JPH056766A - Battery - Google Patents

Abstract

PURPOSE:To prevent the fall and peel of an electrode constituting material from a collector in a battery to prevent the capacity deterioration of the battery or improve the cycle characteristic. CONSTITUTION:A negative electrode 1 having electrode constituting material layers 1a on both surfaces 9a, 9b of a flat collector 9 is formed. The surface roughness of the flat collector 9 is 0.15mum-3.0mum in central line average roughness. A flat separator is laminated on the negative electrode 1, a flat separator is also laminated on a positive electrode formed in the same manner as the electrode 1 with a different electrode constituting material, and the electrodes with separators are laminated to each other and then spirally wound to form a wound electrode body. As the collector 9, a titanium foil or aluminium foil is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery provided with an electrode having an electrode-constituting material layer formed on the surface of a planar current collector.

[0002]

SUMMARY OF THE INVENTION The present invention relates to a battery provided with an electrode in which a layer of electrode constituent material is formed on a planar current collector, and the surface roughness of the planar current collector is 0.15 μm in terms of center line average roughness. The battery performance is improved by the above and 3.0 μm or less.

[0003]

2. Description of the Related Art A so-called non-aqueous electrolyte battery using lithium as a negative electrode active material and an organic solvent as an electrolyte has advantages such as low self-discharge, high nominal voltage, and excellent storage stability. Have A typical example is a lithium manganese dioxide battery, which has been developed as a highly reliable battery for a long time and is widely used as a power source for clocks and memory backups.

However, most of the non-aqueous electrolyte batteries conventionally used are primary batteries, but in recent years, with the widespread use of video cameras, small audio equipment, etc., they have been repeatedly and conveniently used economically as portable power sources. The demand for rechargeable batteries that can be used is increasing, and the development of non-aqueous electrolyte secondary batteries,
Commercialization is in progress.

Several proposals have been made so far regarding the electrode structure of the positive electrode and the negative electrode of the non-aqueous electrolyte secondary battery. For example, in the method of pressing the mixture containing the expanded metal as the current collector and the active material and the binder powder, it is difficult to thin the electrode and the productivity is low.

On the other hand, a strip-shaped electrode obtained by applying a slurry in which an active material and a binder powder are dispersed in an organic solvent to a strip-shaped metal foil as a current collector and drying the strip-shaped electrode together with a strip-shaped separator (spiral shape) According to the spirally wound electrode body obtained by winding the electrode, a large-area electrode can be accommodated in a limited space, so that a lightweight and high-capacity non-aqueous electrolyte secondary battery can be obtained. The metal foil used as the current collector is usually used as it is rolled.

[0007]

However, in the battery assembling process such as the manufacturing process of the wound electrode body as described above,
The electrode constituent material such as an active material may fall off from the metal foil as the current collector, which adversely affects the productivity of battery production.

Further, the active material (or active material carrier) expands and contracts with repeated charging and discharging during use of the battery, and the adhesion between the current collector and the electrode constituent material layer decreases. As a result, there is a drawback in that battery performance is deteriorated such as deterioration of capacity and deterioration of cycle characteristics.

An object of the present invention is to provide a battery in which the adhesion between the current collector and the electrode constituent material layer is improved in the electrode to improve the battery performance.

[0010]

The present invention is based on the finding by the present inventor that it is effective that the surface of the current collector of the electrode is roughened in order to achieve the above object. And a battery comprising an electrode in which an electrode constituent material layer is formed on the surface of a planar current collector,
The surface roughness of the current collector on which the electrode constituent material layer is formed is 0.15 μm or more, preferably 0.17 μm or more and 3.0 μm or less, preferably 0.60 μm or less in terms of center line average roughness. It is characterized by being.

A winding formed by stacking an electrode having an electrode-constituting substance layer on a planar current collector having the above-described surface roughness and a planar separator, and then spirally winding. Batteries equipped with electrode bodies are preferred.

The surface roughness of the current collector is preferably determined within the above-mentioned range in consideration of the thickness of the planar current collector to be used. Further, the current collector having the surface roughness as described above may be used for both the negative electrode and / or the positive electrode.

Next, the definition regarding the surface roughness will be described below. The surface roughness is defined in JIS B0601 with respect to the center line average roughness (Ra), the maximum height (Rmax), and the ten-point average roughness (Rz).

FIG. 6 is for explaining the definition of the center line roughness (Ra), and is a cross-sectional view of an uneven surface. As shown in the figure, the center line is drawn so that the areas surrounded by the surface irregularities (cross-sectional curves) and the straight line are equal on both sides of this straight line. The cross section curve is represented by y = f (x) with the center line as the x-axis and the vertical direction as the y-axis. At this time,

[0015]

[Equation 1]

The value obtained from the equation (1) in units of micrometers (μm) is defined as the center line roughness (Ra).

FIG. 7 is a cross-sectional view of the uneven surface for explaining the definition of the maximum height (Rmax).
As shown in the figure, when a section curve is sandwiched by two straight lines parallel to the center line, the distance between these two straight lines is measured in the y direction of the section curve, and this value is expressed in micrometers. It is defined as (Rmax).

[0018]

Since the surface of the planar current collector is appropriately roughened, the adhesion between the surface of the current collector and the electrode constituent material layer is improved.

[0019]

Embodiments of the present invention will be described below with reference to the drawings.

Experimental Example (Surface Roughening Treatment) First, an experimental example in which the surface of a Ti (titanium) foil used as a current collector is roughened will be described.

A titanium foil with a thickness of 10 μm was added with 30% by weight of H
Dip in ₂ SO ₄ (sulfuric acid) aqueous solution,
Hold at 5 ° C. After a certain period of time, the titanium foil was taken out of the sulfuric acid aqueous solution and thoroughly washed with water, and then the surface roughness (Ra and Rmax) of the titanium foil was measured.

Further, the surface roughness of the titanium foil was measured by changing the roughening treatment time of immersing the titanium foil in the sulfuric acid aqueous solution. The results of these measurements are shown in FIG. 3 as the relationship between the acid treatment time for surface roughening with an aqueous sulfuric acid solution and the surface roughness (Ra and Rmax). As shown in FIG. 3, the center line average roughness (Ra) and the maximum height (Rm
ax) grows together.

Next, the relationship between the center line average roughness (Ra) and the maximum height (Rmax) was investigated by similarly roughening a titanium foil having a thickness of 100 μm. This result is shown in Figure 4.
This is also shown together with the case where the titanium foil is 10 μm thick. From the figure, the relation of Rmax = 8.3Ra (2) was obtained in the range of 0 ≦ Ra ≦ 4.5 μm.

The surface roughness was measured under the following measurement conditions using a surface roughness / contour shape measuring instrument SEF-30D model of Kosaka Laboratory Ltd. Longitudinal magnification: 5000 times Lateral magnification: 100 times Standard length: 2.50 mm Cut-off value: 0.8 mm Feed rate: 0.05 mm / s

Example 1 In Example 1, a negative electrode 1 as shown in FIG. 1 was prepared using the titanium foil obtained in the above experimental example as a current collector, and this negative electrode 1 was used to produce a non-aqueous solution as shown in FIG. An electrolyte secondary battery was produced. First, the negative electrode 1 was obtained as follows. 10μ thickness in the above experimental example
Ra of 0.15 μm Ra obtained from titanium foil of m
A titanium foil having a and 9b was used as a negative electrode current collector 9 as shown in FIG.

90 parts by weight of pitch coke, which is a carbon material as a negative electrode active material support, was mixed with 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder to prepare a negative electrode mixture (negative electrode constituent material). This negative electrode mixture was dispersed in N-methylpyrrolidone as a solvent to form a slurry (paste form).

This negative electrode mixture slurry has a Ra of 0.
Both surfaces 9a of the negative electrode current collector 9 made of 15 μm titanium foil,
9b was evenly applied and dried. Thereafter, by compression molding and cutting, a strip-shaped negative electrode 1 having negative electrode constituent material layers 1a on both surfaces 9a and 9b of a negative electrode current collector 9 as shown in FIG. 1 was obtained. The negative electrode 1 had a thickness of about 170 μm.

Next, the positive electrode 2 was obtained as follows. 91 parts by weight of LiCoO ₂ as a positive electrode active material was mixed with 6 parts by weight of graphite as a conductive agent and 3 parts by weight of polyvinylidene fluoride as a binder to prepare a positive electrode mixture (a positive electrode constituent material). This positive electrode mixture was dispersed in N-methylpyrrolidone to form a slurry (paste form). A band-shaped aluminum foil having a thickness of 20 μm is used as the positive electrode current collector 10,
The positive electrode mixture slurry was uniformly applied to both surfaces of the current collector 10, dried, and then compression molded and cut to obtain a strip positive electrode 2. The positive electrode 2 had a thickness of about 180 μm.

A pair of strip-shaped separators 3a and 3b made of the strip-shaped negative electrode 1, the strip-shaped positive electrode 2 and the microporous polypropylene film having a thickness of 25 μm as described above are laminated in this order on the negative electrode 1, the separator 3b, the positive electrode 2 and the separator 3a. From
The spirally wound electrode body 15 as shown in FIG. 2 was produced by spirally winding this laminated body many times. Reference numeral 33 is a winding core.

Next, such a wound electrode body 15 was housed in a nickel-plated iron battery can 5 as shown in FIG.

At this time, insulating plates 4a and 4b are provided on the upper and lower surfaces of the wound electrode body 15, respectively, and a nickel negative electrode lead 11 led out from the negative electrode current collector 9 is welded to the bottom of the battery can 5. At the same time, the aluminum positive electrode lead 12 led out from the positive electrode current collector 10 was welded to the protruding portion 34 a of the metal safety valve 34.

A non-aqueous electrolytic solution prepared by dissolving LiPF ₆ at a rate of 1 mol / liter in a mixed solvent of equal volume of propylene carbonate and 1,2-dimethoxyethane was injected into the battery can 5.

Thereafter, the battery can 5, the safety valve 34 and the metal battery cover 7 whose outer circumferences are in close contact with each other are caulked via the insulating sealing gasket 6 having asphalt applied to the surface thereof, whereby the battery can 5 was sealed. Thereby, the battery lid 7 and the safety valve 34 were fixed, and the airtightness inside the battery can 5 was maintained. At this time, the lower end of the gasket 6 in FIG. 1 contacts the outer peripheral surface of the insulating plate 4a, so that the insulating plate 4a comes into close contact with the upper surface side of the spirally wound electrode body 15. As described above, diameter 14mm, height 4
A 2 mm cylindrical non-aqueous electrolyte secondary battery was produced. This battery is referred to as battery A for convenience.

The above cylindrical non-aqueous electrolyte secondary battery is
To form a double safety device, a safety valve 34, a stripper 36, and an intermediate fitting body 35 made of an insulating material for integrating the safety valve 34 and the stripper 36 are provided. Although not shown, the safety valve 34 includes the safety valve 3
The battery lid 7 is provided with a cleaving portion that cleaves when the battery 4 is deformed, and holes are provided in the battery lid 7.

In the unlikely event that the internal pressure of the battery rises for some reason, the safety valve 34 will center around the protrusion 34a of the safety valve 34 as shown in FIG.
By deforming upward, the connection between the positive electrode lead 12 and the protrusion 34a is cut off to interrupt the battery current, or the cleaving part of the safety valve 34 cleaves to exhaust the gas generated in the battery. Each is configured as follows.

Examples 2, 3, 4, 5 and 6 In Examples 2 to 6, Ra obtained in each of the experimental examples described above was used.
Is 0.20, 0.30, 0.50, 1.0 and 3.0μ
Cylindrical non-aqueous electrolyte secondary batteries B, C, D, E and F each having a diameter of 14 mm and a height of 42 mm were prepared in the same manner as in Example 1 except that titanium foil of m was used as the negative electrode current collector 9. It was made.

Further, the following batteries were prepared as Comparative Examples 1 and 2 for confirming the effects of the present invention.

Comparative Example 1 In Comparative Example 1, a diameter of 14 mm and a height of 42 mm were obtained in the same manner as in Example 1 except that the negative electrode current collector 9 was the titanium foil having Ra of 5 μm obtained in the above experimental example. Cylindrical non-aqueous electrolyte secondary battery G was manufactured.

Comparative Example 2 In Comparative Example 2, a cylinder having a diameter of 14 mm and a height of 42 mm was used in the same manner as in Example 1 except that a titanium foil having a surface roughness Ra of 0.10 μm was used for the negative electrode current collector 9. Type non-aqueous electrolyte secondary battery H was produced.

The above eight types of batteries A, B, C, D,
For E, F, G, and H, the upper limit voltage was 4.1 V, charging was performed at a constant current of 360 mA for 2 hours, and then a charging / discharging cycle of discharging to a final voltage of 2.75 V with a constant resistance of 18Ω was repeated.

In each battery, the ratio of the energy density at the 10th charge / discharge cycle to the energy density at the 100th charge / discharge cycle is defined as the energy density retention rate (%).

FIG. 5 shows the relationship between the energy density retention rate and the center line average roughness (Ra) of the surface of the negative electrode current collector. The symbols A to H in the figure indicate the respective batteries, and the horizontal axis indicating Ra is a logarithmic scale.

As is clear from FIG. 5, Ra is 0.15 μm
Batteries A, B, C, D, E, F, and G using the negative electrode current collector having the above-described roughened surface have Ra of 0.
The energy density retention rate is higher than that of the battery H of Comparative Example 2 using the negative electrode current collector having a surface of 10 μm.

When the center line average roughness (Ra) is around 0.3 μm (Battery C), the energy density retention rate is the highest, and Ra is 0.
When it exceeds 3 μm, it gradually decreases. And, when Ra is 5 μm (battery G), the energy density retention rate is considerably lowered.

From the above, the preferable range of the center line average roughness (Ra) of the surface of the current collector is 0.15 μm ≦ Ra ≦
3.0 μm, and more preferably 0.17 μm ≦ Ra ≦ 0.60 μm.

As described above, when the current collector has an appropriately rough surface, the area where the electrode constituent substance can contact the surface of the current collector becomes large, and the surface of the current collector and the electrode constituent substance layer. It is considered that the battery performance such as energy density does not deteriorate even if charging and discharging are repeated because the adhesion between the battery and the battery improves.

It is desirable that the surface roughness of the current collector is determined within the above-mentioned range while paying attention to the following points.

That is, when the maximum height (Rmax) becomes more than half the thickness t (thickness before roughening) of the current collector by roughening the surface of the current collector, There is a possibility that holes will be formed on the surface of the electric body.

If the current collector has holes, problems will occur during the application of the slurry in the above electrode manufacturing process. Further, problems such as a decrease in strength of the current collector and a dropout of the electrode constituent substance may be considered. Therefore, the following expression (3) is established. Rmax ≦ 0.5t (3)

Here, it is desirable that the thickness t of the current collector is thin because it is necessary to accommodate an electrode having a large area in a limited space in order to increase the capacity and weight of the battery. If the thickness of the electrode remains constant, the thickness t of the current collector
If the thickness is increased, the amount of active material (or active material-supporting material) provided on the current collector is reduced, so that the battery capacity is reduced.

For the above reason, in order to secure the battery capacity, the thickness t of the current collector in the wound electrode body 15 as described above is used.
Is preferably 50 μm or less. Therefore, Ra ≦ 3.0 μm (4) is obtained from the above equations (2) and (3).

However, since the condition of this equation (4) changes depending on the thickness t of the current collector, it is preferable to determine it according to the current collector used.

Example 7 In Example 7, an experimental example in which the surface of the aluminum foil used as the positive electrode current collector is roughened will be described.

An aluminum foil having a thickness of 20 μm was sufficiently sanded and then dipped in a 20% by weight aqueous hydrochloric acid solution, and after a certain period of time, the aluminum foil was taken out from the aqueous hydrochloric acid solution and thoroughly washed with water to obtain the surface of the aluminum foil. A diameter of 14 mm was obtained in the same manner as in Example 1 except that the roughness was used for the positive electrode current collector and the copper foil having a thickness of 10 μm was used for the negative electrode current collector.
A cylindrical non-aqueous secondary battery I was manufactured.

Example 8 A diameter of 14 mm was obtained in the same manner as in Example 7, except that the aluminum foil obtained by immersing in an aqueous hydrochloric acid solution for a longer time than in Example 7 and using the obtained aluminum foil having Ra of 2.00 μm was used as a positive electrode current collector. A cylindrical non-aqueous secondary battery J having a height of 42 mm was produced.

Comparative Example 3 In Comparative Example 3, a cylindrical non-shaped cylinder having a diameter of 14 mm and a height of 42 mm was prepared in the same manner as in Example 7 except that an aluminum foil having a surface roughness Ra of 0.16 μm was used for the positive electrode current collector. A water secondary battery K was produced.

With respect to the above-mentioned three types of batteries, the upper limit voltage was 4.1 V, the battery was charged with a constant current of 360 mA for 2 hours, and then the cycle of discharging to a voltage of 2.75 V with a constant resistance of 18 Ω was repeated.

In each of the batteries I, J, and K, the ratio (energy density retention rate) of the energy density at the 10th time of the charge / discharge cycle and the energy density at the 100th time was measured, and they were 87%, 93%, and 82%, respectively. Met. Thus, the same effect can be obtained by roughening the surface of the positive electrode current collector.

As described above, according to the non-aqueous electrolyte secondary battery of this embodiment, the center line average roughness (Ra) is 0.15 μm.
By using a metal foil whose surface is roughened in the range of m ≦ Ra ≦ 3.00 μm for the current collector, the capacity does not deteriorate even after repeated charging / discharging, and a strip-shaped electrode having a high capacity can be obtained. .

The method of surface roughening treatment is acid treatment, etching,
A sand brush or the like is used, but the method is not particularly limited. Although the negative electrode current collector is roughened in this example, the positive electrode current collector may be roughened, and the same effect can be obtained. Although titanium was used as the material of the current collector in this embodiment, other metal foils such as Inconel alloy, copper, nickel, and stainless steel can also be used.

Although Li Co O ₂ was used as the positive electrode active material, manganese dioxide, vanadium pentoxide, oxides of transition metals such as iron sulfide, chalcogen compounds, and further these oxides and chalcogen compounds were used. It is possible to use a composite compound of lithium and lithium (such as a lithium-cobalt composite oxide or a lithium-cobalt-nickel composite oxide).

The negative electrode material may be a material that can be doped with lithium ions and dedoped, but among them, a carbon material such as pitch coke is preferable. As such a carbon material, a coke material such as petroleum-based coke or carbon-based coke, an organic polymer fired body obtained by firing an organic polymer in a non-oxidizing atmosphere of preferably 500 ° C. or higher, and a carbon black such as acetylene black. , Graphite, glassy carbon, activated carbon, carbon fiber, and other organic pyrolysis carbons.

As the non-aqueous electrolyte, for example, a non-aqueous electrolytic solution in which a lithium salt is used as an electrolyte and this is dissolved in an organic solvent (non-aqueous solvent) can be used. Here, the organic solvent is not particularly limited, but, for example, propylene carbonate, ethylene carbonate, 1,2-dimethyctoethane, 1,2-diectoethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4-
Methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like can be used alone or in admixture of two or more. Any known electrolyte may be used as the electrolyte, and LiClO ₄ , LiAsF ₆ , LiP may be used.
F ₆ , Li BF ₄ , Li B (C ₆ H ₅ ) ₄ , Li Cl,
_{Li Br, CH 3 SO 3 Li} , CF 3 SO 3 Li and the like.

Further, the non-aqueous electrolyte may be solid, for example, polymer complex solid electrolyte.

[0065]

EFFECTS OF THE INVENTION According to the battery of the present invention, since the planar current collector is appropriately roughened in the electrode, the adhesion between the planar current collector and the electrode constituent material layer becomes good, Since it is possible to effectively prevent the electrode constituent substances from falling off and peeling from the current collector during the electrode manufacturing process and during use of the battery, it is possible to improve the productivity of battery manufacturing and prevent capacity deterioration or improve cycle characteristics. It is possible to achieve the improvement of battery performance such as.

[Brief description of drawings]

FIG. 1 is a perspective view of a negative electrode used in a non-aqueous electrolyte secondary battery according to an example of the present invention.

FIG. 2 is a vertical cross-sectional view showing a schematic vertical cross section of a non-aqueous electrolyte secondary battery using the negative electrode shown in FIG.

FIG. 3 is a diagram showing a relationship between surface roughness (Ra and Rmax) of a metal foil as a current collector obtained in an experimental example of this example and an acid treatment time for roughening.

FIG. 4 is a diagram showing the relationship between the center line average roughness (Ra) and the maximum height (Rmax) obtained in the experimental example of the present embodiment.

FIG. 5 is a diagram showing the relationship between the center line average roughness (Ra) of the surface of the current collector obtained in this example and the energy density retention rate.

FIG. 6 is a cross-sectional view for explaining the definition of center line average roughness (Ra).

FIG. 7 is a cross-sectional view for explaining the definition of maximum height (Rmax).

[Explanation of symbols]

1 Negative electrode (electrode) 1a Anode constituent material layer (electrode constituent material layer) 2 Positive electrode (electrode) 3a Strip separator (planar separator) 3b Strip separator 9 Negative electrode current collector (planar current collector) 15 winding electrode body

Claims (2)

[Claims] 1. A battery comprising an electrode in which an electrode-constituting material layer is formed on the surface of a planar current collector, wherein the current collector on which the electrode-constituting material layer is formed has a surface roughness of a center line. A battery having an average roughness of 0.15 μm or more and 3.0 μm or less. 2. A winding formed by stacking an electrode having an electrode-constituting material layer on a current collector having the surface roughness according to claim 1 and a planar separator, and winding the laminate in a spiral shape. A battery including an electrode body.