JPS61133562A - Secondary battery and its electrode - Google Patents

Abstract

PURPOSE:To obtain a secondary battery having light weight and high energy density by using benzidine or its derivative as an electrode material. CONSTITUTION:Benzidine or its derivative is used in at least one electrode as electrode material. Although benzidine or its derivative can be used in a positive electrode and a negative electrode, use in the positive electrode is preferable because it gives good charge-discharge cycle life, charge-discharge coulomb efficiency, storage life after charging, discharge voltage flatness. For example, a secondary battery is constituted by using N,N'-diphenyl benzidine as material for electrodes 4, 7, fibers mainly comprising carbon as current collectors 2, 8, and a glass fiber filter paper as a separator 5, and propylene carbonate solution containing lithium perchlorate as electrolyte.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an electrode for an electrochemical secondary battery using benzidine or a benzidine derivative as an electrode constituent material, and a secondary battery using this electrode for at least one electrode. It is related to.

Since the oil crisis, energy issues have become more important, and since pollution issues have come to the fore, pollution-free electric vehicles have started to attract attention. Under these circumstances, the development of a new type of battery that is lightweight and has high energy density has been considered, and attempts have been made to apply various materials to electrodes. The development of lightweight, high-energy-density batteries has also been strongly desired in fields such as artificial satellites and aircraft. The present invention provides a novel electrode that meets these demands and a battery using the same.

(Prior Art) Recently, new secondary batteries using polymer compounds as electrodes are being developed. Secondary batteries using this polymer compound as electrodes were not realized until a method called doping was discovered. When polymers, which are originally insulators, are doped with a type of substance through a process called doping, their electrical conductivity is significantly improved, and polymers that exhibit electrical conductivity in the region of semiconductors or good conductors have recently been discovered using phase processes. Served. Examples of these include polyacetylene, polyphenylene, polythiophene, polypyrrole, and the like. In addition, the following two methods are generally adopted as methods of doping operation.

(1) A substance exhibiting Lewis acidity as a dopant (for example, ■2.PF5.803.Fe
e) 3 etc.) and alkali metals (Li, Na, K
etc.) chemical doping method.

(2) Electrochemical doping method in which a polymer is brought into contact with an electrolyte in liquid phase or in the same phase, a positive or negative voltage is applied to the polymer, and the polymer is doped with cations or anions generated by ion dissociation of the electrolyte. .

Among the above two methods, there is a close relationship between electrochemical doping (2) and charging and discharging of secondary batteries, that is, the dopant doped electrochemically is also dedoped electrochemically. 1. Normally, doping and dedoping operations occur reversibly, so a secondary battery was proposed that applied this principle.

□New types of secondary batteries that apply reversible electrochemical doping and dedoping phenomena have recently been invented one after another. 136469.
JP-A-57-121168, etc.), secondary batteries using electrodes mainly composed of polyparaphenylene (JP-A-58-11)
2271, etc.), secondary batteries using electrodes mainly composed of ferrocene-containing conjugated polymers (Japanese Patent Application Laid-Open No. 59-46760, etc.)
There are also secondary batteries (Japanese Unexamined Patent Publication No. 57-197759, etc.) that use electrodes mainly composed of polythiophene.

On the other hand, an example is also known in which 2,4,7-)listlow-9-fluorenone, which is a normal organic compound other than a polymer, is used for the positive electrode, and lithium metal is used for the negative electrode. (
J, Electrochem-5oc-.

Vol, 131. /Ii1, p. 57 (1984)).

(Problems to be Solved) - The inventors of the present invention have conducted extensive research into developing batteries that are lightweight and have high energy density. As a result, benzidine and its derivatives, which are not monopolymers but are usually □ monomers, are superior. It was discovered that the present invention could be used as a material for electrodes for electrochemical secondary batteries, and the present invention was completed.

That is, an object of the present invention is to provide a lightweight, high-energy-density electrochemical secondary battery in which the organic material benzidine or a derivative thereof is used as a constituent material of the electrode, and an electrode for use therein.

Another object of the present invention is to provide an electrochemical secondary battery and an electrode for use therein, which do not require special operations such as polymerization in the production of electrode materials, and use common low-molecular-weight organic compounds as they are. .

Still another object of the present invention is to provide an electrochemical secondary battery whose unused electrodes can be easily disposed of by incineration, and an electrode used for cleaning.

(Means for solving the problem) - Therefore, the gist of the first invention resides in an electrochemical secondary battery characterized in that at least one electrode uses benzidine or a benzidine derivative as an electrode constituent material, What is the gist of the second invention?

The present invention relates to an electrode for an electrochemical secondary battery that uses benzidine or a benzidine derivative as an electrode constituent material.

The battery and electrode of the present invention utilize (2) electrochemical doping of the above-mentioned two types of doping operations, and do not use the conventionally proposed high molecular weight polymer, but instead use (1) the conventional doping operation. It is characterized by the use of organic compounds.

In order to facilitate understanding of the working mechanism of the battery and electrode of the present invention, the case of a polyacetylene electrode which works by an electrochemically similar mechanism will be explained below as an example.

When polyacetylene is used for the positive and negative electrodes, the reaction at the positive electrode is a charging reaction due to the incorporation of anions generated by dissociation of the electrolyte substance (salt) into the polyacetylene (¥-ping), and anion release (dedoping).
The negative electrode reaction is a charging reaction due to the uptake of cations and a discharging reaction due to the release of cations.

When polyacetylene is represented by (CH)n and lithium perchlorate (LI Cl04) is used as the electrolyte, the reaction formula is as follows.

Positive electrode reaction (CH) n+ n xcl 04″″ Negative electrode reaction (CH). +nxe+nxL+ Since a high molecular weight polymer that can be electrochemically oxidized or reduced in this way functions as either the positive electrode or the negative electrode of a secondary battery, it is of course possible to combine it with a negative electrode or positive electrode other than a polyacetylene electrode. A secondary battery can also be constructed using .

However, these high molecular weight polymers that have been proposed in the past must be synthesized by polymerizing monomers, but benzidine and benzidine derivatives used in the present invention cannot be synthesized by polymerizing them. Instead, it is used as is for secondary battery electrodes. Therefore, since the polymerization step necessary for producing a high molecular weight polymer is not necessary, it is also advantageous from the viewpoint of production cost.

Furthermore, since purification of monomers is much easier than purification of polymers, it is easy to obtain highly purified products. The purity of benzidine or its derivative used as the battery or electrode of the present invention is not limited to %, but it goes without saying that higher purity is better. The larger the amount of impurities that do not act as electrodes, the smaller the amount of substances that can act as electrodes per unit weight, which not only lowers the energy density per unit weight, but also causes doping depending on the type of impurity. This is because it is also possible that the dedoping effect is reduced and the function as an electrode material is inhibited.

Benzidine and benzidine derivatives used as electrode materials in the present invention are compounds represented by the following structural formula, and are a completely different type of electrode material from conventional high molecular weight polymers.

In this structural formula, x, x', y and V represent hydrogen, alkyl, alkenyl and aryl residues, and may be the same or different. Zl @ Z2 g
Z3 @Z4 @ Z1' @ Z2' g Z3・
and Z4' represent hydrogen, alkyl, alkenyl, hydrogen, and aryl residues, and each may be the same or different. Preferably, x, x', y and y are hydrogen, methyl or phenyl, and Z1 to z4. zl
' to Z4' are preferably hydrogen or halogen.

Benzidine and benzidine derivatives are commercially available products that can be used as they are or in powder form without any special processing.

The benzidine and benzidine derivative electrodes according to the present invention can be used as both positive and negative electrodes, but it is better to use them as positive electrodes to improve charge/discharge repeatability, charge/discharge coulombic efficiency, storage stability in a charged state, and voltage during discharge. It is preferable because it has particularly excellent flatness.

The mechanism by which benzidine or its derivatives used in the present invention acts as an electrode has not yet been elucidated in detail;
Although the present invention is not restricted in any way by the following explanation, the present inventors believe that the electrode functions as follows. In other words, it is thought that the following reaction occurs at the positive electrode during the charging process. N.

=10- charging It is.

It is thought that during the charging process, doping occurs due to the interaction between the cations generated in the above formula and perchlorate anions (CJ 047 ), and a reverse reaction occurs during the discharging process.

When the same material as the positive electrode is used as the negative electrode, the reaction at the negative electrode is such that during charging, lithium is inserted between the molecules 1'lfl, IIIK benzene rings and benzene rings in the crystal structure of benzidine and its derivatives (intercalation). ) is assumed to be a thing.

Of course, if a metal material is used as the negative electrode.

It works by depositing metallic lithium on the negative electrode.

The same can be considered when using an electrolyte other than lithium perchlorate.

As mentioned above, examples are known in which an electron acceptor such as an organic compound other than a high molecular weight polymer, such as 2,4,7-)Lielow-9-fluorenone, is used in the electrode of a secondary battery. However, in all of these batteries, only the positive electrode is used, and metallic lithium is often used for the negative electrode.

To explain the reaction of these secondary batteries using the case of discharge as an example, metallic lithium in the negative electrode is ionized to become lithium cations, which are doped into the electron acceptor in the positive electrode.

For example, as mentioned earlier, when polyacetylene is used for both electrodes, lithium perchlorate (L) is used as an electrolyte during charging.
Due to the dissociation of iCJO4), lithium cations and perchlorate anions are doped into the negative and positive electrodes, respectively. Furthermore, when polyacetylene is used as the positive electrode and lithium as the negative electrode, lithium cations generated by dissociation of lithium perchlorate, which is the electrolyte, are reduced and deposited on the lithium electrode, which is the negative electrode. The anion is doped into polyacetylene, which is the positive electrode. It is said that the opposite reaction occurs during discharge.

In secondary batteries using electron acceptors, even if lithium perchlorate is used as the electrolyte.

In that only lithium cations are doped and no perchlorate anions are involved, the difference between using a conventionally known low molecular weight electron acceptor as an electrode and using a polymeric material such as polyacetylene as an electrode is that the battery The mechanisms of action are different.

Therefore, the characteristics of a secondary battery using a low molecular weight electron acceptor as an electrode are that it can start discharging immediately after battery assembly without charging, and that the electrode can only use positive electrode pressure. In this respect, it is clearly different from polyacetylene batteries and the like.

The benzidine and benzidine derivatives used in the electrode of the present invention can be used as both electrodes at the same time, like conventional high molecular weight polyacetylene electrodes, and are different from the electrodes using electron acceptors as described above. It is of type.

13- In order to reduce internal resistance in the battery of the present invention, it is preferable to line the benzidine electrode with an auxiliary collector electrode (electrode) such as a metal plate, metal mesh, graphite, carbon fiber, etc. Furthermore, instead of using benzidine or its derivative itself as an electrode, it is also possible to use it in combination with carbon black, since this has the effect of increasing the surface area and improving contact. In addition, various electrolytes can be used as the dopant that is doped during battery charging and discharging, such as lithium perchlorate,
LiBF4, tetraalkylammonium barchlorate.

LiPF6 or the like is used. Examples of non-aqueous solvents that dissolve these electrolytes include propylene carbonate, dichloromethane, sulfolane, and tetrahydrofuran.

Water can also be used as a solvent if all electrodes used are stable to water.

In this case, a wide variety of electrolytes can be used as dopants, such as potassium iodide. When using a metal material as a cathode, lithium metal is usually used, but it is not limited to lithium; other metals such as zinc and aluminum can be used depending on the electrolyte used; It is also possible to use carbon.

When using metallic lithium as the negative electrode in the battery of the present invention, it is necessary to maintain the battery under an argon atmosphere. Although other atmospheres can be used depending on the material of the negative electrode and the type of electrolyte used, it is generally reliable to use an argon atmosphere.

(Effects of the Invention) According to the present invention, a normal low molecular weight organic compound can be used as an electrode as it is without special operations such as polymerization, and it is lightweight and has a high charge density per unit weight (corrosive have.

This provides a battery that is easy to handle, has good charge/discharge efficiency, and has excellent voltage flatness during discharge.

(Example) Next, the present invention will be specifically explained using examples.

Example 1 N,N-diphenylbenzidine powder was used as an electrode material, and carbon-based fiber (manufactured by Nippon Carbon Co., Ltd., trade name: Carboron) was used as a current collector.

A battery having a sandwich structure as shown in FIGS. 1 and 2 was assembled using glass fiber ν paper as a diaphragm.

FIG. 1 is a schematic explanatory diagram showing the configuration of the battery used in this example, and FIG. 2 is a developed diagram thereof.

1 and 9 are current collector terminals, 2 and 8 are current collectors (both 1
2x17mm rectangle with a thickness of 0.31m5+).

3 and 6, a rectangular window of 10 x 15 mm was opened in the center using glass fiber ν paper, and 60 ml of N, N'-
Filled with diphenylbenzidine powder (4 and 7) %5 represents glass fiber F paper septum respectively. 10 is a Teflon plate, and 11 is a polyethylene container with a diameter of 32 m. The purpose of providing the Teflon plate 10 is to disperse the force exerted by the screw from above over the entire layer in order to ensure good and uniform contact between each layer of the battery, and to prevent the metal screw from directly touching the battery. belongs to.

After assembling the battery, while holding it down from the top,
A charge/discharge test was conducted after adding 3 portions of a propylene carbonate solution of lithium perchlorate (1 mol/l) so that 10 Teflon plates were immersed. All battery assembly, charge/discharge tests, etc. were conducted under an argon atmosphere.

1 on both ends of the current collector terminal. A constant current of 0 mA was continuously applied for 60 minutes to charge the battery. At that time, the terminal voltage is 3. 3.2 from OV
It changed to ■. When a constant current discharge of 0.57 FLA was performed immediately after charging, the terminal voltage was initially 3. It was Ov, but after that it went down and became 2.6■ after 30 minutes. After that, it started to go down rapidly.1. Discharge was stopped when the temperature reached Ov.

When this cycle was repeated, the following results were obtained.

Charge Discharge Charge Discharge 13.0
3.23.02.340.8 22.83.33.22.470.0 42.93.53132.375.0 62.93.63.32.375.0 83.03.73.32.373. 0 103.13.73.32.373.3 Charge/discharge Coulombic efficiency is the ratio of the discharge current to the charging current obtained until the discharge voltage reaches 1■.

Example 2 In Example I, 60 ml of N,N'-diphenylbenzidine powder was used as the positive electrode, and lithium chloride (10x
A battery was assembled in the same manner as in Example 1 except that a 15n+ rectangular battery with a thickness of 0.2 mm was used, and a charge/discharge test was conducted.

Charged for 60 minutes at a constant current of 1 mA, and the terminal voltage reached 1.5 mA at a constant current of 0.5 mA. The cycle of discharging until Ov was repeated 10 times and the following results were obtained.

Charge Discharge Charge Discharge (V)
(V) (V) (V) (%)1.4.24.23.
33.070 23.94.23.33.073 44.04.33.32.978 64.24.43.32.8 B1 84.34.53.32.886 104.34.63.32.883 Implementation Example 3 In Example 2, after repeating the 10th charge/discharge cycle, the battery was left to stand for 48 hours, and then the 11th charge/discharge was performed, and the charge/discharge coulombic efficiency was 69%. Further, the battery was charged at a constant current of 1 mA for 1 hour, left for 24 hours, and then discharged at a constant current of 0.5 mA until the terminal voltage reached 1.0 sq. The following results were obtained.

12th charge/discharge result: Initial voltage during charging: 4.3V, final voltage: 4.9
■Initial voltage during discharge 2.9V, final voltage at flat area 2
．． 6V charge/discharge coulombic efficiency 48% Example 4 In Example I, N, N'-diphenylbenzidiy6
A battery was assembled in the same manner as in Example 1, except that 50 ml of N, N, N', N'-tetramethylbenzidine was used in place of omII, and a charge/discharge test was conducted.

Charged at a constant current of 1 mA for 60 minutes, and the terminal voltage reached 1.2 mA at a constant current of 0.27 FIA. The following results were obtained by repeating the cycle of discharging until the voltage reached OV.

4 2.8 3.4 3.2 2.3 5
65 2.8 3.5 3.2 2.4
57 Example 5 In Example 1, N, N-diphenylbenzidine 60
A battery was assembled in the same manner as in Example 1, except that 100 ml of 2.2.5.5-7 trachlorobenzine was used instead of 2.2.5.5-7 trachlorobenzine, and a charge/discharge test was conducted.

A cycle of charging at a constant current of 17 FLA for 60 minutes and discharging at a constant current of 0.2 mA until the terminal voltage reached 1.0 was repeated to obtain the following results.

2 3.3 3.8 3.0 473
3.3 3.9 3.0 504
3.3 4.1 3.0 436
3.7 5.8 3.2 63

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram showing the configuration of the battery used in this example, and FIG. 2 is a developed diagram thereof. 1.9... Current collector terminal, 2,8... Current collector, 3.6.
...Glass fiber filter paper, 4,7... Electrode material made of benzidine or its derivative, 5... Glass fiber paper diaphragm, 10... Teflon plate, 11-... Container. Patent applicant: Maruzen Petrochemical Co., Ltd.

Claims (3)

[Claims] (1) An electrochemical secondary battery characterized in that at least one electrode uses benzidine or a benzidine derivative as an electrode constituent material. (2) The secondary battery according to claim 1, wherein the constituent material of the positive electrode is benzidine or a benzidine derivative. (3) An electrode for an electrochemical secondary battery using benzidine or a benzidine derivative as an electrode constituent material.