JP2632421B2 - Battery electrode - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a battery electrode, and more particularly, to a battery electrode containing a thermosetting resin as a binder.

(Related Art) In recent years, electronic devices have been remarkably reduced in size, thickness, and weight, and accordingly, there has been a great demand for smaller, thinner, and lighter batteries serving as power supplies.

Japanese Patent Application Laid-Open No. 60-170163 filed by the present applicant discloses a heat-treated product of an aromatic condensed polymer comprising carbon, hydrogen and oxygen, wherein the ratio of the number of hydrogen atoms to the number of carbon atoms is increased.
An insoluble infusible substrate having a polyacene-based skeletal structure having a specific surface area of 0.05 to 0.5 and a specific surface area of 600 m ² / g or more by the BET method is used as a positive electrode and / or a negative electrode, and ions that can be doped into the electrode are generated by electrolysis. An organic electrolyte battery characterized by using an aprotic organic solvent solution of the obtained compound as an electrolytic solution has been proposed.

The battery is a promising secondary battery with high performance, the possibility of reduction in thickness and weight, the high oxidative stability of the electrode active material, and its easy molding.

A heat-treated phenolic resin having a polyacene skeleton structure in which the atomic ratio of hydrogen atoms / carbon atoms is 0.5 to 0.05, and having a specific surface area value of at least 600 by the BET method.
In a method for producing a battery electrode comprising an insoluble infusible substrate of m ² / g, a powder of the insoluble infusible substrate is mixed with a conductive material and a binder, and the mixture is subjected to pressure molding or on a support. A method for producing an electrode for a battery, which is characterized by applying or applying pressure, has been proposed.

This method can improve the productivity of the electrode for an organic electrolyte battery, and is practical. However, when the amount of binder is increased to obtain sufficient strength, the electrical conductivity of the electrode decreases, and the internal resistance of the battery increases,
In addition, the electrode manufactured in a region where the amount of binder has a small decrease in the electric conductivity of the electrode has a problem in that the electrode is loosened during the impregnation with the electrolytic solution, whereby the electric conductivity of the electrode is eventually reduced. .

(Problems to be Solved by the Invention) The present inventors have made intensive studies in view of the above problems, and as a result, have completed the present invention. An object of the present invention is to provide an electrode which is strong and has a small decrease in electric conductivity due to loosening of the electrode when impregnated with an electrolytic solution.

(Means for Solving the Problems) The object of the present invention is a heat-treated product of an aromatic condensation polymer comprising carbon, hydrogen and oxygen, wherein the aromatic condensation polymer has (a) a phenolic hydroxyl group. A condensate of an aromatic hydrocarbon compound and an aldehyde, (b) an aromatic hydrocarbon compound having a phenolic hydroxyl group, an aromatic hydrocarbon compound having no phenolic hydroxyl group, a condensate of an aldehyde, and (c) a furan resin. And the hydrogen / carbon atom ratio of the heat-treated product is 0.50-0.05.
A battery electrode formed by using an insoluble and infusible substrate containing a polyacene-based skeleton structure as a main active material, wherein the formed body contains a thermosetting resin as a binder. Is done.

The insoluble and infusible substrate containing a polyacene-based skeleton structure (hereinafter referred to as PAS) according to the present invention is obtained by using an aromatic condensation polymer described in Japanese Patent Application Laid-Open No. 59-3806 filed by the applicant of the present application. It is obtained by heat treatment under specific conditions.

PAS with specific surface area by BET method of 600m ² / g or more
Can be obtained by the method described in JP-A-60-170163 filed by the applicant of the present application.

Specifically, when a high specific surface area is not required, the aromatic condensation polymer used in the present invention includes (a) an aromatic hydrocarbon compound having a phenolic hydroxyl group, such as a phenol-formaldehyde resin, and an aldehyde. Condensate, (b) xylene-modified phenol, formaldehyde resin (phenol partially substituted with xylene)
Examples of suitable compounds include aromatic hydrocarbon compounds having a phenolic hydroxyl group, aromatic hydrocarbon compounds having no phenolic hydroxyl group, condensates of aldehydes, and (c) furan resins.

The aromatic condensation polymer is placed in a non-oxidizing atmosphere (including a vacuum state) at a temperature of 400 ° C. to 1000 ° C., preferably 600 ° C.
PAS can be obtained by gradually heating to a suitable temperature of 800C to 800C to obtain a heat-treated product having an atomic ratio of hydrogen atoms / carbon atoms (hereinafter referred to as H / C) of 0.50 to 0.05, preferably 0.35 to 0.10. 6
In the case of PAS having a specific surface area of at least 00 m ² / g by the BET method, an inorganic salt such as zinc chloride or sodium phosphate is mixed with the aromatic condensation polymer.

The amount to be mixed varies depending on the type of the inorganic salt and the shape and performance of the target electrode, but is preferably 10/1 to 1/7 by weight.

The mixture of the inorganic salt and the aromatic condensation polymer obtained in this manner is cured by heating at a temperature of usually 50 to 180 ° C. for 2 to 90 minutes, although it differs depending on the composition of the polymer, the kind of the inorganic salt, The cured product thus obtained is then heated in a non-oxidizing atmosphere at a temperature of 350 to 800 ° C, preferably 400
The obtained heat-treated body is sufficiently washed with water or dilute hydrochloric acid to remove the inorganic salts contained in the heat-treated body. Thereafter, when this is dried, H / C = 0.05 to 0.05, preferably 0.35 to 0.10 of 6.
PAS having a specific surface area of 00 m ² / g or more is obtained.

PAS used in the present invention is obtained by X-ray diffraction (CuKa ray).
The position of the main peak occurs at 24 or less at 2θ, and 2θ
And those showing a broad peak between 41 and 46 ° C.

In the present invention, PAS is an absorbance ratio (D) represented by the following equation, which is obtained from an infrared series spectrum. D = D _2900-2940 / D _{1560-1640 In the} equation, D _2900-2940 represents 29 in the infrared absorption spectrum.
Absorbance determined from the maximum absorption peak in the range of 00 to 2940 Kaiser, D _{1560 to 1640} in the infrared absorption spectrum
The absorbance determined from the maximum absorption peak in the range of 1560 to 1640 Kaiser is preferably 0.5 or less, and particularly preferably 0.3 or less. The PAS in the present invention is manufactured in a powdery or short fiber shape or in an appropriate shape so that it can be easily molded. Use PAS processed to the shape of.

The battery electrode in the present invention has PAS as a main active material, and may contain a conductive material as needed.

The type of the conductive agent is not particularly limited, for example, activated carbon,
Carbon-based ones such as carbon black and graphite are preferred,
The smaller the particle size, the more effective. It is also possible to use a conductive polymer as the conductive material.

Further, a conductive polymer, metal oxide, metal sulfide, activated carbon, or the like, which can be electrochemically doped and undoped, can be added as an auxiliary active material.

The battery electrode of the present invention is formed by using PAS as a main active material, and the formed body contains a thermosetting resin as a binder. The effect of the present invention can be sufficiently obtained even when a material other than the thermosetting resin is used in combination as a binder, but what is important is that the thermosetting resin is used in a small amount as a common component.

The battery electrode of the present invention can be roughly divided into the following two methods.

The first method is to knead an initial condensate of PAS and a thermosetting resin in a form that is easy to mix such as powder or short fiber, add a solvent such as methanol, toluene or water if necessary, and then knead the mixture at 50 ° C.
The second method is to generally use the PAS in the above-mentioned form for a battery electrode such as polytetrafluoroethylene, polyethylene, or polypropylene. This is a method in which after mixing with a binder to be obtained or kneading and molding as required, the molded body is subsequently impregnated with a solution of an initial condensate of a thermosetting resin, and then dried and cured by a method such as heating.

Examples of the thermosetting resin used in the present invention include those capable of firmly adhering PAS powder or the like and suppressing loosening of the electrode, such as a phenol resin, a melamine resin, and a furan resin.

The proportion of the thermosetting resin in the electrode of the present invention is PAS shape, P
It is determined by the specific surface area of AS, the amount of other types of binders, the strength of the target electrode, and the like.
Not less than 50%. If it is less than 1%, the effect of suppressing the loosening of the electrode is small, and if it exceeds 70%, the amount of the active material is naturally reduced, which is not preferable.

As the battery electrode of the present invention, the above electrode can be used after heat treatment in an inert atmosphere (including vacuum).

For example, when a phenol resin is used as the thermosetting resin, a large amount of hydroxyl groups, carbonyl groups, and the like that easily react with lithium are present, and extra lithium is required when lithium is supported. It is advantageous to keep the groups reduced. Heating temperature is 15
The temperature is 0 ° C. or higher, preferably 250 ° C. to 500 ° C., and as the temperature increases, the electrode strength decreases, and it becomes difficult to obtain the original effects of the present invention.

Generally, when an active material powder or the like is molded using a binder, the strength of the molded body increases in proportion to the amount of the binder, and the electric conductivity of the molded body tends to decrease. However, even when the amount of the thermosetting resin is increased, the electrode of the present invention has a small decrease in electric conductivity and sometimes increases, so that it can sufficiently withstand practical use as a strong electrode.

(Effects of the Invention) The battery electrode of the present invention is an excellent electrode having high strength and little decrease in electrical conductivity due to loosening of the electrode when impregnated with the electrolyte.

 Hereinafter, the present invention will be described specifically with reference to examples.

Example An aqueous solution obtained by mixing a water-soluble resol (about 60% concentration), zinc chloride and water at a weight ratio of 10: 25: 4 was formed on a glass plate by a film applicator. Next, a glass plate is placed on the aqueous solution to prevent water from evaporating.
It was cured by heating at a temperature of 100 ° C. for 1 hour.

The phenolic resin film was placed in a siliconite electric furnace and heated at a rate of 10 ° C./hour under a nitrogen stream and heat-treated to 700 ° C. Next, the heat-treated product was washed with diluted hydrochloric acid, washed with water, and then dried to obtain a PAS film.

This PAS film was pulverized with a disk mill to obtain PAS powder. The H / C of the powder was 0.14, and the specific surface area by BET method was 1700 m ² / g.

Subsequently, 10 parts of polytetrafluoroethylene powder was sufficiently mixed and kneaded with 100 parts of PAS powder, and then formed into a film of about 500 μ using a roller. Then, methanol solution of resol type phenol resin precondensate (10%, 20%,
(30%, 45% concentration) and impregnated with a phenol resin. After drying the impregnated film at 100 ° C all day and night, 250 ° C
For 4 hours under a nitrogen atmosphere.

The electric conductivity of the obtained electrode of the present invention was measured by a DC four-terminal method. Further, the electric conductivity when immersed in a 1 mol / LiClO ₄ -propylene carbonate solution as an electrolytic solution was measured, and the degree of loosening of the electrode was examined.

The phenol resin content in the electrode was calculated from the weight before the phenol resin impregnation and the weight after the impregnation drying and curing.

 The results are summarized in Table 1.

Comparative Example 10 parts, 20 parts, 30 parts, and 40 parts by weight of polytetrafluoroethylene (PT type) powder were added to 100 parts of the PAS powder obtained in the example, and after mixing and kneading, using a roller. Into a film of about 500 μm, and the same measurement as in the example was performed. The results are shown in Table 2.

Claims (1)

(57) [Claims] 1. A heat-treated product of an aromatic condensed polymer comprising carbon, hydrogen and oxygen, wherein the aromatic condensed polymer is (a) a condensate of an aldehyde with an aromatic hydrocarbon compound having a phenolic hydroxyl group, (B) an aromatic hydrocarbon compound having a phenolic hydroxyl group, an aromatic hydrocarbon compound having no phenolic hydroxyl group and a condensate of an aldehyde and (c) a furan resin, and a hydrogen atom / carbon of the heat-treated product. In a battery electrode molded using an insoluble and infusible substrate containing a polyacene-based skeleton structure having an atomic ratio of atoms of 0.50 to 0.05 as a main active material, the molded body contains a thermosetting resin as a binder. Characteristic electrode for batteries.