four, LiPF₆, LiBF_Four, LiAsF₆, LiS
bF ₆, LiCF_ThreeSO_Three, LiC_FourF₉SO_Three, Li
CF_ThreeCO_Two, Li_TwoC_TwoF _Four(SO_Three)_Two, LiN
(CF_ThreeSO_Two)_Two, LiC (CF_ThreeSO_Two)_Three, Li
C_nF_{2n + 1}SO_Three(N ≧ 2) alone or two or more
The above mixture is used. Especially LiPF₆And LiC_FourF₉
SO_ThreeAnd the like are preferable because of good charge / discharge characteristics. Electric
The concentration of the electrolyte salt in the solution is particularly limited
It is not 0.3 to 1.7 mol / l, especially 0.4 to 1.7 mol / l
1.5 mol / l is preferred.

In the present invention, a gel electrolyte, a solid electrolyte, or the like can be used in addition to the above-mentioned electrolyte. Examples of the gel electrolyte and solid electrolyte include inorganic electrolytes, polyethylene oxide, polypropylene oxide, epoxy resin, polyacrylonitrile, urethane resin, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, and vinylidene fluoride. -An organic electrolyte containing a tetrafluoroethylene copolymer or a derivative thereof as a main material.

In the present invention, as the separator, for example, a microporous resin film, a nonwoven fabric or the like is suitably used. Examples of the microporous resin film include a microporous polyethylene film, a microporous polypropylene film, and a microporous ethylene-propylene copolymer film. Further, as the nonwoven fabric, for example,
Examples include a polypropylene nonwoven fabric, a polyethylene nonwoven fabric, a polyethylene terephthalate nonwoven fabric, and a polybutylene terephthalate nonwoven fabric.

In the non-aqueous secondary battery of the present invention, when an electrolyte which is a liquid electrolyte is used as the electrolyte, the above-described microporous resin film or non-woven fabric is used in a normal state as the separator, but the gel-like separator is used. When using an electrolyte,
Nonwoven fabric or the like used as a support for the gel electrolyte may also serve as a separator. Further, when a solid electrolyte is used as the electrolyte, the solid electrolyte may also serve as a separator.

When an electrolytic solution is used as the electrolyte,
In assembling the battery, the electrolytic solution is injected into the battery can after inserting the electrode group into the battery can. In the case of a gel electrolyte, the electrolyte may be held in advance on a support serving as an electrode or a separator.

[0032]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

In the following examples and the like, first, a positive electrode containing flake-shaped metal in a range of 0 to 10 parts by weight in the positive electrode mixture layer and a flake-shaped metal in the negative electrode mixture layer were added.
A negative electrode containing 10 to 10 parts by weight is prepared, and used in combination to make an example and a comparative example. First, the preparation of the positive electrode and the negative electrode will be described.

Preparation of positive electrode: LiCoO as positive electrode active material
₂ 90 parts by weight of 5 parts by weight of carbon black as a conductive additive, 5 parts by weight of polyvinylidene fluoride as a binder, and flake-like aluminum as an additive were added in an amount of 0 to 10 parts by weight (0 to 10 parts by weight) according to the composition shown in Table 1 below. Parts by weight, 1 part by weight, 2 parts by weight, 3 parts by weight, and 10 parts by weight) and mixed uniformly using N-methyl-2-pyrrolidone as a solvent to prepare a positive electrode mixture-containing paste. The paste containing the positive electrode mixture was uniformly applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 25 μm, and dried to form a positive electrode mixture layer. After drying the obtained band-shaped body, it was pressed to a thickness of 1 mm.
The positive electrode was formed by pressing to 30 μm and cut. However, in manufacturing the positive electrode, the positive electrode mixture-containing paste was not applied to part of the aluminum foil, leaving an exposed part of the aluminum foil, which was used as a connection part with the lead.

The flake-shaped aluminum used was a circular shape having a length-to-width ratio of approximately 1: 1, a thickness of 0.8 μm, an average particle size of 4 μm, and a LiCoO ₂ cathode active material. About 0.2 with respect to the average particle diameter (10 μm).
It was four times.

Preparation of negative electrode: natural graphite 9 as negative electrode active material
0 parts by weight of polyvinylidene fluoride 8 as a binder
0 to 10 parts by weight (0 part by weight, 1 part by weight,
2 parts by weight, 3 parts by weight, 10 parts by weight) and N as a solvent.
-Methyl-2-pyrrolidone was used to mix uniformly to prepare a negative electrode mixture-containing paste. The paste containing the negative electrode active material was uniformly applied to both surfaces of a negative electrode current collector made of a copper foil having a thickness of 10 μm, and dried to form a negative electrode mixture layer. After drying the obtained band-shaped body, it was pressed to a thickness of 130 μm.
m, and cut to produce a negative electrode. However, in the production of the above-mentioned negative electrode, the negative electrode active material-containing paste was not applied to a part of the negative electrode current collector as in the case of the positive electrode, leaving an exposed portion of the copper foil and connecting it to the lead body. Part.

The flake-like nickel used in producing the negative electrode was a circular shape having a length-to-width ratio of about 1: 1 and a thickness of 0.8 μm, an average particle size of 3 μm, and a negative electrode active material. Average particle size of natural graphite (7μm)
About 0.4 times.

Preparation of electrolyte solution: L was added to a mixed solvent of propylene carbonate and ethylene carbonate at a volume ratio of 1: 1.
It was prepared nonaqueous electrolytic solution of an organic solvent system by causing the iPF ₆ dissolved 1.22 mol / l.

Examples 1 to 4 Four kinds of positive electrodes among the five kinds of positive electrodes prepared as described above (that is, when the content of flake aluminum was 1 part by weight, 2 parts by weight, 3 parts by weight, 10 parts by weight) Of the above negative electrode and the negative electrode having a flake-like nickel content of 0 parts by weight (that is, a negative electrode not containing flake-like nickel) among the above-mentioned negative electrodes from a microporous polyethylene film having a thickness of 25 μm. , And spirally wound to form an electrode group having a spirally wound structure. After inserting this wound electrode group into a battery can, a predetermined amount of the above-mentioned electrolyte was injected, and then the container was sealed by a conventional method to produce a cylindrical non-aqueous secondary battery having the structure shown in FIG.

Here, the battery shown in FIG. 1 will be described. 1 is the positive electrode and 2 is the negative electrode. However, FIG. 1 does not show the current collectors used for producing the positive electrode 1 and the negative electrode 2 in order to avoid complication.
The positive electrode 1 and the negative electrode 2 are spirally wound with a separator 3 interposed therebetween, and are housed in a battery can 5 together with the electrolytic solution 4 as a spiral electrode body.

The battery can 5 is made of stainless steel, and an insulator 6 made of polypropylene is disposed at the bottom of the battery can 5 before the spiral electrode body is inserted. The sealing plate 7 is made of aluminum and is in the shape of a disk.
In addition, a hole is provided around the thin portion 7a as a pressure introduction port 7b for applying the internal pressure of the battery to the explosion-proof valve 9. The projection 9a of the explosion-proof valve 9 is welded to the upper surface of the thin portion 7a to form a welded portion 11. In addition, the thin portion 7a provided on the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 and the like are shown only in a cut surface so that the drawing can be easily understood, and the outline behind the cut surface is Illustration is omitted. Also, the welded portion 11 of the thin portion 7a of the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 is shown in an exaggerated state in order to facilitate understanding on the drawing.

The terminal plate 8 is made of rolled steel, has a nickel-plated surface, and has a hat-like shape with a peripheral edge formed in a flange shape. The terminal plate 8 is provided with a gas outlet 8a. . The explosion-proof valve 9 is made of aluminum and has a disk shape.
In the center thereof, a protruding portion 9a having a tip portion is provided on the power generation element side (the lower side in FIG. 1), and a thin portion 9b is provided, and the lower surface of the protruding portion 9a is closed as described above. It is welded to the upper surface of the thin portion 7a of the plate 7 to form a welded portion 11. The insulating packing 10 is made of polypropylene and has an annular shape. The insulating packing 10 is disposed above the peripheral edge of the sealing plate 7, and the explosion-proof valve 9 is disposed thereon. The gap between the two is sealed so that the electrolyte does not leak from between the two. The annular gasket 12 is made of polypropylene, and the lead body 13 is made of aluminum. The sealing plate 7 and the positive electrode 1 are connected to each other. An insulator 14 is disposed above the spiral electrode body. The bottom portion is connected by a lead body 15 made of nickel.

In this battery, the thin portion 7 of the sealing plate 7
a and the projecting portion 9a of the explosion-proof valve 9 come into contact at the welded portion 11,
Since the peripheral portion of the explosion-proof valve 9 and the peripheral portion of the terminal plate 8 are in contact with each other, and the positive electrode 1 and the sealing plate 7 are connected by the lead 13 on the positive electrode side, in a normal state, the positive electrode 1 and the terminal plate 8 Means a lead body 13, a sealing plate 7, an explosion-proof valve 9, and their welded parts 1
1 provides an electrical connection and functions normally as an electrical circuit.

When an abnormal situation occurs in the battery, such as when the battery is exposed to a high temperature, and gas is generated inside the battery and the internal pressure of the battery rises, the central pressure of the explosion-proof valve 9 rises due to the rise in the internal pressure. It deforms in the direction of the internal pressure (upward direction in FIG. 1), and accordingly, the thin portion 7a integrated at the welded portion 11 is subjected to shearing force to break the thin portion 7a.
Alternatively, after the welding portion 11 between the projecting portion 9a of the explosion-proof valve 9 and the thin portion 7a of the sealing plate 7 is peeled off, the thin portion 9b provided on the explosion-proof valve 9 is torn, and gas is discharged from the terminal plate 8. The battery is designed to be discharged from the outlet 8a to the outside of the battery to prevent the battery from bursting.

The four types of non-aqueous secondary batteries obtained were examined for high-rate discharge characteristics and subjected to a short-circuit test. Table 1 shows the results.

The high-rate discharge characteristics were 0.2% for each battery.
The discharge capacity at 2C and the discharge capacity at 2C were measured.
The discharge capacity at 2C was represented by the ratio of the discharge capacity at 2C [(discharge capacity at 2C / discharge capacity at 0.2C) x 100].

The short-circuit test was performed on a battery charged at 4.2 V
The measurement was performed by connecting a 0 mΩ lead wire and attaching a thermocouple to the surface of the battery to measure the temperature rise. The result is indicated by the maximum temperature increased by the heat generated by the short circuit. This short-circuit test is intended to clarify how the battery has a function of suppressing the current flow when a large current is about to flow due to a short circuit.

COMPARATIVE EXAMPLE 1 The positive electrode in which the content of flaked aluminum in the five kinds of positive electrodes produced as described above was 0 parts by weight (that is, the positive electrode not containing flaked aluminum) and The negative electrode having a flake-like nickel content of 0 parts by weight (a negative electrode not containing flake-like nickel) in the five types of the prepared negative electrodes was interposed via a separator made of a microporous polyethylene film having a thickness of 25 μm. The electrodes were stacked and spirally wound to form a spirally wound electrode group. Then, a cylindrical non-aqueous secondary battery was manufactured in the same manner as in Example 1 except that this electrode group was used.

Example 1 of the obtained nonaqueous secondary battery
In the same manner as in the above, high-rate discharge characteristics were examined, and a short-circuit test was performed.
Table 1 shows the results.

[0050]

[Table 1]

As shown in Table 1, in Comparative Example 1, the content of flake aluminum was 0 parts by weight, that is,
Although the flake-like aluminum was not contained in the positive electrode mixture layer, in Comparative Example 1, the high-rate discharge characteristics were 59% (that is, the discharge capacity at 2C was 0.2% and the discharge capacity was 0.2%). 59%), and the temperature rose to 150 ° C. or higher in the short-circuit test. However, in Examples 1 to 4, the high-rate discharge characteristics were excellent, and the temperature rise in the short-circuit test was suppressed. The safety at the time was high. Example 1
As is clear from the test results of Examples 2 to 4, the inclusion of flake-like aluminum in the positive electrode mixture improves the high-rate discharge characteristics, and particularly, the content of flake-like aluminum in Example 2 is 2 parts by weight. In Example 3 with 3 parts by weight and Example 4 with 10 parts by weight, high rate discharge characteristics were excellent. Further, with respect to the short-circuit test, in Examples 1 to 4 in which flake-like aluminum was contained in the positive electrode mixture layer, the rise in temperature was suppressed with an increase in the content of the flake-like aluminum, It was apparent that the safety at the time of short-circuiting (that is, the safety against fire due to short-circuiting) was improved by including flake-like aluminum in the positive electrode mixture layer.

Examples 5 to 8 Four kinds of negative electrodes among the five kinds of negative electrodes produced as described above (that is, the content of flake-like nickel was 1 part by weight, 2 parts by weight, 3 parts by weight, 10 parts by weight) Negative electrode) and a positive electrode having a flake-like aluminum content of 0 parts by weight in the positive electrode (that is, a positive electrode not containing flake-like aluminum) from a 25 μm-thick microporous polyethylene film. , And spirally wound to form an electrode group having a spirally wound structure. Then, a cylindrical non-aqueous secondary battery was manufactured in the same manner as in Example 1 except that this electrode group was used.

Regarding the obtained four types of non-aqueous secondary batteries,
High-rate discharge characteristics were examined and a short-circuit test was performed in the same manner as in Example 1. Table 2 shows the results. Table 2 also shows the results of Comparative Example 1 for comparison with Examples 5 to 8.

[0054]

[Table 2]

As shown in Table 2, in Comparative Example 1, the content of flake-like nickel was 0 part by weight, that is, the flake-like nickel was not contained in the negative electrode mixture layer (of course, the positive electrode The mixture layer does not contain flake-like aluminum.) In Comparative Example 1, however, the high-rate discharge characteristics were only 59%, and the temperature rose to 150 ° C. or higher in the short-circuit test. However, in Examples 5 to 8,
The high rate discharge characteristics were excellent, the temperature rise in the short circuit test was suppressed, and the safety at the time of short circuit was high. As is clear from the test results of Examples 5 to 8, the inclusion of flake-like nickel in the negative electrode mixture layer improves the high rate discharge characteristics, and particularly, the content of flake-like nickel is 2% by weight. In Example 6, 3 parts by weight of Example 7, and 10 parts by weight of Example 8, high rate discharge characteristics were excellent. Also,
Regarding the short-circuit test, in Examples 5 to 8 in which flaky nickel was contained in the negative electrode mixture layer, the increase in temperature was suppressed with an increase in the content of the flaky nickel, and the flaky nickel was suppressed. It was clear that by including nickel in the negative electrode mixture layer, the safety at the time of short circuit was improved.

[0056]

As described above, according to the present invention, a non-aqueous secondary battery having excellent high-rate discharge characteristics and high safety in the event of a short circuit can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a secondary battery according to the present invention.

[Explanation of symbols]

 1 positive electrode 2 negative electrode 3 separator

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Ryu Nagai 1-88 Ushitora, Ibaraki-shi, Osaka F-term in Hitachi Maxell, Ltd. (Reference) 5H029 AJ02 AJ12 AK03 AL07 AM00 AM03 AM04 AM07 AM16 BJ02 BJ14 DJ08 DJ16 EJ01 5H050 AA02 AA15 CA08 CB08 DA10 EA02 EA03 EA04 FA11 HA05

Claims (4)

[Claims] 1. A positive electrode in which a positive electrode active material-containing layer is formed on at least a part of a positive electrode current collector, and a negative electrode mixture containing a negative electrode active material on at least a part of a negative electrode current collector A nonaqueous secondary battery in which an electrode group consisting of a negative electrode formed with a layer and a separator interposed between the positive electrode and the negative electrode is packaged with a package, wherein the positive electrode mixture layer or the negative electrode mixture A non-aqueous secondary battery characterized in that at least one of the agent layers contains a flake-like metal. 2. The flake-shaped metal has an average particle diameter of:
0.1 to 1 of the average particle diameter of the positive electrode active material or the negative electrode active material
2. The non-aqueous secondary battery according to claim 1, wherein the secondary battery is doubled. 3. The flake-like metal contained in the positive electrode mixture layer comprises at least one metal selected from the group consisting of aluminum, titanium and stainless steel, and the flake-like metal contained in the negative electrode mixture layer. 3. The non-aqueous secondary battery according to claim 1, wherein the non-aqueous secondary battery comprises at least one metal selected from the group consisting of nickel, cobalt, copper, chromium, iron, titanium, and stainless steel. 4. The non-aqueous secondary battery according to claim 1, wherein the negative electrode active material is made of graphite.