JPH10134795A - Non-aqueous electrolytic battery and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-aqueous electrolytic battery with its high safety in which abnormal heating of the battery due to internal short-circuit is prevented and a manufacturing method thereof. SOLUTION: This battery comprises a positive electrode sheet 1 in which a positive electrode compound is applied to a positive electrode. collector 9, a negative electrode sheet 2 in which a negative electrode compound is applied to a negative electrode collector 10, and a separator 3 interposed between these sheet electrodes. A resin film containing bromine is formed on a surface of the positive sheet 1 and/or a surface of the negative electrode sheet 2.

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 battery, and more particularly to a non-aqueous electrolyte battery with improved battery safety and a method of manufacturing the same.

[0002]

2. Description of the Related Art In general, a lithium battery represented by a non-aqueous electrolyte battery is characterized by a high voltage, a high energy density, and the like. However, since the lithium metal contained therein has an extremely high chemical reactivity, For example, when a charged battery is pressurized and deformed from the outside and an internal short circuit occurs,
At that time, heat may be generated due to decomposition of the electrolytic solution or the electrode constituent material due to a chemical reaction, or the gas may explode due to an increase in internal pressure due to gas generation.

[0003] In particular, in lithium batteries, since the lithium metal and organic electrolyte contained therein are flammable, there is also a risk of ignition due to abnormal heat generation. In the case of a lithium secondary battery, in addition to internal short-circuiting due to pressurization and deformation, as described above, rupture and / or rupture also occur due to internal short-circuiting of dendritic lithium formed on an active material due to continuous overcharge. Troubles such as ignition may occur.

[0004] Conventionally, such a battery having a high chemical reactivity has been provided with various safety mechanisms for preventing rupture or ignition in the event of a battery abnormality and ensuring the safety of the battery.

As such a safety mechanism, for example, an electric current suppressing mechanism using a PTC element having an extremely positive temperature characteristic and reducing the current by a high resistance value of the PTC element when a large current passes. Alternatively, a mechanical explosion-proof mechanism in which a safety valve is provided to release the internal gas to the outside when the internal pressure of the battery increases, thereby preventing a transient increase in pressure. Further, a current interrupting mechanism for mechanically interrupting a current path when the internal pressure of the battery increases is known.

[0006]

However, the above P
In the case of a current suppressing mechanism using a TC element, PT
Due to the mounting method of the C element and the problem of consistency between the temperature rise of the battery and the temperature characteristics of the PTC element, especially in the case of a large-sized battery such as a cylindrical battery, it is possible to effectively reduce heat generation in the event of a battery abnormality. There is a problem that it cannot be suppressed.

In addition, in the explosion-proof mechanism and the current cut-off mechanism using the safety valve, the chemical reaction generally induced by the abnormality of the battery causes the temperature of the battery to rise more rapidly than the internal pressure of the battery. In some cases, the mechanism does not work effectively.

The present invention forms a thin film of a resin containing bromine on an electrode active material and suppresses a chemical reaction induced in the event of a battery abnormality as much as possible, thereby preventing abnormal heat generation of the battery and ensuring high safety. An object is to provide a non-aqueous electrolyte battery and a method for manufacturing the same.

[0009]

That is, according to the first aspect of the present invention, a positive electrode sheet (1) formed by applying a positive electrode mixture to a positive electrode current collector (9); ), A negative electrode sheet (2) formed by applying a negative electrode mixture, and a separator (3) interposed between these sheet electrodes. /
Alternatively, a thin film of a resin containing bromine is formed on the surface of the negative electrode sheet (2).

In the present invention, the resin containing bromine is a phenolic resin.

Further, according to the present invention, first, a reaction product of tetrabromobisphenol A and 1,4-diisocyanatobutane is dispersed in a volatile organic solvent to give a solution concentration of 8 to 15% by weight. % Resin solution,
Next, a positive electrode sheet (1) formed by applying a positive electrode mixture to a positive electrode current collector (9) and / or a negative electrode sheet (2) formed by applying a negative electrode mixture to a negative electrode current collector (10) are prepared as described above. Immersed in a resin solution, then dried the volatile organic solvent,
A resin thin film is formed on the surface of the positive electrode sheet (1) and / or the negative electrode sheet (2), and a separator (3) is interposed between the positive electrode sheet (1) and the negative electrode sheet (2). And a structure in which the wound body is housed in a case (6).

[0012]

FIG. 1 is a longitudinal sectional view showing the internal structure of a wound type non-aqueous electrolyte secondary battery to which the present invention is applied.

First, the structure and assembly of this wound type non-aqueous electrolyte secondary battery will be described with reference to FIG. 1. Reference numeral 1 denotes a positive electrode, and the positive electrode 1 is LiCoO ₂ which is a positive electrode active material. And an aqueous dispersion of carbon powder as a conductive material and an aqueous dispersion of ethylene tetrafluoride resin (PTFE) as a binder in a weight ratio of 100: 10: 10,
A positive electrode mixture prepared by kneading them into a paste with water was coated on both sides of a 30 μm-thick aluminum foil serving as a positive electrode current collector 9, and then dried, rolled, and cut into a belt-shaped positive electrode sheet 1. Things. A part of the mixture on the surface of the positive electrode sheet 1 was scraped off, and a positive electrode lead plate 4 made of titanium was mounted on the exposed positive electrode current collector 9 by spot welding.

The above-mentioned positive electrode active material LiCoO ₂
Used was a mixture of cobalt oxide and lithium carbonate at a molar ratio of 2: 1 and heated at 900 ° C. for 9 hours.

Reference numeral 2 denotes a negative electrode. This negative electrode 2 is prepared by mixing a graphite-based carbon powder and an aqueous dispersion of PTFE as a binder in a weight ratio of 100: 5, and kneading the mixture with water to form a paste. The negative electrode mixture thus obtained was coated on both sides of a copper foil having a thickness of 20 μm serving as the negative electrode current collector 10, and then dried, rolled, and cut into a strip-shaped negative electrode sheet 2. A part of the mixture on the surface of the negative electrode sheet 2 was scraped off, and a negative electrode lead plate 5 made of nickel was attached to the exposed negative electrode current collector 10 by spot welding.

The positive electrode sheet 1 and the negative electrode sheet 2 are placed in a resin solution having a predetermined solution concentration formed by dispersing a mixture of a phenolic compound powder and a crosslinking agent (1,4-diisocyanate butane) in a volatile organic solvent. The sheet electrodes 1 and 2 are immersed to form a thin film of a resin containing bromine on the surface of the sheet electrodes 1 and 2, and the resin-coated positive electrode sheet 1 and negative electrode sheet 2 are swirled with a porous film separator 3 made of polypropylene interposed therebetween. It was wound in a shape. The wound body is inserted into a bottomed cylindrical case 6, and the other end of the positive electrode lead plate 4 is spot-welded to a stainless steel sealing plate 7 so that the positive electrode sheet 1 is inserted through the sealing plate 7. And electrically connected to a positive electrode cap 8 also serving as a positive electrode terminal. The other end of the negative electrode lead plate 5 was spot-welded to the circular bottom surface of the case 6 also serving as a negative electrode terminal, and the negative electrode sheet 2 was electrically connected to the case 6.

After the above operation, an organic electrolyte in which lithium perchlorate (LiClO ₄ ) was dissolved in a mixed solvent of ethylene carbonate and 1,2-dimethoxyethane was injected into the case 6, and the case 6 was sealed. The size of the battery after the assembly is AA type (14.5Φmm × 50 mm).

Reference numeral 11 denotes an insulating gasket made of polypropylene, 14 denotes an insulating plate also made of polypropylene, 13
Reference numeral 12 denotes a safety valve for releasing internal gas to the outside when the internal pressure of the battery rises due to battery abnormality. Reference numeral 12 denotes an insulating bottom plate made of polypropylene.

The above is the schematic configuration of the nonaqueous electrolyte secondary battery to which the present invention is applied. As described above, the surface of the positive electrode sheet 1 and the surface of the negative electrode sheet 2 are coated with bromine. The point is that a thin film of a resin is formed.

It is believed that the chemical reaction from the internal short circuit to the ignition described above involves H radicals and OH radicals generated by decomposition of the organic electrolyte in the contents. By reacting this radical with Br radical generated from a resin containing bromine, a chain reaction leading to ignition can be suppressed.

That is, according to the following reaction formula, H
It is considered that radicals and OH radicals are trapped.

RBr + H ・ → HBr + R ・ OH ・ + HBr → H ₂ O + Br ・ Br ・ + RH → HBr + R ・ In the above reaction formula, RBr represents a resin containing bromine, and H ・ and OH ・It shows H radicals and OH radicals generated by decomposition and resin decomposition.

Therefore, the positive electrode sheet 1 and the negative electrode sheet 2
By forming a thin film of a resin containing bromine on the surface of the resin, H radicals generated by decomposition of an electrolytic solution and the like react with bromine contained in the resin to generate hydrogen bromide (HBr), Hydrogen reacts with OH radicals and is trapped as water. Br produced by this reaction
Hydrogen bromide is generated from the radical and traps the OH radical.

[0024]

The procedure of resin coating for forming the resin film will be described below. The following is concentration 1
In this case, the resin coating is performed using a 0% by weight resin solution.

First, 5.44 g of a phenolic compound, tetrabromobisphenol A (powder), was placed in a beaker.
And 1.40 g of 1,4 diisocyanate butane (liquid) as a cross-linking agent, and 61.56 g of benzene dehydrated with a molecular sieve as a volatile organic solvent was added to the mixture to give a concentration of 10% by weight. Make a resin solution.

Next, the positive electrode sheet 1 and the negative electrode sheet 2 each having the positive electrode lead plate 4 and the negative electrode lead plate 5 covered with a masking tape are immersed in this resin solution for about 1 minute, and then pulled up to dry the benzene on the surface.

Further, the dried positive electrode sheet 1 and negative electrode sheet 2 are heated by a dryer at 100 ° C. for about 12 hours to form a resin thin film on the surface of each electrode sheet.

The thickness of the resin film thus formed is determined by the amount of the volatile organic solvent (benzene solution) added thereto when the mixing amount of the phenolic compound powder and the crosslinking agent is constant. That is, the higher the concentration of the resin solution, the thicker the resin film is formed.

The feature required of the resin film is that it has a network structure through which ions can pass. Br (bromine) for suppressing a radical reaction can be reliably held. Stable against electrolyte and battery reaction. The phenolic resin used in the above embodiment sufficiently satisfies these conditions.

Example 1 Based on the resin coating method described above, the concentration was 8% by weight.
A resin thin film was formed on the surfaces of the positive electrode sheet 1 and the negative electrode sheet 2 using the above resin solution. Using these positive electrode sheet 1 and negative electrode sheet 2, an AA nonaqueous electrolyte secondary battery was produced.

Example 2 A non-aqueous electrolyte secondary battery similar to that of Example 1 was prepared using a resin solution having a concentration of 10% by weight.

Example 3 A non-aqueous electrolyte secondary battery similar to that of Example 1 was produced using a resin solution having a concentration of 15% by weight.

[0033] was used to fabricate a non-aqueous electrolyte secondary battery as in Example 1 using the comparative example 1 of a conventional resin film is not formed on the surface the positive electrode sheet 1 and the negative electrode sheet 2.

Comparative Example 2 A non-aqueous electrolyte secondary battery similar to that of Example 1 was prepared using a resin solution having a concentration of 5% by weight.

COMPARATIVE EXAMPLE 3 A non-aqueous electrolyte secondary battery similar to that of Example 1 was manufactured using a resin solution having a concentration of 20% by weight.

The non-aqueous electrolyte secondary batteries of Examples 1 to 3 and Comparative Examples 1 to 3 were subjected to a charge / discharge cycle test under the following conditions and a battery temperature rise test due to an internal short circuit. went.

The charge / discharge cycle test was performed with a charge / discharge current of 100 m.
A, under the conditions of a charge end voltage of 4.1 V and a discharge end voltage of 3.0 V, the cycle characteristics of each battery are shown in FIG.

As a result, in Comparative Example 3 in which the concentration of the resin solution at the time of forming the thin film using the bromine resin was 20% by weight, the discharge capacity was extremely reduced, but in Examples in which the concentration of the resin solution was 15% by weight or less. No reduction in the discharge capacity was observed for Comparative Examples 1 to 3 and Comparative Examples 1 and 2, and good cycle characteristics were obtained.

Regarding the temperature rise test of the batteries, the batteries according to the respective specifications were charged to a final charging voltage of 4.1 V, and then each battery was compressed to a half of the diameter using a vice. The change in the temperature of the battery surface caused by the internal short circuit at that time was measured, and the result is shown in FIG.

As a result, in Comparative Example 1 which is a conventional product and Comparative Example 2 in which the concentration of the resin solution was 5% by weight, the surface temperature was extremely increased to cause ignition, but the concentration of the resin solution was 8% by weight. % Of Examples 1 to 3 and Comparative Example 3, the rapid increase in the battery surface temperature was suppressed, and no ignition was caused.

According to the results of the charge / discharge cycle test and the temperature rise test, when the resin film formed on the surface of the sheet electrode is too thin, the chemical reaction at the time of battery abnormality cannot be suppressed and abnormal heat generation occurs. If the thickness is too large, the discharge capacity is adversely affected.
It can be determined that 15% by weight is suitable.

In the embodiment described above, the case where the resin film is formed on both the positive electrode sheet 1 and the negative electrode sheet 2 has been described, but the resin film is formed on only one of the positive electrode sheet 1 and the negative electrode sheet 2. In any case, it effectively acts to suppress heat generation.

[0043]

As described above, according to the present invention, an internal short circuit occurs in a battery by forming a thin film of a resin containing bromine on the surface of a positive electrode sheet or a negative electrode sheet. Since the chemical reaction at that time is suppressed and ignition due to abnormal heat generation can be prevented, the safety of the nonaqueous electrolyte battery is significantly improved.

According to the second aspect of the present invention,
The phenolic resin used can reliably retain bromine for suppressing the radical reaction and is stable against the electrolyte solution and the battery reaction. The suppression effect is extremely large.

Further, according to the present invention, the concentration of the resin solution at the time of forming the resin film is 8 to 15% by weight.
, Heat generation can be effectively suppressed without deteriorating the cycle characteristics of the battery.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing the internal structure of a nonaqueous electrolyte secondary battery to which the present invention is applied.

FIG. 2 is a diagram showing charge / discharge cycle characteristics of the non-aqueous electrolyte secondary battery.

FIG. 3 is a diagram showing a change in surface temperature due to an internal short circuit of the non-aqueous electrolyte secondary battery.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 positive electrode sheet 2 negative electrode sheet 3 separator 6 case 9 positive electrode current collector 10 negative electrode current collector

Claims (3)

[Claims] 1. A positive electrode sheet (1) formed by applying a positive electrode mixture to a positive electrode current collector (9), and a negative electrode sheet (2) formed by applying a negative electrode mixture to a negative electrode current collector (10). A non-aqueous electrolyte battery provided with a separator (3) interposed between these sheet electrodes, wherein the surface of the positive electrode sheet (1) and / or the surface of the negative electrode sheet (2) is made of a resin containing bromine. A non-aqueous electrolyte battery, wherein a thin film is formed. 2. The non-aqueous electrolyte battery according to claim 1, wherein the resin containing bromine is a phenolic resin. First, a reaction solution of tetrabromobisphenol A and 1,4-diisocyanate butane is dispersed in a volatile organic solvent to form a resin solution having a solution concentration of 8 to 15% by weight. A positive electrode sheet (1) formed by applying a positive electrode mixture to a positive electrode current collector (9) and / or a negative electrode sheet (2) formed by applying a negative electrode mixture to a negative electrode current collector (10) are mixed with the resin solution. After that, the volatile organic solvent is dried to form a resin thin film on the surface of the positive electrode sheet (1) and / or the negative electrode sheet (2). A negative electrode sheet (2) and a separator (3) are interposed therebetween and wound,
A method for manufacturing a non-aqueous electrolyte battery, wherein the wound body is housed in a case (6).