JP2002260670A - Battery and manufacturing method thereof - Google Patents

Abstract

(57) [Problem] To provide a battery having a current collecting structure with a simple configuration and easily joining a current collecting terminal, and a method for manufacturing the same. SOLUTION: The current collector 111 used in the battery and the manufacturing method of the present invention has, for example, one end of a current collector base 111a having a higher thermal conductivity than a material (aluminum or the like) constituting the current collector base 111a. (A region with low thermal conductivity) 111 which is formed by cladding a material having low thermal conductivity (such as SUS)
b is provided. The current collector 111 is joined to the current collecting terminal 2 by means such as resistance welding on the end surface on the side where the clad portion 111b is located. By providing the region 111b having low thermal conductivity at one end, the junction with the current collecting terminal 2 is easily heated to a higher temperature than the current collector 111 made of only a material having good thermal conductivity. A good joint 2a can be formed between the power supply terminal 2 and the current collecting terminal 2 by resistance welding or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery capable of efficiently forming a current collecting structure with a simple structure, and a method of manufacturing the same. In this specification, the term "battery" is used to include a capacitor in addition to a so-called battery such as a nickel-metal hydride battery and a lithium battery.

[0002]

2. Description of the Related Art A battery having a wound electrode body formed by winding a long positive electrode sheet and a negative electrode sheet and a separator disposed between the two electrode sheets is known. I have. As a current collecting structure in such a battery, as shown in FIG. 9, a region (active material non-formed portion) 911 where the positive electrode active material layer 912 is not formed at the end of the positive electrode current collector foil 911
In general, a positive electrode sheet 91 is used in which a large number of lead tabs 911a separate from the positive electrode current collector foil 911 are joined at regular intervals by means such as ultrasonic welding. That is, this positive electrode sheet 91 is wound together with a negative electrode sheet 92 to which a number of lead tabs 921a are similarly joined and two separators 93 separating the two electrode sheets, thereby producing an electrode body. A number of lead tabs 911a extending from both ends of the body,
The current collecting structure is formed by joining 921a to the current collecting terminals of the positive and negative electrodes. In addition, a plurality of positive electrode side electrode sheets,
Even in a battery provided with a laminated electrode body formed by laminating a negative electrode sheet and a separator, the active material-free portion of the current collector foil constituting each electrode sheet or the lead tab joined to this portion is collected. A current collecting structure joined to a terminal is known.

[0003]

In the battery having the above-mentioned current collecting structure, the current collecting foil and the lead tab are generally made of aluminum,
Materials such as copper are often used. However, these materials such as aluminum and copper have high thermal conductivity and are not suitable for heat welding such as resistance welding. Therefore, there are restrictions on the joining method between the lead tab and the current collecting terminal. Furthermore, in the current collecting structure using the lead tab, it is difficult to improve the manufacturing efficiency of the electrode body because it requires a step of bonding a large number of lead tabs to the current collecting foil. The yield is likely to decrease due to the tear of the current collector foil. On the other hand, there is also known a current collecting structure in which a current collecting terminal is directly joined to an active material-unformed portion of a current collecting foil from the side of a wound electrode body without using a lead tab. However, as described above, since the normal current collector foil is made of a material having high thermal conductivity, it has been difficult to join the current collector foil and the current collector terminal by means such as heat welding.

[0004] It is an object of the present invention to provide a battery having a current collecting structure with a simple configuration and easy to join a current collecting terminal, and a method of manufacturing the same.

[0005]

In order to solve the above-mentioned problems, a battery according to claim 1 uses a current collector having at least one end provided with a region having lower thermal conductivity than a current collector base. An electrode body is formed, and a current collecting terminal is joined to an end surface of the electrode body on the side where the one end is located. As described above, by providing a region having low thermal conductivity at one end of the current collector (corresponding to a portion to be joined to the current collecting terminal), compared to a conventional current collector made of only a material having good thermal conductivity. The part to be joined is easily heated to a high temperature, and joining by heat welding (for example, resistance welding) or the like becomes easy. Therefore, a battery in which the electrode body and the current collecting terminal are directly and satisfactorily joined can be obtained.

The region having low thermal conductivity may be provided discontinuously (for example, at regular intervals) at one end of the current collector, but is preferably provided continuously. In addition, in order to obtain good current collection efficiency, it is preferable that an active material layer is not formed over the low thermal conductivity region. Therefore, as described in claim 2, it is preferable that the region having low thermal conductivity is a band-shaped region provided in the active material non-formed portion of the current collector.

According to a third aspect of the present invention, the region having a low thermal conductivity is formed by cladding or plating a material having a lower thermal conductivity than the material constituting the current collector base on the current collector base. It is preferable that the region is formed as follows. Less than,
The material clad on the base of the current collector is also referred to as a “cladding material”, and a portion of the current collector composed of the cladding material (a region having low thermal conductivity) is also referred to as a “cladding portion”.

The shape of the cladding will be described with reference to the drawings. Cladding part 7 provided on current collector base 71
2 is preferably exposed on the side end face 7a of the current collector 7 as shown in FIG. In addition, since the material used for the clad portion 72 is generally lower in electrical conductivity than the material forming the current collector base 71, the active material layer 73 is formed on the clad portion 72 from the viewpoint of current collection efficiency. Preferably not. Therefore, when the active material layer 73 is provided on both surfaces of the current collector 7 as shown in FIGS.
It is preferable to form the clad portion 72 in the range on the a side (the portion where the active material is not formed). On the other hand, as shown in FIG.
When the active material layer 73 is provided only on one surface (front surface) of the current collector 7 and the entire other surface (back surface) of the current collector 7 is an active material non-formed portion, Alternatively, a clad portion 72 may be formed on the back surface of the current collector 7 up to the area where the active material layer 73 is formed on the front surface, and the clad portion may be formed on the entire back surface.

[0009] As shown in FIG.
The thickness a of the current collector 7 at the portion where the
It is preferable that the thickness is substantially the same as the thickness b of the current collector 7 in the portion where 2 is not formed. In this case, the current collector 7
Since the thickness of each part is substantially uniform, for example, the active material layer 7
In the formation of 3 (for example, application and drying of the active material paste), wrinkles and uneven winding are unlikely to occur when the current collector 7 is unwound or fed, and the workability is good. The thickness a of the portion where the clad portion 72 is formed may be larger than the thickness b of the portion where the clad portion 72 is not formed. However, as shown in FIG. 8B, members and layers (for example, the active material layer 73 provided on the current collector 7,
It is preferable to make the difference (ab) in the thickness of each part of the current collector 7 smaller than the total thickness D of the counter electrode sheet 74 and the separator 75). In particular, in the wound electrode body, since it is easy to form a tightly wound electrode body,
It is preferable that (ab) <D. The current collector having the clad portion can be manufactured by a conventionally known method for manufacturing a clad material.

The clad material constituting the clad portion may be selected from materials having lower thermal conductivity than the current collector base depending on the type of the battery, and appropriate materials in consideration of electrical stability and the like. Can be selected and used. For example, when the current collector base is made of copper, aluminum, or the like, and the electrolyte is a non-aqueous electrolyte (such as a lithium secondary battery), an iron-based alloy such as stainless steel (for example, SUS306), nickel, or the like is used. It is preferably used. As described above, the clad portion made of a material having lower thermal conductivity than the current collector base can be easily heated to a high temperature in resistance welding or the like as compared with the current collector base. The heat of the clad makes it possible to heat the base of the current collector close to the clad to a degree sufficient for welding. This allows
The side end surface of the current collector on the side where the clad portion is provided (which is located at one end surface of the electrode body) and the current collecting terminal can be easily joined by heat welding such as resistance welding or laser welding. .

[0011] Further, using a current collector in which the region having low thermal conductivity is formed by a clad of a "brazing material", the "brazing material" is melted by heating at the time of heat welding such as resistance welding and the like. The electric body and the current collecting member may be joined. As the brazing material, solder, copper-based brazing, or the like can be used. In this configuration, even if the current collector base itself is not heated to the welding temperature, the current collector base and the current collecting terminal can be joined by the brazing material. If the current collector base can be heated sufficiently, the current collector base may be welded together with the brazing material.

As a method other than the cladding for forming the region having low thermal conductivity, a method of plating a material having lower thermal conductivity than the current collector main body on one end of the current collector main body may be used. . As the current collecting terminal, a terminal made of the same material as the material constituting the low thermal conductivity region can be used. For example, it is preferable to use a current collecting terminal made of the same material as either the material forming the current collector base or the material forming the clad portion. In this case, there is an advantage that the joining property when joining the electrode body and the current collecting terminal by resistance welding or the like is good.

The other part of the battery of the present invention can be made of a conventionally known material or the like. For example, when the present invention is applied to a lithium secondary battery, a metal such as aluminum, nickel, or copper can be used as a material forming a current collector base for a positive electrode or a negative electrode. Further, porous polyethylene or the like can be used as the separator.

As the positive electrode active material, a lithium-containing oxide or the like is preferably used. Specific examples include a lithium manganese oxide such as LiMn ₂ O ₄ , a lithium nickel oxide such as LiNiO ₂ , and a lithium cobalt oxide such as LiCoO ₂ . And compounds used as a positive electrode active material of a conventional lithium secondary battery, such as lithium iron oxide such as LiFeO ₂ . As the negative electrode active material, a carbon material such as amorphous carbon and graphite, or Si, S
An alloy or oxide of a metal such as n or In with Li and an oxide can be used. Alternatively, metallic lithium may be used as the negative electrode. As a binder for forming the positive electrode active material layer or the negative electrode active material layer, polyvinylidene fluoride (P
VDF), polytetrafluoroethylene (PTFE), and the like, and carbon black, graphite, pitch coke, and the like can be used as a conductive material for forming the positive electrode active material layer.

[0015] As an electrolytic solution of this lithium secondary battery,
One or more selected from various aprotic solvents used in conventional lithium secondary batteries, for example, ethylene carbonate (EC), propylene carbonate (P
C), γ-butyrolactone, 1,2-dimethylethane,
Tetrahydrofuran, 1,3-dioxane, methyl acetate, diethyl carbonate (DEC) and the like can be used. As the electrolyte, various lithium salts used in conventional lithium secondary batteries, for example, LiPF ₆ , Li
BF ₄ , LiCF ₃ SO ₃ , LiClO ₄ , LiAsF ₆ ,
LiSbF ₆ , LiC ₄ F ₉ SO ₃ , LiN (CF ₃ SO ₂ )
₂ , SiC (CF ₃ SO ₂ ) _{3 and the} like can be used, of which LiPF ₆ and LiBF ₄ are preferable. The electrolyte concentration in the electrolyte is usually about 0.05 to 10 mol / L, preferably about 0.1 to 5 mol / L.

Preferably, the electrode body is a wound electrode body formed by winding the current collector. Although the present invention can be applied to a battery having a stacked electrode body, in a battery having a wound electrode body, the effect of the current collecting structure of the present invention is particularly effectively exhibited. That's because.

Claims 6 and 7 relate to a method of manufacturing the battery. That is, in the method for manufacturing a battery according to claim 6, the electrode body is configured using a current collector having at least one end provided with a region having lower thermal conductivity than the current collector base. It is characterized in that a current collecting terminal is joined to the end face on the side where one end is located. The connection of the current collecting terminals is preferably performed by resistance welding.

[0018]

Embodiments of the present invention will be specifically described below with reference to the drawings. Embodiment 1 FIG. 2 shows a wound type lithium secondary battery to which the present invention is applied. This battery includes a positive electrode sheet (hereinafter, also referred to as a “positive sheet”) 11 and a separator 1.
3, the negative electrode sheet (hereinafter, also referred to as “negative electrode sheet”) 12 and the separator 13 are laminated in this order and joined to the wound electrode body 1 and the upper end surface of the electrode body 1 in FIG. The battery pack includes a positive electrode current collecting terminal and a bottomed cylindrical battery case joined to a lower end surface of the electrode body. The battery case 3 also functions as a negative electrode current collecting terminal. The positive current collecting terminal 2 is connected to a lead wire (not shown) or the like.
It is electrically connected to a member capable of conducting with the outside.

FIG. 1 is an enlarged sectional view of the vicinity of the junction between the upper end surface of the electrode body 1 and the positive electrode current collecting terminal 2 in FIG. The positive electrode sheet 11 includes a long positive electrode current collector 111,
It comprises a positive electrode active material layer 112 formed on both surfaces thereof.
Here, one end of the positive electrode current collector 111 along the longitudinal direction is
Active material non-formed portion 11 where positive electrode active material layer 112 is not formed
It is 11. Also, the active material non-formed portion 1111
Has a band-shaped clad portion 1 in which a material having lower thermal conductivity than the material forming the positive electrode current collector base 111a is clad.
11 b is formed so as to be exposed on the side end surface of the positive electrode current collector 111. The upper end surface of the electrode body 1 shown in FIG. 2 is constituted by the side end surface of the positive electrode current collector 111 on the side where the clad portion 111b is provided, and the positive electrode current collector terminal 2 is joined to this portion by resistance welding.

Similarly, the negative electrode sheet 12 also includes a long negative electrode current collector 121 and negative electrode active material layers 122 formed on both surfaces thereof. One end of the negative electrode current collector 121 along the longitudinal direction is an active material non-formed portion, and a strip-shaped clad portion in which a material having lower thermal conductivity than the material forming the negative electrode current collector base is clad. 121 b is formed to be exposed on the side end surface of the negative electrode current collector 121. The lower end surface of the electrode body 1 shown in FIG. 2 is constituted by the side end surface of the negative electrode current collector 121 on the side where the clad portion 121b is provided,
The inner bottom surface of the electrode container 3 is joined to this portion by resistance welding. Note that FIG. 2 does not show the positive electrode active material layer 112 and the negative electrode active material layer 122.

Hereinafter, a method of manufacturing this lithium secondary battery will be described. As shown in FIGS. 3 and 4, the overall shape is a metal foil having a width of 160 mm × a thickness of 10 μm, and a base 121 a thereof is made of copper, and one surface has a width of 6 mm × a thickness at a central portion in the width direction. A copper-SUS clad foil 123 provided with a band-shaped clad portion 121b made of a 5 μm stainless material (a material having lower thermal conductivity than copper) was prepared. On both sides of the clad foil 123, two negative electrode active material layers 122 are formed in the longitudinal direction, leaving an active material non-formed portion 1211 of 2 mm at both ends in the longitudinal direction of the clad foil 123 and 10 mm at the center of the clad foil 123. Was formed. The negative electrode active material layer 122 can be formed by, for example, applying a negative electrode active material paste formed by mixing a negative electrode active material, a binder, and a solvent and drying the paste. Then, the cladding foil 123 is cut at the cutting line 123 set at the center in the width direction.
a along the two negative electrode sheets 12
Was prepared.

The overall shape is 160 mm in width × 15 in thickness.
μm metal foil, the base 111a of which is made of aluminum and has a width of 6 mm at the center in the width direction on one surface.
× Strip-shaped cladding 111 made of stainless steel (material having lower thermal conductivity than aluminum) with a thickness of 7.5 μm
After the positive electrode active material layer 112 is formed in the same manner as the negative electrode active material layer 122 using the Al-SUS clad foil provided with b, the clad foil is cut at the center to produce two positive electrode sheets 11. did.

Thereafter, as shown in FIG.
1, the separator 13, the negative electrode sheet 12, and the separator 13 in this order, the position where the positive electrode active material layer 112 and the negative electrode active material layer 122 are formed and the position of the separator 13 are overlapped, and the cladding portion 111 b and the cladding portion 12
1b protruded from the opposite side of the separator 13. The upper end surface of the electrode body 1 formed by winding this is constituted by the positive electrode current collector 111. This part of the positive electrode current collector 1
11 is a SUS clad portion 11 as shown in FIG.
1b occupies half of the thickness, and the other half is composed of a current collector base 111a made of Al. When the upper end surface is resistance-welded to the positive electrode current collector terminal 2, the clad portion 11 made of a material (SUS) having lower thermal conductivity than the current collector base 111 a is used.
1b can be easily heated to a high temperature.
a can be heated to a degree sufficient for welding. Therefore, the upper end surface of the electrode body 1 (the positive electrode current collector 111)
Between the positive current collecting terminal 2 and the positive current collecting terminal 2 by resistance welding.

Similarly, at the lower end surface of the electrode body 1, half of the thickness of the negative electrode current collector 121 constituting the lower end surface is made of the SUS clad portion 121b. By heating to a high temperature, the heat of the clad portion 121b can heat the copper current collector base 121a to a degree sufficient for welding, so that the gap between the lower end surface of the electrode body 1 and the inner bottom surface of the electrode container 3 can be increased. A good joint can be formed. Electrode body 1
FIG. 6 shows a state in which the current collecting terminal 2 and the electrode container 3 are joined together. In the drawing, reference numeral 2a indicates a joint between the positive electrode current collector 111 and the positive electrode current collector terminal 2, and reference numeral 3a indicates a joint between the negative electrode current collector 121 and the battery case 3. FIG. 6 corresponds to the view in the direction of arrow VI in FIG.

In the above embodiment, the clad portion having a thickness occupying about half of the thickness of the current collector is formed. However, the ratio of the thickness of the clad portion to the thickness of the current collector is not limited to this. Not something. For example, assuming that the thickness of the entire current collector in the portion where the clad portion is formed is 100%, the thickness of the clad portion is preferably in the range of 20 to 80%, more preferably in the range of 30 to 70%. is there. If the thickness of the clad portion is less than 20% of the thickness of the current collector, the clad portion is too thin with respect to the thickness of the current collector base portion. Heating may not be possible. On the other hand, when the thickness of the clad portion exceeds 80% of the thickness of the current collector, the internal resistance of the battery tends to increase because the thickness of the current collector base in this portion becomes small.

In the above embodiment, the width of the clad in the current collector is 3 mm, but the width of the clad is not particularly limited. However, if the width of the clad portion is too small, the current collector base may not be sufficiently heated when performing resistance welding or the like, and it is difficult to manufacture the clad material. On the other hand, if the width of the clad portion is too large, the internal resistance of the battery tends to increase. Further, in the case where a clad portion is provided in an active material non-formed portion in a current collector having an active material layer on both surfaces, it is necessary to increase the width of the active material non-formed portion in order to form a wide clad portion. This leads to an increase in the size and weight of the battery. From the above viewpoints, the width of the clad portion can be, for example, 0.5 to 100 mm, and preferably 1 to 10 mm.

Further, in the above embodiment, the regions having low thermal conductivity are formed on both the positive electrode current collector and the negative electrode current collector, but only one of the positive electrode current collector and the negative electrode current collector has heat conductivity. A low region may be formed. For example, the above-mentioned clad foil is used as the negative electrode current collector, and the lower end face of the electrode body and the electrode container are joined by resistance welding, while a lead tab is joined to one end of the positive electrode current collector in the same manner as in the past. The lead tab and the current collecting terminal may be joined by a method similar to the conventional method. Further, although resistance welding is used in the present embodiment, other heating joining methods such as laser welding can be used.

[0028]

The battery of the present invention has a current collecting structure in which a region having low thermal conductivity is provided at one end of a current collector, and this end is connected to a current collecting terminal. Thus, when the current collector and the current collecting terminal are joined by resistance welding or the like, the above-mentioned one end can be easily heated to a high temperature necessary for welding, as compared with a conventional current collector made of only a material having good thermal conductivity. Can be heated. Therefore, a battery in which the electrode body and the current collecting terminal are satisfactorily joined can be obtained.

In the battery of the present invention, the current collecting terminal is directly joined to the end face of the current collector, and no member such as a lead tab is interposed between the current collector and the current collecting terminal. This eliminates the need for a step of joining the lead tab to the current collector compared to conventional batteries that use lead tabs, thereby improving manufacturing efficiency, reducing the number of components, and enabling a smaller and lighter battery. Becomes Further, since the current collector and the current collection terminal are directly joined, the internal resistance of the battery can be reduced as compared with the case where the current collector is provided through the lead tab. In particular, when a region having low thermal conductivity is provided continuously at one end of the current collector,
Since the entire end face of the current collector can be joined to the current collecting terminal and current can be collected from the entire end face of the current collector, current collection efficiency is good. The battery of the present invention can be suitably manufactured by the manufacturing method of the present invention and the like.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view showing the vicinity of a joint between an electrode body and a current collecting terminal in a battery to which the present invention is applied.

FIG. 2 is a sectional view showing a battery to which the present invention is applied.

FIG. 3 is a plan view showing an electrode sheet used for manufacturing a battery to which the present invention is applied.

FIG. 4 is a sectional view taken along line IV-IV of FIG. 3;

FIG. 5 is a plan view showing a step of forming an electrode body in a battery to which the present invention is applied.

FIG. 6 is a side view showing a battery to which the present invention is applied,
FIG. 6 is a view in the direction of arrow VI in FIG. 2.

FIGS. 7A, 7B, and 7C are cross-sectional views showing various shapes of a current collector having a clad portion.

FIGS. 8A and 8B are cross-sectional views showing various shapes of a current collector having a clad portion.

FIG. 9 is a plan view showing a step of forming an electrode body in a conventional battery.

[Explanation of symbols]

1; electrode body, 11; positive electrode sheet, 111; positive electrode current collector,
111a; positive electrode current collector base; 111b; clad (low thermal conductivity region); 1111; active material non-formed portion, 11
2, negative electrode active material layer, 12; negative electrode sheet, 121; negative electrode current collector, 121a; negative electrode current collector base, 121b; clad portion (low thermal conductivity region), 122; negative electrode active material layer, 1
211; active material-unformed portion, 13; separator, 2; positive electrode current collecting terminal, 2a; bonding portion, 3; battery container (negative electrode current collecting terminal), 3a;

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference)

Claims (7)

[Claims] An electrode body is formed by using a current collector having at least one end provided with a region having a lower thermal conductivity than a current collector base, and an end face of the electrode body on the side where the one end is located. A battery having a current collecting terminal joined thereto. 2. The battery according to claim 1, wherein the region having low thermal conductivity is a band-shaped region provided in an active material-free portion of the current collector. 3. The low thermal conductivity region is a region in which a material having lower thermal conductivity than the material forming the current collector base is clad on the current collector base. 2. The battery according to 2. 4. The battery according to claim 1, wherein the current collecting terminal is made of the same material as a material constituting the low thermal conductivity region. 5. The battery according to claim 1, wherein the electrode body is a wound electrode body formed by winding the current collector. 6. An electrode body is formed by using a current collector having at least one end provided with a region having lower thermal conductivity than the current collector base, and an end face of the electrode body on the side where the one end is located. A method for manufacturing a battery, comprising joining current collecting terminals. 7. The method for manufacturing a battery according to claim 6, wherein the current collecting terminals are joined by resistance welding.