JP2003243038A - Positive electrode plate and lithium secondary battery using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lithium secondary battery accomplishing a thin construction and a higher capacity without dropping the discharging rate characteristic and excellent in the safety in the event of shortcircuiting. <P>SOLUTION: An electricity collector consisting of a positive electrode black mix layer and an aluminum thin film having a thin film resistivity of 2-20 mΩ.cm is formed on a separator by means of evaporation, sputtering, or CVD. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positive electrode plate and a lithium secondary battery using the same, and more particularly to a lithium secondary battery ensuring safety by using an aluminum thin film as a current collector of the positive electrode plate.

[0002]

2. Description of the Related Art In recent years, portable electronic devices such as AV devices, notebook type personal computers, and portable communication devices have been rapidly made portable and cordless. Conventionally, power sources for driving these electronic devices have been Nickel-cadmium storage batteries and nickel-hydrogen storage batteries were mainly used, but with the progress of portable and cordless electronic devices and its establishment, high energy density and small size and lightweight of secondary batteries as driving power sources have been established. The demand for conversion is becoming stronger.

Under such circumstances, a carbon material capable of inserting and extracting lithium ions is used as a negative electrode active material, and a lithium-containing composite oxide showing a high charge / discharge voltage, such as LiCo.
A lithium secondary battery represented by a lithium ion secondary battery using O ₂ as a positive electrode active material and utilizing insertion and removal of lithium ions is becoming mainstream. This lithium secondary battery is small and lightweight, yet it can be charged quickly,
It has a very remarkable feature of having a high energy density.

However, in order to meet the demand for further thinning and higher capacity, it is necessary to reduce the thickness of the foil or the lathed current collector and reduce the mass thereof, but the active material and the binder are included. Some strength is required due to stable running when applying, drying, and rolling the paste, and the load during rolling,
There was a limit.

[0005]

Therefore, as a method of obtaining a battery that meets the demand for thinning and high capacity, there has been proposed a method using a current collector in which a conductive thin film is formed on a resin film. Japanese Unexamined Patent Publication No. 9-120818 discloses 5 to 20.
A method of using a current collector in which a conductive metal film (copper, nickel, aluminum) is formed on a resin sheet having a thickness of μm is disclosed in Japanese Patent Application Laid-Open No. H9-90187
No. 213338 discloses that a conductive thin film (aluminum,
A method using a current collector having copper) is disclosed in JP-A-9-25.
Japanese Patent No. 9891 discloses a method of using a plastic film on which a metal thin film (aluminum, copper) is formed as a current collector, and Japanese Patent Application Laid-Open No. 11-102711 discloses a melting point of 130 to 17
A method of using a current collector in which a metal layer (aluminum, copper) of 0.5 to 3 μm is formed on a film made of a polyolefin resin having a low melting point of 0 ° C. has been proposed.

However, in these methods, the mixture layer is formed on the current collector in which the conductive thin film is formed on the resin film, and since the surface of the conductive thin film is smooth, the binder in the mixture is formed. If the amount is not increased, it is easy to peel off, and it is necessary to dry the mixture at a temperature not higher than the heat resistant temperature of the resin film.

Further, in order to ensure the safety at the time of internal short circuit due to the burr of the electrode plate, external short circuit between the positive and negative external connection terminals, and nailing, the safety of the PTC element, the thermal fuse, the current interruption function, etc. Although a lithium secondary battery having a function has been developed, the lithium secondary battery having these safety functions has a high internal resistance and is expensive.

The present invention has been made in view of the above problems, and realizes a thin lithium secondary battery having a high capacity without deteriorating discharge rate characteristics, and a lithium secondary battery excellent in safety at the time of short circuit. The main purpose is to provide a battery.

[0009]

The present invention for solving the above problems is characterized in that a positive electrode material mixture layer and a current collector made of an aluminum thin film are integrally formed on a separator. It is a positive electrode plate, and the thin film resistivity of the current collector is preferably 2 mΩ · cm to 20 mΩ · cm, and the current collector is vapor deposition, sputtering, CVD (Chem).
It is preferable that the current collector is formed by at least one means selected from the chemical vapor deposition).

The thin film resistivity can be changed by the thickness of the aluminum thin film formed on the positive electrode mixture layer or by doping with a different metal such as cobalt, chromium or manganese.

Further, the present invention is a lithium secondary battery in which a positive electrode plate including the aluminum current collector and a negative electrode plate group are housed in a case.

Since the positive electrode mixture layer and the current collector made of an aluminum thin film having a thin film resistivity of 2 mΩ · cm to 20 mΩ · cm are integrally formed on the separator, the positive electrode plate can be formed without lowering the discharge rate characteristics. The thickness and mass of the can be reduced. Further, the thin film resistivity of the current collector is 2 mΩ · cm to 2
Since it is 0 mΩ · cm, the thin film generates heat due to the short circuit current at the time of short circuit and scatters to recover the insulation, thereby suppressing abnormal heat generation of the battery and ensuring safety.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a sectional view of a lithium polymer battery, and FIG. 2 shows a sectional view of a prismatic lithium ion battery.

In the lithium polymer battery shown in FIG. 1, a positive electrode active material layer 4 is produced by applying a paste containing a positive electrode active material and a binder on a heat-resistant film, drying and rolling, and then vapor deposition, sputtering, and CVD. A current collector is formed by one means selected from the above to prepare a positive electrode plate. Next, a paste containing a negative electrode active material and a binder is applied to the negative electrode current collector 7, dried, and rolled to produce a negative electrode plate having the negative electrode active material layer 6.

The positive electrode plate and the negative electrode plate thus produced are stacked via a separator 5 which absorbs and holds a non-aqueous electrolyte, and the electrode plate group is housed in a laminated bag-like case 1 and After pouring the water electrolyte and sealing it with the welded seal part 2 of the bag-shaped case, it is aged to gelate the non-aqueous electrolyte,
It can be manufactured by charging and discharging.

The positive electrode current collector 3 is formed by vapor deposition, sputtering,
It consists of an aluminum layer formed by at least one means selected from CVD and has a thin film resistivity of 2 mΩ · c.
m to 20 mΩ · cm.

Since a thin film having a thin film resistivity of more than 20 mΩ · cm is not a uniform thin film, the thin film resistivity is not stable, the internal resistance of the battery is increased, and the discharge rate characteristic is deteriorated, which is not preferable. On the other hand, even if the thin film resistivity is less than 2 mΩ · cm, the discharge rate characteristics hardly change, but the short circuit current at the time of short circuit causes the thin film to generate heat and scatter to recover the insulation, suppressing abnormal heat generation of the battery and ensuring safety. Is difficult to secure, which is not preferable.

The positive electrode active material layer 4 comprises a positive electrode active material and a binder,
A conductive film, a thickener, and a plasticizer are added if necessary, and a paste prepared by kneading and dispersing in a solvent is a heat-resistant film such as polyethylene terephthalate (PET) resin, polyimide (PI) resin, polyester resin, or polyphenylene sulfide (PPS) resin. It is prepared by applying it on top, drying and rolling.

As the positive electrode active material, a lithium-containing transition metal compound capable of accepting lithium ions as a guest is used. For example, cobalt, manganese, nickel,
LiCoO ₂ , a composite metal oxide of at least one metal selected from chromium, iron and vanadium and lithium, LiCoO ₂ ,
LiMoO ₂ , LiNiO ₂ , LiCo _x Ni _(1-x) O
₂ (0 <x <1) LiCrO ₂ , αLiFeO ₂ , LiV
O _{2 and the} like are preferable.

The binder is not particularly limited as long as it can be kneaded and dispersed in a solvent. For example, a fluorine-based binder, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber (SBR), Acrylic polymer,
A vinyl polymer or the like can be used alone, or as a mixture or copolymer of two or more kinds. As the fluorine-based binder, for example, polyvinylidene fluoride (PVD)
F), a copolymer of vinylidene fluoride (VDF) and propylene hexafluoride (HFP) (P (VDF-HFP)) or a dispersion of polytetrafluoroethylene (PTFE) resin is preferable.

As the conductive material which can be added if necessary, acetylene black, graphite, carbon fiber or the like is preferable, or a mixture of two or more kinds is preferable, and the thickening agent is ethylene-vinyl alcohol copolymer, carboxymethyl cellulose. , Methyl cellulose and the like are preferable, and as the plasticizer, phthalic acid esters such as diisobutyl phthalate, diethyl phthalate, di-n-butyl phthalate, dipropyl phthalate and dihexyl phthalate are preferable.

As the solvent, a solvent capable of dissolving the binder is suitable, and in the case of an organic binder, N-methyl-2-pyrrolidone, N, N-dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethylsulfoxide. , Hexamethylsulforamide, tetramethylurea,
An organic solvent such as acetone or methyl ethyl ketone is preferably used alone or as a mixed solvent in which these are mixed, and in the case of an aqueous binder, water or warm water is preferable.

It is also possible to add various dispersants, surfactants, stabilizers, etc., if necessary, at the time of kneading and dispersing the above-mentioned slurry mixture.

The negative electrode active material layer 6 comprises a negative electrode active material and a binder,
If necessary, a conductive material and a plasticizer may be added, and a paste prepared by kneading and dispersing in a solvent may be applied on the negative electrode current collector 7, dried, and rolled to prepare.

The negative electrode current collector is made of copper foil, lath-processed foil, or etching-processed foil, and preferably has a thickness of 10 μm to 50 μm.

Examples of the negative electrode active material include graphite, activated carbon, and a material obtained by firing and carbonizing phenol resin, pitch, or the like. Particularly, from the viewpoint of safety, charge / discharge cycle characteristics, etc., the lattice plane (002) plane The interval (d ₀₀₂ ) is 3.3
A carbon material having a graphite type crystal structure of 50 to 3.400Å is preferable.

The same binder, a conductive material that can be added if necessary, a thickening material, and a plasticizer can be the same as those used for the positive electrode.

The coating and drying is not particularly limited, and the slurry mixture prepared by kneading and dispersing as described above can be used, for example, in a slit die coater, reverse roll coater, lip coater, blade coater, knife coater, gravure. Using a coater, dip coater, etc.
It can be easily applied, and drying close to natural drying is preferable, but in consideration of productivity, it is preferable to dry at a temperature of 70 ° C to 200 ° C for 5 hours to 10 minutes.

Rolling is carried out by using a roll press machine or a flat plate press machine to a linear pressure of 1000 to 2000 until a predetermined thickness is obtained.
It is preferable to carry out rolling several times at kg / cm or to carry out rolling while changing the linear pressure.

For the separator 5, a polymer similar to the binder is used and a polymer paste obtained by dissolving or dispersing it in the solvent is polyethylene terephthalate (PET) resin, polyimide (PI) resin, polyester resin, polyphenylene sulfide (PPS). It is produced by forming a film on a heat resistant film such as a resin and drying it, or by laminating this separator and a separator made of a non-woven fabric made of a microporous polyolefin resin, the positive electrode and the negative electrode are heated via this separator 5. By applying pressure and laminating, the electrode plate group is manufactured. The temperature at this time is 0.2MPa while being heated from 40 ° C. to a temperature below the softening point of the binder in the electrode plate group.
It is preferable to press at a pressure of a to 5.0 MPa.

The laminated bag-shaped case 1 is a laminated sheet in which a metal foil is placed between films of a polyolefin resin and the whole is laminated and integrated. The adhesive layer and the metal foil are in contact with the laminated electrode plates from the inside. , Insulating layers are sequentially stacked. The adhesive layer is preferably an acid-modified polyolefin resin having excellent adhesiveness to leads, the metal layer is preferably an aluminum metal foil having excellent gas barrier properties and light shielding properties, and the insulating layer is preferably a polyamide resin having excellent mechanical strength.

The non-aqueous electrolytic solution is composed of a non-aqueous solvent and an electrolyte, and the non-aqueous solvent contains a cyclic carbonate and a chain carbonate as main components. As the cyclic carbonate, ethylene carbonate (EC),
At least one selected from propylene carbonate (PC) and butylene carbonate (BC) is preferable. The chain carbonate is preferably at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and the like.

As the electrolyte, for example, a lithium salt having a strong electron-withdrawing property is used, and for example, LiPF ₆ or LiB is used.
F ₄ , LiClO ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , L
iN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , Li
C (SO ₂ CF _{3) 3} and the like. These electrolytes may be used alone or in combination of two or more. These electrolytes are preferably dissolved in the non-aqueous solvent at a concentration of 0.5 to 1.5M.

The welded seal portion 2 of the bag-shaped case 1 is sealed by heat welding.

Aging is carried out at a temperature of 45 ° C to 90 ° C.
The polymer is preferably gelled by aging for 0.5 to 3 hours.

Charge / discharge is 95% to 1% of battery capacity at room temperature.
It is preferable to charge to an electric capacity of 05%.

The prismatic lithium ion battery shown in FIG. 2 is made of a microporous polyolefin resin and absorbs a non-aqueous electrolyte,
A positive electrode active material layer 14 is produced by applying a paste containing a positive electrode active material and a binder to the separator 15 to be held, drying and rolling, and collecting the positive electrode current by at least one means selected from vapor deposition, sputtering, and CVD. Form body 13. Next, a paste containing a negative electrode active material and a binder is applied to the negative electrode current collector 17, dried and rolled to produce a negative electrode plate having the negative electrode active material layer 16.

Then, the positive electrode plate and the negative electrode plate thus produced are wound through the separator 15 on the electrode plate group wound in a non-circular spiral shape by applying temperature and pressure to the metal case 1.
5 is made into an elliptical electrode plate group that is easy to insert into 5, and is then housed in a metal case 11 and the sealing plate 12 and the metal case 11 are welded together. After injecting the electrolytic solution, the injection stopper is sealed with a laser. Furthermore, by charging and discharging and aging, a prismatic lithium ion battery can be manufactured.

As the positive electrode active material layer 14, the negative electrode current collector 17, and the negative electrode active material layer 16, the same materials as those of the positive electrode active material layer 4, the negative electrode current collector 7, and the negative electrode active material layer 6 can be used, respectively. The same applies to the electrolytic solution.

The separator 15 is preferably made of a microporous polyolefin resin such as polyethylene resin, polypropylene resin and a laminated type of these resins.

The metal case 11 is a bottomed rectangular flat case having an open upper end, and is made of aluminum or an aluminum alloy, and from the viewpoint of pressure resistance, aluminum containing a trace amount of a metal such as manganese or copper. Alloy No. The 3000 series aluminum alloy is most suitable.

Charge / discharge is 95% to 1% of battery capacity at room temperature.
It is preferable to charge to an electric capacity of 05%.

Aging is performed at room temperature to 60 ° C.
Aging for 3 to 10 hours is preferable to stabilize the battery characteristics.

[0045]

EXAMPLES The present invention will be described in detail with reference to Examples and Comparative Examples, but these do not limit the present invention in any way.

Example 1 A positive electrode plate was prepared by using 100 parts by weight of LiCoO ₂ as a positive electrode active material, 5 parts by weight of acetylene black as a conductive material, and a copolymer (P (VDFF) of vinylidene fluoride and hexafluoropropylene as a binder. -HF
P)) 8 parts by weight and 10 parts by weight of phthalate-n-dibutyl phthalate (DBP) as a plasticizer are kneaded and dispersed in N-methyl-2-pyrrolidone (NMP) as a solvent,
After coating and drying on a PET film having a thickness of 50 μm,
The positive electrode active material layer 4 was produced by rolling.

Next, aluminum is sputtered so that the thickness becomes 50 nm, and the thin film resistivity is 5.4 mΩ.
A positive electrode plate having a current collector 3 of cm was produced.

The negative electrode plate is made of spherical graphite 10 as a negative electrode active material.
0 parts by weight, 2 parts by weight of vapor grown carbon fiber as a conductive material, 15 parts by weight of (P (VDF-HFP)) as a binder, and 30 parts by weight of n-dibutyl phthalate (DBP) as a plasticizer as a solvent The negative electrode paste kneaded and dispersed in acetone was applied on both sides of a current collector 7 which was lathed with a copper foil having a thickness of 50 μm and an aperture ratio of 50%, and dried, and then rolled to form the negative electrode active material layer 6. Was prepared.

The separator is (P (VDF-HFP))
A solution prepared by dissolving a resin in a mixed solvent consisting of acetone and cyclohexanone is formed on a PET film substrate and dried at a temperature of 80 ° C. to remove the mixed solvent to produce a separator 5 having a thickness of 25 μm. did.

From the positive electrode plate thus obtained, PET
After laminating the positive electrode active material layer having a current collector obtained by peeling the base material of the film and the negative electrode plate via the P (VDF-HFP) resin layer obtained by peeling the PET film from the separator, 1
A laminated electrode plate group was prepared by thermocompression bonding at a temperature of 30 ° C. and a pressure condition of 0.4 MPa for 1.5 seconds, and then this electrode plate group was immersed in a xylene solution at a temperature of 60 ° C. for 20 minutes. Then, the plasticizer DBP was removed.

Next, an acid modification with a thickness of 30 μm was performed from the inside.
Polypropylene resin layer, 50 μm thick aluminum foil
Layer consisting of a polyamide resin layer with a thickness of 20 μm
After storing the electrode plate group in the bag-shaped case 1 of
Ren carbonate (EC) and ethyl methyl carbonate
(EMC) in a mixed solvent of 2: 1 and LiPF ₆
Was injected at a concentration of 1.0 M to inject a non-aqueous electrolyte solution.

Then, thermocompression bonding was performed for 2.0 seconds at a temperature of 230 ° C. under a pressure of 0.3 MPa, and sealing was performed at the welded seal portion 2. However, the temperature rise on the positive electrode plate and the negative electrode plate was in a negligible range.

Finally, after aging at a temperature of 60 ° C. for 3 hours to gel the polymer and the separator in the positive electrode plate and the negative electrode plate and hold the non-aqueous electrolytic solution, 10% of the battery capacity is kept at room temperature. After the battery was charged to 100% of the battery capacity at the current value, it was discharged to the voltage of 3.0 V at the current value of 20% of the battery capacity.

Thus, with an average value of n = 5, the longitudinal dimension is 35.2 mm, the lateral dimension is 61.8 mm, and the thickness is 3.
A lithium secondary battery having a size of 32 mm and a battery capacity of 700 mAh was produced.

Example 2 A positive electrode plate was prepared by placing 100 parts by weight of LiCoO ₂ as a positive electrode active material, 3 parts by weight of acetylene black as a conductive material, and 3 parts by weight as a binder on a separator 15 made of microporous polyethylene resin having a thickness of 25 μm. The positive electrode active material layer 14 was prepared by coating, drying, and rolling the positive electrode paste kneaded and dispersed in 30 parts by weight of an N-methyl-2-pyrrolidone (NMP) solution of polyvinylidene fluoride (PVDF) (solid content 12%). .

Next, in the same manner as in Example 1, aluminum was vapor-deposited so that the thin film resistivity was 2 mΩ · cm, and a positive electrode plate with a separator having a current collector 13 was produced. The thickness of the thin film at this time was 135 nm.

The negative electrode plate contained 100 parts by weight of artificial lump graphite as a negative electrode active material, 4 parts by weight of styrene-butadiene rubber (SBR) dispersion (solid content 50%) as a binder, and a carboxymethyl cellulose aqueous solution (as a thickener). A negative electrode paste prepared by kneading and dispersing 140 parts by weight of solid content (1%) is applied to one surface of a current collector 17 made of a copper foil having a thickness of 15 μm, dried, and then rolled to have a negative electrode active material layer 16. A negative electrode plate was produced.

The electrode plate group obtained by winding the positive electrode plate with separator and the negative electrode plate thus obtained in a non-circular spiral shape was subjected to a pressure condition of 4.5 MPa at a temperature of 60 ° C. from the long side surface. For 30 seconds to produce an elliptical electrode plate group.

The width of this elliptical electrode group was 30.0 m.
m, the height dimension is 48.0 mm, the thickness is 5.30 mm, and the wall thickness is 0.20 mm.
Square metal case made of 0 series aluminum alloy 11
After being housed inside and sealing the metal case 11 and the sealing plate 12 by laser welding, from the liquid injection hole provided in the sealing plate 12,
A mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a ratio of 2: 1 was added to LiP.
After injecting a non-aqueous electrolyte solution in which F ₆ was dissolved at a concentration of 1.0 M, the injection hole was laser-welded and sealed.

Finally, after aging at a temperature of 45 ° C. for 6 hours to stabilize the battery characteristics, as in Example 1,
100% of battery capacity at current value of 10% of battery capacity at room temperature
After charging up to 3.0V at a current value of 20% of the battery capacity
Discharged to a voltage of. In this way, the battery capacity is 70
A 0 mAh lithium secondary battery was produced.

Example 3 After the positive electrode active material layer 4 was prepared in the same manner as in Example 2, the thin film resistivity was 20 mΩ · cm.
A lithium secondary battery having a battery capacity of 700 mAh was manufactured in the same manner as in Example 2 except that aluminum was vapor-deposited to form a positive electrode plate having the current collector 3. The thickness of the thin film at this time was 14 nm.

(Example 4) After the positive electrode active material layer 4 was prepared in the same manner as in Example 2, manganese-doped aluminum was vapor-deposited so that the thickness was 65 nm, and the thin film resistivity was 5.1 Ω. The battery capacity was 700 m in the same manner as in Example 2 except that a positive electrode plate having a current collector 3 of cm was produced.
A lithium secondary battery of Ah was produced.

Comparative Example 1 The same positive electrode paste as in Example 1 was used, with a thickness of 50 μm, an aperture ratio of 50% and a resistivity of 0.00.
The same as Example 1 except that the positive electrode plate having the positive electrode active material layer 4 was produced by applying aluminum foil having a thickness of less than 1 mΩ · cm to both sides of the lathed current collector 3 and drying and then rolling. Then, a lithium secondary battery having a battery capacity of 700 mAh was produced. The obtained dimension is an average value of n = 5, the longitudinal dimension is 35.2 mm, the lateral dimension is 61.8 mm, the thickness is 3.55 mm, and the thickness is 0.23 from Example 1.
mm increased. (Comparative Example 2) A positive electrode active material layer 4 was prepared in the same manner as in Example 2, and then aluminum was vapor-deposited so that the thin film resistivity was 30 mΩ · cm to obtain a positive electrode plate including the current collector 3. The battery capacity is 700 in the same manner as in Example 2 except that the battery is manufactured.
A mAh lithium secondary battery was produced. The thickness of the thin film at this time was 9 nm.

(Comparative Example 3) A positive electrode active material layer 4 was prepared in the same manner as in Example 2, and then aluminum was vapor-deposited so that the thin film resistivity was 1 mΩ · cm, and the positive electrode plate including the current collector 3 was prepared. A lithium secondary battery having a battery capacity of 700 mAh was manufactured in the same manner as in Example 2 except for manufacturing. The thickness of the thin film at this time was 270 nm.

With respect to the lithium secondary batteries of Examples 1 to 4 and Comparative Examples 1 to 3 thus produced,
The discharge rate characteristics and nail penetration test were conducted.

The discharge rate characteristics were measured using 10 batteries for each 20
In the environment of ℃, after constant current charging of 490mA (0.7CmA) until the battery voltage reaches 4.2V, the current value further attenuates to 35mA (0.05Cm).
After charging until A), 140mA (0.2Cm
The battery capacity after three cycles of charging / discharging under the charging / discharging conditions of discharging to the discharge end voltage of 3.0 V with the constant current of A) was taken as the initial capacity. Next, after charging under the same charging conditions as above, 700 mA (1.0 CmA) and 1400 mA
Table 1 shows the results of measuring the battery capacity when discharged to a discharge end voltage of 3.0 V at a constant current of (2.0 CmA) and determining the respective discharge rates with respect to the initial capacity.

The nail penetration test was carried out at 20 ° C. using 5 batteries each.
After charging under the above-mentioned charging conditions under the above environment, a nail having a diameter of 2.5 mm is penetrated in a direction perpendicular to the electrode plate group surface of the battery at room temperature to evaluate the presence or absence of rupture or ignition. The method was performed and the results are shown in Table 1.

[0068]

[Table 1]

As is clear from Table 1, in the case of Examples 1 to 4, the thin film resistivity was 2 mΩ · cm to 20 mΩ ·.
cm current collector made of an aluminum thin film is integrally formed, and since the current collector and the positive electrode mixture layer have excellent adhesiveness, the thickness of the positive electrode plate without decreasing the discharge rate characteristics,
The mass can be reduced, and even if an internal short circuit is forced by the nail penetration test, the thin film resistivity is 2 mΩ · cm to 2
It was found that since the thin film generates heat because it is 0 mΩ · cm and the insulation can be recovered by scattering, and only a slight amount of heat generation is observed, and safety can be secured. However, in the case of Comparative Example 1, since the thickness of the current collector made of aluminum was as thick as 50 μm, it was found that the short circuit current continued to flow even if an internal short circuit was made, and the battery generated heat and exploded.

In the case of Comparative Example 2, the thin film resistivity is 3
Since it is as high as 0 mΩ · cm, the discharge rate characteristic is poor, and Comparative Example 3
In this case, since the thin film resistivity was as low as 1 mΩ · cm, it was found that the thin film could not be immediately scattered to restore the insulation and safety could not be ensured.

[0071]

As described above, according to the positive electrode plate of the present invention, it is possible to realize a thinner lithium battery and a higher capacity without lowering the discharge rate characteristics, and to provide a lithium secondary battery which is excellent in safety during a short circuit. We were able to provide the next battery.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a lithium polymer battery according to an embodiment of the present invention.

FIG. 2 is a sectional view of a prismatic lithium-ion battery according to an embodiment of the present invention.

[Explanation of symbols]

1 bag case 2 Welding seal part 3, 13 Positive electrode current collector 4, 14 Positive electrode active material layer 5, 15 separator 6, 16 Negative electrode active material layer 7, 17 Negative electrode current collector 11 metal cases 12 Seal plate

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5H017 AA03 AS02 AS10 BB00 BB16                       BB17 CC01 DD05 EE05 EE08                       HH05 HH10                 5H029 AJ02 AJ03 AJ12 AK03 AL07                       AM03 AM07 BJ02 BJ04 BJ12                       BJ14 CJ03 CJ06 CJ24 DJ04                       DJ07 DJ17 EJ01 HJ12 HJ20                 5H050 AA02 AA08 AA15 BA17 CA07                       CA08 CA09 CB08 DA02 DA08                       DA19 FA02 FA04 FA18 GA03                       GA08 GA24 HA12 HA17

Claims (4)

[Claims] 1. A positive electrode plate, characterized in that a current collector comprising an electrode mixture layer and an aluminum thin film is integrally formed on a separator. 2. The thin film resistivity of the current collector is 2 mΩ · cm
The positive electrode plate according to claim 1, wherein the positive electrode plate has a resistance of about 20 mΩ · cm. 3. The current collector is vapor deposition, sputtering, C
The positive electrode plate according to claim 1 or 2, which is a current collector formed by at least one means selected from VD. 4. A lithium secondary battery containing a positive electrode plate and a negative electrode plate group according to any one of claims 1 to 3 in a case.