JPS59173970A - Manufacture of battery - Google Patents

Abstract

PURPOSE:To enable a liquid-holding member containing gel electrolyte to be manufacture in a short time successively by irradiating microwave on a gelling agent and electrolyte to turn them into a gel or a solid. CONSTITUTION:After the amount of electrolyte to be held by a nonwoven polypropylene fabric used as a base material is set, the amount of PMMA to be applied to the above nonwoven polypropylene fabric is calculated from the set amount and the specific gravity of the electrolyte. After the calculated amount of PMMA is weighed, it is dissolved in a proper amount of tetrahydrofuran or methyl ethyl ketone which is a good solvent for PMMA. After the base material coated with PMMA is put in a heat-resisting glass Petri dish, 45mul of the electrolyte is poured onto the base material and an upper lid is placed over the dish, then this is put in a microwave range having a frequency of 2,450MHz and an output of 600W before being subjected to microwave irradiation. As a result, a gel-like electrolyte is easily obtained since gamma-butyrolactone having a high boiling point is evaporated with difficulty. The thus obtained electrolyte layer 5 is combined with a sealing plate 1, a case 4, a polypropylene gasket 6 and the like, thereby constituting a battery.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention uses a light metal such as lithium as a negative electrode active material, and solidifies or gels the electrolyte with a polymer, or uses a polymer containing almost no solvent. The present invention relates to a method for producing a battery having an ion-conducting electrolyte consisting of an electrolyte (supporting salt) and an electrolyte (supporting salt), and particularly aims at solidifying these ion-conductors or improving the method for producing the solid electrolyte.

Conventional Structures and Problems Current small electronic devices often use power sources that use alkaline electrolytes, such as silver oxide batteries and alkaline manganese batteries. Alkaline electrolytes inherently have creep properties, and in addition, the potential of the battery has a synergistic effect electrochemically, making it extremely difficult to suppress leakage over a long period of time.
Reliability from this point of view is said to be 3 to 5 years at most.

On the other hand, ``IJ using organic electrolytes, which has recently been in the spotlight,''
Although lithium batteries have better leakage resistance than alkaline batteries, they cannot be said to be perfect.

Therefore, the present inventors have previously discovered a method of solidifying the electrolyte of an organic electrolyte battery using a light metal such as lithium as a negative electrode with a polymer, particularly polymethyl methacrylate or polyethyl methacrylate. If the electrolyte is solidified, the leakage resistance will be greatly improved, and the sealing of the small battery will become easier, or there is a possibility that the entire battery can be sealed with resin. Electronic devices also tend to consume less current, and the device life and battery life tend to be almost the same, so this slight decrease in ionic conductivity due to solidification hardly poses a problem.

There are several methods to solidify the electrolyte, but
Due to its solubility and stability in the electrolytic solution, such as high boiling point γ-butyrolactone (GBL) and propylene carbonate (PC), it is recommended to use polymethacrylic acid methylalcohol or polymethacrylate as described in 2. Ethyl acid is suitable;
The method used was to mix an electrolytic solution and a gelling agent and heat the mixture externally to form a gel.

When gelling a battery in this way, the positive electrode is molded with ultrafine gelling agent particles dispersed in the mixture, and when a predetermined amount of electrolyte is injected and impregnated, the molded body itself becomes saturated with electrolyte. Because of its holding power, even if it is installed as a battery,
The electrolyte does not ooze out and can naturally gel within the positive electrode during battery aging. However, in this state, the electrolyte necessary for discharge is insufficient, so it is necessary to make the positive electrode extremely porous or to provide a separate gel layer between the positive and negative electrodes that can hold the electrolyte. Until now, the following methods have been adopted. For example, JP-A-65-1o○
As disclosed in Japanese Patent Application No. 666, a gelling agent, methyl polymonometate mononolate, is applied in advance to a nonwoven fabric made of polypropylene or the like, and the fabric is punched out to a predetermined size. This is placed on a heat-exchanging glass petri dish, a predetermined amount of electrolyte is injected, the top of the dish is covered, and the dish is heated at a temperature of 90° C. for about 30 minutes to form a gelled liquid retaining material.

This is placed on the positive electrode and sealed during battery assembly, but the manufacturing process has the drawback of being very time consuming.

OBJECTS OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and to provide a method for continuously producing VCm with a liquid retaining material having an electrolyte that gels in a short period of time.

Structure of the Invention The present invention is characterized in that the gelling agent and the electrolytic solution are gelled or solidified by irradiation with microwaves.

In this regard, methods using microwave irradiation in the battery field include a method of producing dehydrated manganese dioxide for lithium batteries by directly dehydrating hydrated manganese dioxide, such as electrolytic manganese dioxide, by direct microwave irradiation (Japanese Patent Application Laid-Open No. 56 -500
61) and a method in which hydrated manganese dioxide is immersed in an organic solvent and irradiated with microwaves to dehydrate it (Japanese Patent Application Laid-open No. 75535/1983). Both methods work directly on the target water, dehydrating it by heating due to the frictional heat of water molecules.

The present inventors considered that the organic solvents used in lithium batteries, such as propylene carbonate and γ-butyrolactone, are dielectric substances and generate heat when irradiated with microwaves. Instead of the external heating method, which requires a long time, we succeeded in improving productivity by applying a short and efficient microwave irradiation method.

Description of examples FIG. 1 shows the coin-type battery used in the example.

In the figure, 1 is a sealing plate made of general-purpose stainless steel SUS 304 with a thickness of 0.20 mm, and 2 is an outer diameter of 14 m.
m, a lithium negative electrode with a thickness of 0.24 mm, and the negative electrode is press-bonded to the inner surface of the sealing plate 1. 3 is a positive electrode, 4 is a case made of stainless steel with a high chromium content, 6 is a positive electrode 3, 100 parts by weight of heptanoated graphite, 10 parts by weight of acetylene black, 5 parts by weight of styrene-butadiene rubber as a binder, and further gelled. Methyl methacrylate (hereinafter referred to as PM) as an agent
Fine particles (expressed by MA) (average particle size 0.07 mm)
1.05+ g of a mixture containing 11 parts by weight of
Form into a 55mm tissue and dry to form positive electrode case 4.
45 μl of electrolyte was injected into the tube.

fx o, 1 morph in γ-butyrolactone in the electrolyte
A solution containing 1 liter of lithium borofluoride was used.

In the above positive electrode, a gel-like electrolyte is formed from the electrolytic solution and PMMA after battery assembly. The mixing ratio of PMMA used here was calculated in advance from the amount of liquid absorbed by the pores in the positive electrode, and was set so that the amount of polymer PMMA in the gel electrolyte would be 17% by weight.

Reference numeral 5 denotes a gel electrolyte layer based on a polypropylene nonwoven fabric adsorbed between the positive and negative electrodes, and the amount of polymer in this layer is also set to be 17% by weight, similar to the positive electrode.

To explain the manufacturing method of this electrolyte layer 5, first, the amount of electrolyte to be held in the polypropylene non-woven fabric serving as the base material is set, and from this and the specific gravity of the electrolyte, the amount of PMMAO to be applied to the polypropylene non-woven fabric, which will be profitable, is calculated. Ru. Next, for example, this base material is cut into a size of 30 cm x 30 cm, and the amount of PMMA is calculated and weighed, and dissolved in an appropriate amount of tetrahydrofuran, methyl ethyl ketone, etc., which are good solvents for PMMAK.

Methods for applying PMMA to the base material 113 include the rotary printing method, the spraying method, and the Caste method. ), the polypropylene nonwoven fabric is immersed therein, and the solvent is distilled off by heating or hot air to form a PMMA-coated irrigation system. This can be punched out to a predetermined size. Next, the base material coated with this PMMA was placed in a heat-resistant glass petri dish, 46μβ of the above electrolyte was poured onto it, the top of the petri dish was covered, and the plate was placed in a microwave oven with a frequency of 24501Hz and an output of soo. When stored and subjected to V microwave irradiation for about 1 minute, γ-butyrolactone, which has a high boiling point, is difficult to evaporate and a gel-like electrolyte can be easily obtained. How did you get the thickness o?
A battery is constructed by combining a 4 mm thick electrolyte layer 5 with the above sealing plate, case, and polypropylene gasket 6.

The battery thus obtained has a maximum outer diameter of 20. Omm, maximum total height 1
．． It is 6mm. Here, microwave irradiation was applied only when producing the gel electrolyte between the positive and negative electrodes, but the positive electrode after being impregnated with the electrolytic solution described above can also be gelled in the same manner.

Table 1 shows the internal resistance values of a battery A made using a gel electrolyte layer obtained by microwave irradiation and a battery A made using a gel electrolyte layer obtained by the conventional external heating method8 Table 1 Further, Table 2 shows the capacity (2V final) when these batteries were discharged at 30Ω at 20°C.

As is clear from the results in Table 2 and above, using microwave irradiation to produce a gel-like solidified electrolyte can significantly shorten the production time compared to the conventional method using external heating. In terms of characteristics, it has the same properties as conventional products. By devising the cavity inside the microwave oven that performs microwave irradiation, continuous production is possible in combination with a belt conveyor.

In the examples, lithium is used for the negative electrode, but a light metal such as sodium may be used.The electrolyte is not limited to γ-butyrolactone, but may also be propylene carbonate, and the supporting salt may also be lithium perchlorate or lithium trifluorosulfonate. good. The positive electrode may also be manganese dioxide, copper oxide, or the like.

The gelling agent polymer may also be polyacrylonitrile, polyvinyritine fluoride, etc. Here,
For example, polyethylene oxide or polypropylene oxide, which is obtained by distilling off acetonitrile or methanol, which has a low boiling point and is easily evaporated, from acetonitrile-polyethylene oxide or polypropylene oxide lithium borosulfate solution is used to produce a gel electrolyte. It can also be used for the production of thin film electrolytes of lithium satohufonide complexes.

Effects of the Invention As described above, according to the present invention, a battery using a gel-like solidified electrolyte or a solid polymer electrolyte can be easily manufactured.

[Brief explanation of the drawing]

The drawing is a longitudinal cross-sectional view of a battery used in an example. 2... Negative electrode, 3... Positive electrode, 6... Electrolyte layer.

Claims (1)

[Claims] A method for manufacturing a battery having a negative electrode using a light metal as an active material, a positive electrode, and a gel-like solidified electrolyte made of a polymer or a solid polymer electrolyte, the method comprising heating a mixture of an organic solvent, a supporting salt, and a polymer with microwaves. A method for manufacturing a battery, comprising the step of gelling or solidifying an electrolytic solution by irradiating it.