JPH0298044A - Organic solvent battery - Google Patents

Abstract

PURPOSE:To enhance storage performance and to stabilize performance by forming a layer comprising a mixture of at least one selected from metallic powder which is inactive against a positive mix and conductive ceramic powder, and SiO2 in the contact area of a positive current collector with a positive mix. CONSTITUTION:A layer 4a comprising a mixture of at least one selected from metallic powder which is inactive against a positive mix and conductive ceramic powder, and SiO2 is formed in the contact area of a positive current collector 4 with a positive mix 2. As the metallic powder, Ag powder, Ti powder, Au powder, or powder of stainless steel such as SUS 304, SUS 447JI, and SUS XMZ7 is used. As the conductive ceramic powder, TiN powder, TiC powder, or SiC powder is used.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an organic solvent battery, and more particularly to an organic solvent battery with excellent storage characteristics.

(Prior Art) Organic solvent batteries are attracting attention because they have a high discharge voltage, a large energy density, little deterioration of characteristics during storage, and a wide operating temperature range. An example of the structure of the battery is shown in FIG. 3 as a longitudinal sectional view.

In FIG. 3, 1 is a negative electrode active material, such as Li, N
a. It is composed of a foil body of a light metal such as an alkali metal such as Mg or an alkaline earth metal. Reference numeral 2 is a positive electrode mixture, in which a mixture is prepared by mixing a positive electrode active material such as calcined manganese dioxide powder, a conductive material such as graphite powder, and a binder such as polytetrafluoroethylene in a predetermined ratio. It is molded into a shape (for example, pellet shape). 3 is a separator made of a nonwoven fabric made of polypropylene or polyethylene, which is interposed between the negative electrode active material 1 and the positive electrode mixture 2; It is impregnated and held in a non-aqueous electrolyte solution in which the electrolyte is dissolved in a non-aqueous solvent such as propylene carbonate or dimethoxyethane to a predetermined concentration. These three are usually called power generation elements.

Reference numeral 4 denotes a positive electrode container, in which the power generating element is housed with its positive electrode mixture 2 facing down. Therefore, the positive electrode mixture 2 and the bottom surface of the positive electrode container 4 are in direct contact, and the positive electrode container 4 itself also functions as a positive electrode current collector. Such cathode containers are typically constructed from materials such as AJ2, Ni, Fe, Cu, and stainless steel.

A negative electrode container 5 is attached to the negative electrode active material 1 and also serves as a negative electrode current collector. The peripheral edge of the negative electrode container 5 is press-fitted into an electrically insulating backing 6, and the upper open end of the positive electrode container 4 is further bent inward to encapsulate the entire power generating element in a liquid-tight manner.

However, the following problems occur in the organic solvent battery having the above structure during its storage process. This problem is caused by the fact that the positive electrode mixture is in direct contact with the positive electrode container. That is, in the battery storage process.

Due to the action of the electrolyte that has permeated into the positive electrode mixture, the positive electrode container gradually dissolves, and in extreme cases, a hole may form in the container, and even if there is no hole, a nonconducting layer may form on the surface of the positive electrode container. It occurs.

When a nonconductor layer is formed on the surface of the positive electrode container, the contact resistance between the positive electrode container, which is also a positive electrode current collector, and the positive electrode mixture increases, and the drop in discharge voltage during battery discharge becomes severe.

On the other hand, metal ions generated as the cathode container dissolves move toward the anode in the electrolyte to promote dissolution of the anode active material, and at the same time, they precipitate on the surface of the anode active material, resulting in the dissolution of the anode. This causes activation of the battery, resulting in a non-functional state of the battery.

In order to solve these problems, various methods have been proposed. For example, Japanese Patent Laid-Open No. 50-91719 discloses a method in which chlorosulfonated polyethylene and carbon black are mixed with toluene and then added thereto. Tribasic lead maleate was added as a sulfurizing agent, and the resulting solution was applied to an expanded metal made of Ti, and the whole was heated to promote vulcanization and hardening of the resin polymer, and carbon black was attached to the surface. A method of manufacturing a positive electrode current collector, or a method of spraying colloidal carbon onto an expanded metal and then drying the expanded metal at 50 to 60° C. to form a positive electrode current collector is disclosed.

Further, JP-A-50-138341 discloses a method in which a positive electrode current collector is immersed in a 20% aqueous solution of colloidal carbon and then dried at 80° C. for 2 hours to coat the surface with carbon.

(Problem to be Solved by the Invention) However, since pinholes inevitably exist in the carbon coating layer formed by the above method, during the storage process, the positive electrode container gradually forms through these pinholes. In addition, in the former method, since the binder is an organic compound, the binder swells and dissolves in the organic non-aqueous electrolyte during storage of the battery, which deteriorates the battery characteristics. gives rise to the problem of instability.

The present invention solves the above problems and includes a positive electrode current collector that does not dissolve in the electrolyte and therefore does not form a nonconducting layer on its surface even during the storage process. The purpose of the present invention is to provide an organic solvent battery that has excellent storage characteristics and stable battery characteristics.

[Structure of the Invention] (Means for Solving the Problems) The present inventor has formed a coating layer on the surface of the positive electrode container (positive electrode current collector) that comes into contact with the positive electrode mixture to prevent the positive electrode current collector from dissolving. As a result of extensive research on effective coating layers, we discovered that the layer described below has no pinholes and is highly stable, and the organic solvent battery of the present invention incorporates this fact. We have come to develop this.

That is, the organic solvent battery of the present invention includes a mixture of silicon dioxide (Sin, It is characterized by comprising a positive electrode current collector on which a coating layer consisting of is formed.

The structure of the battery of the present invention is different from that shown in FIG. 3, except that a coating layer, which will be described later, is formed on at least the portion of the positive electrode container (positive electrode current collector) that comes into contact with the positive electrode mixture. A specific example of this is shown in Figure 1.

Numbers in the figures represent the same elements as in Figure 3.
4a is a coating layer that characterizes the battery of the present invention. This coating layer 4a is required to be formed on at least a portion of the positive electrode container (positive electrode current collector) 4 that contacts the positive electrode mixture 2, but for example, it may extend to a portion that contacts the backing 6. There is no inconvenience.

Now, this coating layer 4a is made of one or both of metal powder and conductive ceramics that are inert to the positive electrode mixture.
It is composed of two types of mixtures with S i Om. Here, the metal powders include Ag powder, Ti powder, Au powder, 5U powder,
S304.5US447J1. Stainless steel copper powder such as SUSXM2T can be used. These metal powders may be used alone or in an appropriate combination as a mixed powder. Examples of the conductive ceramic powder include TiN powder, TiC powder, and SiC powder. Each of these powders may be used alone or may be used in an appropriate combination as a mixed powder.

5iO= is generated and mixed in the coating layer when the coating layer is formed by the method described below.

The mixing ratio of the powder and 5ins in the formed coating layer is preferably 40 to 80% by weight, more preferably 50 to 70% by weight. If it is too small, the conductivity of the coating layer will decrease and the discharge characteristics of the battery will deteriorate, and if it is too large, the amount of SiO□ will decrease, causing the problem of peeling of the coating layer and poor conductivity. be. Further, the thickness of the coating layer is preferably 7 to 30 F, more preferably 10 to 25 F, from the viewpoint of not reducing the volume of the positive electrode mixture and preventing dissolution of the positive electrode container.

Such a covering layer can be formed as follows. That is, first, when heated under the conditions described later, the compound to be thermally decomposed and added to S i O* is dissolved in a solvent. Compounds used at this time include, for example, tetraethoxysilane (St(QCs Ha ) 4), ethyltriethoxysilane (C* Hs Si (OC
i Hs) s), diethyljethoxysilane (
(CzHs)sSi(OC-Hs)*), tetramethylsilicate (Si(OCR,)-), tetraphenylsilicate ((CaHsO)-Si
) can be mentioned. Further, the solvent may be any solvent as long as it can dissolve the above compound, and examples thereof include isopropyl alcohol, ethyl alcohol, methyl alcohol, and butyl alcohol.

Next, a predetermined amount of the metal powder and/or conductive ceramic powder described above is added thereto, and the whole is sufficiently mixed to prepare a slurry having a predetermined viscosity.

At this time, the amount of each used is selected so as to achieve the mixing ratio as described above when forming the coating layer.

Specifically, compound 10, which is thermally decomposed and converted to 5ins
It is preferable that the amount of the solvent is 50 to 400 parts by weight and the amount of the conductive powder is 20 to 400 parts by weight relative to 0 parts by weight.

The prepared slurry is applied to a predetermined portion of the positive electrode container (positive electrode current collector) 4, such as the bottom surface of the container, to a predetermined thickness.

As the coating method, for example, a stamping coating method or a spray coating method can be applied.

Finally, the positive electrode container (positive electrode current collector) is subjected to heat treatment.
It is necessary to carry out the process under conditions such that it remains as iO
It is preferable that it is 30 minutes.

In this way, a positive electrode container (positive electrode current collector) having a coating layer according to the present invention formed in a predetermined portion is manufactured, and by storing a power generating element and the like therein, an organic solvent battery of the present invention can be obtained.

(Examples of the Invention) Example 1 80 parts by weight of isopropyl alcohol was added to 20 parts by weight of tetraethoxysilane, and further, an average particle size of 10F was added to 20 parts by weight of tetraethoxysilane.
5 parts by weight of 5US304 powder was added and the whole was thoroughly mixed.

The obtained slurry was applied to the bottom surface of the positive electrode container 2 made of 5US304 shown in FIG. 1, and then heated at a temperature of about 120° C. for about 30 minutes. A coating layer 4a having a thickness of 15 units was formed. In this coating layer, 5US304 powder and SiO
The mixing ratio with * was 46:52 by weight.

Afterwards, the power generation elements were housed here. The positive electrode mixture was formed by molding 0.4 g of a mixture of 90 parts by weight of calcined manganese dioxide, 10 parts by weight of graphite powder, and 3 parts by weight of polytetrafluoroethylene into a pellet with a diameter of 15 mm and a thickness of 0.7 mm. It is Li foil. The electrolyte was a mixed solvent of propylene carbonate and dimethoxyethane (volume ratio, 1:1) containing lithium perchlorate at a concentration of 1 mol/l.
It was dissolved to give I2. The separator was a nonwoven fabric made of polypropylene.

A negative electrode container 5 made of 5US304 was capped, and the upper opening line of the positive electrode container 4 was bent inward through a polypropylene backing 6 to seal the whole to obtain a battery of the present invention.

Example 2 A coating layer 4a having a thickness of 20 layers was formed in the same manner as in Example 1, except that 5 parts by weight of TiN powder with the same average particle size was used instead of SUS304 powder. The battery of the present invention was assembled in the same manner. TiN and 5i in the coating layer
The ratio with ns is 46:52 by weight.

Example 3 Instead of 5 parts by weight of 5US304 powder with an average particle size of 10, 3 parts by weight of 5US304 powder with an average particle size of 10 and an average particle size of 10
A coating layer 4a having a thickness of 10 μm was formed in the same manner as in Example 1, except that a mixed powder of F and 2 parts by weight of TiC was used. 5US304 powder, TiC and S in the coating layer 4a
The mixing ratio with iO□ was 28:18:52 by weight. A battery of the present invention was assembled in the same manner as in Example 1.

Comparative Example Colloidal carbon (trade name: Hitazol GA-37D, manufactured by Hitachi Metals Jisan Co., Ltd.) was applied to the bottom of a positive electrode container to form a 3F thick coating layer. A battery was assembled in the same manner as in Example 1.

The discharge characteristics of the above four types of batteries immediately after assembly were measured. The discharge conditions at this time were a temperature of 20°C,
15 is a constant resistance of Ω.

Next, after storing these batteries for 100 days in a constant temperature bath at a temperature of 60°C and a relative humidity of 50%, the discharge characteristics were measured under the same discharge conditions as above.The results of 0 or more were shown in Figure 6 in Figure 2. , the solid line is the characteristic curve immediately after production, and the broken line is the characteristic curve after storage.

[Effects of the Invention] As is clear from the above description, the characteristics of the battery of the present invention do not deteriorate even after long-term storage compared to the comparative battery.

This is because the battery of the present invention has the above-mentioned coating layer formed on the portion of the positive electrode container (positive electrode current collector) that comes into contact with the positive electrode mixture. That is, in the coating layer according to the present invention, the 5i0 particles, which are stable to the electrolyte, function as a binder that binds the metal powder or conductive ceramic powder to the positive electrode container (positive electrode current collector), and therefore, the electrolyte Even if the binder comes into contact with the electrolyte, the binding material will not dissolve in the electrolyte and cause defects such as pinholes in the coating layer, and as a result, the dissolution of the positive electrode container (positive electrode current collector) or the formation of a non-conducting layer will be prevented. Because it does.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the battery of the present invention. FIG. 2 is a diagram showing the discharge characteristics of the example battery and the comparative example battery before and after storage. FIG. 3 is a longitudinal sectional view of a battery with a conventional structure. 1 - Negative electrode active material 2 - Positive electrode mixture 3 - Separator 4 - Positive electrode container 4a - Covering layer 5 - Negative electrode container 6 - Packing diagram

Claims (1)

[Claims] A positive electrode current collector is provided with a coating layer made of a mixture of silicon dioxide and at least one kind of metal powder or conductive ceramic powder that is inert to the positive electrode mixture, at least in a portion that contacts the positive electrode mixture. An organic solvent battery comprising: