JPH05182647A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To prevent looseness of a wound electrode in the case of using a spiral type electrode by arranging a resin layer on an internal surface of a battery sheath can. CONSTITUTION:A resin layer 20 is arranged on an internal surface of a battery sheath can 5, and after inserting a spiral type electrode 15 into the sheath can 5 of arranging this resin layer 20, an electrolyte is injected to assemble a nonaqueous electrolyte secondary battery. In this way, even when a clearance is provided between an external diameter of the electrode 15 and an internal diameter of the sheath can 5 at the time of inserting the electrode 15, the resin layer 20 is expanded by injecting the electrolyte thus to uniformly apply a pressure continuously in the center axial direction from the peripheral side relating to the electrode 15. Accordingly, looseness of the electrode 15 is prevented, and a good cycle characteristic can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery using a spiral electrode as an electrode.

[0002]

2. Description of the Related Art Recent remarkable advances in electronic technology have made electronic devices smaller and lighter one after another. Along with this, there is an increasing demand for batteries as mobile power sources that are smaller, lighter, and have higher energy density.

Conventionally, an aqueous solution type battery such as a lead battery or a nickel-cadmium battery has been mainly used as a secondary battery for general use. However, although these aqueous solution type batteries have excellent cycle characteristics, they cannot be said to be sufficiently satisfactory in terms of battery weight and energy density.

Recently, non-aqueous electrolyte secondary batteries using lithium or a lithium alloy as a negative electrode have been actively researched and developed. This non-aqueous electrolyte secondary battery has high energy density, little self-discharge, and is lightweight. However, in this non-aqueous electrolyte secondary battery, with the progress of the charge / discharge cycle, lithium grows in a dendrite-like crystal during charging, and there is a drawback that the possibility of reaching the positive electrode and causing an internal short circuit increases. However, this is a major obstacle to practical use.

On the other hand, the non-aqueous electrolyte secondary battery using a carbon material for the negative electrode has lithium preliminarily supported on the carbon material by chemical and physical methods, lithium in the crystal structure of the positive electrode active material, Such as lithium dissolved in the electrolyte,
It utilizes doping / dedoping between carbon layers, and does not show dendrite-like precipitation during charging even if the charging / discharging cycle progresses, and shows excellent charging / discharging cycle characteristics exceeding 1000 times.

The non-aqueous electrolyte secondary battery using these materials can be used as a power supply for video cameras, laptops, personal computers, etc., but such devices consume a relatively large amount of current. Since many of them are used, the spiral electrode structure is suitable as the battery structure. This spiral electrode is formed by spirally winding a strip-shaped positive electrode and a strip-shaped negative electrode with a separator interposed therebetween, and has a large electrode area, so that it can bear a heavy load.

[0007]

By the way, when inserting such a spiral type electrode into the battery outer can, a certain amount of clearance must be provided between the outer diameter of the electrode and the inner diameter of the battery outer can from the viewpoint of productivity. I have to. On the other hand, the battery characteristics tend to be better when pressure is applied inwardly to the electrodes so that the spiral electrodes do not loosen. Therefore,
In the spiral electrode, the winding end portion of the outermost circumference of the electrode and the electrode body are fixed with an adhesive tape so that the wound electrode does not get warm during assembly. However, when using an adhesive tape, depending on the combination of the electrolytic solution and the adhesive tape, the adhesive may dissolve after the electrolyte is injected and the ability to fix the adhesive tape may be lost, which may cause loosening of the electrode and cycle characteristics. However, the battery characteristics are deteriorated.

Therefore, the present invention has been proposed in view of such a conventional situation, and when a spirally wound electrode is used, the wound electrode does not loosen and good cycle characteristics are obtained. It is an object of the present invention to provide a non-aqueous electrolyte secondary battery capable of achieving high productivity.

[0009]

In order to achieve the above-mentioned object, the non-aqueous electrolyte secondary battery of the present invention comprises a cylindrical battery outer can with a belt-shaped positive electrode and a belt-shaped negative electrode via a separator. A spiral wound electrode and a non-aqueous electrolyte secondary battery containing a non-aqueous electrolyte, wherein a resin layer is provided on the inner surface of the battery outer can. Is.

Further, the present invention is characterized in that the resin constituting the resin layer is a resin whose volume increases by being immersed in the non-aqueous electrolyte solution. Further, the negative electrode active material of the negative electrode has a (002) plane spacing of 3.70 Å or more, a true density of less than 1.70 g / cm ³ , and a heat generation of 700 ° C. or more in a differential thermal analysis in an air stream. It is characterized by being a carbonaceous material having no peak.

In the present invention, in order to prevent the spiral electrode from loosening and to obtain a non-aqueous electrolyte secondary battery having excellent cycle characteristics, a resin layer is provided on the inner surface of the side surface of the battery outer can. Then, the spiral electrode is inserted into the battery outer can in which this resin layer is arranged, and the electrolytic solution is further injected to form the battery.

That is, in a non-aqueous electrolyte secondary battery using a spiral electrode, the insertion of electrodes is facilitated,
In order to improve productivity, it is necessary to provide some clearance between the battery outer can and the electrode. However, in the case of a battery, if such a clearance is provided, the electrode becomes loose and a stable charge / discharge reaction cannot be obtained.

In such a non-aqueous electrolyte secondary battery,
When a resin layer is provided on the inner surface of the battery outer can, even if there is a clearance between the electrode and the battery outer can when the electrode is inserted, the resin layer swells due to the injection of the electrolytic solution to form a spiral electrode. On the other hand, pressure is applied uniformly from the outside toward the central axis. Therefore, the loosening of the electrode is suppressed by this, and the electrode comes to fully exhibit its function during charging and discharging.

As the resin coating material for the resin layer, when the resin layer is formed, it swells by coming into contact with one or more of the organic solvents that make up the electrolytic solution,
Further, it is possible to select one having a property of not being dissolved in all the constituent solvents of the electrolytic solution. As such resin paint,
Various kinds of acrylic resin paints, alkyd resin paints, urethane resin paints, epoxy resin paints, vinyl resin paints and the like can be used, and particularly for electrolytic solutions commonly used in batteries of this type, It is desirable to use an acrylic resin paint containing an acrylic resin as a main element, a vinyl resin paint containing vinyl chloride, a chloride / vinyl acetate copolymer, a vinyl butyral resin, etc. as a main element. The thickness of the resin layer is preferably 10 to 500 μm after swelling.
If it is less than μm, the effect is small, and conversely, if it is more than 500 μm, the decrease in battery capacity becomes large. The thickness increased by swelling is preferably 10% or more of the thickness of the resin layer before swelling.

As the electrolytic solution, for example, an electrolytic solution in which a lithium salt is used as an electrolyte and this is dissolved in an organic solvent is used. Here, the organic solvent is not particularly limited, but for example, propylene carbonate, ethylene carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3 -Dioxolane, 4-
Methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile and the like may be used alone or in combination of two or more kinds. Any known electrolyte can be used as the electrolyte, such as LiClO ₄ , LiAsF ₆ , LiPF ₆ , and Li.
BF ₄ , LiB (C ₆ H ₅ ) ₄ , LiCl, LiBr,
_{CH 3 SO 3 Li, CF 3} SO 3 Li and the like are used.

As the negative electrode active material used for the above negative electrode,
Dope an alkali metal such as lithium along with the charge / discharge reaction.
A material for dedoping can be used. Examples of such a material include conductive polymers such as polyacetylene and polypyrrole, and carbon materials such as coke, polymer charcoal, and carbon fiber, but carbon materials are preferable because of their large energy density per unit volume. desirable.

In particular, among the above carbon materials, (0
02) surface spacing is 3.70Å or more, true density 1.70g
/ Cm ³ and a carbonaceous material which has no exothermic peak at 700 ° C. or higher in a differential thermal analysis in an air stream has a large lithium doping ability and is preferable.

Here, the negative electrode active material capable of being doped / dedoped with lithium has a property of increasing in volume by being doped with lithium. Therefore, when used in a spiral electrode, a pressure is generated in the electrode, which is advantageous for preventing the spiral electrode from loosening. On the other hand, a carbon material having a large (002) plane spacing of 3.70 Å or more has excellent lithium doping ability,
The volume increase due to lithium doping is small. For this reason, when used in a spiral electrode, the above-mentioned effect can hardly be expected, and in particular, it was difficult to sufficiently exert its function.However, according to the present invention, a sufficient pressure is applied to the electrode by the resin layer. Therefore, even if a carbon material with a large (002) plane spacing of 3.70Å or more is used,
The electrode will not be loosened, and the doping ability of the carbonaceous material will be sufficiently exhibited.

Examples of the material having the above-mentioned morphological parameters include a carbonaceous material obtained by carbonizing an organic material by a method such as firing, and furfuryl alcohol or furfural homopolymer or copolymer is used as a starting material for carbonization. Furan resin consisting of is preferred. Specifically, a polymer composed of furfural + phenol, furfuryl alcohol + dimethylol urea, furfuryl alcohol, furfuryl alcohol + formaldehyde, furfuryl alcohol + furfural, furfural + ketones, etc. is a non-aqueous electrolyte secondary battery. It has very good characteristics as a negative electrode active material.

Alternatively, a petroleum pitch having a hydrogen / carbon atom ratio of 0.6 to 0.8 is used as a raw material, a functional group containing oxygen is introduced into the petroleum pitch, and so-called oxygen cross-linking is performed to obtain an oxygen content of 10 to 20% by weight. A carbonaceous material obtained by firing after the precursor of is also suitable. Further, a carbonaceous material having a large doping amount with respect to lithium by adding a phosphorus compound or a boron compound when carbonizing the furan resin, petroleum pitch or the like can also be used.

On the other hand, as the positive electrode active material used for the positive electrode, transition metal oxides such as manganese dioxide and vanadium pentoxide, transition metal chalcogenides such as iron sulfide and titanium sulfide, and further, these and lithium are used. A complex compound or the like can be used. Particularly, a lithium / cobalt / nickel composite oxide or a lithium / cobalt / nickel composite oxide is preferable because a high voltage and a high energy density are obtained and the cycle characteristics are excellent.

[0022]

[Function] In the non-aqueous electrolyte secondary battery using the spiral electrode, the electrode can be easily inserted into the battery case,
In order to improve productivity, it is necessary to provide some clearance between the battery outer can and the electrode. However, in the case of a battery, if such a clearance is provided between the battery case and the electrode, the electrode becomes loose and a stable charge / discharge reaction cannot be obtained.

In the non-aqueous electrolyte secondary battery of the present invention, a resin layer is provided on the inner surface of the battery outer can, and the spiral electrode is inserted into the battery outer can provided with the resin layer. Can be assembled by injecting. Therefore, even if there is a clearance between the outer diameter of the electrode and the inner diameter of the battery case when the electrode is inserted, the resin layer swells due to the injection of the electrolytic solution, which causes the spiral electrode to move from the outer peripheral side toward the central axis direction. The pressure is applied continuously and evenly. Thereby, the loosening of the electrode is prevented, and the charge / discharge reaction proceeds smoothly.

At this time, in particular, the negative electrode active material has a (002) plane spacing of 3.70 Å or more and a true density of 1.7.
When a carbonaceous material having a lithium doping capacity of less than 0 g / cm ³ and having no exothermic peak at 700 ° C. or higher in a differential thermal analysis in an air stream is used, the carbonaceous material has a high lithium doping ability, and thus exhibits good cycle characteristics. An increase in discharge capacity can also be obtained.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described with reference to the drawings.

Example 1 This example is an example in which an acrylic resin is used as the resin of the resin layer provided on the inner surface of the battery outer can.

FIG. 1 shows a schematic vertical cross-sectional view of the battery of this example, which was prepared as follows.

First, the negative electrode 1 was manufactured as follows.

Petroleum pitch was used as a starting material, and 10 to 20% by weight of a functional group containing oxygen was introduced into this (so-called oxygen cross-linking), followed by firing at 1000 ° C. in an inert gas stream to approximate glassy carbon. A carbonaceous material with properties was obtained. As a result of X-ray diffraction measurement of this carbonaceous material, the spacing between (002) planes was 3.76A. The true specific gravity measured by the pycnometer method was 1.5.
It was 8 g / cm ³ . This carbonaceous material was crushed to obtain a carbon material powder having an average particle size of 10 μm.

The carbon material powder thus obtained was used as a negative electrode active material carrier, and 90 parts by weight of this material were mixed with 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder to prepare a negative electrode mixture. This negative electrode mixture was dispersed in N-methylpyrrolidone as a solvent to form a slurry (paste form).

A strip-shaped copper foil having a thickness of 10 μm was used as the negative electrode current collector, and the negative electrode mixture slurry was applied to both surfaces of this current collector, dried and then compression-molded to produce strip-shaped negative electrode 1.
The thickness of the mixture after molding was 80 μm on both sides, and the width of the electrode was 41.5 mm and the length was 700 mm.

The positive electrode 2 was manufactured as follows. 1 mol of lithium carbonate and 0.5 mol of cobalt carbonate were mixed and fired in air at a temperature of 900 ° C. for 5 hours to obtain LiCoO ₂ . 91 parts by weight of this LiCoO ₂ as a positive electrode active material,
6 parts by weight of graphite as a conductive agent and 3 parts by weight of polyvinylidene fluoride as a binder were mixed to obtain a positive electrode mixture.
This positive electrode mixture was dispersed in N-methylpyrrolidone to form a slurry (paste form).

A strip-shaped aluminum foil having a thickness of 20 μm was used as the positive electrode current collector, and the positive electrode mixture slurry was uniformly applied to both surfaces of this current collector, dried, and then compression-molded to produce the band-shaped positive electrode 2. .. The mixture thickness after molding is 80 μm on both sides
The width of the electrode is 40.5 mm and the length is 650 m.
m.

Strip negative electrode 1, strip positive electrode 2 and thickness 25 μ
The separator 3 made of a microporous polypropylene film having a width of 44 mm and a width of 44 mm is laminated in the order of the negative electrode, the separator, the positive electrode, and the separator, and then the laminated body is spirally wound many times to obtain the spiral wound type shown in FIG. The electrode body 15 was produced. The inner diameter of the hollow portion at the center of this spiral electrode body was 3.5 mm, and the outer diameter was 20 mm.

Next, an acrylic resin (acrylic lacquer) is applied to the inside of the side surface of the nickel-plated iron battery case 5.
Was applied and dried at room temperature for 24 hours to form a resin layer 20.

Then, as shown in FIG. 1, the spirally wound electrode body 1 is attached to the battery case 5 having the resin layer 20 disposed on the inner side surface thereof.
Stored 5. Insulating plates 4 are provided on both upper and lower surfaces of the spirally wound electrode, an aluminum positive electrode lead 12 is led out from the positive electrode current collector, and a nickel negative electrode lead 11 is led out from the negative electrode current collector to a battery can. Welded to 5. An electrolytic solution prepared by dissolving LiPF _{6 in a} mixed solvent of equal volume of propylene carbonate and 1,2-dimethoxyethane at a ratio of 1 mol / l was injected into the battery can 5.

The battery can 5 was caulked through an insulating sealing gasket whose surface was coated with asphalt to fix the battery lid 7 and maintain airtightness in the battery. Through the above steps, a cylindrical non-aqueous electrolyte battery having a diameter of 20 mm and a height of 50 mm was prepared.

In order to examine the swelling property of the resin layer made of the acrylic resin used in this example, a resin layer was formed by separately applying the acrylic resin on the inner side surface of the battery outer can and drying the solvent. The thickness of this resin layer was measured. Then, the electrolytic solution was injected and left at room temperature for 24 hours, and the thickness of the resin layer immediately after removing the electrolytic solution was measured. Table 1 shows the thickness of the resin layer before and after the immersion in the electrolytic solution and the swelling ratio due to the immersion in the electrolytic solution.

[0039]

[Table 1]

Example 2 This example is an example in which a vinyl chloride resin is used as the resin of the resin layer provided on the inner surface of the battery outer can.

Instead of using an acrylic resin as the resin applied to the inner surface of the battery outer can, a vinyl chloride resin (vinyl chloride / vinyl acetate copolymer) is applied to coat the resin layer 20.
A non-aqueous electrolyte secondary battery was made in the same manner as in Example 1 except that the above was formed.

With respect to the vinyl chloride resin paint, the swelling property was examined in the same manner as the acrylic resin paint. The results are shown in Table 2.

[0043]

[Table 2]

Comparative Example A non-aqueous electrolyte battery was prepared in the same manner as in Example 1 except that no resin layer was provided on the battery case.

Twenty batteries each having the above-described structure were produced, and the upper limit voltage of each battery was set to 4.1 V and charged with a constant current of 1 A for 2.5 hours, and then with a constant resistance of 7.5 Ω. 7
The charging / discharging cycle of discharging to 5 V was repeated, and the change of the energy density with the repeating charging / discharging cycle was examined.

FIG. 4 shows the relationship between the number of cycles of each battery and the energy density. In Table 3, energy density at 10th cycle (hereinafter referred to as initial energy density), 200
The energy density of the cycle and the average cycle deterioration rate are shown. The average cycle deterioration rate is the average cycle deterioration rate per cycle obtained from the ratio of the energy density at the 200th cycle to the initial energy density. The energy densities shown in Table 3 and FIG. 3 are average values (n = 20).

[0047]

[Table 3]

As can be seen from Table 3 and FIG. 3, Example Battery 1 and Example Battery 2 have a higher initial energy density than Comparative Example Battery 1 and a low average cycle deterioration rate per cycle of 200. A sufficient energy density is maintained even after the cycle. Therefore,
In a non-aqueous electrolyte secondary battery using a spiral electrode,
It was found that disposing the resin layer on the inner surface of the outer can of the battery can has a high energy density and is effective in obtaining good charge / discharge cycle characteristics.

Further, the effect of the present invention is particularly excellent in the lithium doping ability, but since the volume expansion coefficient after lithium doping is small, it is difficult to exert a sufficient function, that is, on the (002) plane. Non-aqueous electrolyte using a carbonaceous material having a surface spacing of 3.70 Å or more and a true density of less than 1.70 g / cm ³ and having no exothermic peak at 700 ° C. or more in differential thermal analysis in an air stream. In the case of a secondary battery, it is particularly large, and the function is dramatically improved by the present invention.

[0050]

As is apparent from the above description, the non-aqueous electrolyte secondary battery of the present invention is provided with a resin layer on the inner surface of the battery outer can, and the battery outer can in which this resin layer is disposed. After inserting the spiral electrode into the assembly, the assembly is performed by injecting the non-aqueous electrolyte, which makes it easy to insert the electrode, improving productivity, and preventing loosening of the electrode, and good cycle characteristics. It is possible to obtain

In particular, as a negative electrode active material for the negative electrode, (00
2) Face spacing is 3.70Å or more, and true density is 1.70g.
If the carbonaceous material is less than / cm ³ and does not have an exothermic peak at 700 ° C. or higher in the differential thermal analysis in the air flow, the cycle characteristics can be improved and the battery capacity can be increased. Therefore, according to the present invention,
It is possible to obtain a non-aqueous electrolyte secondary battery that is suitable as a power supply for devices with large current consumption, such as video cameras, laptops, and personal computers.

[Brief description of drawings]

FIG. 1 is a schematic vertical sectional view showing an example of a non-aqueous electrolyte secondary battery of the present invention.

FIG. 2 is a schematic diagram showing an example of a spiral electrode used in the non-aqueous electrolyte secondary battery.

FIG. 3 is a characteristic diagram showing the relationship between the number of cycles and the energy density of a non-aqueous electrolyte secondary battery.

[Explanation of symbols]

 1 ... Negative electrode 2 ... Positive electrode 3 ... Separator 20 ... Resin layer

Claims (3)

[Claims] 1. A spirally wound electrode formed by winding a strip-shaped positive electrode and a strip-shaped negative electrode through a separator in a cylindrical battery case, and a non-aqueous electrolyte secondary containing a non-aqueous electrolyte. In the battery, a non-aqueous electrolyte secondary battery in which a resin layer is provided on the inner surface of the battery outer can. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the resin constituting the resin layer is a resin whose volume increases by being immersed in the non-aqueous electrolyte. 3. The negative electrode active material of the negative electrode has a (002) plane spacing of 3.70 Å or more, a true density of less than 1.70 g / cm ³ , and a differential thermal analysis of 700 in air flow.
The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is a carbonaceous material having no exothermic peak at a temperature equal to or higher than ° C.