JPH0750601B2 - Non-aqueous electrolyte battery - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to non-aqueous electrolyte batteries, and in particular to separators thereof.

2. Description of the Related Art Non-aqueous electrolyte batteries having a light metal such as lithium as a negative electrode have high energy density and have the advantage of little self-discharge, but in recent years, as an electrode body of this non-aqueous electrolyte battery,
A spirally wound electrode body has been used in which a separator is inserted between a positive electrode and a negative electrode, and the positive electrode, the separator, and the negative electrode are wound.

The non-aqueous electrolyte battery provided with this spiral electrode body is very excellent in extracting a large current because the facing area between the positive electrode and the negative electrode can be made wide, but on the other hand, when an external short circuit occurs, Had the following problems. That is, when an external short circuit occurs, a large short-circuit current flows in the battery, Joule heat is generated, the temperature rises in the battery, and the non-aqueous electrolyte is vaporized or decomposed and gasified. Is accumulated in the battery and the pressure in the battery rises. Thus, the gas accumulated in the battery is flammable, which is dangerous, especially when a highly active light metal such as lithium is used as the negative electrode active material. There was a point.

Therefore, in order to solve the above-mentioned problems and ensure the safety of the non-aqueous electrolyte battery, the applicant uses a separator as described in JP-A-60-23954 (HO1M 2/16). A non-aqueous electrolyte battery using a microporous membrane has already been proposed. According to the non-aqueous electrolyte battery, even if the temperature of the battery rises due to the generation of Joule heat due to a short-circuit current, when the temperature inside the battery reaches the melting point of the separator, the separator melts and closes the micropores. , Prevents the movement of ions between the positive and negative poles.
As a result, it became difficult for current to flow, the temperature rise of the battery was suppressed, and the safety of the non-aqueous electrolyte battery was improved to some extent.

Problems to be Solved by the Invention By the way, according to the non-aqueous electrolyte battery as described above, when an external short circuit occurs, the separator melts and the temperature rise of the battery is suppressed. The micropores are not always blocked, and a small amount of current may continue to flow.

When a small amount of current flows in this way, one battery is considered to be a normal discharge reaction, and no particular problem occurs. However, as described above with a plurality of batteries connected in series, If such an external short circuit occurs, the following problems occur.

In other words, the internal structure of each of the plurality of batteries is rarely completely the same physically, and there is usually a slight variation, but a plurality of non-aqueous electrolyte batteries are connected in series. When an external short circuit occurs in the state where the separators are connected to each other, the separators in each battery are hardly melted at the same time and at the same ratio to close the micropores. Therefore, for example, a case where two non-aqueous electrolyte batteries are connected in series will be described as an example. Among the two batteries, one of the two batteries, in which the separator started to melt first, blocked the micropores, and became difficult to pass current. The battery (hereinafter referred to as “battery I”) acts as a resistance against the other battery (hereinafter referred to as “battery II”) whose separator has not started melting, but the battery II continues to discharge, so Even if the voltage of the whole system is 0V when the batteries I and II are connected in series, the voltage of each battery is 0V.
If, for example, the voltage of the battery I is −3V, then the battery II
Voltage is + 3V. As described above, in the batteries I and II, not all the micropores of each separator are closed, so that a small amount of current continues to flow as in the case where one battery causes an external short circuit. . In this state, the battery II carries out a normal discharge reaction, but in the battery I in which the separator first started to melt, the non-aqueous electrolyte in the battery decomposes to generate gas, and the negative electrode component is electrodeposited on the positive electrode. To do.

If the short circuit is continued for a long time in such a state, the non-aqueous electrolyte solution of the battery I of which the separator has started to melt first out of the two batteries connected in series is gasified, and the gas is accumulated in the battery. Electrodeposition of the negative electrode component on the positive electrode continues as it continues, and the electrodeposited negative electrode component sometimes breaks through the separator, and internally short-circuits the positive electrode and the negative electrode. When an internal short circuit occurs in this way, a large current flows concentrated in the short-circuited portion, and a rapid temperature rise occurs in this portion. Further, if a spark occurs in the gas-filled battery when an internal short circuit occurs, it is considered that the spark may serve as an ignition source and cause the battery to ignite.

It goes without saying that the above-mentioned problems also occur when three or more non-aqueous electrolyte batteries are connected in series and an external short circuit occurs.

It seems that this problem can be solved by increasing the thickness of the separator film, but the separator should be as thin as possible (thickness 50 μm or less) in order to increase the facing area of the positive and negative electrodes in the limited battery container. However, it is not possible to increase the thickness of the separator.

The present invention has been made in view of the above problems, and even if a plurality of non-aqueous electrolyte batteries are externally short-circuited in series, there is no partial rapid temperature rise in the battery.

Means for Solving the Problems In order to achieve the above object, the present invention includes a positive electrode using a metal compound having an oxidizing power as an active material, a negative electrode using a light metal as an active material, and the positive electrode and the negative electrode. In a non-aqueous electrolyte battery including a spirally wound electrode body having a separator and a non-aqueous electrolyte, the separator has a microporous film mainly composed of polypropylene having different melting points, and a micro-particle mainly composed of polyethylene. It is characterized in that a porous film is attached to form a bag shape, and either one of the positive and negative electrodes is inserted into the bag shape.

Action According to the above configuration, when the battery causes an external short circuit and the battery temperature rises, the portion of the separator made of the microporous film mainly composed of polyethylene is melted to close the micropores of the separator and become an insulator. . As a result, the reaction area of the battery (the area where the positive and negative electrodes face each other) decreases, the current flowing in the battery decreases, and the temperature of the battery does not rise any more. On the other hand, since the temperature rise of the battery is suppressed, the part of the separator, which is composed of the microporous film mainly composed of polypropylene, does not melt and retains the original function of the separator.

Example FIG. 1 is a partially cutaway front view of a non-aqueous electrolyte battery according to an example of the present invention. In the figure, reference numeral 1 denotes a non-aqueous electrolyte battery, which is composed of a spiral electrode body 7 formed by winding a positive electrode 2, a negative electrode 3, and a separator 4 interposed between the positive and negative electrodes, and an insulating resin. A pair of upper and lower insulating sleeves 8 (the lower insulating sleeve is not shown), a non-aqueous electrolyte (not shown), a positive electrode terminal portion 5a is formed at the lower end, and the above-mentioned spiral electrode body 7 and the like are internally opened. It is made up of a stainless steel cylindrical container 5 and a convex stainless lid 6 mounted via an insulating packing 10 made of an insulating resin.

In addition, the lid body 6 includes an upper lid 6c on which the negative electrode terminal 6a is formed.
And a nickel negative electrode tab 9 whose one end is connected to the negative electrode 3.
And a lower lid 6b electrically connected to the lower lid 6b. Reference numeral 8a is a hollow portion through which the negative electrode tab 9 penetrates.

The separator 4 is a bag in which two 25 μm-thick polyethylene microporous membranes 4a and 25 μm-thick polypropylene microporous membranes 4b are bonded together to form a bag, in which the negative electrode 3 is inserted and wound together with the positive electrode 2. The spiral electrode body 7 is formed by turning. The positive electrode 2 located on the outermost side of the spiral electrode body 7 is brought into contact with the inner wall of the container 5, and the spiral electrode body 7 is
The lead of the positive electrode 2 is led out through the insulating sleeve and spot-welded to the inner surface of the container 5 on the lower surface of the container.

As the positive electrode 2, manganese dioxide, which is an example of a metal compound having an oxidizing power, is used as an active material, graphite is used as a conductive agent, and ethylene tetrafluoride is used as a binder, and each volume% is manganese dioxide: graphite: tetrafluoroethylene. = 90: 6: 4, and the mixture was mixed with water to form a paste, which was applied to a stainless lath plate, heat-treated and dried.

As the negative electrode, one using lithium as an example of a light metal as an active material was used.

Further, the non-aqueous electrolytic solution contains propylene carbonate and 1,
A solution was used in which lithium perchlorate was dissolved in a mixed solvent with 2-dimethoxyethane (volume ratio 1: 1), and the one adjusted such that the concentration of the lithium perchlorate was 0.75M was used.

FIG. 2 shows that the non-aqueous electrolyte battery of the present invention and a conventional non-aqueous electrolyte battery using a polypropylene microporous membrane as a separator were connected in series two by two to cause an external short circuit. It is a characteristic view which shows the relationship between the voltage (V) and time in a case. The solid line shows the non-aqueous electrolyte battery of the present invention, and the broken line shows the conventional non-aqueous electrolyte battery. The curve shown on the minus side shows the characteristics of one battery I in which the separator first started to melt, and the curve shown on the plus side shows the characteristics of the other battery II in which the separator did not start melting. Show.

As is apparent from FIG. 2, in the conventional non-aqueous electrolyte battery, after the short circuit, the voltage of one battery is almost the same as that before the short circuit, while in the non-aqueous electrolyte battery of the present invention, the battery I And battery
With II, it was confirmed that the voltage quickly approached 0 V and the capacity of the battery was consumed in a short time.

FIG. 3 is a characteristic diagram showing the relationship between the current (A) and time.

As can be seen from FIG. 3, in the conventional non-aqueous electrolyte battery, almost no current flows after the initial large current is rapidly reduced due to an external short circuit. It has been confirmed that the electrolytic solution battery can pass an electric current that can occur in a normal discharge reaction, the temperature of the battery does not rise, and the nonaqueous electrolytic solution battery is not likely to ignite or burst.

As described above, in the non-aqueous electrolyte battery of the present invention, since the separator is formed of the polypropylene microporous film and the polyethylene microporous film having different melting points, the portion having a low melting point polyethylene is melted first. It closes the micropores of polyethylene and becomes an insulator, suppressing the temperature rise in the battery.
Further, the part made of polypropylene having a high melting point has the original function of the separator without being melted. Therefore, decomposition of the non-aqueous electrolytic solution and electrodeposition of the negative electrode component are less likely to occur, and a certain amount of current (current that occurs in a normal discharge reaction) can be passed even after the portion of the separator made of polyethylene is melted, The capacity of the battery is consumed in a relatively short time and the discharge is completed, the temperature rise of the battery can be suppressed, ignition,
A highly safe non-aqueous electrolyte battery that is free from the risk of bursting can be obtained, and the intended purpose can be achieved.

Incidentally, the present invention is not limited to the above-mentioned embodiment, and for example, if the separator is a non-aqueous electrolyte battery consisting of a microporous film formed of a plurality of kinds of materials having different melting points, the same effect as above can be obtained. Needless to say.

Effects of the Invention According to the above configuration, since the separator of the non-aqueous electrolyte battery according to the present invention is made of a microporous film formed of a plurality of kinds of materials having different melting points, a plurality of external short-circuits are connected in series. Even if the above occurs, there is an effect that a temperature rise of the battery can be suppressed, the battery does not ignite or burst, and a highly safe non-aqueous electrolyte battery can be obtained.

[Brief description of drawings]

FIG. 1 is a partially cutaway front view of a non-aqueous electrolyte battery according to an embodiment of the present invention, and FIG. 2 shows a voltage when two non-aqueous electrolyte batteries are connected in series and externally short-circuited. FIG. 3 is a characteristic diagram showing the relationship between time and current when two non-aqueous electrolyte batteries are connected in series and externally short-circuited. 2 ... Positive electrode, 3 ... Negative electrode, 4 ... Separator.

Claims (1)

[Claims] 1. A spirally wound electrode body in which a positive electrode using a metal compound having an oxidizing power as an active material, a negative electrode using a light metal as an active material, and a separator interposed between the positive and negative electrodes are wound.
In a non-aqueous electrolyte battery provided with a non-aqueous electrolyte, the separator is a bag formed by laminating a microporous film mainly composed of polypropylene having different melting points and a microporous film mainly composed of polyethylene, and the bag. A non-aqueous electrolyte battery, characterized in that either one of the positive and negative electrodes is inserted into the shape.