JPH028421B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a positive electrode for a non-aqueous battery using an organic solvent as an electrolyte, and its object is to provide a non-aqueous electrolyte battery with good discharge characteristics.

As a primary battery that uses a non-aqueous electrolyte, an alkali metal such as lithium or sodium is used as the negative electrode active material, and a metal oxide, sulfide, chloride, or halogenated carbon compound is used as the positive electrode active material. Propylene carbonate, γ-butyl lactone,
Some use a solution in which an inorganic salt such as lithium perchlorate, lithium aluminum chloride, or lithium borofluoride is dissolved in an organic solvent such as 1,2-dimethoxyethane. These batteries are known to have a number of advantages, such as high battery voltage, high energy density, and low self-discharge. Primary batteries using carbon fluoride or manganese dioxide as specific positive electrode active materials have been put into practical use. In recent years, there has been a great deal of interest in non-aqueous electrolyte secondary batteries. Recently, non-aqueous electrolyte secondary batteries using chalcogen compounds of transition metals as positive electrode active materials have been proposed, and some have been put into practical use, such as lithium secondary batteries using titanium dioxide as positive electrode active materials. There are some things.

The positive electrode of a non-aqueous electrolyte battery as described above is constructed by mixing a positive electrode active material with a conductive agent and a binder, and press-molding the mixture onto a current collector (electrode core) such as stainless steel net, or It is constructed by making a paste of a mixture of a positive electrode active material, a conductive agent, and a binder, applying it to the current collector, and drying (press molding as appropriate).

The binder conventionally used as a binder for positive electrodes with such a structure is a high-molecular organic compound, and its melting point is generally around 300°C, so such high-temperature treatment is not required to bind it. It will not harden if heat treated at lower temperatures. Furthermore, many polymeric compounds with low melting points dissolve in the organic solvent of the electrolytic solution, and are therefore not suitable.

Furthermore, the conventional positive electrode using a polymeric organic compound binder has a problem of poor compatibility with the electrolytic solution and poor discharge characteristics, especially at high current densities.

This invention has been made to solve these problems. Thus, according to the present invention, there is provided a positive electrode for a non-aqueous electrolyte battery, which is formed by coating a current collector with a paste containing a positive electrode active material, a conductive agent, and a binder as main components, wherein the binder is A positive electrode for a non-aqueous electrolyte battery is provided, which is characterized by being a phosphate-based heat-resistant inorganic adhesive.

The phosphate-based heat-resistant inorganic adhesive in this invention is made by dissolving or dispersing an acidic metal phosphate such as an acid salt of phosphoric acid such as aluminum, magnesium, or calcium in water.
It contains a curing agent, a heat-resistant pigment, a dispersion stabilizer, etc. as appropriate. These acidic metal phosphates undergo dehydration condensation and hardening upon heating, thereby achieving binding.

Incidentally, aggregate such as aluminosilicate may be added to this binder in order to improve heat resistance and adhesive performance.

Such a phosphate-based heat-resistant inorganic adhesive is easily available under the name Aron Ceramic (trade name of Toagosei Kagaku Co., Ltd.).

The heat-resistant inorganic adhesive (binder) is mixed with a positive electrode active material and a conductive agent used in the field,
It is made into a paste by adding water as appropriate. On this occasion,
For example, a small amount of polyvinyl alcohol may be added as a viscosity modifier.

This paste is then applied to a current collector used in the field and subjected to heat treatment.

At this time, the heat-resistant inorganic adhesive is cured by maintaining a temperature of 150° C. or higher for about 1 hour, so it is convenient for manufacturing because it does not require high temperatures unlike conventional polymer binders. Therefore, even when press molding a positive electrode, for example, the molded product can be cured simply by setting the molded product to an arbitrary temperature of 150° C. or higher.

The positive electrode of the present invention thus obtained has high mechanical strength and good compatibility with the electrolyte.
It has been found that the liquid content is higher, the battery voltage is higher than that of batteries using conventional positive electrodes, and the increase in internal resistance accompanying discharge is small, resulting in stable discharge characteristics. In particular, the present invention provides a non-aqueous electrolyte battery that exhibits excellent discharge characteristics and is suitable for high-rate discharge.

Hereinafter, this invention will be explained in more detail with reference to Examples.

Example 1 90 parts by weight of positive electrode active material powder obtained by heat-treating commercially available manganese dioxide in air, 6 parts by weight of acetylene black as a conductive agent, and a phosphate-based heat-resistant inorganic adhesive as a binder (Aron Ceramic D: Toagosei Chemical Co., Ltd.) Approximately 500 g of water was added to 2 kg of a composition obtained by mixing 4 parts by weight of 4 parts by weight of 4 parts by weight of 2 kg of water (manufactured by Co., Ltd.) to make a paste. This paste was applied to a current collector (stainless steel net), and after drying, it was punched into a predetermined shape. Thereafter, heat treatment was performed at about 200° C. in a vacuum atmosphere for the purpose of removing moisture and binding, to obtain a positive electrode of the present invention.

Example 2 90 parts by weight of positive electrode active material powder obtained by heat-treating commercially available manganese dioxide in air, 6 parts by weight of acetylene black as a conductive agent, and 3 parts by weight of a phosphate-based heat-resistant adhesive (same as in Example 1) as a binder. and 1 part by weight of polyvinyl alcohol powder, and add about 500 g of water to 2 kg of this composition to form a paste.
The paste was applied to a current collector, dried, and then punched into a predetermined shape. This was air-treated at 250°C for 1 hour to decompose the polyvinyl alcohol, and then heat-treated at about 200°C in a vacuum atmosphere to obtain the positive electrode of the present invention.

The positive electrode obtained in the above example, the negative electrode pressed onto a negative electrode cap punched from metallic lithium, and an electrolytic solution containing 1 mole of lithium perchlorate dissolved in an organic mixed solvent of propylene carbonate and 1,2-dimethoxyethane. Battery A (Example 1) composed of
and 1K at 20°C using Battery B (Example 2)
The Ω constant load discharge characteristics were investigated. As a comparative example, a similar conventional battery C using a polymeric organic compound (polytetrafluoroethylene) as a binder added to the positive electrode was also investigated in the same manner.

These results are shown in FIG.

As is clear from the characteristic diagram, batteries A and B using the positive electrode of the present invention have improved battery characteristics when compared to battery C.

The reason for this is that conventional battery positive electrodes use polymeric organic compounds as binders.
The internal resistance increases as the discharge progresses due to poor compatibility with the electrolyte and low liquid content.
When a heat-resistant inorganic adhesive is used as a binder as in the battery of the present invention, it has good compatibility with the electrolyte, which increases the liquid content and suppresses an increase in internal resistance as discharge progresses. This is thought to be due to.

[Brief explanation of drawings]

FIG. 1 is a graph showing an example of the discharge characteristics of a specific example of a nonaqueous electrolyte battery using the positive electrode of the present invention, together with a comparative example.

Claims (1)

[Claims] 1 A positive electrode for a nonaqueous electrolyte battery formed by applying a paste containing a positive electrode active material, a conductive agent, and a binder as main components to a current collector, and the binder is a phosphate-based heat-resistant inorganic adhesive. A positive electrode for a non-aqueous electrolyte battery, characterized in that it is a positive electrode.