JPH0393164A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To prevent internal short-circuit by coating a collector with an electrode black mixture leaving both ends in the width direction in a cylinder type drain electrolyte secondary battery having an electrode structure, wherein a band electrode having a positive electrode and a negative electrode is spirally wound through a separator. CONSTITUTION:A nonaqueous electrolyte secondary battery has an electrode structure wherein a band electrode having a positive electrode 1 and a negative electrode 2 is spirally wound through a separator 3. The band electrode is composed of a band collector 10 and of a layer of an electrode black mixture 20 coating the collector 10 leaving both end parts in the width direction. That is, when the negative electrode 2 and the positive electrode 1 are manufactured, a black mixture slurry is applied to both sides of the collector 10 leaving both end parts of the collector 10 for manufacturing the battery. Internal short-circuit of the battery can be therefore prevented so that the secondary battery having big energy density and an excellent rapid charge and discharge cycle characteristic.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to the structure of a cylindrical nonaqueous electrolyte secondary battery having an electrode structure in which positive and negative strip electrodes are spirally wound with a separator in between. It is something.

[Conventional technology]

In recent years, there has been a remarkable increase in performance and miniaturization of electronic devices such as video cameras and headphone stereos, and there is also a demand for improved heavy load characteristics and higher capacity of the secondary batteries that power these electronic devices. It's getting stronger. As secondary batteries, lead secondary batteries and nickel-cadmium batteries have traditionally been used. Furthermore, non-aqueous electrolyte secondary batteries that use metallic lithium, lithium alloys, or substances that can be doped and dedoped with lithium ions as negative electrode active materials,
It is actively being developed because it can provide high energy density. Among these, in particular, a cylindrical spiral type non-aqueous electrolyte secondary battery (hereinafter referred to as a spiral type non-aqueous electrolyte secondary battery) in which the electrode area of the positive and negative electrodes is spirally wound through a separator to increase the electrode area. ) has recently attracted attention as it is capable of rapid charging and discharging. However, this battery has a problem in that it is susceptible to internal short circuits due to the electrode material at both widthwise ends of the strip electrode breaking through the separator. This type of electrode is often made by applying a slurry in which the active material or electrode mixture is dispersed in a solvent to the entire surface of a band-shaped current collector, drying it, and then compressing or shaping it using a roller press. This is produced by cutting it to a predetermined width, but the electrode obtained by this method has sharp edges at both cut ends, which tend to break through the separator and cause an internal short circuit.

[Problem to be solved by the invention]

An object of the present invention is to improve the structure of both ends in the width direction of an electrode consisting of a band-shaped current collector coated with an active material or an electrode mixture, and to improve the structure of a spiral non-aqueous electrolyte secondary that does not cause the above-mentioned problems. The purpose is to provide batteries.

[Means to solve the problem]

The non-aqueous electrolyte secondary battery of the present invention is a spiral type non-aqueous electrolyte secondary battery having an electrode structure in which a positive electrode and a negative electrode are spirally wound with a separator in between. , at least one of the electrodes is characterized by comprising a band-shaped current collector and a layer of active material or electrode mixture covering the current collector except for both ends in the width direction. Here, at both ends of the current collector in the width direction, the width of the portion that is not covered with the active material or electrode mixture layer is 0.0% of the current collector width.
It is preferable that it is 0.05 times or less.

The present invention can be applied to a battery using an electrode formed by coating a band-shaped current collector with a layer of an active material or an electrode mixture. Examples include a negative electrode in which a current collector is coated with a pulverized organic polymer fired body or pitch coke, and a positive electrode in which a current collector is coated with lithium manganese oxide or lithium cobalt oxide.

Further, as the electrolytic solution according to the present invention, for example, a non-aqueous electrolytic solution in which a lithium salt is used as an electrolyte and is dissolved in an organic solvent (non-aqueous solvent) is used. Here, the organic solvent is
Examples include, but are not limited to, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1,3-dioxolane, 4
-Methyl-1.3-dioxolane, diethyl ether,
A single solvent or a mixture of two or more solvents such as sulfolane, methylsulfolane, acetonitrile, and probionitrile can be used. Any conventionally known electrolyte can be used, for example, LiCIOn, LiAsFb, L
iPFb. ．． LiBF4, LiB(CJs)4, LI
Cl% LiBr, CHzSOiLi, CF+SO:
+Li etc.

[Effect]

By covering both widthwise ends of the current collector with the active material or electrode mixture, internal short circuits can be prevented.

[Example] FIG. 3 is a cross-sectional view schematically showing the structure of a two-volume spiral non-aqueous electrolyte secondary battery according to the present invention.

Examples and comparative examples will be described below with reference to FIG.

Example 1 A battery was produced using LiCoO as a positive electrode active material and needle coke as a negative electrode active material. 90 parts by weight of crushed 21 dollar coke and 10 parts by weight of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture. Then, this negative electrode mixture was dispersed in a solvent N-methylpyrrolidone to form a slurry (paste). Next, 34. 5+
0.5 mm from each end on both sides of a strip-shaped negative electrode current collector made of copper foil with a thickness of IO μm cut to a width of ++m.
This negative electrode mixture slurry was applied to the remaining parts and dried.

After drying, it was compressed and shaped using a roller press to form a strip-shaped negative electrode 2. In this strip-shaped negative electrode 2, the negative electrode mixture was formed on both sides of the negative electrode current collector with approximately the same film thickness, and the sum of these film thicknesses was about 175 μm.

Next, a positive electrode was produced as follows. 1 mole of lithium carbonate and 1 mole of cobalt carbonate were mixed and fired in air at 900°C for 5 hours to obtain powdered LiCo02. This was used as a positive electrode active material, and graphite 6 was added as a conductive material to 91% of this LiCoOz91 weight. parts by weight, and 3 parts by weight of polyvinylidene fluoride as a binder were added and mixed to prepare a positive electrode mixture. This positive electrode mixture was then dispersed in the solvent N-methylpyrrolidone to form a slurry (paste). Next 33.5mm
A strip of aluminum foil with a thickness of 20 μm was cut to have a width of 0.0 μm on both sides of the positive electrode current collector.
This positive electrode mixture slurry was applied leaving a gap of 5 ms and dried. After drying, compression molding was performed using a roller press to obtain a strip-shaped positive electrode 1. In this strip-shaped positive electrode 1, the positive electrode mixture is formed on both sides of the positive electrode current collector with approximately the same film thickness,
The sum of these film thicknesses was approximately 175 μm.

Then, a strip-shaped positive electrode 1, a strip-shaped negative electrode 2 and a thickness of 25 μm
Sebarator 3 made of microporous polypropylene film
were laminated in the order of negative electrode 2, separator 3, positive electrode 1, and separator 3, and then this laminated body was wound spirally many times to produce a wound body. The volume thus produced was housed in a nickel-plated iron battery can 5 having an inner diameter of 13.3 lIIml, as shown in FIG. Then, in order to collect current from the positive electrode 1, one end of the aluminum positive electrode lead is attached to the positive electrode 1, and the other end is attached to the battery M7.
Welded to. Further, in order to collect current from the negative electrode 2, one end of a nickel negative electrode lead was attached to the negative electrode 2, and the other end was welded to the battery can 5. In this battery can 5, there is 1 mol/I of lithium hexafluorophosphate! ．． An electrolytic solution obtained by mixing dissolved propylene carbonate and 1,2-dimethoxyethane was injected. Next, an insulating plate 4 was placed inside the battery can 5 so as to face the top and bottom surfaces of the wound body. Finally, the battery can 5 and the battery lid 7 were caulked together with an insulating sealing gasket 6 interposed therebetween, and the battery lid 7 was sealed. As described above, a spiral non-aqueous electrolyte secondary battery having a diameter of 13.8 ms and a height of 42 mm was produced.

Example 2 When producing a negative electrode and a positive electrode, the mixture slurry was applied to both sides of the current collector, leaving lIII1 from both ends of the current collector, and a battery was produced in the same manner as in Example 1 except for that.

Example 3 When producing a negative electrode and a positive electrode, the mixture slurry was applied to both sides of the current collector, leaving 1.8 mm+ from both ends of the current collector, and a battery was otherwise produced in the same manner as in Example 1. .

Comparative Example 1 The negative electrode was prepared by coating and drying the negative electrode mixture slurry jJ- on the entire surface of the current collector, compressing it with a roller press machine, and then
It was cut to a width of 34.5mm. The positive electrode was prepared by applying a positive electrode mixture slurry to the entire surface of the current collector, drying it, pressing it into a shape using a roller press, and then cutting it into a width of 33.5 mm. A battery was produced in the same manner as in Example 1 except for this.

Comparative Example 2 The negative electrode was made by coating and drying a negative electrode mixture slurry on the entire surface of an aggregate cut into a width of 34.5 ma+, and compressing or shaping this with a roller press.
A positive electrode mixture slurry was coated and dried on the entire surface of a current collector cut into a width of n+m, and this was compressed or shaped using a roller press machine. A battery was produced in the same manner as in Example 1 except for the above.

When the cross sections of the positive and negative strip electrodes obtained in Examples and Comparative Examples were observed under a microscope, the following results were obtained. Figure 1 shows
FIG. 3 is a diagram schematically showing the cross section of the electrodes obtained in Examples 1, 2, and 3. FIG. 2A is a diagram schematically showing a cross section of the electrode obtained in Comparative Example 1, and FIG. 2B is a diagram schematically showing a cross section of the electrode obtained in Comparative Example 2. As shown by the above results, the edges of the end faces in the width direction of all the electrodes obtained in the examples are shifted. On the other hand, the electrode obtained in Comparative Example 1 has a sharp end face in the width direction. Further, although the edges of the electrode obtained in Comparative Example 2 have been removed in the width direction, there is no current collector at both ends of the electrode, as shown in FIG. 2B. Five batteries each of Examples ①, 2, and 3 and Comparative Examples Ⅰ and 2 were used.
They were each charged at a current of 190n+A at an upper limit voltage of 4.1v for 3 hours, and then an i6
Perform 30 charge/discharge cycles to discharge to a final discharge voltage of 2.9V with a constant resistance of 0Ω, then charge again under the above conditions and leave it at room temperature for 10 days. The occurrence rate was investigated as an internal short circuit product. In addition, among these batteries, those that were not internally short-circuited were discharged under the conditions described above, and their capacities were also investigated.

The results are shown in Table 1.

As can be seen from this table, the battery of Comparative Example 1 had an extremely high incidence of internal short circuits. When this internally short-circuited battery was disassembled and examined, it was observed that some of the electrode mixture at both ends of the electrode had penetrated the separator. Also, comparative example 2
Internal short circuits also occur in batteries, but when we disassembled and examined the batteries with internal short circuits, we found that the electrode mixture at both ends of the electrodes had fallen off from the electrodes and had broken through the separator. observed.

In the batteries of Examples 1, 2, and 3, no internal short circuit occurred, and therefore, it is considered that the effect of not covering both ends of the current collector with the electrode mixture is great. Regarding the discharge capacity, comparing Examples 1, 2, and 3, the larger the width of the portion of the current collector not covered with the electrode mixture, the smaller the discharge capacity. In Example 3, where the width of the part not covered with the electrode mixture at both ends is 0.05 times or more the width of the current collector, compared to Comparative Example 1 in which the entire surface of the current collector was coated with the electrode mixture. Therefore, the discharge capacity is reduced by more than IO%, which is not preferable.

As shown in the above examples, it is preferable that both ends of the current collector are not coated with the active material or electrode mixture for both the positive and negative electrodes. However, it goes without saying that it is effective in preventing internal short circuits.

〔Effect of the invention〕

According to the present invention, it has become possible to prevent internal short circuits in the spiral non-aqueous electrolyte secondary battery, which was one of the problems. As a result, the energy density is large,
It is now possible to provide a secondary battery with excellent rapid charge/discharge cycle characteristics, which has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the strip-shaped electrode of the example, and FIG.
, B are schematic cross-sectional views of band-shaped electrodes of comparative examples, and FIG. 3 is a schematic cross-sectional view showing the structure of the spiral non-aqueous electrolyte secondary battery of the present invention. In Fig. 1 and Fig. 2 A and B, work 0 is the current collector, ゛20
indicates the electrode mixture. In Figure 3, 1 is a positive electrode, 2 is a negative electrode, 3 is a separator,
5 indicates a battery can. Figure 2 B

Claims (1)

[Claims] 1. In a cylindrical non-aqueous electrolyte secondary battery having an electrode structure in which positive and negative strip electrodes are spirally wound with a separator interposed therebetween, at least one of the strip electrodes is A cylindrical non-aqueous electrolyte secondary battery comprising a band-shaped current collector and a layer of an active material or an electrode mixture covering the current collector except for both ends in the width direction. 2. The width of the portions at both ends in the width direction of the band-shaped current collector that are not covered with the active material or electrode mixture is 0.0 of the width of the current collector.
The cylindrical non-aqueous electrolyte secondary battery according to claim 1, which is 5 times or less.