JP2001185095A - Secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary battery which can obtain a large discharge capacity after recharge and discharge are repeated in the case of a high end voltage. SOLUTION: A winding electrode body 20 in which band shaped positive electrode 21 and negative electrode 22 are wound via a separator 23 is provided at an inside of battery can 11. The battery can 11 is configured so that a core material is made of copper. The battery can 11 may have the core made copper only. Further, an outer circumferential surface of copper may be covered with a coated layer formed with nickel plating, or may be constituted with a clad material of copper and, stainless steel. According to this constitution, it is possible to prevent the copper from being corroded so that the corrosion resistance of the battery can 11 can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery in which an electrode body provided with an electrolyte together with a positive electrode and a negative electrode is covered by an exterior member.

[0002]

2. Description of the Related Art In recent years, with the advance of electronic technology, electronic equipment has been improved in performance, downsized and portable.
There is an increasing demand for higher energy densities of secondary batteries used in electronic devices.

Conventionally, nickel-cadmium batteries, lead-acid batteries, and the like have been used as secondary batteries used in electronic equipment. However, these nickel-cadmium batteries and lead-acid batteries have a problem that the battery voltage at the time of discharge (hereinafter, also referred to as discharge voltage) is low and a sufficiently high energy density cannot be obtained.

Therefore, instead of nickel-cadmium batteries and lead-acid batteries, so-called lithium-ion secondary batteries have been actively researched and developed as secondary batteries having a higher discharge voltage than nickel-cadmium batteries and lead-acid batteries. This lithium ion secondary battery uses a material such as a carbonaceous material capable of absorbing and releasing lithium for the negative electrode, uses a lithium-containing compound such as lithium-cobalt composite oxide for the positive electrode, and uses a non-aqueous solvent for the non-aqueous solvent. A non-aqueous electrolyte in which an electrolyte salt is dissolved is interposed between the positive electrode and the negative electrode. In addition to the high discharge voltage, the self-discharge is small, and the charge and discharge cycle life is long. I have. Normally, in this lithium ion secondary battery, an electrode body composed of the above-described positive electrode, negative electrode and electrolyte is sealed inside an exterior member made of stainless steel or the like.

In portable electronic devices such as mobile phones, the operating voltage of a built-in IC (Integrated Circuit) has been reduced, and the demand for miniaturization of electronic devices has increased. In many cases, a battery pack composed of one secondary battery (single cell) is used as the power source. When a battery pack composed of such a single cell is used as a power source for a portable electronic device, the discharge time (ie, It is preferable to use a secondary battery having a small change in voltage with respect to the depth of discharge. In addition, when a battery pack composed of single cells is used, a large current flows from the positive electrode to the negative electrode during discharge, but the magnitude of the discharge capacity required at that time is becoming larger than before, and at the same time, In addition, it is required that a certain large discharge capacity can be obtained even when charge and discharge are repeated.

[0006]

However, in a secondary battery currently used, if charging and discharging are repeated, it is not possible to obtain a discharge capacity sufficient to constitute a single cell of a battery pack. There was a problem.

Japanese Patent Application Laid-Open No. 10-21889 discloses a container for a lithium ion secondary battery in which a core made of an aluminum-based material is covered with copper. According to the container of this lithium ion secondary battery, the weight of the container can be reduced, and the reaction between the inner peripheral surface of the can and lithium can be prevented. However, there is no description on characteristics when a charge / discharge cycle is repeatedly performed.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a secondary battery capable of obtaining a large discharge capacity after repeated charging and discharging even when the final voltage is high. Is to do.

[0009]

In a secondary battery according to the present invention, an electrode body provided with an electrolyte together with a positive electrode and a negative electrode is electrically connected to a first exterior member electrically connected to the positive electrode and to the negative electrode. A secondary battery covered by the second exterior member, wherein at least one core of the first exterior member or the second exterior member is made of copper (Cu). is there.

[0010] In the secondary battery according to the present invention, since at least one of the core members of the first exterior member and the second exterior member is made of copper, the voltage changes with respect to the discharge time even if the discharge is repeated. It has a characteristic of being small, and a large discharge capacity can be obtained.

[0011]

Embodiments of the present invention will be described below in detail with reference to the drawings. Here,
A description will be given of an example of a secondary battery in which lithium (Li) is inserted and extracted from the negative electrode.

FIG. 1 shows a sectional structure of a secondary battery according to an embodiment of the present invention. The secondary battery is a so-called cylindrical type, and has a substantially hollow cylindrical shape. For example, inside a battery can 11 having one end closed and the other end open, a band-shaped positive electrode 21 and a negative electrode 22 are provided. It has a wound electrode body 20 wound with a separator 23 interposed therebetween. Inside the battery can 11, a pair of insulating plates 12 and 13 are respectively arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20. At the open end of the battery can 11, a battery cover 14, a safety valve mechanism 15 provided inside the battery cover 14, and a PTC (Positive Temperature Coeffic
ient) The element 16 is attached by caulking via a gasket 17, and the inside of the battery can 11 is sealed. Here, the battery can 11 corresponds to a specific example of the “second exterior member” of the present invention. Also,
The battery cover 14 corresponds to a specific example of “first exterior member” of the present invention.

The safety valve mechanism 15 includes a PTC element 16
Is electrically connected to the battery cover 14 through the disk. When the internal pressure of the battery becomes equal to or higher than a predetermined value, the disk plate 15a is inverted to cut off the electrical connection between the battery cover 14 and the wound electrode body 20. It has become. Further, the PTC element 16 limits the current by increasing the resistance value when the temperature rises, and prevents abnormal heat generation due to a large current.

The battery can 11 is formed using copper (Cu) as a core material. Copper is widely used for electric wires and conductors of electric equipment, and is a material having a small electric resistivity (specific resistance). Therefore, even after the charge / discharge cycle is repeated, the amount of decrease in voltage with respect to the discharge time (that is, the depth of discharge) can be reduced. Therefore, a large discharge capacity can be obtained even if the end voltage increases. In particular, even when a large current flows at the time of discharging, such as when used as a secondary battery for a battery pack composed of a single cell, a decrease in battery voltage is small and a large discharge capacity can be obtained. it can.

The battery can 11 may be constituted only by copper as a core material, or may be constituted by containing other materials. Examples of the configuration including copper and other materials include those in which at least a portion of copper is covered by a coating layer, and those configured by a cladding material of copper and another material. No. here,
The clad material refers to layered-metal composites in which dissimilar metals are overlapped and completely bonded. As the clad material, a clad material of copper and stainless steel is preferable. This is because the corrosion resistance of the battery can 11 can be improved.

In the case where a coating layer is provided or a clad material is used, if the specific resistance of a material other than copper used for the coating layer is larger than the specific resistance of copper, compared to a battery can made of copper alone, The discharge capacity after repeating the charge / discharge cycle becomes small. However, if the outer peripheral surface of the battery can 11 is made of copper, the battery can 11 may be gradually corroded from the outside when the secondary battery is used or stored for a long time. The battery can 11 is formed by coating copper with a material having excellent corrosion resistance, or forming the battery can 11 from a clad material of a material having excellent corrosion resistance and copper.
It is preferable to improve the corrosion resistance of the steel.

FIG. 2 shows that the battery can 11 is formed so as to cover a core material 11a made of copper and an outer peripheral surface of the core material 11a (the surface opposite to the surface in contact with the laminated electrode body 20). This is an example in which the cover layer 11b is used. The coating layer 11b is made of, for example, a nickel film formed by performing a nickel (Ni) plating process on the core material 11a. Thus, the coating layer 11
By providing b, corrosion of copper can be prevented. In particular, if it is formed of nickel which is effective as a corrosion resistant material, corrosion can be effectively prevented.

When the covering layer 11b is provided, the structure is not limited to the structure shown in FIG. 2, but may be, for example, as shown in FIG. It may be provided also on the side (surface in contact with the electrode body 20). By thus providing the coating layer 11b also on the inner peripheral surface side, corrosion of copper (core material 11a) can be more effectively prevented.

The battery cover 14 is composed of a core made of, for example, copper and a coating layer made of, for example, nickel formed so as to cover the inner peripheral surface of the core.
The reason why the inner peripheral surface of the core material is covered is to prevent the copper constituting the battery cover 14 from coming into contact with an electrolytic solution described later. The battery cover 14 may also be provided with a coating layer on the outer peripheral surface, or may be made of a clad material made of stainless steel or the like and copper.

The wound electrode body 20 includes, for example, a center pin 2
4, a positive electrode lead 25 is drawn out from the positive electrode 21, and a negative electrode lead 26 is drawn out from the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery cover 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

The positive electrode 21 has a structure in which, for example, a positive electrode mixture layer is provided on both surfaces of a positive electrode current collector layer made of a metal foil. The positive electrode mixture layer preferably contains an active material (here, lithium) in an amount sufficient to obtain a large charge / discharge capacity. For example, the positive electrode active material, a conductive agent such as graphite, And a binder such as vinylidene chloride. As the positive electrode active material, for example, a lithium composite oxide or lithium composite sulfide containing lithium is preferable. In particular, in order to increase the energy density, the lithium composite oxide mainly composed of Li _x M _y O _z being preferred. Note that M is preferably one or more transition metals or aluminum. As transition metals, cobalt (Co), nickel, manganese (M
n), iron (Fe), vanadium (V) and titanium (T
At least one of i) is preferred, and at least one of cobalt, nickel and manganese is particularly preferred. Usually, x is a value in the range of 0 <x <2, y is a value in the range of 0 <y ≦ 2, and z is a value in the range of 2 ≦ z.

The negative electrode 22 is, for example, similar to the positive electrode 21,
It has a structure in which a negative electrode mixture layer is provided on both surfaces of a negative electrode current collector layer made of a metal foil. The negative electrode mixture layer includes, for example, a material capable of inserting and extracting lithium and a binder such as polyvinylidene fluoride. As a material capable of inserting and extracting lithium, for example, a material containing one or more of a carbonaceous material, a crystalline or amorphous oxide, and a polymer material Is mentioned. Among them, a carbonaceous material is preferable because the change in crystal structure that occurs during charge and discharge is very small. In addition, as a carbonaceous material,
For example, pyrolytic carbons, cokes such as pitch coke, needle coke, petroleum coke or coal coke, graphites, glassy carbons, and organic polymer compound fired bodies (for example, fired phenol resin or furan resin) , Carbon fiber or activated carbon. Examples of the oxide include tin oxide (SnO ₂ ), and examples of the polymer material include polyacetylene and polypyrrole. Further, instead of these negative electrode materials, it is also possible to use a lithium metal or a lithium alloy.

The separator 23 is made of, for example, a porous film made of a polyolefin-based material such as polypropylene or polyethylene, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. It may have a structure in which porous films are stacked.

The separator 23 is impregnated with an electrolytic solution. The electrolyte is obtained by dissolving a lithium salt as an electrolyte salt in a non-aqueous solvent. As the non-aqueous solvent, for example, propylene carbonate, ethylene carbonate,
Vinylene carbonate, 1,2-dimethoxyethane, diethyl carbonate, γ-butyl lactone, tetrahydrofuran, 1,3-dioxolan, 4-methyl-1,3
-Dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile or propionitrile are suitable, and two or more of these may be used in combination.

As the lithium salt, for example, LiClO
_{4, LiAsF 6, LiPF 6,} LiBF 4, LiB
(C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃ L
i or CF ₃ SO ₃ Li is appropriate, and two or more of these may be used in combination.

This secondary battery can be manufactured, for example, as follows.

First, a positive electrode mixture is prepared by mixing a positive electrode active material, a conductive agent and a binder, and dispersed in a solvent such as N-methylpyrrolidone to form a positive electrode mixture slurry. The slurry is applied to both sides of the positive electrode current collector layer and dried,
The positive electrode mixture layer is formed by compression molding, and the positive electrode 21 is manufactured.

Next, for example, a material capable of inserting and extracting lithium and a binder are mixed and dispersed in a solvent such as N-methylpyrrolidone to obtain a negative electrode mixture slurry. Is applied to both surfaces of the negative electrode current collector layer, dried, and compression-molded to form a negative electrode mixture layer, whereby the negative electrode 22 is produced.

Subsequently, the positive electrode lead 26 is attached to the positive electrode current collector layer by welding or the like, and the negative electrode lead 27 is attached to the negative electrode current collector layer by welding or the like. After that, the positive electrode 21 and the negative electrode 22 are wound in large numbers through the separator 23, and the distal end of the negative electrode lead 26 is welded to the battery can 11, and the distal end of the positive electrode lead 25 is welded to the safety valve mechanism 15. The rotated positive electrode 21 and negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and housed inside the battery can 11 having the above-described configuration. The positive electrode 21 and the negative electrode 22 are connected to the battery can 11
After that, the electrolytic solution is injected into the battery can 11 and impregnated into the separator 23, and the battery cover 11 having the above-described configuration and the safety valve mechanism 1 are placed at the open end of the battery can 11.
5 and PTC element 16 are fixed by caulking via gasket 17. Thus, the secondary battery shown in FIG. 1 is formed.

This secondary battery operates as follows.

In this secondary battery, when charged, for example, lithium is ionized and desorbed from the positive electrode 21 and occluded in the negative electrode 22 through the electrolytic solution impregnated in the separator 23. When the discharge is performed, for example, lithium is ionized and desorbed from the negative electrode 22 and is occluded in the positive electrode 21 through the electrolytic solution impregnated in the separator 23. Here, since the core material of the battery can 11 and the battery lid 14 is made of copper, a large discharge capacity can be obtained even if charging and discharging are repeated.

As described above, according to the secondary battery of the present embodiment, the core material of the battery can 11 and the battery cover 14 is made of copper. A secondary battery with a small change in voltage can be obtained. Therefore, a large discharge capacity can be obtained even when the end voltage is increased. Further, a large discharge capacity can be obtained even under heavy load discharge in which a large current flows during discharge.

Further, when the battery can 11 is constituted by the core material 11a and the coating layer 11b or by the clad material of the core material and another material, the corrosion of copper can be prevented. Thus, the corrosion resistance of the battery can 11 can be improved.

[0034]

Next, a specific embodiment of the present invention will be described in detail with reference to FIG.

Example 1 First, 30 parts by weight of a coal tar pitch as a binder was added to 100 parts by weight of coal-based coke as a filler, and about 1 part thereof was added.
After heating and mixing at 00 ° C., the mixture was compression molded by a press machine to obtain a precursor of a carbon molded body. Next, this precursor was calcined at a temperature of 1000 ° C. or lower to obtain a carbon molded body. Subsequently, the step of impregnating the carbon molded body with the coal tar pitch melted at a temperature of 200 ° C. or less and the step of firing the carbon molded body at a temperature of 1000 ° C. or less are repeated several times. It was graphitized by heat treatment at 2800 ° C. in an inert atmosphere, and further pulverized and classified to obtain a powder.

Structural analysis of the obtained powdery material by X-ray diffraction revealed that the (002) plane spacing was 0.337 nm and the (002) plane C-axis crystallite thickness was 50. 0.0 nm. The true density determined by the Pycnometer method was 2.23 g / cm ³ , and the bulk density determined by the method described in JIS K-1469 was 0.98 g / cm ³ . Further, when the specific surface area was determined by a BET (Brunauer, Emmett, Teller) method, the specific surface area was 1.6 m ² / g, and the breaking strength of the graphitized particles was measured using a Shimadzu micro-compression tester (MCTM-500, manufactured by Shimadzu Corporation). Was found, and the average value was 7.
It was 0 × 10 ⁻⁵ Pa / mm ² (7.1 kgf / mm ² ). When the particle size distribution was determined by a laser diffraction method, the cumulative 10% particle size was 13.3 μm, the cumulative 50% particle size was 30.6 μm, and the cumulative 90% particle size was 55.7 μm.
The average particle size was 33.0 μm.

After obtaining the powdered graphitized material, 90 parts by weight of the obtained graphitized material and 10 parts by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture, which was used as a solvent. It was dispersed in N-methylpyrrolidone to form a slurry (paste).

Subsequently, the slurry-like negative electrode mixture was applied to both sides of a negative electrode current collector layer made of a strip-shaped copper foil having a thickness of 10 μm, dried, and compression-molded by applying a constant pressure to form a negative electrode 22. Was prepared. Thereafter, a copper negative electrode lead 26 was attached to one end of the negative electrode current collector layer.

Further, lithium carbonate (Li ₂ CO ₃ ) 0.1.
5 mol and 1 mol of cobalt carbonate (COCO ₃ ) were mixed and calcined in air at 900 ° C. for 5 hours. After that, when a structural analysis was performed on the fired product by X-ray diffraction measurement, the L value registered in the JCPDS file was determined.
The diffraction peak of iCoO ₂ was well matched, and it was confirmed that the obtained fired product was LiCoO ₂ . Furthermore,
This LiCoO ₂ was pulverized to obtain a LiCoO ₂ powder having a cumulative 50% particle size of 15 μm obtained by a laser diffraction method.

Subsequently, 95 parts by weight of the obtained LiCoO ₂ powder and 5 parts by weight of lithium carbonate powder were mixed, and then 91 parts by weight of this mixture as a positive electrode active material, 6 parts by weight of flake graphite as a conductive agent, Polyvinylidene fluoride as a binder was mixed at a ratio of 3 parts by weight to prepare a positive electrode mixture, and the mixture was dispersed in N-methylpyrrolidone as a solvent to form a slurry. Thereafter, a slurry-like positive electrode mixture was applied to both sides of a positive electrode current collector layer made of a 20-μm-thick strip-shaped aluminum foil, dried, and then subjected to compression molding by applying a certain pressure to produce a positive electrode 21. After producing the positive electrode 21,
A positive electrode lead 2 made of aluminum is provided at one end of the positive electrode current collector layer.
5 was attached.

After each of the positive electrode 21 and the negative electrode 22 was manufactured, a separator 23 made of a microporous polypropylene film having a thickness of 25 μm was prepared, and the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 were laminated in this order to form a spiral. The wound electrode body 20 was wound by many turns. The outer diameter of the wound electrode body was 18 mm.

After the wound electrode body 20 is manufactured, the wound electrode body 20 is sandwiched between a pair of insulating plates 12 and 13 and the positive electrode lead 2
5 to the safety valve mechanism 15 and the negative electrode lead 26
Was welded to a battery can 11 made of copper, and the wound electrode body 20 was housed inside the battery can 11. The wound electrode body 20 is connected to the battery can 11
After that, the electrolytic solution was injected into the battery can 11. As the electrolytic solution, a solution obtained by dissolving LiPF ₆ as an electrolyte salt at a ratio of 1.0 mol / liter in a solvent obtained by mixing ethylene carbonate and dimethyl carbonate in equal volumes was used. Thereafter, a battery cover 14 made of a copper material covered with nickel is caulked to the battery can 11 via a gasket 17 coated with asphalt on the surface thereof, thereby obtaining a cylindrical type having a diameter of 18 mm and a height of 65 mm shown in FIG. Was obtained.

The secondary battery thus obtained was subjected to a charge / discharge test at 23 ° C. In particular,
First, charge / discharge was performed for one cycle, and the discharge capacity up to 3 V was determined. At that time, charging was performed at a constant current of 0.7 A until the battery voltage reached 4.2 V, and thereafter, charging was performed at a constant voltage of 4.2 V until the total charging time reached 4 hours. On the other hand, when the battery voltage is 2 at a constant current of 5 A,
V was reached. Table 1 shows the obtained results. FIG. 4 (data A) shows the relationship between the battery voltage and the discharge time at this time. In FIG. 4, the vertical axis represents the battery voltage (unit: V), and the horizontal axis represents the discharge time (unit: hou).
r).

[0044]

[Table 1]

Next, charging is performed under the same conditions as those for determining the discharge capacity in the first cycle described above, and 0.2 A
The battery was charged / discharged at a constant current until the battery voltage reached 3 V for 600 cycles. Subsequently, charging and discharging were performed under the same conditions as when the discharge capacity in the first cycle was determined, and the discharge capacity after 600 cycles was determined. Table 1 shows the obtained results. The relationship between the battery voltage and the discharge time at this time is shown in FIG. 4 (data B).

Example 2 Example 1 was repeated except that a battery can 11 was used in which copper was used as a core material and the inner and outer peripheral surfaces of the core material were plated with nickel using an electroplating method.
A secondary battery was produced in the same manner as described above. Note that NiSO ₄ —NiCl ₂ —H ₃ BO ₃ was used for plating and nickel was used for the anode. Also in this example, the obtained secondary battery was subjected to a charge / discharge test in the same manner as in Example 1, and after the first cycle and after 600 cycles, the discharge capacity was obtained, and the battery voltage and the discharge time were compared. Each relationship was examined. The obtained results are shown in Table 1 and FIG. In FIG. 4, data C shows the result of the first cycle of the present embodiment, and data D shows the result of the sixth cycle of the present embodiment.
The results after 00 cycles are shown.

(Example 3) A secondary battery was fabricated in the same manner as in Example 1 except that a battery can 11 made of copper as a core material and a clad material of copper and stainless steel was used. The ratio of copper to stainless steel was set to copper: stainless steel = 75: 25. Also in this example, the obtained secondary battery was subjected to a charge / discharge test in the same manner as in Example 1, and after the first cycle and after 600 cycles, the discharge capacity was obtained, and the battery voltage and the discharge time were compared. Each relationship was examined. Table 1 shows the obtained results.
And FIG. In FIG. 4, data E indicates the result of the first cycle of the present embodiment, and data F indicates the result after 600 cycles of the present embodiment.

As a comparative example with respect to Examples 1 to 3, Examples 1 to 3 were used except that a battery can was used in which iron was used as a core material and the inner and outer peripheral surfaces of the core material were plated with nickel. In the same manner as in No. 3, a secondary battery was produced. Also in the comparative example, the obtained secondary battery was subjected to the charge / discharge test in the same manner as in Examples 1 to 3, and the first cycle and the 600th cycle were performed.
After the cycle, the discharge capacity was determined, and the relationship between the battery voltage and the discharge time was examined. The obtained results are shown in Table 1 and FIG. In FIG. 4, data G shows the result of the first cycle of the comparative example, and data H shows the result of the comparative example after 600 cycles.

As can be seen from Table 1, when the batteries were discharged at a current of 5 A after 600 cycles, the secondary batteries of Examples 1 to 3 all obtained a large capacity of 222 mAh or more, and after 600 cycles, It was confirmed that sufficient discharge was possible even if there was. In particular, in the secondary batteries of Examples 1 and 2, a large capacity of 300 mAh or more was obtained. On the other hand, in the comparative example, only an extremely small capacity of 20 mAh was obtained. That is,
It was found that if the battery can 11 was formed using copper as a core material, a large discharge capacity could be obtained even when charge and discharge were repeated.

As described above, although the discharge capacity in the first cycle was almost the same in all of Examples 1 to 3 and Comparative Example, a difference was found in the capacity by repeating the charge / discharge cycle. This is largely affected by the discharge capacity up to 3V. That is, as shown in FIG. 4, the battery element gradually deteriorated due to the charge / discharge cycle and the internal resistance increased. The voltage drop is large. As a result, in the secondary battery of the comparative example, the voltage became 3 immediately after the start of discharge.
V or less, and the discharge capacity became extremely small. However, the specific resistance of copper is 1.7 × 10
⁻⁶ Ω · cm and the specific resistance of iron (9.8 × 10 ⁻⁶ Ω · c
m), the secondary batteries of Examples 1 to 3
Since the voltage change immediately after the start of discharge is small and the voltage reaches 3 V after discharging for a certain period of time, a large discharge capacity was obtained.

After 600 cycles, the discharge capacity of the secondary battery of Example 1 was larger than the discharge capacity of the secondary battery of Example 2 because of the specific resistance of nickel (6. 9 × 10 ⁻⁶ Ω · cm) is considered to be larger than that of copper.

As described above, the present invention has been described with reference to the embodiment and the examples. However, the present invention is not limited to the above-described embodiment and each example, and can be variously modified.
For example, in the above-described embodiment, both the cores of the battery can 11 and the battery cover 14 are made of copper. However, if at least one of the cores is made of copper, the effects of the present invention can be obtained. be able to.

Further, in the above embodiment, the coating film 11b formed by subjecting the core material 11a to nickel plating has been described as a specific example. CVD (Chemical Vapor Depositio)
It may be formed using another method such as the n) method. Further, in the above embodiment, the coating film 11b is provided on the inner peripheral surface or the outer peripheral surface of the core material 11b.
The coating film 11b may be provided on at least a part of the core material 11b.

In the above embodiment, a secondary battery using an electrolyte which is a liquid electrolyte has been described. However, instead of the electrolyte, a gel electrolyte in which a polymer compound holds the electrolyte is used. Another electrolyte such as a solid electrolyte in which an electrolyte salt is dispersed in a polymer compound having ion conductivity or a solid inorganic electrolyte may be used.

In addition, in the above embodiment, a specific example of the cylindrical secondary battery having a wound structure has been described. However, the present invention relates to a cylindrical secondary battery having another configuration. Can also be applied. Further, the present invention can be similarly applied to secondary batteries having other shapes such as a coin type, a button type, and a square type other than the cylindrical type.

[0056]

As described above, according to the secondary battery according to any one of the first to eighth aspects, at least one of the core members of the first exterior member or the second exterior member is used. Since the battery is made of copper, a secondary battery having a small change in battery voltage with respect to the discharge time even after repeated charge and discharge can be obtained. Therefore, there is an effect that a large discharge capacity can be obtained even when the end voltage is increased.

In particular, according to the secondary battery as set forth in any one of claims 2 to 4, since the coating layer is provided on at least a part of the core material made of copper, This has the effect of preventing corrosion of the material and improving the corrosion resistance of the exterior member.

According to the secondary battery of claim 5 or 6, at least one of the first exterior member and the second exterior member is made of a clad material of copper as a core material and another material. Therefore, there is an effect that the corrosion resistance of the exterior member can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a secondary battery according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a configuration example of a battery can of the secondary battery illustrated in FIG.

FIG. 3 is a cross-sectional view illustrating another configuration example of the battery can of the secondary battery illustrated in FIG.

FIG. 4 is a characteristic diagram showing a relationship between a battery voltage and a discharge time for secondary batteries according to Examples 1 to 3 of the present invention and a comparative example.

[Explanation of symbols]

Reference numeral 11: battery can, 11a: core material, 11b: coating layer, 12,
13: insulating plate, 14: battery lid, 15: safety valve mechanism, 16
... PTC element, 17 ... gasket, 20 ... wound electrode body,
21 ... Positive electrode, 22 ... Negative electrode, 23 ... Separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... Negative electrode lead

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Atsushi Komaru 1-1-1 Shimosugishita, Takakura, Hiwada-cho, Koriyama-shi, Fukushima F-term within Sony Energy Tech Co., Ltd. 5H011 AA03 CC06 CC10 CC12 DD18 DD21 5H029 AJ02 BJ02 BJ14 DJ02 EJ01

Claims (8)

[Claims] An electrode body including an electrolyte together with a positive electrode and a negative electrode is covered with a first exterior member electrically connected to the positive electrode and a second exterior member electrically connected to the negative electrode. A secondary battery according to claim 1, wherein at least one of the core members of the first exterior member and the second exterior member is made of copper (Cu). 2. The secondary battery according to claim 1, wherein at least a part of the core made of copper (Cu) is covered with a coating layer. 3. The secondary battery according to claim 2, wherein the coating layer is formed by performing a plating process. 4. The coating layer according to claim 3, wherein the coating layer is formed by nickel (Ni) plating.
The secondary battery according to any one of the preceding claims. 5. At least one of the first exterior member and the second exterior member includes copper (C) as the core material.
2. The secondary battery according to claim 1, comprising a clad material of u) and another material. 6. The secondary battery according to claim 5, wherein the other material is stainless steel. 7. The secondary battery according to claim 1, wherein the negative electrode contains a material capable of inserting and extracting lithium (Li). 8. The secondary battery according to claim 1, wherein the electrolyte includes an electrolyte salt and a non-aqueous solvent that dissolves the electrolyte salt.