JPS6145568A - Nonaqueous electrolyte battery - Google Patents

Abstract

PURPOSE:To suppress the rapid increase in the internal resistance of a nonaqueous electrolyte battery having a positive electrode the apparent volume of which is increased by discharge reaction by using a microporous polyethylene film as a separator which is located between the positive and the negative electrodes and the periphery of which is held and fixed by the sealing area. CONSTITUTION:The nonaqueous electrolyte battery of this invention has a negative electrode 2 the active material of which is either a light metal such as lithium or sodium or its alloy, a positive electrode 1 the apparent volume of which is increased by discharge reaction and a separator 3 which is made of a microporous polyethylene film; the separator 3 is located between the positive and the negative electrodes 1 and 2 and the periphery of the separator 3 is held and fixed by the sealing area. Even when the apparent volume of the positive electrode 1 is increased due to discharge reaction up until when the positive and the negative electrodes 1 and 2 touch the separator 3 in some area of which a liquid electrolyte 4 is not appreciably increased because the distance between the positive and the negative electrodes 1 and 2 is very short. Since the microporous polyethylene films has high elasticity and therefore can extend deep into the negative electrode 2 as the volume of the positive electrode 1 increases, the utilization rate of the active material is increased and the discharge capacity of the battery is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a non-aqueous electrolyte battery equipped with a positive electrode whose apparent volume increases due to a discharge reaction.

(b) Conventional technology examples include fluorocarbon, silver comate, manganese dioxide, etc. disclosed in Japanese Patent Publication No. 54-356537, and metals disclosed in Japanese Patent Application Laid-Open No. 174871/1982. Sulfide, oxide oxide, bismuth oxide, etc. have the property of increasing the apparent volume due to discharge reaction, so when a non-aqueous electrolyte battery is installed using a material that is rejected as a positive electrode active material, the following will occur. There's a problem.

That is, as described in the above-mentioned prior art document,
Polypropylene nonwoven fabric is generally used as a separator member in this type of battery, but when the volume of the positive electrode increases due to a discharge reaction, the separator made of polypropylene nonwoven fabric interposed between the positive and negative electrodes is compressed and the impregnated holding cell is compressed. The m solution is squeezed out completely, and the polypropylene nonwoven fabric in which almost no electrolyte is present is partially located between the positive and negative electrodes, causing a rapid increase in internal resistance and deterioration of battery characteristics.

(c) Problems to be Solved by the Invention The main purpose of the present invention is to reduce the rapid increase in internal resistance accompanying discharge of a non-aqueous electrolyte battery equipped with a positive electrode whose volume apparently increases due to a discharge reaction. The goal is to suppress the increase. or,
The purpose of the present invention is 1! Furthermore, the purpose of the present invention is to improve the utilization rate of the electrode active material and increase the discharge capacity.6Furthermore, it is an object of the present invention to prevent internal short circuits caused by destruction of the separator due to the positive electrode body M intensifying port accompanying the discharge reaction. The aim is to suppress the

(d) Means for solving problem 1 The present invention is a method for solving the first problem.
A negative electrode having such an alloy as a live material fft, a positive electrode whose volume apparently increases due to a discharge reaction, and a separator located between the positive and negative electrodes and whose approximate periphery is held and fixed by a sealing part, The non-aqueous electrolyte battery is characterized in that the separator is made of a microporous film made of polyethylene.

(E) Effect According to the battery of the present invention, when the apparent volume of the positive electrode increases due to a discharge reaction, the separator interposed between the positive and negative electrodes is composed of an extremely thin layer of microporous polyalene film. Therefore, even if the volume of the positive electrode increases until the positive and negative electrodes come into contact with the separator where there is almost no Ryukaku 7 liquid present in some areas, the distance between the positive and negative electrodes will be extremely short and the internal resistance will increase extremely. That's not the case.

In addition, since the polyethylene microporous film is highly ductile, it can follow the volume increase of the positive electrode and extend deep into the consumable negative electrode, improving the utilization rate of the electrode active material, increasing the discharge capacity, and making it difficult to break. Internal short circuits can be suppressed.

(f) Tora Example Figure 1 is a longitudinal cross-sectional view of a battery according to an example of the present invention, in which (1) is a positive electrode in which 85% by weight of iron disulfide is used as an active material and graphite is used as a conductive agent. A mixture of 10% by weight and 5g of fluororesin powder as a binder and 1% by weight of fluororesin powder was pressure molded at a pressure of 2 tons/cTl'12 to give a diameter of about 11. Q
mn, thickness approximately 1.81111+1'(7) Pellet I. is baked at a temperature of 200 to 300°C. (2)
The negative electrode is a lithium rolled plate with a thickness of about 2.2 inches and is punched into a diameter of about 7.5 mm. (3) is a separator made of a microporous polyethylene film having a thickness of about 0.0251 T1 m and punched out to a diameter of about 11 Q mm. (4) is an electrolytic solution layer made of an electrolytic solution that fills the gap between the negative II (2) and the separator (3).

The battery of FIG. 1 is assembled as follows.

In other words, first insert-molding the insulation backing around the periphery)
・A lithium negative electrode (2) is crimped onto the negative electrode current collector (7) fixed to the inner bottom surface of the negative electrode terminal-cum-sealing lid (6) on which the negative electrode terminal (5) is placed, and the lithium negative electrode (2) is A gap is formed between the lithium negative electrode (2) and the annular insulating bank (5).゛On the other hand, a positive electrode current collector is fixed to the inner bottom surface of the outer case (8) which also serves as a positive electrode terminal. A positive electrode <1) is pressed onto (9) and a positive electrode (1
) and place the separator (3) on top of the outer can.
8) Fit the seal M(6) into the opening.

Then, this temporarily assembled t/IjJ was placed in a sealed container and vacuumed for 31 minutes, and then 1 mol/β of lithium boroborofluoride was dissolved in a mixed solvent of B: bivin carbonate) and 1°2 methquine ethane. The electrolyte is infiltrated into the battery by immersing it in the electrolyte solution, and the gap is filled with the electrolyte solution.
4) Form. Thereafter, the open edge of the outer can (8) is clamped to the insulating backing (5) to obtain a completed battery.

FIG. 2 shows a longitudinal cross-sectional view of a comparative battery, which differs from the battery of the present invention shown in FIG. 1 in that there is no electrolyte layer and that the separator members are different. Separator in comparison battery (
13) is made of polypropylene nonwoven fabric with a thickness of about 0.5111 m.

Figure 3 shows the voltages and voltages of battery A of the present invention, reference battery A' using a microporous polypropylene film that was separated overnight, and battery B for comparison at 5 and 6 Ω constant load discharge at 20°C. Changes in internal resistance over time.

As is clear from FIG. 3, inventive battery A and reference battery A' exhibit flat discharge voltage characteristics because the internal resistance does not increase rapidly, whereas comparative battery B exhibits flat discharge voltage characteristics. In this case, the internal resistance increases rapidly during discharge, resulting in an any-stage discharge voltage characteristic.

Considering the reason for this, in the case of Comparative Battery B, as the discharge progresses, the power solution retained in the polypropylene nonwoven fabric as a separator is squeezed out, and the polypropylene nonwoven fabric, in which almost no electrolytic solution is present, is partially squeezed out. The thick polypropylene nonwoven fabric interposed between the positive and negative electrodes acts as a kind of insulator, resulting in a rapid increase in internal resistance. However, as the discharge progresses further, the thickness of the polypropylene nonwoven fabric decreases, so the internal resistance increase curve becomes gentler, but the battery voltage progresses at a lower value.

On the other hand, in the case of the present invention /1I2A and the reference battery A', the distance between the positive and negative electrodes remains the same even if the volume of the positive 4 jo increases, because Hakushu's microporous resin film is used as the separator. Because it is short, internal resistance does not increase rapidly.

Further, when comparing the battery A of the present invention and the reference battery A', it can be seen that the battery of the present invention has a larger discharge capacity.

The reason for this is that the polyethylene film used for the separator of the battery of the present invention is more ductile than polypropylene film, so it cannot keep up with the volume increase of the positive electrode. This is thought to be due to an improvement in the utilization rate of the active material. Furthermore, due to its highly ductile nature, it breaks apart when the volume of the positive electrode increases, and as a result, it has the advantage of suppressing internal short circuits.

(G) As described above, the present invention suppresses the internal resistance associated with non-aqueous electrolytic/positive battery discharge, reduces the old discharge capacity, and suppresses the internal short circuit phenomenon. Its industrial value is extremely large in expanding the uses of ffI batteries.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a battery of the present invention, FIG. 2 is a vertical cross-sectional view of a comparative battery, and FIG. 3 shows battery voltage characteristics and internal I/O voltage characteristics with respect to discharge time. 1)...Positive electrode, (2)...Negative electrode, (3)...Separator made of polyethylene film, (4>...
Electrolyte layer, (5)...Insulating bar/knocking, (6)
Sealing lid, (8)...Exterior can, (A)...Battery of the present invention,
(A') Reference battery, (B)... Comparison battery.

Claims (1)

[Claims] (1) A negative electrode whose active material is a light metal such as lithium or sodium or an alloy thereof, a positive electrode whose apparent volume increases due to a discharge reaction, and a negative electrode located between the positive and negative electrodes and whose peripheral parts are clamped and fixed by a sealing part. 1. A non-aqueous electrolyte battery, comprising: a separator comprising: a non-aqueous electrolyte battery; the separator comprising a microporous film made of polyethylene;