JPS60240060A - Nonaqueous solvent cell - Google Patents

Abstract

PURPOSE:To improve the mechanical strength of the porous carbon body of a positive electrode and dissolve cell failures due to the fragility of the carbon body. CONSTITUTION:Melamine resin, phenol resin, polyamide resin, chlorinated polypropylene resin, chlorinated polyethylene resin, vinyl acetate resin, vinyl chloride resin, and vinyl chloride-vinyl acetate copolymer can be used as a high molecular compound to be solved in a liquid oxyhalogenide. A porous carbon body molded with a binding agent used jointly with such a high molecular copolymer holds a positive electrode via the binding action of only polytetrafluoroethylene, because the high molecular compound in the porous carbon body is solvent in the liquid oxyhalogenide after a cell is assembled. As a result, the absorption of the volume expansion due to the discharge reaction of the positive electrode is not entirely impeded owing to the spider web-like fiber-forming action of polytetrafluoroethylene, thereby the positive electrode utilization factor can be prevented from being decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a non-aqueous solvent battery, and particularly to a non-aqueous solvent battery in which the binder of the positive electrode is improved.

[Technical background of the invention and its problems]

In recent years, lithium-thionyl chloride-based non-aqueous solvent batteries have attracted attention as batteries with high energy density and excellent long-term storage characteristics. The most important feature of such batteries is that they use a liquid oxylognide such as thionyl chloride as the positive electrode active material, and stains are eliminated by electrochemical reduction of the liquid active material on the porous positive electrode surface. The reaction progresses.

Generally, a cylindrical lithium/thionyl chloride-based non-aqueous solvent battery has a lithium negative electrode arranged inside the can, and a metal current collector such as a wire mesh placed inside the negative electrode through a mother plate. It has a structure in which it houses a positive electrode made of a porous carbon body in which ions are contained, and the positive electrode is impregnated with an electrolytic solution containing thionyl chloride as a main component and which also serves as a positive electrode active material.

In a battery having such a structure, the p-cell discharge characteristics are greatly influenced by the characteristics of the positive electrode, and the catalytic activity of the positive electrode active material with respect to the reaction responsible for electrification, porosity, electrical conductivity, etc. are important factors.

By the way, as the porous carbon material of the positive electrode of the above-mentioned cylindrical battery, cyacetylene brane has conventionally been used.

Polytetrafluoroethylene is added as a binder to carbon black such as carbon black, kneaded, and then molded into a predetermined shape.

When viewed microscopically, such a porous carbon body of the positive electrode has the following characteristics:
Carbon plastic particles are trapped in the polytetrafluoroethylene fibers shaped like six webs), and discharge products from the positive electrode reaction are precipitated between the carbon black particles. It acts to smoothly and uniformly absorb the volumetric expansion of the positive electrode that sometimes occurs, contributing to improving the utilization rate of the positive electrode.The bonding method of this "spider-like" fiber formation is based on polytetrafluoroethylene bonding. This is the agent's greatest feature, and cannot be achieved with other binders. Polytetrafluoroethylene also has extremely excellent durability against liquid oxyhalodanides.

However, nine-carden black bound with polytetrafluoroethylene does not form a strong solid, but is a clay-like semi-solid, and a porous material obtained by forming it into a predetermined shape by press molding etc. Carbon bodies are extremely fragile. For this reason, when assembling a battery in which a metal current collector is embedded in the porous carbon body and loaded into a case as a positive electrode, defects such as cracks and chips may occur in the porous carbon body after the battery is assembled. The mechanical impact may cause it to separate from the metal current collector or cause poor adhesion to the separator.

As a result, in a battery having such a positive electrode, the discharge voltage may drop irregularly, and in the worst case, an internal short circuit may occur.

[Purpose of the invention]

The present invention aims to eliminate battery defects caused by weak mechanical strength in the porous carbon body of the positive electrode, and to provide a non-aqueous solvent battery with excellent discharge voltage stability and heavy load characteristics. .

[Summary of the invention]

The present invention uses a mixture of polytetrafluoroethylene as a binder for carbon black, which is the main material of the porous carbon body of the positive electrode, and a polymer compound that is dissolved in a liquid oxyhalodanide that also serves as the positive electrode active material of the electrolytic solution. The main points are as follows. A porous carbon body formed using a binder containing such a polymer compound in combination with a binder containing such a polymer compound dissolves in the liquid oxyhalodanide after the battery is assembled. In the porous carbon body, the positive electrode is held by the binding action of polytetrafluoroethylene alone. As a result, the absorption of the volumetric expansion accompanying the discharge reaction of the positive electrode due to the "spider-like" fiber-forming effect of polytetrafluoroethylene is not inhibited at all, so that a decrease in the positive electrode utilization rate can be prevented.

In addition, since the porous carbon material can be firmly solidified, it not only makes handling easier during the positive electrode manufacturing process and battery assembly, but also improves the adhesion and shape retention of the metal current collector, which in turn improves the battery The stability of the discharge voltage is improved, and the voltage during heavy load discharge can also be improved. Although the use of a polymer compound that is insoluble in liquid oxyhalodanide facilitates handling during the positive electrode manufacturing process and battery assembly, even after battery assembly, polytetrafluorocarbon, which is another binder, may be used as the polymer compound. The polymer compound remains in the 6-web-shaped fibers of ethylene, and the absorption effect of the volume expansion of the porous carbon material due to the "spider-web shape" is inhibited, so the positive electrode cannot be used as described above. Good rate - ph
It becomes difficult to achieve u.

Examples of the polymer compound include melamine resin, phenol resin, polyamide resin, chlorinated polypropylene resin, chlorinated polyethylene resin, vinyl acetate resin, vinyl chloride resin, vinyl chloride-vinyl acetate copolymer, and the like. 4? Polyamide resins, chlorinated polyzolopyrene resins, and chlorinated polyethylene resins are effective because they have excellent binding properties to carbon black, have good solubility in liquid oxyhalides, and are difficult to decompose by liquid oxyhalides. It is. In addition, by dissolving these resins and vinyl polymers such as vinyl acetate resin in liquid oxyhalide,
This is useful because it has the effect of suppressing the formation of a LiC2 film on the surface of the lithium negative electrode, which causes a voltage drop during initial large current discharge.

It is desirable that the blending ratio of the above-mentioned polymer compound is in the range of 5 to 20% by weight relative to car black. The reason for this is that if the blending ratio is less than 5% by weight, the shape retention and strength of the porous carbon body will be insufficient; A polymer compound is generated and suspended, which may reduce the porosity of the porous carbon body and adversely affect the discharge performance.

[Embodiments of the invention]

Hereinafter, an example in which the present invention is applied to a AA type lithium/thionyl chloride battery will be described with reference to FIG.

Reference numeral 1 in the figure is a bottomed cylindrical can made of stainless steel, for example, with an open top that also serves as a negative electrode terminal. A cylindrical negative electrode 2 made of metallic lithium is crimped onto the inner surface of the can 1. A positive electrode 3 is placed inside the can 1 inside the negative electrode 2.
It is provided via a seven-layer plate 4 made of glass fiber non-woven fabric arranged on the inner surface. Note that an insulating paper 5 is interposed between the positive electrode 3 and the bottom surface of the can body 1. The positive electrode 3
It is composed of a cylindrical porous carbon body 6 and a metal current collector 7 made of a cylindrical wire mesh placed inside the hollow part of the porous carbon body 6. The positive electrode 3 was prepared by adding 7% by weight of polytetrafluoroethylene (trade name: Teflon, manufactured by Mitsui Fluorochemical Co., Ltd.) to commercially available acetylene black, and dissolving 8% by weight of commercially available nylon-6 in the mixture in acetone. After adding the solution and kneading, it is press-formed to a length of 38111% (outer diameter 11.5 m +) inner diameter 5I.
It was made by inserting a 40 m long nickel mesh (40 meshes) cylindrical metal current collector into the hollow part of III11, pressing it together, and drying and solidifying it at 100°C for 12 hours. It is.

Further, in the can body 1 above the positive electrode 3, an insulating paper 8 supported by the mono 4 plater 4 and having a hole in the center is disposed. A metal trough f9 is sealed to the upper opening of the can body 1 by Rede welding or the like. This metal top 9
A hole 10 is opened in the center of the hole 1o. An isometric positive electrode terminal 11 is fixed to the metal terminal 9 by a glass sealing material 12 in an electrically insulated state. This positive electrode terminal 11 is connected to the metal current collector 7 of the positive electrode 3 via a lead wire 13 attached to its lower end. Furthermore, an electrolytic solution 14 injected from the tube-shaped positive electrode terminal 11 is housed in the can body 1 .

This electrolytic solution 14 contains, for example, 1.5 mol/LtAtCt4.
It consists of thionyl chloride (5oct2) dissolved in In addition, an enclosure 15 made of stainless steel, for example, is inserted into the pipe-shaped positive terminal 11, and the hole in the positive terminal 11 is opened in order to laser weld the tip of the terminal 11 and the inserted enclosure 15. It is sealed.

Comparative Example: 7% by weight of polytetrafluoroethylene was added to commercially available acetylene black, and only acetylene containing no nylon-6 was added to the mixture, kneaded, and then molded into a knot shape in the same manner as in the example. A cylindrical metal current collector was inserted and pressed into the hollow part of the body, and further dried and solidified at 100° C. for 12 hours to prepare a positive electrode. Using these positive electrodes, a battery with the same structure as the example was assembled.

Therefore, regarding the present example and comparative example, the number of defects such as cracks and chips in the positive electrode (porous carbon body) during the assembly process such as loading the positive electrode into the can body, and the number of defects such as cracks and chips as shown in Fig. 2 were 3000. As shown in the discharge curve under load, the number of batteries such as a good product (B) and a defective product (B) that did not maintain a flat voltage at the end of discharge was investigated. The results are shown in the table below.

-10~ Also, the heavy load discharge characteristics of the batteries of this example and comparative example were investigated. These results are shown in FIG. Note that A in the figure 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 the above table and FIG. 3, the battery of the present invention has extremely fewer cracks and chips in the porous carbon material of the positive electrode than conventional batteries, and is also superior in terms of discharge voltage stability and heavy load characteristics. I know that there is.

〔Effect of the invention〕

As detailed above, according to the present invention, it is possible to improve the mechanical strength of the porous carbon body of the positive electrode, thereby solving battery failures caused by the brittleness of the carbon body, and furthermore, it is possible to improve the stability of the discharge voltage and the heavy load characteristics. It is possible to provide a non-aqueous solvent battery.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a lithium-thionyl chloride dissociator showing an example of the present invention, and FIG. 2 is a diagram showing changes in discharge voltage over time in a lithium-thionyl chloride battery.
FIG. 3 is a diagram showing heavy load discharge characteristics. 1... Can body, 2... Negative electrode, 3... Positive electrode, 6...
Porous carbon body, 7... Metal current collector, 9... Metal dog, 11... 9 Ig-shaped positive electrode terminal, 14... Electrolyte solution. Applicant's representative Patent attorney Takehiko Suzue Figure 1 5 Figure 2 Discharge special grade time opening (hr)

Claims (2)

[Claims] (1) Consisting of a negative electrode made of a light metal, a positive electrode mainly composed of porous carbon bound with a binder, and an electrolytic solution mainly composed of a liquid oxyhalodanide, which also serves as the positive electrode active material. A non-aqueous solvent battery, characterized in that the binder 6 of the positive electrode is a mixture of /IJ tetrafluoroethylene and a polymer compound soluble in the liquid oxyhalodanide. (2) The polymer compound according to claim 1, wherein the polymer compound is at least one selected from polyamide P resin, chlorinated polypropylene resin, and chlorinated polyethylene resin. Water solvent battery.