JP3511476B2 - Lithium secondary battery - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention has high productivity,
Even in a high output cycle operation, such that a good charge and discharge characteristics are maintained, the tab its for current collection in the current take-off path
In particular, the present invention relates to a lithium secondary battery that has a uniform resistance (reduction of variations) in the connection between both ends of the tab and that is preferably used for driving a motor of an electric vehicle.

[0002]

2. Description of the Related Art In recent years, against the backdrop of increasing environmental protection movements, carbon dioxide emission regulations have been urgently desired, and in the automobile industry, electric vehicles (EVs) have been replaced with fossil fuel-containing vehicles such as gasoline vehicles. ) And hybrid electric vehicles (HEVs) are being actively promoted.
The lithium secondary battery as a motor drive battery, which holds the key to practical use of EVs and HEVs, not only has a large battery capacity, but also has a large battery output that greatly affects the acceleration performance and climbing performance of the vehicle. Is required.

Generally, an internal electrode body of a lithium secondary battery is wound or wound so that the positive electrode plate and the negative electrode plate are not directly in contact with each other via a separator made of a porous polymer film. It is configured by stacking. For example, as shown in FIG. 1, a wound-type internal electrode body 1 is manufactured by winding a positive electrode plate 2 and a negative electrode plate 3 with a separator 4 in between, and the positive electrode plate 2 and the negative electrode plate 3 (hereinafter, referred to as “ Electrode plate 2.3 "
Say. ) Each of positive electrode tab 5A and negative electrode tab 5B
(Hereinafter, described as "tabs 5A and 5B".).

The electrode plates 2 and 3 of the tabs 5A and 5B
The end portion on the opposite side connected to is attached to the current extraction terminal 13 such as the external terminal 11 or the internal terminal member 12 that conducts to the external terminal 11. That is, tabs 5A and 5B
Plays a role as a lead wire that conducts current from the electrode plates 2 and 3 and conducts with the current extraction terminal 13. The external terminal is an electrode terminal for taking out the electric current to the outside of the battery, the internal terminal member is a member for temporarily collecting the electric current inside the battery, and the current taking-out terminal is a general term for these. Therefore, it is possible to form the current extraction terminal by integrating the external terminal and the internal terminal member.

Here, FIG. 2 shows a plan view of the electrode plates 2 and 3 when the internal electrode body 1 is expanded. Electrode plate 2.3
Is formed by using aluminum or the like for the positive electrode plate 2 and metal foil such as copper or the like for the negative electrode plate 3 as the current collector substrate 15, and applying the electrode active material 16 to each of them. Since the tabs 5A and 5B are arranged on one side of the current collecting substrate 15 as described above, it is preferable to use thin strip-shaped ones. It is preferable that they are arranged at substantially equal intervals so as to generate electricity. In general, the material of the tab 5 is the same as the material of the current collector substrate 15 to which the tab 5 is attached.

[0006]

By the way, in a lithium secondary battery for EV or HEV, one battery is
A current of 100 A or more may flow. Even when such a large current flows, it is necessary to reduce the internal resistance of the entire battery as much as possible so that the output loss of the battery becomes small.

Therefore, it is needless to say that it is preferable to reduce the resistance of the internal electrode body. However, if attention is paid to the connection path between the internal electrode body (electrode plate) and the current output terminal described above, the current collection It is preferable that the resistance of the substrate itself, the tab, and the members of the current output terminal itself is small. However, there is a certain limit to the reduction of the resistance value of the current collector substrate due to the limitation of the material and the restrictions on the shape of the battery and the energy density.

On the other hand, the tab and the current output terminal can be freely set in shape as long as the shape can be set within the gap between the battery case housing the internal electrode body and the internal electrode body. There is a tolerance in the setting. Also,
Since the tab and the current collecting board are integrated by welding, the resistance of these connection parts does not change significantly except for extreme welding defects.However, regarding the connection between the tab and the current extraction terminal, Since various methods are conceivable, there is room for reducing the contact resistance.

For example, particularly for thin tabs, a method of stacking the tabs by stacking them in a certain direction is preferable because it is easy in terms of the manufacturing process of the battery and the internal structure of the battery does not become complicated. However, in this case, as the number of tabs increases, the number of tabs contacting each other increases, which causes a problem that the contact resistance on the contact surface of each tab increases and the variation in the contact resistance also increases. Therefore, in order to reduce the contact resistance as well as the variation in the contact resistance, it is considered necessary to study the tab fixing method and the materials used in detail.

Nevertheless, conventionally, regarding the material of the tab and the current extraction terminal itself, and the method of connecting the tab and the current extraction terminal, the resistance of the tab and the current extraction terminal itself and their connection resistance are From the internal resistance of
Since it does not occupy a large proportion, it is not considered important.Therefore, the effect of the variation (distribution) of resistance caused by the connection between the tab and the current extraction terminal on the output characteristics and charge / discharge cycle operation characteristics has been clarified so far. Was not.

[0011]

Means for Solving the Problems The present invention has been made in view of the above-mentioned problems of the conventional techniques, i.e., according to the present invention, a separator made of the positive and negative electrode plates of a porous polymer And the internal electrode body wound or laminated with the first electrode inside the battery and the other end inside the battery.
Multiple positive tabs connected to the current extraction terminals of the
One end is the negative electrode plate and the other end is the second current output terminal inside the battery.
A lithium secondary battery comprising a plurality of negative electrode tabs connected to each other, each resistance value of the positive electrode tab (member and
In addition to the resistance value of the positive electrode tab itself,
Contact resistance between the plate and the first current output terminal
Including a) has an average resistance value of the positive electrode tab and X situ
In the range of X ± 0.2X (0.8X to 1.2X) ,
And the resistance value of each of the negative electrode tabs (member and
In addition to the resistance value of the negative electrode tab itself,
Contact resistance between the plate and the second current output terminal
Is included) , the average resistance value of the negative electrode tab is Y.
In this case, there is provided a lithium secondary battery characterized by being within a range of Y ± 0.2Y (0.8Y to 1.2Y) .
As described above, the "tab resistance value" includes the contact resistance between the tab and the current output terminal, that is, the one end portion of the tab connected to the positive electrode plate or the negative electrode plate, and other tabs. It refers to the resistance with the current output terminal connected to the end, not the resistance value of the tab itself as a member.

Further, Oite the present invention, the positive electrode tab and the negative electrode tab, and / or, a first current lead terminal and the second
It is preferable that O material is used for the current output terminal.
Yes .

In such a lithium secondary battery of the present invention, a plurality of positive electrode tabs and negative electrode tabs are assembled at one location for each electrode, and one of the first and second tabs is formed by pressure bonding or welding.
And the second current output terminal. Also, the positive electrode tab and the negative electrode tab, for each pole, crimping a plurality beforehand, was integrated by welding or eyelet, the first and
Crimping the second current lead terminal, it is also preferable to connect stopping welding or screws. Incidentally, here, a structure in which only one first and second current extraction terminals are provided for each pole, that is, all positive electrode tabs are collectively connected to one first current extraction terminal,
It is preferable that the same applies to the negative electrode tab because the battery can be easily manufactured, and variations in the resistance of the tab (including the contact resistance with the current output terminal, the same applies hereinafter) can be suppressed.

The thickness of each of the positive electrode tab and the negative electrode tab is preferably 5 μm or more and 100 μm or less .
And a positive electrode tab collectively connected to one second current extraction terminal
And and when the total thickness of the negative electrode tab is respectively 200μm or more, when the tab is at least 10 or more sheets respectively which are set connected to the first and second current extraction one terminal,
The effect of reducing the variation in the resistances of the positive electrode tab and the negative electrode tab , that is, making the resistance uniform, becomes significant. Such uniform resistance of the tabs is remarkably effective in improving charge / discharge characteristics and the like in a lithium secondary battery having a battery capacity of 5 Ah or more. Thus, the lithium secondary battery of the present invention is suitably adopted as a lithium secondary battery for electric vehicles or hybrid electric vehicles by utilizing the excellent charge / discharge characteristics obtained in this way.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The lithium secondary battery of the present invention is
Since the resistance from the positive electrode plate / negative electrode plate to the electrode lead-out terminal is made uniform, the current collection from the positive electrode plate / negative electrode plate can be made uniform, and the battery reaction in the positive electrode plate / negative electrode plate can be made uniform. It is possible to stably discharge a large current, and
Since the local deterioration of the battery material is suppressed, it has excellent durability even in cycle operation. Hereinafter, embodiments of the present invention will be described, but it goes without saying that the present invention is not limited to the following embodiments.

In the internal electrode body of the lithium secondary battery (hereinafter, referred to as “battery”) of the present invention, the positive electrode plate and the negative electrode plate are directly connected to each other through the separator made of the porous polymer film. It is wound or laminated so as not to come into contact with. Specifically, as shown in FIG. 1, the wound-type internal electrode body 1 is formed by winding the positive electrode plate 2 and the negative electrode plate 3 with the separator 4 interposed therebetween. Are provided with tabs 5A and 5B.

On the other hand, in the laminated internal electrode body 7, as shown in FIG. 3, positive electrode plates 8 and negative electrode plates 9 are alternately laminated with a separator 10 interposed therebetween, and positive and negative electrode plates 8 and 9 (hereinafter,
It is called "electrode plate 8.9". ) Each of the positive electrode tab 6A
And the negative electrode tab 6B are connected. When such a tab is used as a reference of a battery element, the internal electrode bodies 1 and 7 should be regarded as a structure in which a plurality of element batteries composed of a positive electrode plate 2.8 and a negative electrode plate 3.9 facing each other are connected in parallel. You can

Both the positive electrode plates 2 and 8 and the negative electrode plates 3 and 9 are formed in a thin plate shape by applying respective electrode active materials to a current collecting substrate. Examples of the form of the current collecting substrate include foil and mesh. In the present invention, aluminum foil is used as the current collecting substrate for the positive electrode plates 2 and 8, and copper foil is used as the current collecting substrate for the negative electrode plates 3 and 9. Are each preferably used.

In any battery having any of the above structures, generally, the positive electrode active material is lithium cobalt oxide (LiCoO ₂ ) or lithium nickel oxide (L).
iNiO ₂ ) or lithium manganate (LiMn ₂ O
₄ ) Lithium-transition metal composite oxide such as is used. In order to improve the conductivity of these positive electrode active materials, carbon powder such as acetylene black or graphite powder is often mixed with the electrode active material. on the other hand,
As the negative electrode active material, an amorphous carbonaceous material such as soft carbon or hard carbon, or a carbonaceous powder such as natural graphite or artificial graphite is used.

As the separators 4 and 10, those having a three-layer structure in which a lithium ion permeable polyethylene film having micropores is sandwiched between porous lithium ion permeable polypropylene films are preferably used. This is because the polyethylene film is softened at about 130 ° C. and the micropores are crushed when the temperature of the internal electrode body is increased, and the micropores are crushed, which also serves as a safety mechanism for suppressing the movement of lithium ions, that is, battery reaction. Then, by sandwiching this polyethylene film between polypropylene films having a higher softening temperature, the separator 4
It is possible to prevent contact and welding between the electrode 10 and the electrode plates (2, 3) and (8, 9).

Next, a method of connecting the tab to the internal electrode body (electrode plate) and the current output terminal will be described by taking the case of the wound type internal electrode body 1 as an example. As mentioned above, FIG.
FIG. 2 is a plan view of the electrode plates 2 and 3 when the wound type internal electrode body 1 shown in FIG. 1 is developed. Here, when the battery capacity is constant, the width D of the electrode plates 2 and 3 is shown. If the length is taken longer, the length L in the winding direction can be shortened.

However, when the width D of the electrode plates 2 and 3 is long, the distance between the tabs 5A and 5B and the electrode active material 16 near the side opposite to the side where the tabs 5A and 5B are attached is long. Therefore, there is a disadvantage that the internal resistance increases. Therefore, the width of the electrode plates 2 and 3 is usually 10c.
It is preferable to set in the range of m to 40 cm, and when the width of the electrode plates 2 and 3 is in such a range, the tab 5A
It is preferable that the number of 5B arranged in the winding direction length L on the electrode plates 2 and 3 is about 6 to 10 sheets per 1 m.

The arrangement of the tabs 5A and 5B on the electrode plates 2 and 3 does not complicate the inside of the battery as shown in FIG. 11 described later, and the tabs 5A and 5B can be attached to the current output terminal 13 only. To make it easier to do, when winding the electrode plates 2 and 3,
It is preferable that the tabs 5A and 5B are arranged so as to be arranged substantially linearly in the radial direction of the internal electrode body 1.

As a method of connecting the electrode plates 2 and 3 and the tabs 5A and 5B, resistance welding or ultrasonic welding can be mentioned. However, except for extreme welding defects, the tabs 5A and 5B and the electrode plates 2 and 3 can be connected. The contact resistance of is not significantly different. However, it goes without saying that it is preferable that the contact resistance between the tabs 5A and 5B and the electrode plates 2 and 3 be substantially constant.

The tabs 5 thus arranged at substantially equal intervals
Each of A and 5B contributes to the transfer of electrons involved in the battery reaction in the electrode areas of the electrode plates 2 and 3 which are substantially equal to each other. However, if there is variation in resistance in the current collection path from the current output terminal to the electrode plates 2 and 3,
There will be variations in the extraction of current. That is, the current may concentrate on the tabs connected so that the resistance becomes small. In this case, not only the battery reaction is not uniform, but also the part where the battery reaction is most active (the low resistance tab is There is also concern about the problem of rapid material deterioration in the connected parts).

In order to avoid such a problem, in the present invention, when each resistance value of at least a plurality of positive electrode tabs 5A connected to the positive electrode plate 2 is X, the average resistance value of the positive electrode tabs 5A , X ± 0.2X (0.8X to 1.2
X) , and the same applies to the negative electrode tab 5B. Incidentally, the resistance value of the tab here includes the contact resistance between the tab and the current output terminal, that is, the portion of one end of the tab connected to the positive electrode plate or the negative electrode plate, as is clear from the above-mentioned problem. And the current output terminal connected to the other end of the tab, not the resistance value of the tab itself as a member.

Therefore, it is preferable that all the tabs 5 are gathered at one place and connected to the current extraction terminal by crimping or welding. However, it is possible to provide two or more current extraction terminals for each pole. In this case, the condition of the resistance distribution is not satisfied for each current extraction terminal, and all the tabs for each pole are not satisfied. It is necessary to satisfy the above conditions. That is, it is necessary to keep the connection state of the tabs at each current extraction terminal substantially constant.

Specifically, as shown in FIG. 4, a rivet 22 is used as the current output terminal 13 attached to the battery cap 23, and the tabs 5 A (5 B) can be collectively connected to the rivet 22 by crimping. Is. Even in this case, the tab 5A (5
The resistance value of B) can be set within the above resistance distribution range. Note that the tab 5A (5B) is welded instead of crimped.
May be connected to rivet 22 or tab 5A (5B)
After crimping to the rivet 22, the connecting portion may be further welded and integrated.

As shown in FIG. 5, a plurality of tabs 5A (5B), preferably all tabs 5A (5B), are preliminarily integrated with each other by using a metal plate 26 such as a copper plate or an aluminum plate, and then the current output terminal 13 is formed. A connection method in which the bolt 24 is fitted and inserted, and the nut 25 is tightened and screwed is also suitably used. In addition to the crimping, a method such as welding or eyelet can be used for integrating the tabs 5A (5B). When the integrated tabs 5A (5B) are attached to the current extraction terminal 13, welding or eyelets can be used. A method such as pressure bonding can also be used.

As described above, since the metal foil is preferably used as the current collecting substrate of the electrode plates 2 and 3, the tab 5 is also preferably in the shape of a thin strip and has a thickness of 5 μm. It is preferably 100 μm or more and 100 μm or less.
In the present invention, a positive electrode tab 5A made of aluminum and a negative electrode tab 5B made of copper or nickel are preferably used.

In view of the above-mentioned problems, it is most preferable that both of the electrode plates 2 and 3 satisfy the above condition regarding the variation in resistance, but if only one of the electrode plates satisfies the above condition, the conventional method will be used. The battery characteristics are improved as compared with the technology.

Further, the tabs 5A and 5B are the current output terminals 1
While the tabs 5A and 5B are connected to the electrode plates 2 and 3 by the number of the tabs 5A and 5B, the shortest tabs are used respectively. However, there is a difference in the resistance value of each tab, which is not preferable. Therefore, the tab to be used should be the one that requires the longest length, or if tabs with different lengths are used, the resistance value should be adjusted to the same value by changing the thickness and width. It is preferable.

In connection with the above-mentioned current extraction terminal of the tab, the material of the tab and / or the current extraction terminal is also considered to have a great influence on the state of variations in productivity and resistance. In consideration of this, in the present invention, tabs and / or current output terminals made of O material are preferably used.

The O (O) material is also called as annealed material or A material, and is not subjected to cold working after softening annealing (including solution treatment) or hardening is caused. It refers to a material that has been subjected to light cold working to the extent that it does not exist, and is distinguished from cold-worked H material.

When the tabs are collectively connected to the current output terminal, the tabs are often bent and stored in the battery case. However, when the tabs are made of O material, Since it is easily bent by the applied force and the repulsive force is small, there is an advantage that the cap to which the current output terminal is attached can be easily positioned and fixed in the battery manufacturing process. When an O material is used for the tab, especially when the tabs are bundled by pressure bonding,
There is an advantage that the contact state between the tabs can be kept good.

Regarding the current extraction terminal, for example, as shown in FIG.
When the O material is used for the rivet 22 shown in (1), the malleability of the portion to be crimped is large, breakage of the rivet 22 due to the crimping is easily avoided, the production yield is improved, and the contact with the tab is good. Therefore, there is an advantage that it contributes to the reduction of the variation of the contact resistance between the tab and the current output terminal. Therefore, it is preferable to use the O material for both the tab and the current output terminal.

By the way, when the above-mentioned method of collective connection of tabs is adopted or when O material is used for the tab and / or the current extraction terminal, the total thickness of the tabs collectively connected to one current extraction terminal is 200 μm. In the above case, and when the number of tabs collectively connected to one current extraction terminal is 10 or more, the effect of suppressing the variation in the resistance of the tabs is significantly exhibited, which is preferable.

Although the wound-type internal electrode body 1 has been mainly described above, it goes without saying that the same applies to the electrode plates 8 and 9 forming the laminated-type internal electrode body 7.
Disposing a plurality of tabs per one of the electrode plates 8 and 9,
Alternatively, one positive electrode tab 6A and one negative electrode tab 6B can be connected to one electrode plate 8/9, respectively, and can be connected to the current extraction terminal.

By adopting the above-mentioned battery structure,
Since the current is taken out from the internal electrode body in one battery evenly through each tab, the charge / discharge efficiency is improved, the large current discharge is facilitated, and the durability is improved. Such an effect remarkably appears particularly in a large-capacity battery having a battery capacity of 5 Ah or more, which requires the arrangement of a large number of tabs, and the battery of the present invention is preferably used as a battery for EV or HEV. it can. Hereinafter, the present invention will be described by way of examples, but it goes without saying that the present invention is not limited to the following examples.

[0040]

Example (Tab resistance measurement) In manufacturing a battery, first, in order to investigate the variation in resistance due to the difference in the connection method of the tab to the current output terminal, the tab 5A (5B) as shown in FIG. Rivet 22 which is a current output terminal
Using the connection method of crimping to, the 30 positive electrode tabs made of aluminum foil were bundled and crimped to the positive electrode rivet made of aluminum, while the 30 negative electrode tabs made of copper foil were bundled and crimped to the negative electrode rivet made of copper. . The positive electrode rivet and the negative electrode rivet with the tabs crimped in this way were set as one set, and the crimping pressure was set to 1 ton / cm ² as Example 1, and the crimping pressure was ² ton / cm ² as Example 2. To do.

Next, as shown in FIG. 6, the resistance value of the tab 5A (5B) is measured by measuring the voltage when a current of 1A is applied between each of the tabs 5A (5B) and the rivet 22. Was measured. Then, the average value of the obtained resistance values was calculated, and the resistance value of each of the tabs 5A (5B) was standardized with the average value being 100% to obtain the distribution of the resistance values.

On the other hand, as Comparative Example 1, the above-mentioned Example 1,
In the same manner as in 2, press-fit pressure is 500 kg / cm ²
As a result, the tab was crimped to the rivet and the resistance value of the tab was measured. Further, as Comparative Example 2, as shown in FIG. 7, a current extraction terminal composed of a bolt 24 and a nut 25 was used.
As shown in FIG. 5, the tabs 5A (5B) of 0 sheets are not integrated as shown in FIG. 5, and the individual tabs 5A (5B) are screwed to each other.
The resistance value of each of the tabs 5A (5B) was measured.

FIG. 8 shows how the resistance of the positive electrode tab 5A varies in the above Examples 1 and 2 and Comparative Examples 1 and 2. In Examples 1 and 2, the variation in resistance of the positive electrode tab 5A is within ± 20% of the average value, but in Comparative Examples 1 and 2, the variation in resistance is ±± of the average value.
It can be seen that it has become wider than the range of 20%. Although not shown, the variation in resistance of the negative electrode tab 5B also showed a distribution similar to that in FIG. 8, and in Examples 1 and 2 and Comparative Example 1, it was within ± 20% of the average value. Example 2 did not fall within this range. In Comparative Example 1, the reason why the resistance variation is large in the positive electrode tab 5A and the resistance variation is small in the negative electrode tab 5B is due to the material and the nature of the oxide film formed on the surface thereof, as described later. it is conceivable that.

The results are explained as follows.
That is, first, in the case of using the bolt 24 and the nut 25 of Comparative Example 2, as shown in FIG.
(5B) is provided with a hole for inserting into the screw thread 27 of the bolt 24.
Since the tab 5A (5B) is larger than the diameter of 7 and the tab 5A (5B) is thin, the area where the side surface of the hole of the tab 5A (5B) contacts the thread 27 is very small. Therefore, the current in the tabs 5A (5B) will flow to the adjacent tabs 5A as indicated by arrow 50.
It will flow to the bolt 24 through (5B) or to the bolt 24 through the adjacent tab 5A (5B) and nut 25, and it is difficult to flow in the direction indicated by the arrow 60.

On the other hand, the same applies to the case where the rivet 22 is used as in the case of Examples 1 and 2 and Comparative Example 1, and in this case as well, as shown in FIG.
Since the area where the side surface of B) contacts the rivet 22 becomes very small, the current of the tab 5A (5B) flows to the rivet 22 in the direction indicated by the arrow 50, that is, through the adjacent tab 5A (5B), It becomes difficult to flow in the direction indicated by 60.

That is, the above Examples 1 and 2 and Comparative Examples 1 and 2
In either case, the current flows through the contact interface between the tabs 5A (5B). Therefore, among the bundled tabs 5A (5B), the closer to the center, the larger the number of contact interfaces with the bolt 24 or the rivet 22 and the larger the resistance value.

Therefore, in order to reduce the variation in the resistance of the tab, it is necessary to reduce the resistance of the contact interface generated in the tab. It is known that alumina tabs are more likely to form an alumina insulating coating on the surface of aluminum foil tabs. The more bundled thin strip tabs, the greater the effect of the insulating coating on the tab resistance distribution. Become. Therefore, in order to reduce the variation in the resistance of the tab, it is necessary to destroy the insulating film to ensure contact with the metal material portion of the original tab.

The same applies to tabs made of copper foil. However, since the oxide film formed on the surface of the copper foil is a semiconductor, the influence of the contact interface is smaller than that when the aluminum foil is used. However, since the electronic conductivity is naturally superior to that of a semiconductor, it is preferable to destroy the oxide film on the surface of the copper foil as well to secure the contact between the metals.

Therefore, for the connection between the tab and the current output terminal, it is preferable to use a method such as crimping which can ensure contact between the metals, and in Examples 1 and 2, crimping at an appropriate pressure can be performed to make the tab surface It is considered that the variation in the resistance of the tab was suppressed as a result of the destruction of the oxide film of and the securing of the contact between the metal materials. However, even when crimping is used, as shown in the results of Comparative Example 1, when the crimping pressure is small, the oxide film is not evenly broken, and as a result, the tabs are connected unevenly. It is considered that the pressure bonding effect cannot be obtained due to the occurrence of the above phenomenon. Further, in Comparative Example 2, it is considered that the tightening pressure for screwing does not easily reach the pressure required to destroy the oxide film on the tab, and as a result, the variation in the resistance of the tab increases. .

It should be noted that the variation in resistance of the tabs is an average value ±
To fit within 20%, in the case of using an aluminum foil as a tab crimping pressure should be at 1 ton / cm ² or more 50ton / cm ² or less, whereas, in the case of using a copper foil, 500 kg / cm ² or more 100 to
It had to be less than n / cm ² .

As described above, the aluminum foil is one of the reasons why the required pressure range is different between the aluminum foil and the copper foil in order to keep the variation in the resistance value within the predetermined range. It is considered that the oxide film is more easily formed than the copper foil and the difference in the electrical properties of the oxide film described above. The upper limit of the crimping pressure of the tab is the pressure when the tab is damaged at the end of the rivet.

(Production of Battery) A lithium secondary battery was produced by the following method. First, LiMn ₂ O ₄ powder is used as a positive electrode active material, acetylene black for imparting conductivity is added thereto, and a binder and a solvent are further mixed to prepare a paste, and the paste having a thickness of 20 μm is prepared. Apply to both sides of aluminum foil, winding direction length 3600
A positive electrode plate having an electrode surface shape of mm × width 200 mm was produced. On the other hand, using highly graphitized carbon powder as a negative electrode active material, a binder and a solvent were mixed to prepare a paste, which was applied on both sides of a copper foil having a thickness of 10 μm, and a length in a winding direction of 4000 was obtained.
A negative electrode plate having an electrode surface shape of mm × width 200 mm was produced.

Next, as shown in FIG. 11, the produced positive electrode plate 2 and negative electrode plate 3 were wound while being insulated while using a polypropylene separator 4 having a width of 210 mm, and at the same time, in Example 1 and the like. The same positive electrode tab 5A made of aluminum and the negative electrode tab 5B made of copper, which are the same as those used, are arranged in a substantially straight line in the radial direction of the internal electrode body 1, each of 30 pieces.
In addition, the electrode plates 2 and 3 are arranged so that they are arranged at substantially equal intervals when the electrode plates 2 and 3 are expanded, and one electrode is formed at one end of the internal electrode body 1. It was attached by ultrasonic welding.

The produced internal electrode body 1 was fitted into the aluminum battery case 17, and the tabs 5A and 5B for each of the positive and negative electrodes were set to 1 ton / cm by the same method as in the first embodiment.
^At the pressure of ^2, the positive and negative pole rivets 22A and 22B, which are current output terminals, are crimped, the negative electrode rivet 22B is attached with a battery cap, and the negative electrode side of the battery case 17 is sealed. From the positive electrode side of 17,
1 mol of electrolyte LiPF ₆ in a mixed solvent of EC (ethylene carbonate) and DEC (diethyl carbonate)
Inject the electrolytic solution that was dissolved so that the concentration becomes%, and then
A battery cap was attached to the positive electrode rivet 22A to seal the battery case 17. The battery case 17 may be sealed from the positive electrode side. In this way, the battery manufactured by using the method of connecting the tab and the current output terminal of the first embodiment is referred to as the battery of the first embodiment.

Subsequently, except for the method of connecting the tab and the current output terminal, the method of connecting the tab and the current output terminal was the same as in the battery of Example 1, and the above-mentioned Example 2 and Comparative Examples 1 and 2 were used. Each battery was produced by using the method.
The batteries thus produced were replaced with the batteries of Example 2,
The battery of Comparative Example 1 and the battery of Comparative Example 2 are used.

The battery capacities of the manufactured batteries were both 2
Although it was 5 Ah, the charge / discharge characteristics were evaluated by a cycle operation test. Here, the charging is 25A constant current-
The charging was performed by 4.1 V constant voltage charging, and the discharging was performed by constant current discharging with a discharge rate of 1 C (25 A) up to the discharge end voltage of 2.5 V, and this charging and discharging was repeated.
Then, the discharge capacity of each time is 100% of the discharge capacity of the first time.
Standardized as.

FIG. 12 shows how the discharge capacity changes in the cycle operation test. The batteries of Examples 1 and 2 in which the variation in the resistance of the tab was small showed a small decrease in capacity, and there was no great difference in the change between them. On the other hand, in the battery of Comparative Example 2 in which the variation in resistance was large in both the positive and negative electrode tabs, a large decrease in capacity was observed, the variation in resistance only in the positive electrode tab was large, and the variation in resistance in the negative electrode tab was small. The intermediate characteristics between Examples 1 and 2 and Comparative Example 2 were shown. It is considered that such a result is caused by the unevenness of the battery reaction in the internal electrode body due to the variation in the resistance of the tab and the partial deterioration of the positive and negative electrode plates.

[0058]

As described above, in the lithium secondary battery of the present invention, the variation in the resistance of the plurality of tabs is within a certain range, so that the current collection from the electrode plate is uniform, and The battery reaction in the internal electrode body is made uniform, and a large current can be stably discharged, which is an excellent effect. As a result, local deterioration of the battery material is suppressed, and an excellent effect of having excellent durability even in cycle operation is exhibited.

[Brief description of drawings]

FIG. 1 is a perspective view showing a structure of a wound type internal electrode body.

FIG. 2 is a plan view showing a state in which positive and negative electrode plates of a wound type internal electrode body are expanded.

FIG. 3 is a perspective view showing an embodiment of a structure of a laminated internal electrode body.

FIG. 4 is a cross-sectional view showing an embodiment of a method of connecting the tab and the current output terminal in the lithium secondary battery of the present invention.

FIG. 5 is an explanatory diagram showing another embodiment of a method of connecting a tab and a current output terminal in the lithium secondary battery of the present invention.

FIG. 6 is an explanatory view showing a method for measuring the resistance of the tab in the lithium secondary battery of the present invention.

7 is an explanatory diagram showing a method of connecting a tab and a current output terminal in a lithium secondary battery of Comparative Example 2. FIG.

FIG. 8 is an explanatory diagram showing variations in resistance of tabs in Examples and Comparative Examples.

FIG. 9 is an explanatory diagram showing the flow of current from the tab to the current extraction terminal composed of a bolt and a nut.

FIG. 10 is an explanatory diagram showing a current flow from a tab to a current extraction terminal composed of a rivet.

FIG. 11 is an explanatory diagram showing steps up to connection of the tab to the current output terminal in the production of the lithium secondary battery of the present invention.

FIG. 12 is an explanatory diagram showing cycle operation test results in Examples and Comparative Examples.

[Explanation of Codes] 1 ... Internal electrode body, 2 ... Positive electrode plate, 3 ... Negative electrode plate, 4 ... Separator, 5A ・ 6A ... Positive electrode tab, 5B ・ 6B ... Negative electrode tab,
7 ... Internal electrode body, 8 ... Positive electrode plate, 9 ... Negative electrode plate, 10 ... Separator, 11 ... External terminal, 12 ... Internal terminal member, 13 ...
Current output terminal, 15 ... Current collecting substrate (metal foil, etc.), 16 ... Electrode active material, 17 ... Battery case, 22 ... Rivet, 22A
... Positive rivet, 22B ... Negative rivet, 23 ... Battery cap, 24 ... Bolt, 25 ... Nut, 26 ... Metal plate,
27 ... screw thread, 50 ... current flow, 60 ... current flow.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-9-92258 (JP, A) JP-A-9-92238 (JP, A) JP-A-9-35701 (JP, A) JP-A-7- 326336 (JP, A) JP-A-6-333545 (JP, A) JP-A-57-845 (JP, A) Actual break flat 3-71562 (JP, U) Actual break flat 2-148561 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 2/20-2/34 H01M 10/36-10/40

Claims (10)

(57) [Claims] 1. A positive electrode plateas well asNegative electrodeBoardFrom porous polymer
Electrode body wound or laminated with a separator
And one end of the positive electrode plate and the other end of the first battery inside the battery.
Connect the positive electrode tabs connected to the outlet terminal and
Connect the other end of the negative electrode plate to the second current output terminal inside the battery.
With a plurality of negative electrode tabs connected to each otherWith lithium secondary battery
ThereSaid positive Resistance value of each pole tab(The above-mentioned positive as a member
In addition to the resistance value of the electrode tab itself,
Including contact resistance with the first current output terminal)
But, The aboveAverage resistance of positive electrode tabWhere X is X ±
0.2X (0.8X-1.2X)Within the range ofWith
To the negativeResistance value of each pole tab(Before as a member
In addition to the resistance value of the negative electrode tab itself,
And the contact resistance between the second current output terminal and
Mu)But, The aboveAverage resistance of negative electrode tabLet Y be Y
± 0.2Y (0.8Y to 1.2Y)Be within the range of
A lithium secondary battery characterized by. Wherein the positive electrode tab and the negative electrode tab, and / or, taken the first current lead terminal and said second current
Claim that the O material is used for the output terminal
Item 2. The lithium secondary battery according to Item 1 . Wherein the positive electrode tab and the negative electrode tab, for each pole, a plurality is gathered in one place, are connected by crimping or welding to one of said first and second current lead terminal The lithium secondary battery according to claim 1 or 2 , wherein Wherein said positive electrode tab and the negative electrode tab, for each pole, crimping plurality in advance, after being integrated by welding or eyelet, crimped to the first and second current lead terminal,
The lithium secondary battery according to claim 1, wherein the lithium secondary battery is connected by welding or screwing. Wherein said first and second current extraction terminal, the lithium secondary battery according to claim 3 or 4, characterized in that it is provided only one per each pole. Wherein said positive electrode tab and the thickness of one negative electrode tab, the lithium secondary battery according to any one of claims 1 to 5, characterized in that a 5μm or 100μm or less, respectively. 7. The total thickness of the positive electrode tab and the negative electrode tab is set connected to one said first and second current extraction terminal, as claimed in claim 6, characterized in that at each 200μm or more Lithium secondary battery. Wherein said positive electrode tab and the negative electrode tab is set connected to one said first and second current lead terminals, but it
The lithium secondary battery according to claim 6 or 7, characterized in that respectively at least 10 or more sheets. 9. The lithium secondary battery according to claim 1, which has a battery capacity of 5 Ah or more. 10. Use for an electric vehicle or a hybrid electric vehicle, as claimed in any one of claims 1 to 9.
The lithium secondary battery according to any one of 1.