JPH0265057A - Thin type battery - Google Patents

Abstract

PURPOSE:To suppress the decomposition of an electrolyte solvent on the surface of a metal oxide which is a positive electrode active material and prevent the occurrence of expansion at the time of storage at a high temperature by bringing a positive material black mix using the metal oxide as the active material into contact with the steam of 1,2-dimethoxyethane after heating and drying. CONSTITUTION:A separator 5 impregnated with a nonaqueous electrolyte using propylene carbonate as a solvent is inserted between a negative electrode pressed with a lithium metal 4 to a negative electrode terminal plate 3 and a positive electrode formed with a positive electrode black mix 2 using a metal oxide as a active material on a positive electrode terminal plate 1. Peripheries of the positive and negative electrode terminal plates 1 and 3 are sealed by an insulating seal body 6. To manufacture the positive electrode terminal plate 1, a positive electrode body made of manganese dioxide, graphite and polytetrafluoroethylene is formed on a steel plate, then it is dried for dehydration. The steel plate 11 formed with the positive electrode black mix 2 is sent to a processing chamber 12 of the dry atmosphere, and the steam 15 of 1,2-dimethoxyethane is brought into contact with the positive electrode black mix 2 to be absorbed by it. The decomposition of propylene carbonate on the surface of the metal oxide after a battery is constituted is thereby suppressed, and expansion can be suppressed at the time of storage at a high temperature.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to improvements in thin batteries.

[Background Art and Problems] As electronic devices have become smaller and thinner in recent years, batteries that serve as their power sources have also become smaller and thinner.

Among these, ultra-thin batteries with a thickness of 0.5 mm or less are in demand as power sources for card-type battery devices such as card-type calculators and IC cards.

By the way, the above-mentioned thin battery has a thickness of 0.
A negative electrode made of a pressure tube of lithium metal on a negative electrode terminal plate made of an annealed stainless steel plate or annealed nickel plate of 02 to 0.05a+, and a positive electrode terminal plate made of the same material as the negative electrode terminal plate, in which a metal oxide is used as an active material. A separator made of propylene nonwoven fabric impregnated with a nonaqueous electrolyte is interposed between the positive electrode and the positive electrode, which is formed by forming a positive electrode mixture consisting of a positive electrode mixture (for example, manganese dioxide, a conductive agent, and a binder). A structure having a thickness of 0.5 μm or less in which the periphery of the daughter plate is sealed with an insulating sealing body made of polynylefin resin is known.

The electrolyte used in the above battery is electrochemically stable and has lithium perchlorate dissolved as a supporting salt in an aprotic organic solvent such as propylene carbonate, which has a high boiling point of 241.7°C. It is used. Since this propylene carbonate has a high boiling point of 241.7°C, a separator containing the positive electrode mixture and electrolyte and lithium metal are placed between the positive terminal plate and the negative terminal plate, and the surrounding area is insulated in the form of a frame. Connect the positive and negative terminal plates 100 to 200' through the sealing body.
When heat-sealing with C, deterioration of battery performance due to evaporation of the electrolyte and swelling due to evaporation of the electrolyte when the battery is stored at high temperatures can be suppressed.

On the other hand, in normal batteries, 1,2-dimethoxyethane is added to propylene carbonate to increase the specific conductivity of the electrolyte.
It has been attempted to improve battery performance by containing 5% by volume. However, the boiling point of 1,2-jethoxymethane is 84
．． Since the temperature is as low as 7°C, the addition of 1,2-jethoxymethane is inappropriate for the thin battery which is subjected to heat treatment at 100 to 200°C during sealing, and carbonate is used exclusively as a solvent for the non-aqueous electrolyte. Only propylene is used.

However, although the propylene carbonate used as the solvent is 71i chemically stable, since it is an ester as shown in the structural formula below, the carbonyl group attracts electrons due to the electron isomerism effect, and the alkyl group Due to this effect, the electron density at the two carbon (C) positions that bond with oxygen (0), respectively, decreases because electrons are donated. For this reason, for example, in the presence of hydroxide ions, propylene carbonate undergoes alkaline hydrolysis due to a nucleophilic reaction between the hydroxide ions and propylene carbonate at the carbon position as shown in equation (1) below. ,5aadl and W, H,L
ee.

T, Chcra, Soc, (B), 19
Reported in 6B, 1.

CIl3-CIl-C1! □ From the above reports, propylene carbonate has problems such as being easily hydrolyzed in the presence of acids or alkalis, and decomposing and generating gas in the presence of certain solutes. In particular, the decomposition of the propylene carbonate is accelerated during high temperature storage.

If such gas generation becomes significant, not only will the battery expand and cause the thin battery to swell, but the decomposition products will reduce the battery performance, and furthermore, the liquid volume will decrease, making it impossible to discharge. Put it away.

The above-mentioned phenomenon becomes remarkable when a metal oxide such as manganese dioxide is used as the positive electrode active material. As a result of examining this cause, the following three points are predicted 71-j.

That is, ■ there are trace amounts of hydroxyl groups on the surface of the metal oxide,
The proportion varies depending on the type of metal oxide, but the hydroxyl group on the surface becomes an active proton under certain conditions, plays the role of a Brønsted acid, and decomposes propylene carbonate. ■ Adhesion on the metal oxide surface It is thought that water is involved and promotes the decomposition of propylene carbonate by releasing hydroxide ions, and (2) propylene carbonate is oxidized and decomposed by active oxygen on the surface of manganese dioxide.

The present invention was made to solve the above-mentioned conventional problems, and suppresses the decomposition of propylene carbonate, which is a solvent for an electrolytic solution, on the surface of a metal oxide, which is a positive electrode active material, after assembly, so that it can be stored at high temperatures. The purpose is to provide a high-performance, highly reliable thin battery that prevents the occurrence of swelling, etc.

[Means for Solving the Problems] The present invention provides a solution between a negative electrode formed by pressing lithium metal onto a negative terminal plate and a positive electrode formed by forming a positive electrode mixture containing a metal oxide as an active material on the positive terminal plate. In a thin battery having a structure in which the periphery of the positive and negative terminal plates is sealed with an insulating sealing body with a separator impregnated with a non-aqueous electrolyte consisting of at least one solute using propylene carbonate as a solvent, the metal The positive electrode mixture containing an oxide as an active material becomes 1,2- after heating and drying.
This is a thin battery characterized by being brought into contact with dimethoxyethane vapor.

Examples of the metal oxide as the active material include manganese dioxide, molybdenum trioxide, cobalt sesquioxide, tricobalt tetroxide, cupric oxide, bismuth sesmuth oxide, vanadium pentoxide, and trilead tetroxide. can.

When bringing the positive electrode mixture containing the above-mentioned metal oxide as an active material into contact with 1,2-dimethoxyethane, it is preferable to bring it into contact immediately after heating and drying in view of the functions and effects described below. 1.2-
It is desirable that the contact with dimethoxyethane be carried out for 10 minutes or more.

[Function] According to the present invention, by heating and drying a cathode mixture containing a metal oxide as an active material and then bringing it into contact with 1,2-dimethoxyethane vapor, propylene carbonate is released on the surface of the metal oxide after battery construction. It is possible to obtain a highly reliable, high-performance thin battery that suppresses decomposition and swelling during high-temperature storage. The effect of contact with 1,2-dimethoxyethane vapor is
D, N, ) is 20 and propylene carbonate (D, N, ;
This is thought to be due to the fact that it is higher than 15.1).

That is, when a metal oxide is brought into contact with vapor of 1,2-dimethoxyethane with a high N content, active protons that are easily released from hydroxyl groups on the surface of the metal oxide are reduced, and electrolysis by the surface hydroxyl groups occurs after battery construction. It has the effect of suppressing the decomposition of propylene carbonate in the liquid, and even when active oxygen on the oxide surface is a problem, 1,2-dimethoxyethane reduces the active oxygen, reducing the potential of the metal oxide surface after battery construction. This is thought to have the effect of suppressing the oxidative decomposition of propylene carbonate.

Note that since the 1,2-dimethoxyethane adsorbed on the surface of the metal oxide is a small amount in terms of volume, it does not have any adverse effect on the sealing process by thermal fusion of the positive and negative electrode terminal plates and the insulating sealing body.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

Embodiment FIG. 1 is a sectional view showing a thin battery. 1 in the diagram is
The positive terminal plate is made of 5US304 and has a thickness of 0.03 mm, and on this terminal plate 1 is a positive electrode composite made of manganese dioxide, graphite, and polytetrafluoroethylene that has been brought into contact with 1,2-dimethoxyethane vapor by the method described later. Agent 2 is formed. 3 in the figure is a negative electrode terminal plate made of 5US304 and having a thickness of 0.03 am, and a negative electrode sheet 4 made of metallic lithium is crimped onto this terminal plate 3. The positive and negative electrode terminal plates 1.3 are made of polypropylene impregnated with a non-aqueous electrolyte in which lithium perchlorate is dissolved in propylene carbonate at a concentration of 1 mole/no between the positive electrode mixture 2 and the negative electrode sheet 4. They are laminated with a separator 5 made of nonwoven fabric interposed therebetween. Further, a frame-shaped insulating sealing body 6 made of modified polypropylene is arranged between the positive and negative electrode terminal plates 1.3 so as to surround the positive electrode mixture 2, the separator 5, and the negative electrode sheet 4. The positive and negative terminal plates 1.
3 and an insulating sealing body 6 at 200° C., the positive electrode mixture 2, separator 5, and negative electrode sheet 4 are sealed to form a thin battery with a thickness of 0.5 mm.

To produce the positive terminal plate 1 having the positive electrode mixture 2 brought into contact with the 1,2-dimethoxyethane vapor, first, a positive electrode body having a composition of manganese dioxide, graphite, and polytetrafluoroethylene is formed to a thickness of 0.5 mm. After forming on a 03H 5US304 steel plate, it was dried at 250° C. for 5 hours for dehydration. Subsequently, as shown in FIG. 2, the steel plate 11 on which the positive electrode mixture 2 has been formed is transferred to a processing chamber 12 in a dry atmosphere with a relative humidity of 1% or less, and the steel plates 1 and 2 housed at the bottom of the processing chamber 12 are
- Dimethoxyethane liquid 13 was heated by heater 14 to generate steam 15, which was brought into contact with positive electrode mixture 2 and adsorbed. Thereafter, the steel plate 11 was taken out from the processing chamber 12 and punched into a predetermined shape to produce a positive terminal plate.

Comparative Example 1. A thin battery having the same configuration as in Example was assembled, except that a positive electrode mixture that was not brought into contact with 2-dimethoxyethane vapor was used.

Therefore, the thin batteries of this example and comparative example were each
The changes in the total height of the batteries (average value per 100 batteries) with respect to the number of days of storage when the batteries were manufactured individually and stored at 60° C. were investigated, and the characteristic diagram shown in FIG. 3 was obtained. In addition, A in FIG. 3 shows the characteristic line of the battery of this example, and B shows the characteristic line of the battery of the comparative example. As is clear from FIG. 3, it can be seen that the thin battery of this example has a smaller change in total battery height than the thin battery of the comparative example and is superior in high-temperature storage performance.

In addition to the electrolytic solution using propylene carbonate as an organic solvent, it is also applicable to electrolytic solutions using γ-butyrolactone or ethylene carbonate.

[Effects of the Invention] As detailed above, according to the present invention, after assembly, the decomposition of propylene carbonate, which is the solvent of the electrolytic solution, on the surface of the metal oxide, which is the positive electrode active material, is suppressed, and swelling during high-temperature storage is suppressed. It is possible to provide a high-performance, highly reliable thin battery that prevents the occurrence of damage, etc.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a thin battery according to an example of the present invention, and Figure 2 is an embodiment of a device used to contact and absorb 1,2-dimethquinethane vapor into the positive electrode mixture in this example. FIG. 3 is a characteristic diagram showing changes in total height with respect to the number of days of high-temperature storage of the thin batteries of the present example and comparative example. DESCRIPTION OF SYMBOLS 1... Positive electrode terminal plate, 2... Positive electrode mixture, 3... Negative electrode terminal plate, 4... Negative electrode sheet, 5... Separator, 6
...Insulating sealing body, 11...5US304 steel plate, 12
...Processing chamber, 13...1 2-diemeshikiethane liquid.

Claims (1)

[Claims] Between the negative electrode formed by pressing lithium metal onto the negative terminal plate and the positive electrode formed by forming a positive electrode mixture containing a metal oxide as an active material on the positive terminal plate, at least one solute is mixed with propylene carbonate as a solvent. In a thin battery having a structure in which the periphery of the positive and negative electrode terminal plates is sealed with an insulating sealant with a separator impregnated with a non-aqueous electrolyte interposed therebetween, the positive electrode mixture containing the metal oxide as the active material is heated and dried. A thin battery characterized in that it is subsequently brought into contact with vapor of 1,2-dimethoxyethane.