JPH01186557A - Nonaqueous electrolyte cell - Google Patents

Abstract

PURPOSE:To prevent the deterioration in the cell characteristic by using thermoplastic polyester resin as the binding agent of a positive electrode. CONSTITUTION:Thermoplastic polyester resin is used for the binding agent of a positive electrode. Polyethylene terephtalate resin or polybutylene terephtalate resin is used for the thermoplastic polyester resin. The addition of the thermoplastic polyester resin is set to 0.5-5.0wt.% against the positive electrode. The decomposition temperature of the binding agent is 300 deg.C or above, thereby the positive electrode can be processed at a high temperature, the moisture in the positive electrode can be sufficiently removed, and the deterioration in the cell characteristic due to the remaining moisture can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to non-aqueous electrolyte batteries, and particularly to improvements in positive electrodes.

(b)) Conventional technology Non-aqueous electrolyte batteries have a high energy density and can be used to reduce the weight of small plates.
It is used as a source for precision equipment such as electronic watches.

The positive electrode of this type of power source is made by heat-treating a mixture of an active material such as a metal oxide, sulfide, or halide, to which a 4-electrode agent and a binder are added.

Here, the binder must not only have electrolytic solution resistance but also be able to withstand heat treatment in the water removal process.
The fluororesin disclosed in the above publication is generally used.

However, when using fluororesin, in order to maintain the mechanical strength of the positive electrode to a practical level, it must be used in a large amount, such as 5 to 10% by weight, based on the positive electrode, and a large amount of binder must be used. There are disadvantages in that the use of such a battery causes a decrease in the liquid absorption of the positive electrode, a decrease in the discharge utilization rate of the active material, and a decrease in the amount of active material per unit volume, resulting in a decrease in the discharge capacity of the battery.

In order to improve these drawbacks, instead of reducing the amount of binder added, the outer periphery of the positive electrode is reinforced with a stainless steel can, or
As disclosed in Japanese Patent No. 250257, it has been proposed to place a porous conductor such as a wire mesh on one side or the inner surface of the positive electrode for reinforcement, but these methods require an increase in the number of man-hours when molding the electrode plate; Parts other than power generation elements (rented etc.)
Incorporating this into the battery results in a decrease in the effective volume within the battery.

In JP-A No. 59-189559, it is proposed to use a fluororesin binder and a viscous agent such as polyvinyl alcohol in combination, but this method requires the mixing process of the positive electrode mixture and the heating of the positive electrode. The processing process is complicated and requires a large number of man-hours, and although the obtained electrode plate has better strength than an electrode plate using only fluororesin, it is not sufficient, especially when the thickness is 2.
When an extremely thin electrode plate, such as an electrode plate used in a battery of size M or less, is produced by this method, there is a drawback that the electrode plate may crack or break during assembly. Furthermore, a positive electrode mixture using a fluororesin binder has poor fluidity, which results in poor accuracy when weighing the positive electrode mixture, and there is a problem with workability and uniformity during electrode plate manufacture.

Therefore, various alternatives to fluororesins have been proposed.

For example, addition of sodium polyacrylate (JP-A-57-69)
666), addition of a silicate-based or phosphate-based heat-resistant inorganic adhesive (JP-A-58-147964), addition of an organic solvent solution of a polyimide resin precursor (
JP-A No. 58-147965) or the addition of a copolymer of sodium polyacrylate and polyacrylamide (JP-A No. 58-225567) have been proposed, but both have problems in battery characteristics or manufacturing. Moreover, the strength of the electrode plate was insufficient even if it was extremely thin.

(c) Problems to be Solved by the Invention The present invention solves the problem of reducing battery characteristics due to the conventional binder mentioned above.
This is an attempt to solve work-related problems.

+=E1 Means for Solving the Problem The present invention is characterized in that a thermoplastic polyester resin is used as a binder for the positive electrode.

As the heat-fusible polyester resin, polyethylene terephthalate resin or polybutylene terephthalate resin is preferable.

Also, what is the amount of thermoplastic polyester resin added? ) and α is preferably in the range of 5 to 5.0% by weight.

(E) Function Since the binder according to the present invention has a decomposition temperature of 500°C or higher, it is possible to perform island temperature heat treatment of the positive electrode, and water in the positive electrode can be sufficiently removed, suppressing deterioration of battery characteristics due to residual water. sell.

Furthermore, even when the binder according to the present invention is used alone, sufficient mechanical strength can be obtained in an ultra-thin electrode plate, so it is sufficient to add a small amount of the binder and a large amount of the binder can be added. In addition to suppressing the deterioration of battery characteristics caused by this, a viscous agent such as polyvinyl alcohol becomes unnecessary, and as a result, the heat treatment step for removing the viscous agent can be omitted, improving workability.

(f) Example Examples of the present invention will be described in detail below.

Example 1 Manganese dioxide powder as a positive electrode active material, graphite as a conductive agent, and polyethylene terephthalate resin as a binder were mixed in a weight ratio of 88:10:2 and dried at 90° C. for 5 hours. After drying, the product was pulverized, passed through 52 meshes, and then pressure molded.
A positive electrode was prepared by heat treatment at °C for 2 hours. Positive electrode size is diameter 1
6.3131° thickness α5711.

The negative electrode is made by rolling a lithium plate to a predetermined thickness with a roller in an argon-substituted dry box.
．． It was punched out to a size of 4g.

In addition, a button-type non-aqueous electrolyte battery with a diameter of 2 mm and a thickness of 16 mm was constructed using a polypropylene nonwoven fabric as a separator, using an electrolyte in which lithium perchlorate was dissolved in a mixed solvent of propylene carbonate and t2 dimethoxyethane. Created.

This invention battery is assumed to be a person.

Next, for comparison, manganese dioxide powder as a positive electrode active material and graphite as a conductive agent were mixed at a weight ratio of 90:10, as disclosed in Japanese Patent Publication No. 189559/1982, and this mixture was 1% by weight of die version of polytetrafluoroethylene and 25% by weight of pure water were added to the mixture, kneaded, dried at 150'C, and crushed to give 52%
The mesh is passed to obtain a first powder. And this first
Polyvinyl alcohol solution 1:1% by weight based on the powder
The mixture was added, kneaded, dried at 100°C, and subjected to a 32-mesh bath to obtain a second powder. This second powder body has a diameter of 1
6"1M, thickness α57+EI to obtain a molded body, and then heat treated in air at 250°C for 1 hour to remove the polyvinyl alcohol thin film adhering to the powder surface of this molded body. After that, heat treatment is performed at 270''C for 2 hours under vacuum to obtain a positive electrode. A ratio/magnetic battery C was produced in the same manner as in Example 1 except for using this positive electrode.

Figure 1 shows the battery according to the invention and the comparison battery C at a temperature of 26°C1.
A characteristic comparison diagram when discharging to load 12 under the condition of Ω is shown.
From FIG. 1, it can be seen that the battery A of the present invention suppresses the increase in internal resistance at the end of discharge and has an increased discharge capacity compared to the comparative battery CK.

FIG. 2 shows the relationship between the amount of polyethylene terephthalate resin added as a binder and the strength of the positive electrode plate. As shown in Fig. 3, the strength of the electrode plate is defined as the positive electrode +41 is placed in the large diameter hole (3) that communicates with the small diameter hole (2) of the metal ferrule (11), and the positive electrode +41 is placed on the punch (5). This shows the load when the positive electrode is pressurized and the positive electrode breaks.

As is clear from Figure 2, when the amount of polyethylene terephthalate resin added is 0.5% by weight or more, the plate strength is 1.
You can see that it exceeds 00F. Incidentally, the strength of the positive electrode plate of comparative battery C is about 802.

On the other hand, the fourth column shows the relationship between the amount of polyethylene terephthalate resin added and the battery discharge time. The discharge conditions are a temperature of 25°C, a load of 12 Ω, and a discharge end voltage of 2. It was Ov.

As is clear from FIG. 4, when the amount of polyethylene terephthalate resin added is 5.0% by weight or more, the discharge time becomes shorter. This is considered to be because the amount of active material decreases as the binder increases, and the permeability of the electrolyte into the electrode decreases due to the film-forming action of the binder.

Therefore, it can be seen from FIGS. 2 and 4 that the amount of polyethylene terephthalate resin added is preferably in the range of 0.5 to 5.0% by weight.

The table below compares the battery characteristics of the battery A of the present invention and the comparative battery C when stored at a temperature of 60° C. and a relative humidity of 90%.

Below is a blank space Example 2 Manganese dioxide powder as a positive electrode active material, graphite as a conductive agent, and polybutylene terephthalate resin as a binder were mixed at a weight ratio of 88:10:2.
Dry for 5 hours at °C. After drying, the product was crushed, passed through 32 meshes, and then pressure molded, and the molded product was heat-treated at 270° C. for 2 hours under vacuum to obtain a positive electrode. Seitetsu dimensions are diameter 1 (,5 ras.

The thickness is CL57B.

Hereinafter, the battery B of the present invention is obtained in the same manner as in Example 1.

Figure 5 shows a characteristic comparison diagram when battery B of the present invention and battery C of the present invention are discharged at a temperature of 26°C and a load of 12 Ω. It can be seen that the increase in internal resistance at the final stage of discharge is suppressed and the discharge capacity is also increased.

FIG. 6 shows the relationship between the amount of polybutylene terephthalate resin added as a binder and the strength of the positive electrode plate.

As is clear from FIG. 6, when the amount of polybutylene terephthalate resin added is 5% by weight or more of CL, the plate strength exceeds 100y.

Incidentally, the strength of the main plate of comparative battery C is about 80P.

On the other hand, FIG. 7 shows the relationship between the amount of polybutylene terephthalate resin added and the discharge time of the battery. The discharge conditions are a temperature of 23°C, a load of 12 ohms, and a discharge end voltage of 2. It was Ov.

As is clear from FIG. 7, when the amount of polybutylene terephthalate resin added is 5.0% by weight or more, the discharge time becomes shorter. This is considered to be because the amount of active material decreases as the binder increases, and the permeability of the electrolyte into the electrode decreases due to the film-forming action of the binder.

Therefore, it can be seen from FIGS. 6 and 7 that the addition 1 of polybutylene terephthalate resin is preferably in the range of 0.5 to 5.0% by weight.

(g) Effects of the invention As mentioned above, by using a thermoplastic polyester resin as a binder for the positive electrode of a non-aqueous electrolyte battery, a) the strength of the diaphragm can be increased with a small amount of binder, so the discharge capacity can be increased; This is useful for increasing the amount of carbon and making ultra-thin electrode plates.

b. Since it is stable even at high temperatures, there is no generation of impurities due to thermal decomposition, and an increase in internal resistance can be suppressed.

It has the following effects, and its industrial value is extremely large.

[Brief explanation of the drawings] Figures 1 and 5 are discharge characteristic comparison diagrams of the present invention battery and comparative battery, and Figures 2 and 6 are diagrams of the relationship between the amount of binder added and the strength of the positive electrode plate. FIG. 6 is a schematic cross-sectional view of the positive electrode plate strength measuring device, and FIGS. 4 and 7 are diagrams showing the relationship between the amount of binder added and the discharge time. (1) Mold, (2) Small diameter hole, (3)
...Large diameter hole, (4)...Positive electrode, (Death...Punch,
Prisoner ■...Battery of the present invention, 0...ratio! 1121iC pond.

Claims (3)

[Claims] (1) Comprising a negative electrode using a light metal such as lithium or sodium as an active material, a positive electrode using a metal oxide, sulfide, or halide as an active material, and a non-aqueous electrolyte, which is used as a binder for the positive electrode. A nonaqueous electrolyte battery characterized by using thermoplastic polyester resin. (2) The nonaqueous electrolyte battery according to claim (1), wherein the thermoplastic polyester resin is a polyethylene terephthalate resin or a polybutylene terephthalate resin. (3) The nonaqueous electrolyte battery according to claim 2, wherein the amount of the thermoplastic polyester resin added is 0.5 to 5.0% by weight based on the positive electrode.