JPS6321311B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a secondary battery that is small in size and has a large discharge capacity, and more particularly to a battery that uses lithium as a negative electrode active material.

Conventionally, high energy density batteries using lithium as a negative electrode active material, for example, halogens such as Br ₂ and I ₂ , CuF 2 , AgF 2 , AgF, CuF ₂ , AgF ₂ , AgF,
NiF ₂ , CuCl ₂ , AgCl ₂ , NiCl ₂ , CoF ₃ , CrF ₃ ,
MnF ₃ , SbF ₃ , CdF ₂ , AsF ₃ , HgF ₂ , CuBr,
Metal halides such as CdCl ₂ , PbCl ₂ and Cocl ₂ etc., metal rhodan compounds such as AgSCN, CuSCN and Ni(SCN) ₂ , MnO ₂ , Cr ₂ O ₃ , V ₂ O ₅ ,
SnO ₂ , PbO ₂ , TiO ₂ , Bi ₂ O ₂ , CrO ₃ , Fe ₃ O ₄ ,
Metal oxides such as NiO, AgO, HgO, Cu ₂ O, CuO, Ag ₂ WO ₄ etc., NiS _x , AgBs, CuBS,
Metal sulfides, such as Pb ₂ B ₂ O ₅ and MnB ₄ S ₄ etc.
Layered compounds such as TiS ₂ , NbSe ₂ and WS ₂ etc.
Graphite fluoride, as well as organic compounds such as benzoquinones and dinitrobenzene, as well as POCl ₃ , SOCl ₂ and
Batteries using oxyhalides such as SO ₂ Cl ₂ have been proposed.

Specifically, a battery has been proposed that uses an intercalation compound of graphite and fluorine as the positive electrode active material and lithium metal as the negative electrode active material (see US Pat. No. 3,514,337). Lithium batteries using manganese dioxide as a positive electrode active material and lithium batteries using manganese dioxide as a positive electrode active material are already commercially available. However, these batteries have the disadvantage that they are not rechargeable and cannot be used as secondary batteries, and their battery characteristics are also unsatisfactory.

The present invention aims to eliminate the above-mentioned drawbacks and provide a small battery that has a large discharge capacity, a high energy density, and is rechargeable. Specifically, the present invention uses a ligand or a metal complex as a positive electrode active material,
A material that uses lithium as a negative electrode active material, is chemically stable with respect to the positive electrode active material and negative electrode active material as an electrolyte material, and does not inhibit the movement of lithium ions for electrochemical reaction with the positive electrode active material. The aim is to provide a small battery using

The ligand and metal complex used as the positive electrode active material of the small battery of the present invention are selected from the following compounds. Co chelate of 2-hydroxy-1,4-naphthoquinone, 2-hydroxy-
Co〓chelate of 1,4-naphthoquinone, Fe〓chelate of 2-hydroxy-1,4-naphthoquinone,
Iron ()benzoylacetonate, acetoacetyl Be salt, acetoacetyl Fe salt, acetoacetyl
Co〓 salt, acetoacetyl Co〓 salt.

The metal complex used as the positive electrode active material in the small battery of the present invention forms a stable complex with Li ⁺ .
Specifically, the electrons transferred from lithium are localized in the vacant d orbital of the metal ion at the center of the metal complex, and if the ligand in the metal complex has an aromatic ring, π-electron conjugation occurs. Since the electrons also begin to enter the system, a stable complex is formed. As a result, an increase in discharge capacity can be expected, and furthermore, charging and discharging becomes possible. Further, even if a ligand is used as the positive electrode active material in the small battery of the present invention, similar electron transfer can be expected, and it is expected that a rechargeable and stable small battery will be realized. Judging from the difficulty of reduction, in the case of metal complexes, part of the metal will be reduced during battery discharge (e.g., Fe〓→Fe〓), and then when the oxidation number of the metal is high (i.e., part of the metal will be reduced). It is thought that the oxygen and nitrogen used to coordinate the metal before the reduction occurs (before the discharge reaction) are reduced to lithium. Then, charging is possible if the number of electrons involved in the reaction does not destroy the structure (for example, the oxygen atom is removed as Li ₂ O from the metal complex or the ligand).

The positive electrode of the small battery of the present invention is produced by pressure-molding a ligand or a metal complex, or a mixture of the ligand or metal complex and a binder powder onto a support such as nickel or stainless steel, into a film shape, or by disposing the mixture. Mix carbon powder to impart conductivity to the ligand or metal complex, place the mixture (positive electrode mixture) in a metal container, or mix the mixture with a binder and place it on a support such as nickel or stainless steel. It may be created by compression molding or the like. Further, the negative electrode of the small-sized battery of the present invention may be made by forming lithium, which is a negative electrode active material, into a sheet form in the same manner as in general lithium batteries. Furthermore, the sheet-like lithium may be pressed onto a nickel or stainless steel mesh.

Electrolyte materials for the small battery of the present invention include, for example, aprotic organic solvents such as propylene carbonate, ethylene carbonate, γ-butyrolactone, dimethylsulfoxide, acetonitrile, formamide, dimethylformamide, nitromethane, and 1,2-dimethoxyethane, and LiClO ₄ ，
Combinations with lithium salts such as LiAlCl ₄ , LiBF ₄ , LiCl, LiPF ₆ , CiAsF ₆ , solid electrolytes or molten salts using Li ⁺ as a conductor, and other known materials commonly used in batteries using lithium as the negative electrode active material. electrolyte may be used.

Furthermore, in the small battery of the present invention, a diaphragm made of porous polypropylene or the like may be disposed between the positive electrode and the negative electrode if necessary for the battery configuration.

The small battery of the present invention will be specifically explained below with reference to Examples, but it will be clear that the present invention is not limited to these specific Examples.

In each of the following Examples, battery fabrication and measurements were performed in an argon atmosphere.

Example 1 A small battery of the present invention was fabricated to have the button-shaped structure shown in FIG. 1, and its characteristics were measured. 1 is a Ni-plated brass container with a cylindrical recess of 26 mm in diameter. Reference numeral 2 denotes a positive electrode, which is placed at the bottom of the recess of the container 1. Reference numeral 3 denotes a disc-shaped porous polypropylene diaphragm, which is laminated on the positive electrode 2 with a disc-shaped carbon fiber felt 4 impregnated with an electrolyte substance interposed therebetween. Reference numeral 5 denotes a cylindrical first fixing body made of Teflon, and the diaphragm 3 and the felt are fixed by fitting a spiral portion formed on the outer peripheral surface into a spiral portion formed on the inner peripheral wall of the recess of the container 1. 4. Press and fix the positive electrode 2. Reference numeral 6 denotes a disk-shaped lithium negative electrode with a diameter of 20 mm, which is disposed in the internal cavity of the first fixed body 5. Reference numeral 7 denotes a second cylindrical fixing body made of Teflon, and a spiral portion bored on the outer peripheral surface is connected to the first fixed body.
The lithium negative electrode 6 is compressed and fixed to the diaphragm 3 by fitting into a spiral portion formed in the inner circumferential surface of the fixing body 5 . Reference numeral 8 denotes a lead wire made of Ni, which is placed in a pore of the second fixed body 7, one end of which is connected to the lithium negative electrode 6, and the other end of which is extended from the pore to the outside.

In this example, a positive electrode mixture was prepared by mixing 0.05 g of Co chelate of 2-hydroxy-1,4-naphthoquinone (the structural formula is shown in Figure 12a) and 0.05 g of acetylene black. An electrolyte material, that is, a /mol/l solution of LiClO ₄ dissolved in distilled and dehydrated propylene carbonate was kneaded, and the cathode 2 was formed from this kneaded body. Further, by dropping the electrolyte material onto the felt 4 placed on the positive electrode 2, the felt 4 and the diaphragm 3 were impregnated with the electrolyte material.

The open circuit voltage of the small battery of the present invention produced in this manner was 3.08V. Furthermore, when a constant current discharge of 1 mA was performed, the relationship between the discharge time and the voltage was as shown in Figure 2, and the 2-hydroxy-1,4-
Based on the weight of the naphthoquinone Co chelate, the discharge capacity at a final voltage of 1V, that is, the discharge capacity until the voltage decreased to 1V, was 610Ah/Kg, and the energy density was 966Wh/Kg. It was also possible to charge it.

Example 2 0.05 g of Cu chelate of 2-hydroxy-1,4-naphthoquinone (the structural formula is shown in Figure 12b)
A battery having the same structure as in Example 1 was prepared except that a positive electrode mixture was prepared by mixing 0.05 g of acetylene black and 0.05 g of acetylene black.

The open circuit voltage of the battery made in this way is
It was 3.25V. When a constant current discharge of 1 mA was performed, the relationship between discharge time and voltage was as shown in Figure 3. The discharge capacity at 1V final voltage is 130Ah/Kg for the weight of Co chelate of 2-hydroxy-1,4-naphthoquinoline, and the energy density is
It was 244Wh/Kg. It was also possible to charge it.

Example 3 0.05 g of Fe chelate of 2-hydroxy-1,4-naphthoquinone (the structural formula is shown in Figure 12c)
A battery having the same structure as in Example 1 was prepared except that a positive electrode mixture was prepared by mixing 0.05 g of acetylene black and 0.05 g of acetylene black.

The open circuit voltage of the battery made in this way is
It was 2.35V. When a constant current discharge of 1 mA was performed, the relationship between discharge time and voltage was as shown in Figure 4. 2-hydroxy-1,4-naphthoquinoline
The discharge capacity at 1V final voltage is 280Ah/Kg for the weight of Fe〓chelate, and the energy density is 484Wh/Kg
It was hot. It was also possible to charge it.

Example 4 A battery having the same structure as Example 1 except that 0.05 g of iron ()benzoylacetonate (the structural formula is shown in Figure 12 d) and 0.05 g of acetylene black were mixed to prepare a positive electrode mixture. was created.

The open circuit voltage of the battery made in this way is
It was 3.15V. When a constant current discharge of 1 mA was performed, the relationship between discharge time and voltage was as shown in Figure 5. The discharge capacity at a final voltage of 1V is 910Ah/Kg for the weight of iron ()benzoylacetonate,
The energy density showed a high value of 1367Wh/Kg.
It was also possible to charge it.

Example 5 0.05 g of acetoacetyl Be salt (with structural formula 1)
A battery having the same structure as Example 1 was prepared, except that a positive electrode mixture was prepared by mixing 0.05 g of acetylene black (shown in Figure 2e) and 0.05 g of acetylene black.

The open circuit voltage of the battery made in this way is
It was 3.15V. When a constant current discharge of 1 mA was performed, the relationship between discharge time and voltage was as shown in Figure 6. The discharge capacity at a final voltage of 1 V was 130 Ah/Kg and the energy density was 153 Wh/Kg based on the weight of the acetoacetyl Be salt. It was also possible to charge it.

Example 6 0.05 g of acetoacetyl Fe〓 salt (the structural formula is
A battery having the same structure as Example 1 was prepared, except that a positive electrode mixture was prepared by mixing 0.05 g of acetylene black (as shown in Figure 2 f) and 0.05 g of acetylene black.

The open circuit voltage of the battery made in this way is
It was 2.68V. When a constant current discharge of 1 mA was performed, the relationship between discharge time and voltage was as shown in Figure 7. The discharge capacity at a final voltage of 1 V was 235 Ah/Kg and the energy density was 353 Wh/Kg based on the weight of the acetoacetyl Fe salt. It was also possible to charge it.

Example 7 0.05 g of acetoacetyl Co〓 salt (the structural formula is
A battery having the same structure as Example 1 was prepared, except that a positive electrode mixture was prepared by mixing 0.05 g of acetylene black (as shown in Figure 2g) and 0.05 g of acetylene black.

The open circuit voltage of the battery made in this way is
It was 3.25V. When a constant current discharge of 1 mA was performed, the relationship between discharge time and voltage was as shown in Figure 8. The discharge capacity at a final voltage of 1 V was 315 Ah/Kg and the energy density was 495 Wh/Kg based on the weight of the acetoacetyl Co salt. It was also possible to charge it.

Example 8 0.05 g of acetoacetyl Co salt (with structural formula
A battery having the same structure as in Example 1 was prepared except that a positive electrode mixture was prepared by mixing 0.05 g of acetylene black (as shown in Figure 2h) with 0.05 g of acetylene black.

The open circuit voltage of the battery made in this way is
It was 2.90V. When a constant current discharge of 1 mA was performed, the relationship between discharge time and voltage was as shown in Figure 9. The discharge capacity at a final voltage of 1 V was 430 Ah/Kg and the energy density was 648 Wh/Kg based on the weight of the acetoacetyl Co salt. It was also possible to charge it.

Example 9 Example 1 except that 0.03 g of Co chelate of 2-hydroxy-1,4-naphthoquinone and 0.03 g of acetylene black were mixed to prepare a positive electrode mixture.
A battery with the same structure was fabricated.

This battery was discharged at a constant current of 1mA for 6 hours (discharge capacity of 200Ah/Kg), then rested for 1 hour,
Next, a cycle test was performed in which the battery was charged at a constant current of 1mA for 6 hours (charging capacity of 200Ah/Kg) and then rested for 1 hour.The relationship between the discharge time and voltage in the first cycle was as shown in Figure 10a. becomes 6
The voltage after discharging for an hour was 0.80V. The relationship between the discharge time and voltage in the third cycle is as shown in Figure 10b, the voltage after 6 hours of discharge is 1.10V, and the relationship between the discharge time and voltage in the fourth cycle is as shown in Figure 10c. The voltage after 6 hours of discharge was 1.20V. The relationship between the discharge time and voltage in the sixth cycle was as shown in FIG. 10d, and the voltage after 6 hours of discharge was 0.95V. discharge voltage
Five cycles were possible until the voltage dropped below 1V.

Example 10 0.03g of iron()benzoylacetonate and
A battery having the same structure as Example 1 was prepared except that 0.03 g of acetylene black was mixed to prepare a positive electrode mixture.

This battery was discharged at a constant current of 1mA for 6 hours (discharge capacity of 200Ah/Kg), then rested for 2.5 hours, then charged at a constant current of 1mA for 6 hours (charge capacity of 200Ah/Kg), then rested for 2.5 hours. When a cycle test was conducted, the relationship between the discharge time and charge time of the first cycle and the voltage was as shown in FIG. 11a, and the voltage after 6 hours of discharge was 1.52V. The relationship between the discharge time and charge time and the voltage in the 10th cycle is as shown in Figure 11b, and the voltage after 6 hours of discharge is 1.42V, and the relationship between the discharge time and charge time and the voltage in the 19th cycle is 1.42V. Relationship is the 11th
The voltage after 6 hours of discharge is as shown in Figure c.
It was 1.20V. The relationship between the discharge time and charge time and the voltage in the 25th cycle was as shown in FIG. 11d, and the voltage after 6 hours of discharge was 1.10V.
25 cycles were possible before the discharge voltage dropped below 1V.

Conventionally, the discharge capacity of the most commonly used dry battery (negative electrode is zinc, positive electrode is MnO ₂ ) is 70 to 140 Ah/Kg.
It is. As shown in the examples, the lithium battery according to the present invention exhibits a higher capacity than a dry battery, for example, in the case of iron ()bazoylacetonate, 6.5~
Indicates 13 times more capacity. Furthermore, while dry batteries are not rechargeable, the battery of the present invention also has the advantage of being rechargeable.

As is clear from the above, according to the present invention, by using a ligand or a metal complex as a positive electrode active material of a lithium battery, a small, high energy density, chargeable and dischargeable battery can be formed.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of the battery of the present invention, FIGS. 2 to 11 are explanatory diagrams of characteristics of the embodiment of the present invention, and FIG. 12 shows a positive electrode active material of the embodiment of the battery of the present invention.

Claims (1)

[Claims] 1 The positive electrode active material is Co chelate of 2-hydroxy-1,4-naphthoquinone, 2-hydroxy-1,
Co〓chelate of 4-naphthoquinone, Fe〓chelate of 2-hydroxy-1,4-naphthoquinone, iron () beizoylacetonate, acetoacetyl
Be salt, acetoacetyl Fe salt, acetoacetyl
It is a ligand or metal complex that forms a complex with a metal selected from Co〓 salt, acetoacetyl Co〓 salt compounds, the negative electrode active material is lithium, and the electrolyte material is chemically 1. A secondary battery characterized by being a material that is physically stable and does not inhibit the movement of lithium ions because it undergoes an electrochemical reaction with a positive electrode active material.