JPH08250109A - Secondary battery - Google Patents

Abstract

PURPOSE: To provide a nonaqueous electrolytic secondary battery excellent in conductivity and capable of stably exhibiting a high charge and discharge effect for a long period. CONSTITUTION: A current collector foil 11 used in a negative electrode for nonaqueous electrolytic secondary battery is formed of a current collecting part 111 having a plurality of holes 113 provided in the width and length directions, respectively, and a lead part 112 extended from one end of the current collecting part 111. A negative electrode active material paste obtained by mixing a carbonaceous material with a thermosetting resin is applied to both surfaces of the current collecting part 111, dried and press-molded, and then baked in an inert gas, whereby a negative electrode active material 12 as baked body is provided. Since the negative electrode active material 12 has a structure in which the first negative electrode active material 121 formed on one surface of the current collector foil 11 and the second negative electrode active material layer 112 formed on the other surface are mutually connected by connecting parts 123 formed in the holes 113, the negative electrode active material 12 is surely fixed to the current collector foil 11.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a non-aqueous electrolyte secondary battery.

[0002]

2. Description of the Related Art Conventionally, as a non-aqueous electrolyte secondary battery, there is a non-aqueous electrolyte secondary battery comprising an electrode (a positive electrode and a negative electrode) which absorbs and releases an alkali metal such as lithium, and an electrolytic solution containing the salt of the alkali metal. As the negative electrode active material in the electrode, for example, a carbon material is used as described in JP-A-62-90863. This is because the carbon material suppresses dendrite generation and realizes a battery that is safe and has excellent cycle life. Conventionally, as a method for producing a battery from a carbon material, carbon powder has been mixed with a resin binder such as polytetrafluoroethylene to be molded. This method
It has the advantage of being simple.

[0003]

However, according to the above-mentioned method in which the carbon powder is mixed with the resin binder to be molded, since the resin binder is insulative, the conductivity of the electrode is lowered and the electrolytic property is lowered. There arises a problem that the contact between the liquid and the electrode becomes insufficient. In addition, the resin binder itself may react with the electrolytic solution, which makes it difficult to maintain the binding force against the volume change of the carbon material due to charging and discharging. Further, since the surface of the carbon powder is covered with the resin binder, the lithium ions (Li ⁺ ) are prevented from entering and leaving the electrode, so that there is a problem that the capacity is lowered when the charge and discharge are rapidly performed.

On the other hand, JP-A-6-132027 discloses that a carbon material and a thermosetting resin are mixed, and the thermosetting resin is completely cured and then baked in an inert gas. A non-aqueous electrolyte secondary battery using the sintered body as a negative electrode is disclosed. According to this, since the surface of the carbon powder is not covered with the resin, Li ⁺ to the negative electrode is
Can be easily moved in and out, and conductivity is improved by a resin carbide generated by carbonization of the thermosetting resin during firing.

However, according to the above-mentioned Japanese Patent Laid-Open No. 6-132027, the carbon powder is fixed on the metal foil as the current collector with the thermosetting resin and then fired to make the active material a fired body. Depending on the handling conditions during or after firing, there is a problem that the active material is peeled off from the current collector foil, the active material is broken, or the active material is chipped off from the current collector foil. When the active material peels off or falls off from the current collector foil, the contact area between the current collector foil and the active material decreases, and the conductivity decreases.

An object of the present invention is to provide a non-aqueous electrolyte secondary battery which has excellent conductivity and can stably exhibit a high charge / discharge effect for a long period of time.

[0007]

In order to solve the above-mentioned problems, the non-aqueous electrolyte secondary battery according to claim 1 of the present invention comprises:
A secondary battery comprising an electrode and an electrolytic solution, wherein the electrode is provided with an active material made of a mixture of a carbon material and a resin on the surface of a current collector foil having a plurality of holes, and the active material is not charged. It is characterized by being manufactured by firing in an active gas to obtain a sintered body.

The non-aqueous electrolyte secondary battery according to claim 2 of the present invention is the non-aqueous electrolyte secondary battery according to claim 1, wherein the hole diameter d (mm) of the holes is 0.05 ≦ d ≦ 10. The distance L (mm) between the holes is 0.05 ≦ L ≦ 15, and two or more holes are provided in each of the width direction and the length direction of the current collector foil. And The non-aqueous electrolyte secondary battery according to claim 3 of the present invention is the non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the current collector foil has a surface on which the active material is provided. And a lead portion extending from one end of the current collecting portion, and the hole is provided only in the current collecting portion.

The non-aqueous electrolyte secondary battery according to claim 4 of the present invention is the non-aqueous electrolyte secondary battery according to claim 1, 2 or 3, wherein the active material is 0.1 to 0.1 before firing. 10t / c
It is characterized by being pressed at a molding pressure of m ² . The non-aqueous electrolyte secondary battery according to claim 5 of the present invention is the non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the current collector foil is made of copper, nickel, or It is made of stainless steel.

The non-aqueous electrolyte secondary battery according to claim 6 of the present invention is the non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the current collector foil is made of copper. The firing temperature of the active material is 400 ° C. to 1000 ° C. The non-aqueous electrolyte secondary battery according to claim 7 of the present invention is the non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, wherein the current collector foil is made of nickel or stainless steel. The firing temperature of the active material is 400
It is characterized in that the temperature is from ℃ to 1200 ℃.

The non-aqueous electrolyte secondary battery according to claim 8 of the present invention is the non-aqueous electrolyte secondary battery according to any one of claims 1 to 7, wherein the resin is a thermosetting resin. It is characterized by

[0012]

According to the non-aqueous electrolyte secondary battery of claim 1, since the current collector foil has a plurality of holes,
When an active material is provided on both surfaces of the current collector, the active material applied to one surface of the current collector foil and the active material applied to the other surface by the active material filled inside the holes Are connected. As a result, the active material is reliably fixed to the current collector foil, so that cracking of the active material or peeling of the active material from the current collector foil is unlikely to occur. Further, even when the active material is cracked or peeled off from the current collector foil, the active material is unlikely to fall off from the current collector foil. Since the active material is in a state in which the particles of the carbon material are bonded by the carbide of the resin, cracking is unlikely to occur. Since the resin is carbonized by firing the active material, the resin does not inhibit the lithium ions from entering and leaving the electrode, and thus exhibits an excellent battery function. Since the electrode is made of a carbon material and resin carbide, it has excellent conductivity, and since the carbide also functions as an active material, the capacity of the electrode can be improved without waste. Since the resin is carbonized, the electrode is prevented from being corroded by the electrolytic solution, so that a stable high discharge effect can be obtained for a long period of time.
Therefore, the non-aqueous electrolyte secondary battery can be used for a long period of time.

According to the second aspect of the non-aqueous electrolyte secondary battery, since the pore diameter d is 0.05 mm ≦ d ≦ 10 mm, the active material can be easily and properly filled in the pores. Since the distance L between the holes is 0.05 mm ≦ L ≦ 15 mm, cracks are unlikely to occur in the current collector foil when the active material is press-molded.
Since two or more holes are provided in each of the width direction and the length direction of the current collector foil, the active material is reliably fixed to the current collector foil.

According to the non-aqueous electrolyte secondary battery of claim 3,
And there are no holes in the lead of the collector foil.
Maintain the bending strength of the lead part and cause cracks in the lead part.
To prevent This enables reliable non-aqueous electrolysis
A quality secondary battery can be obtained. The non-hydroelectric battery according to claim 4.
According to the degradable secondary battery, 0.1-10 t / cm before firing
²Since the active material is pressed with the molding pressure of
To properly fix the active material on the collector foil.
You can Also, increase the amount of active material per unit volume.
This has the effect of improving the battery capacity.

According to the non-aqueous electrolyte secondary battery of the fifth aspect, the current collector foil is made of copper, nickel, or stainless steel, and thus has good conductivity. According to the non-aqueous electrolyte secondary battery of claims 6 and 7, when the current collector foil is made of copper, the active material is fired at 400 ° C to 1000 ° C, and when the current collector foil is made of nickel or stainless steel. Fires the active material at 400 ° C to 1200 ° C. This allows
It is possible to obtain a highly reliable non-aqueous electrolyte secondary battery by carbonizing the resin and preventing the current collector foil from melting or lowering in strength.

According to the non-aqueous electrolyte secondary battery of the eighth aspect, by using the thermosetting resin as the resin, when the thermosetting resin is cured before firing, the active material is less likely to collapse during firing. There is an effect.

[0017]

EXAMPLES Examples of the present invention will be described in detail below. A non-aqueous electrolyte secondary battery 10 according to an embodiment of the present invention is shown in FIGS.
As shown in FIG. As shown in FIGS. 2 to 5, the non-aqueous electrolyte secondary battery 10 has a structure in which the electrode group 5 in which the negative electrodes 1 and the positive electrodes 2 are alternately stacked with the separator 3 interposed therebetween is housed in the case 61. There is. The separator 3 is made of a polyethylene microporous film having an aperture ratio of 40% and a film thickness of 25 μm. An electrolytic solution 4 in which a non-aqueous electrolyte is dissolved in a non-aqueous solvent is injected into the case 61, and the electrode group 5 is immersed in the electrolytic solution 4. An upper lid 62 attached to the upper opening of the case 61
Includes a positive electrode terminal 7 and an electrolyte 4 which are insulated by a rubber packing.
An explosion-proof plate 8 for preventing the explosion of the inlet 9 and the battery 10 for injecting is provided. Inlet 9 is for electrolyte 4
Is sealed except when the injection is performed. The explosion-proof plate 8 is provided with a notch-shaped groove so that when the pressure inside the case 61 rises abnormally, the pressure inside the case 61 escapes from this groove. The inside of the case 61 is sealed by laser welding the upper lid 62 to the case 61.

As shown in FIG. 1, the negative electrode 1 is a copper current collector foil 11 having a rectangular current collector 111 and a narrow lead 112 extending from one end of the current collector 111, and a current collector. The negative electrode active material 12 is provided on both surfaces of the portion 111.
The current collector 111 is provided with a plurality of holes 113 at equal intervals. The negative electrode active material 12 is a porous fired body made of a carbonaceous material and a resin carbide, and the electrolytic solution 4 is impregnated into the voids of the fired body. The negative electrode active material 12 is the current collector 1
First negative electrode active material layer 121 formed on one surface 11
And the second negative electrode active material layer 122 formed on the other surface
And the first negative electrode active material layer 12 formed inside the hole 113.
1 for connecting the first negative electrode active material layer 122 and the second negative electrode active material layer 122
And 3.

The positive electrode 2 is provided on both sides of the current collector, and a collector foil made of aluminum having a rectangular current collector and a narrow lead portion 212 extending from one end of the current collector. And a positive electrode active material. At the end portion of the electrode group 5 on the upper lid 62 side, the lead portion 112 of the negative electrode 1 is at the right end portion in FIG.
The negative electrode 1 and the positive electrode 2 are alternately laminated so that the lead portion 212 of the positive electrode 2 is located at the left end portion in FIG.
The lead portion 112 of the negative electrode 1 is bent and bundled to form the case 61.
It is connected to the. The lead portion 212 of the positive electrode 2 is connected to the positive electrode terminal 7.

The electrolytic solution 4 is prepared by dissolving a non-aqueous electrolyte in a non-aqueous solvent. In this example, the non-aqueous solvent was propylene carbonate: diethyl carbonate = 50 vol.
%: 50 vol% mixed solvent was used, and LiPF ₆ as a non-aqueous electrolyte was dissolved in this mixed solvent to a concentration of 1 mol / liter to prepare an electrolytic solution 4. Next, the positive electrode 2
The manufacturing method of will be described.

The positive electrode 2 is made of LiCoO 2 as a positive electrode active material.
₂ 94 wt%, graphite 4 wt% and the binder 2 wt% as a conductive agent were mixed, as a solvent N- methyl-2
Pyrrolidone was added to obtain a positive electrode active material paste. The positive electrode active material paste is applied to the current collector foil, dried, and then pressure-molded into a predetermined shape to obtain the positive electrode 2 in which the positive electrode active material is provided on both surfaces of the current collector foil.

Next, a method for producing the negative electrode 1 will be described. Non-graphitizable carbon as carbonaceous material (Nippon Carbon, MC0510: average particle size 2 to 30 μm) 90 wt%
And 10 wt% of a phenol resin (PR-50273 manufactured by Sumitomo Dures Co., Ltd.) as a binder were sufficiently mixed, and N-methyl-2-pyrrolidone as a solvent was added to obtain a negative electrode active material paste having a viscosity of 140 Ps. To this negative electrode active material paste, 3 wt% of polyethylene glycol (molecular weight 600) as a high boiling point material was added to the phenol resin.
%Added. Next, this negative electrode active material paste is applied to both sides of the current collector foil 11 and dried, and the temperature is 150 ° C. and 3 t / cm.
Press molding is performed under the conditions of ² to obtain a negative electrode active material molded body having a predetermined shape. The negative electrode active material 1 is formed on both surfaces of the current collector foil 11 by firing the current collector foil 11 and the negative electrode active material molded body in an argon stream at 750 ° C. for 3 hours to obtain a negative electrode active material fired body.
A negative electrode 1 having 2 is prepared.

The current collector foil 11 will be described in more detail. As shown in FIG. 6, a plurality of holes 113 are formed in the current collector 111 of the current collector foil 11 at equal intervals. Hole 1
The shape of 13 may be any shape such as a circle, a hexagon, a quadrangle, a triangle, and an ellipse, but a circle is preferable. This is because, by making the hole 113 circular, the current collector foil 11 is less likely to break during press molding, and the negative electrode active material 1 is formed in the hole 113 during application of the negative electrode active material paste and press molding.
2 is easily filled at a high density, and the strength of the connecting portion 123 of the negative electrode active material 12 formed inside the hole 113 is increased. Further, the hole 113 is provided only in the current collector 111, and is not provided in the lead 112. This is the lead portion 512 of the current collector foil 51 as shown in FIG.
If the holes 513 are also provided in the lead portions 512 when the lead portions 512 are bent and bundled for connecting to the case.
Is easily broken.

(Experimental Example 1) When the holes were circular, the negative electrode was prepared as described above by changing the number of holes formed in the current collector foil, the hole diameter d, and the hole interval L, and The difference in the effect of preventing the chipping of the negative electrode active material depending on the shape was compared. The shape of the collector foil is 42 mm wide x 32 mm long, 12 μm thick
Is. The effect of preventing chipping off was evaluated as ◯ when no chipping of the negative electrode active material was visually observed when the electrodes were stacked after firing and inserted into the case, and as x when it was found. Table 1 shows the shape of the current collector foil and the evaluation results.

[0025]

[Table 1]

As can be seen from Table 1, in the conventional example in which the current collector foil does not have holes, the negative electrode active material fired body is cracked and peeled from the current collector foil due to the lamination of electrodes and the insertion into the case. As a result, chipping of the negative electrode active material occurred. When the pore diameter was as small as 0.03 mm (Comparative Example 1), the negative electrode active material was not properly filled in the pores, and thus the negative electrode active material was found to be chipped off as in the conventional example. Also, the pore size is 1
When it is as large as 1.00 mm (Comparative Example 5), the negative electrode paste that has entered the holes during application is dropped and the holes are opened, so that the negative electrode active material is not properly filled in the holes and the negative electrode active material is chipped off. Was discovered. It may be possible to increase the viscosity of the negative electrode active material paste in order to improve the filling property of the negative electrode active material when the pore size is large, but if the viscosity is excessively high, application to the current collector foil becomes difficult.

On the other hand, when the hole spacing is as narrow as 0.03 mm (Comparative Example 2), cracks occur in the current collector foil during pressure molding after coating the negative electrode active material paste. Conversely, the hole spacing L is 1
When it is as wide as 6.00 mm (Comparative Example 4), the negative electrode active material fired body is cracked and peeled off from the current collector foil due to the lamination of the electrodes and the insertion into the case, which causes the negative electrode active material to fall off. There has occurred.

When the number of holes is only one in the width direction of the current collector foil (Comparative Example 3), the bonding of the negative electrode active material fired body between both sides of the current collector foil is weak, The fired body of the negative electrode active material was cracked and peeled from the current collector foil, which caused chipping of the negative electrode active material. From the above results, the shape of the current collector foil is such that two or more holes are provided in the width direction and the length direction of the current collector foil, and the hole shape has a hole diameter d of 0.05 mm ≦ d. ≦ 10 mm, hole spacing L is 0.0
It can be seen that it is desirable that 5 mm ≦ L ≦ 15 mm.

In order to obtain a small secondary battery having a large discharge capacity, the thickness of the collector foil is preferably 100 μm or less. (Experimental Example 2) The influence of press molding conditions after coating the negative electrode active material paste on the current collector foil and drying it was examined on the battery capacity and the effect of preventing the negative electrode active material from falling off.

A negative electrode was produced in the same manner as in Experimental Example 1 except for press molding conditions. In Experimental Example 2, the diameter d of the holes provided in the current collector foil was 1 mm, and the distance L between the holes was 0.2.
mm. Battery capacity is 1.0mA / cm ² charging current
Constant voltage constant current charging up to 4.2V and discharge current 1.
The initial discharge capacity was defined as the value obtained by dividing the discharge capacity when constant current discharge was performed at ² mA / cm ^{2 up} to 2.75 V by the weight of the negative electrode active material. The larger the initial discharge capacity, the better. Judgment of the chipping prevention effect was performed in the same manner as in Experimental Example 1. The molding conditions and the evaluation results are shown in Table 2.

[0031]

[Table 2]

As can be seen from a comparison of Examples 14, 15, 18, 19, 20, and 21, 0.1-10 t / cm ²
In the above range, the higher the molding pressure, the higher the molding density of the negative electrode active material in the pores and the larger the amount of the negative electrode active material per unit volume, and the higher the initial discharge capacity.
When the molding pressure is less than 0.1 t / cm ² (Comparative Example 6), the negative electrode active material is not properly filled in the holes, so that the negative electrode active material peels off from the current collector foil. Further, when the molding pressure was large over 10 t / cm ² , the current collector foil was cracked.

From the above results, the molding pressure range of the negative electrode is
It can be seen that it is preferably 0.1 to 10 t / cm ² . Since molding pressure 5t / cm ² ~10t / cm molding pressures by increasing the molding pressure in the ^second range does not change, the molding pressure is more preferably set to 1~5t / cm ^2. Good results are obtained even when the press molding is carried out at room temperature as in Example 16, but the thermoforming as in Examples 17 and 18 improves the molding density of the negative electrode active material and improves the battery. It is preferable because the capacity is improved. When a thermosetting resin such as a phenol resin is used as the binder, it is preferable to perform heat molding at a temperature not higher than the curing temperature of the resin. Here, when a high boiling point solvent such as polyethylene glycol is added, curing of the thermosetting resin can be suppressed, so that molding can be performed at a higher temperature, the molding density can be further improved, and the battery capacity can be improved. . In this case, the heat molding temperature can be increased to about 280 ° C.

As described above, according to the present embodiment,
The current collector foil 11 is provided with a plurality of holes 113. Therefore, when the negative electrode active material paste is applied to both surfaces of the current collector foil 11, dried and press-molded, one surface of the current collector foil 11 is connected through the hole 113 to the other surface of the negative electrode active material. It becomes a material compact. When this negative electrode active material molded body is fired in an inert atmosphere, a first negative electrode active material layer 121 and a second negative electrode active material layer 122 are connected by a plurality of connecting portions 123 to obtain a negative electrode active material fired body. The negative electrode active material 12 is obtained. As a result, the negative electrode active material 12 is firmly fixed to the current collector foil 11, so cracking and peeling are less likely to occur. In addition, when the negative electrode active material 12 is cracked or peeled off,
Due to the plurality of connecting portions 123, the negative electrode active material 12 does not easily fall off from the collector foil 11.

Further, the negative electrode active material molded body slightly contracts during firing. At this time, since the current collector foil 11 is provided with the plurality of holes 113, the first negative electrode active material layer 121 and the second negative electrode active material layer 122 connected by the connecting portion 123.
The negative electrode active material molded body shrinks so that and become closer to each other from both sides of the current collector foil 11. As a result, the contact between the current collector foil 11 and the negative electrode active material 12 is improved and the contact resistance is reduced, so that the conductivity is improved and the current collector foil 11 and the negative electrode active material 1 are improved.
2 can be charged and discharged at high speed.

Since the negative electrode active material 12 is in a state in which the particles of the carbon material are bonded by the carbide of the resin, the negative electrode active material 12 is strong and hardly cracks. The negative electrode active material 12 is fired, and the resin coating the carbon material is carbonized in a porous form. Therefore, the electrolytic solution 4 easily penetrates into the voids of the porous negative electrode active material 12 and does not inhibit the lithium ions from entering and leaving the negative electrode 1, thus exhibiting an excellent battery action.

Further, since the negative electrode 1 is made of a carbon material and a resin carbide, it has excellent conductivity, and since the carbide also functions as an active material, the capacity of the electrode can be improved without waste. Since the resin is carbonized, the negative electrode is prevented from corroding due to the electrolytic solution, so that a stable and high discharge effect can be obtained for a long period of time. Therefore, the non-aqueous electrolyte secondary battery can be used for a long period of time.

The non-aqueous electrolyte secondary battery of this example is small in size and can stably obtain a high discharge effect for a long period of time.
It is preferably used for a handy terminal such as a bar code reader with a thermal transfer printing function and a meter reading device, a notebook personal computer, an electric bicycle, an electric wheelchair and an electric vehicle. Further, it can be used for mobile phones, video and video-integrated televisions.

The non-aqueous solvent used for the preparation of the electrolytic solution 4 is not limited to the propylene carbonate: diethyl carbonate mixed solvent used in this example, but may be, for example, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, 1 , 2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, sulfolane, methylsulfolane, acetonitrile, propionitrile, methyl formate, ethyl formate, methyl acetate , Ethyl acetate, trimethyl phosphate, triethyl phosphate, triethylhexyl phosphate, trilauryl phosphate and the like, or a mixture of two or more thereof in a desired ratio can be used. Alternatively, a lithium ion conductive solid electrolyte may be used. On the other hand, as the non-aqueous electrolyte, Li used in this example was used.
Not limited to PF ₆ , for example, LiBF ₄ , LiClO ₄ ,
LiAsF ₆ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li,
Any one kind of lithium salt such as (CF ₃ SO ₂ ) ₂ NLi or a mixture of two or more kinds at a desired ratio can be used.

As the separator 3, it is possible to use, for example, a polypropylene microporous film or a polypropylene / polyethylene / polypropylene 3-layer microporous film in place of the polyethylene microporous film used in this embodiment. Further, as the positive electrode active material, in addition to LiCoO ₂ used in this example, lithium ion can be dedoped and doped, and lithium can be used as a reference electrode (0
A substance having a potential of 3.5 V or more when V) is used can be used. Examples of such substances include the following.

Li _x CoO ₂ (0 <x ≦ 1), Li
_x Co _y M _z O ₂ (M is at least one metal selected from Al, In and Sn, 0.5 <y ≦ 1, z ≦ 0.
1) such as lithium cobalt oxide. Li _x NiO ₂ (0 <x ≦ 1), Li _x Co _y Ni
Lithium nickel oxide such as _z O ₂ (0 <x ≦ 1, y + z = 1).

Li _x MnO ₂ (0 <x ≦ 1), Li
_x Mn ₂ O ₄ (0 <x ≦ 1), LiCo _x Mn _2-x O ₄
Lithium manganese oxide such as (0 <x ≦ 0.5). As the conductive agent mixed with the positive electrode active material, Ketjen black or the like may be used instead of the graphite used in this example. As the binder mixed with the positive electrode active material, for example,
Organic polymers such as polytetrafluoroethylene, polyvinylidene fluoride, fluororubber, carboxymethyl cellulose, polyvinyl alcohol, polyacrylic acid, polyimide resin, polybutadiene, styrene-butadiene rubber, nitrile rubber, and polyacrylonitrile can be used.

As the solvent to be added to the mixture of the positive electrode active material, the conductive agent and the binder, in addition to N-methyl-2-pyrrolidone used in this example, positive electrode active materials such as alcohols and ketones such as acetone are used. A solvent capable of adjusting the viscosity of the paste may be appropriately selected according to the type of binder. Further, the collector foil 21 used for the positive electrode 2 is not limited to the aluminum foil used in this embodiment, but aluminum,
A metal foil made of nickel, stainless steel or the like, a mesh body, a metal porous body, or the like can be used.

Further, the carbonaceous material used for the negative electrode 1 is not limited to the non-graphitizable carbon used in this example, but also the graphitizable carbon, natural graphite, artificial graphite, pitch coke powder, organic carbonized powder and these. Mixtures can be used. Also,
A composite carbonaceous material in which graphite is coated with amorphous carbon may be used. The carbonaceous shape may be any of scale-like shape, spherical shape, fibrous shape, and irregular polygonal shape obtained by pulverization. Although the non-graphitizable carbon having an average particle diameter of 2 to 30 μm is used in this embodiment, the average particle diameter of the carbonaceous material is more preferably 3 to 15 μm.

As the binder mixed with the carbonaceous material,
The binder used for producing the positive electrode 2 can be used, but it is more preferable to use a thermosetting resin. When the thermosetting resin is present in the negative electrode active material, the negative electrode active material paste is applied to the current collector foil and dried, and then the thermosetting resin is cured, the particles of the carbonaceous material are mutually separated by the cured resin. Since it is firmly bound, the negative electrode active material molded body is less likely to collapse during firing. Further, the thermosetting resin may be baked as it is without being cured before baking, and may be cured by heat during baking. In this example, the thermosetting resin is cured before firing by performing press molding to obtain a negative electrode active material molded body at 150 ° C. Further, the thermosetting resin is carbonized by being heated in an atmosphere of an inert gas such as argon or nitrogen to become a resin carbide, and the resin carbide firmly bonds the particles of the carbonaceous material after firing to each other. It The binder is 5 to 5 in the mixture with the carbonaceous material.
It is preferably 40% by weight. 5% by weight of binder
If the amount is less than the range, the binding property of the carbon material particles in the negative electrode active material sintered body may be deteriorated. On the other hand, when the binder content exceeds 40% by weight, characteristics such as the electrode capacity of the negative electrode active material sintered body may deteriorate.

As the thermosetting resin to be mixed with the carbonaceous material, in addition to the phenol resin used in this example, for example,
It is possible to use an organic compound such as furan resin, pitch, cellulose, rayon, polyacrylonitrile, or polyimide which is carbonized by firing in an inert gas atmosphere. As the solvent added to the mixture of the carbonaceous material and the binder, in addition to N-methyl-2-pyrrolidone used in this example, alcohols, ketones such as acetone, and the like, the viscosity of the negative electrode active material paste can be adjusted. A suitable solvent may be appropriately selected according to the type of binder. In addition, a binder such as polytetrafluoroethylene or polyethylene is added in a small amount of about 1 to 5%, and the powdery mixture of the carbonaceous material and the binder is directly press-molded to easily obtain a negative electrode active material molded body. be able to. Alternatively, a negative electrode active material paste can be prepared by using a liquid binder.

In this example, the negative electrode active material molded body was fired in an argon stream at 750 ° C. for 3 hours, but the lower limit of the firing temperature of the negative electrode active material molded body was 400 ° C. This is because, as shown in FIG. 7, the resins used as the binder are carbonized at about 400 ° C. or higher. In FIG. 7, assuming that the initial weight of each resin is 100%, 40
The weight of each resin is greatly reduced in the range of 0 ° C to 600 ° C,
It can be seen that each resin was carbonized.

On the other hand, the upper limit of the firing temperature depends on the material of the collector foil. As the current collector foil, copper, nickel, stainless steel, or the like can be used, and it has been experimentally found that a breaking strength of 0.1 MPa or more is required to stack and insert the electrodes. FIG. 8 shows the bending strength when each material is fired at various temperatures. When nickel is used as the material of the current collector foil, if the firing temperature is higher than 1200 ° C., the nickel becomes hard and the electrode easily breaks. Further, since the lead portion is also easily broken by bending, the firing temperature when nickel is used is 1200 ° C. or lower. When copper is used as the material of the collector foil, the melting point of copper is 1083 ° C., so the firing temperature is 1000 ° C. or less. When stainless steel was used as the material of the collector foil, the firing temperature was 10% as shown in FIG.
If the temperature exceeds 00 ° C, carbon diffuses into the iron and the current collector foil becomes brittle and easily broken, so the firing temperature is set to 1000 ° C or lower.

Since the collector foil 11 is fired together with the negative electrode active material molded body, it is vulnerable to bending, and the lead portion 112 is easily broken particularly near the boundary between the collector portion 111 and the lead portion 112. . Here, as shown in FIG. 10, when the corner bent portion 412a is provided at the root portion of the lead portion 412 of the current collector foil 41, there is an effect of preventing breakage of the lead portion 412. When the radius of curvature of the corner curved portion is less than 0.05 mm, the effect of preventing breakage of the lead is insufficient. When the radius of curvature of the corner curved portion exceeds 10 mm and is large, the lead portion of the positive electrode is short-circuited and an internal short circuit is likely to occur, and it becomes difficult to bend the lead portion 412 into a predetermined shape. Therefore, the radius of curvature of the corner curved portion is 0.05 mm to 10 mm, preferably 0.1 m
m to 3 mm is preferable.

[Brief description of drawings]

1 shows a negative electrode of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention, (A) is a perspective view, (B) is its I-.
It is an I line sectional view.

FIG. 2 is a partial cross-sectional view showing a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 3 is a view on arrow III in FIG.

FIG. 4 is a view on arrow IV in FIG.

FIG. 5 is a perspective view showing an electrode group of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 6 is a plan view showing a current collector foil used as a negative electrode of a non-aqueous electrolyte secondary battery according to an embodiment of the present invention.

FIG. 7 is a characteristic diagram showing a carbonization temperature of a resin.

FIG. 8 is a characteristic diagram showing the relationship between heat treatment temperature and elongation of metal.

FIG. 9 is a characteristic diagram showing the relationship between the firing temperature and bending strength of a metal.

FIG. 10 is a plan view showing a collector foil in which a lead portion is provided with a corner curved portion.

FIG. 11 is a plan view showing a current collector foil having holes in lead portions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Negative electrode (electrode) 2 Positive electrode 3 Separator 4 Electrolyte 5 Electrode group 10 Non-aqueous electrolyte secondary battery 11 Current collector foil 12 Negative electrode active material (active material) 61 Case 111 Current collecting part 112 Lead part 113 Hole 121 First Negative electrode active material layer (active material) 122 Second negative electrode active material layer (active material) 123 Connection part (active material) 212 Lead part

Claims (8)

[Claims] 1. A secondary battery comprising an electrode and an electrolytic solution, wherein the electrode is provided with an active material made of a mixture of a carbon material and a resin on the surface of a current collector foil having a plurality of holes, A non-aqueous electrolyte secondary battery manufactured by firing the active material in an inert gas to form a sintered body. 2. The hole diameter d (mm) of the hole is 0.05 ≦ d
≦ 10, and the distance L (mm) between the holes is 0.05 ≦ L
The non-aqueous electrolyte secondary battery according to claim 1, wherein ≦ 15, and two or more holes are provided in each of the width direction and the length direction of the current collector foil. 3. The current collector foil comprises a current collector having a surface provided with the active material and a lead extending from one end of the current collector, and the hole is provided only in the current collector. The non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein 4. The active material is 0.1-10 t before firing.
The non-aqueous electrolyte secondary battery according to claim 1, 2 or 3, which is pressed at a molding pressure of / cm ² . 5. The current collector foil is made of copper, nickel, or stainless steel.
5. The non-aqueous electrolyte secondary battery according to any one of items 1 to 4. 6. The nonaqueous electrolyte electrolyte according to claim 1, wherein the current collector foil is made of copper, and the firing temperature of the active material is 400 ° C. to 1000 ° C. Next battery. 7. The current collector foil is made of nickel or stainless steel, and the firing temperature of the active material is 400 ° C.
It is -1200 degreeC, The non-aqueous electrolyte secondary battery as described in any one of Claim 1 to 4 characterized by the above-mentioned. 8. The non-aqueous electrolyte secondary battery according to claim 1, wherein the resin is a thermosetting resin.