JPH04267057A - Secondary battery - Google Patents

Abstract

PURPOSE:To bind both the electrode active materials strongly, and while obtain the excellent charge-discharge characteristic in a secondary battery. CONSTITUTION:In a secondary battery which consists of the positive electrode active material and the negative electrode active material, which can be charged and discharged, and the electrolyte having ion conductivity, cellulose derivative, which is substituted with at least more than one kind of acetyl cellulose derivative, hydroxyethyl cellulose, or more than two kinds of different functional groups, is included in the positive electrode compound agent or the negative electrode compound agent.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery with improved charging and discharging characteristics.

0002

[Prior Art] In aqueous electrolytes such as manganese dry batteries, alkaline dry batteries, and nickel-cadmium secondary batteries, starch, polyvinyl alcohol, and carboxymethyl cellulose (JP-A-1-175-171, JP-A-1-1-1) are used as binders for electrode active materials. 105471, JP-A-51-5538, JP-A-50-2
6500, etc.), hydroxypropylcellulose (Japanese Unexamined Patent Publications No. 63-245859, No. 54-49541), regenerated cellulose (Unexamined Japanese Patent Application No. 61-91872), polyvinyl chloride, polyvinylpyrrolidone, etc. As the electrolyte, Teflon or the like is generally used. (Battery Handbook, published by Denki Shoin, 1980) In particular, charge transfer during charging and discharging of secondary batteries requires the speed and reversibility of ions in and out of the electrode active material, and ensuring a path for this is necessary for charging and discharging characteristics. In particular, it is an important factor for cycle life and rapid charge/discharge characteristics. Securing this path and bonding the electrode active materials are considered to have contradictory effects. Therefore, it is conceivable that the use of a strong binder may result in impairing the charge/discharge characteristics.

0003

SUMMARY OF THE INVENTION An object of the present invention is to strongly bond electrode active materials to each other in a secondary battery and to achieve good charge/discharge characteristics.

0004

[Means for Solving the Problems] The above object is to provide a secondary battery comprising a chargeable and dischargeable positive electrode active material, a negative electrode active material, and an electrolytic solution having ion conductivity, which contains at least one acetyl cellulose derivative, hydroxyethyl cellulose, etc. Alternatively, this could be achieved by including a cellulose derivative substituted with two or more different functional groups in the positive electrode mixture and/or the negative electrode mixture. As the acetylcellulose derivative, diacetylcellulose and triacetylcellulose are preferred. As the cellulose derivative substituted with at least two or more different functional groups, carboxymethylhydroxyethylcellulose, hydroxypropylcarboxymethylcellulose, acetylbutyrylcellulose, acetylcytolylcellulose, acetylmethylsuccinylcellulose, etc. are used. As for these compounds, cellulose organic acid ester compounds described in "Great Organic Chemistry 19 Natural Polymer Compounds 1" (published by Asakura Shoten in 1960) can be used. Among them, carboxymethyl hydroxyethyl cellulose and hydroxypropyl carboxymethyl cellulose are preferred. Among the above cellulose derivatives, hydroxyethylcellulose, hydroxypropylcarboxymethylcellulose, diacetylcellulose, and triacetylcellulose are particularly preferred, and diacetylcellulose is more preferred. Although the amount used varies depending on the electrode active material to be mixed, it is preferably 0.1 to 20% by weight, particularly preferably 1 to 15% by weight, based on the electrode active material. The solvent used may be any solvent that dissolves the compound of the present invention, and preferably the same solvent as the electrolyte. Further, for diacetylcellulose, a volatile solvent such as acetone is also preferred. It is also possible to mix without using a solvent.

[0005] The active material that can be used in the present invention may be any electrode material that can be charged and discharged, but in particular Co oxide (Japanese Patent Laid-Open No. 52-12 , 424, DE 2,606,915, etc.), Li-Co oxides (US 3,945,848, US
4,340,652, etc.), Li-Ni-Co oxides (
EP243,926A, JP 63-114,063,
63-211,565, 63-299,056, JP 1-120,765, etc.), V oxide (FR21,
611,796, JP 55-53,077, JP 62-
140,362, 62-227,358, etc.), Li
-V oxide (Electrochemistry 48, 432 (1980), Journal of Electrochemical Society, 130, 1225 (1983), JP-A-2-12,
769, etc.), Mn oxides (EP269,855, JP-A-63-58,761, etc.), Li-Mn oxides (JP-A-56-136,464, JP-A-114,064, JP-A-114)
,065, 148,550, 221,559, JP 1-5,459, 1-109,662, 1-12
8,371, 1-209,663, 2-27,66
0), Li-Ni-Mn oxide (JP-A-63-210,
028, etc.).

[0006] Further, in alkaline secondary batteries, Ni compounds are generally used. (Battery Handbook, published by Denki Shoin)

Among organic polymer positive electrode active materials, polyaniline derivatives (Molecular Crystal and Liquid Crystal, Vol. 121, 173 (198
5), JP-A-60-197,728, JP-A-63-46,2
23, 63-243,131, JP-A-2-219,8
23), pyrrole derivatives (Journal of
Chemical Society Chemical Communication 854 (1979), DE3, 223, 544A3
A, 307,954A, JP-A-62-225,517
, 63-69,824, JP-A-1-170,615, etc.), polythiophene derivatives (JP-A-58-187,4, etc.)
32, Japanese Patent Publication No. 1-12,775, etc.), polyacene derivatives (Japanese Patent Publication No. 58-209,864, etc.), and polyparaphenylene derivatives. Each derivative also includes a copolymer. Regarding this organic polymer compound, please refer to “Conductive Polymers” edited by Naoya Ogata, Kodansha Scientific (
1990).

[0008] As a secondary battery negative electrode active material that can contain the compound of the present invention, in a lithium secondary battery, a fired carbonaceous compound capable of absorbing lithium ions or lithium metal (Japanese Patent Laid-Open No. 58-209,864, 61-21
4,417, 62-88,269, 62-216,
170, 63-13,282, 63-24,555
, 63-121,247, 63-121,257,
63-155,568, 63-276,873, 63-314,821, JP-A-1-204,361, JP-A-1-221,859, JP-A-1-274,360, etc.). When adding the compound of the present invention to this calcined carbonaceous compound, the group that reacts with lithium contained in the compound of the present invention may be deactivated by adding a compound that reacts with a hydroxyl group, such as an isocyanate group. is preferred.

[0009] Further, as a secondary battery negative electrode active material that can contain the compound of the present invention, for nickel-hydrogen secondary batteries, a hydrogen storage alloy ("Hydrogen Storage Alloy" published by Yono Shobo) can be mentioned. The electrode mixture usually contains carbon, silver (
Conductive materials such as JP-A-63-148,554) or polyphenylene derivatives (JP-A-59-20,971) can be included.

[0010] In the case of a lithium secondary battery, lithium metal, lithium alloy (Al, Al
-Mn (US4,820,599), Al-Mg (JP-A-57-98977), Al-Sn (JP-A-63-6,
742), Al-In, Al-Cd (Unexamined Japanese Patent Publication No. 1-144
, 573).

[0011] As the electrolyte, propylene carbonate, ethylene carbonate, γ-butyrolactone, 1,2
-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3
-Dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, phosphoric acid triester (JP-A-60-23,973), trimethoxymethane (JP-A-61-4,170), dioxolane derivatives (JP-A-62) -15,771, 62-22,
372, 62-108,474), sulfolane (JP 62-31,959), 3-methyl-2-oxazolidinone (JP 62-44,961), propylene carbonate derivatives (JP 62-290) , 069, 62
-290,071), tetrahydrofuran derivative (JP-A-63-32,872), ethyl ether (JP-A-63-32,872), ethyl ether (JP-A-63-32,872),
-62,166), 1,3-propane sultone (JP-A-63-102,173) and other aprotic organic solvents and lithium salts soluble in the solvent, such as ClO4 - , BF6 − ,
PF6 − , CF3 SO3 − , CF3 CO2
−, AsF6 −, SbF6 −, B10Cl
10 (JP 57-74,974), (1,2-dimethoxyethane)2ClO4 - (JP 57-74,9
77), lower aliphatic carboxylic acid salts (JP-A-60-41,
773), AlCl4-, CI-, Br-, I
- (JP-A-60-247,265), chloroborane compound (JP-A-61-165,957), tetraphenylboric acid (JP-A-61-214,376), etc. Among them, propylene carbonate 1
, 2-dimethoxyethane containing LiClO4 or LiBF6 is typical.

[0012] In addition to the electrolytic solution, the following solid electrolytes can also be used. Solid electrolytes are divided into inorganic solid electrolytes and organic solid electrolytes. Li nitrides, halides, oxyacid salts, and the like are well known as inorganic solid electrolytes. Among them, Li3 N, LiI, Li5
NI2, Li3 N-LiI-LiOH, LiSi
O4, LiSiO4-LiI-LiOH (Unexamined Japanese Patent Publication No. 4
9-81,899)xLi3PO4-(1-x)L
i4 SiO4 (JP-A-59-60,866), Li
2 SiS3 (JP-A-60-501,731), phosphorus sulfide compounds (JP-A-62-82,665), and the like are effective. For organic solid electrolytes, polyethylene oxide derivatives or polymers containing such derivatives (Japanese Unexamined Patent Publication No. 63-135,
447), polypropylene oxide derivatives or polymers containing such derivatives, polymers containing ionic dissociative groups (JP-A No. 62-254,302, No. 62-254,303, No. 6
3-193,954), a mixture of a polymer containing an ionically dissociable group and the aprotic electrolyte described above (U.S. Pat. No. 4,792)
, 504, 4,830,939, JP-A-62-22,
375, 62-22,376, 63-22,375
, 63-22,776, JP-A-95,117), phosphate ester polymer (JP-A-61-256,573)
is valid. Furthermore, there is also a method of adding polyacrylonitrile to the electrolyte (Japanese Patent Application Laid-Open No. 62-278,774).
. Also known is a method of using an inorganic and an organic solid electrolyte in combination (Japanese Patent Application Laid-Open No. 60-1,768).

[0013] The separator has high ion permeability,
It is an insulating thin film with a certain mechanical strength. Olefin nonwoven fabrics such as polypropylene and glass fibers are used because of their organic solvent resistance and hydrophobicity. It is also known to add the following compounds to electrolytes for the purpose of improving discharge and charge/discharge characteristics. For example, pyridine (JP 49-108,525), triethyl phosphite (JP 47-4,376), triethanolamine (JP 52-72,425), cyclic ether (
JP-A-57-152,684), ethylenediamine (JP-A-58-87,777), n-glyme (JP-A-58-87,777),
-87,778), hexaphosphoric acid triamide (JP-A-5
8-87,779), nitrobenzene derivatives (Japanese Unexamined Patent Publication No.
8-214,281), sulfur (JP-A-59-8,280
), quinoneimine dye (JP-A-59-68,184),
N-substituted oxazolidinone and N,N'-substituted imidazolidinone (JP-A-59-154,778), ethylene glycol dialkyl ether (JP-A-59-205,16)
7), Quaternary ammonium salt (JP-A-60-30,065
), polyethylene glycol (JP-A-60-41, 77
3), pyrrole (JP 60-79,677), 2-methoxyethanol (JP 60-89,075), Al
Cl3 (JP 61-88,466) Monomer of conductive polymer electrode active material (JP 61-161,673)
, triethylene phosphoramide (JP-A-61-208,
758), trialkylphosphines (JP-A-62-80)
,976), Morpholine (JP-A-62-80,977)
), aryl compounds with a carbonyl group (Japanese Patent Application Laid-open No. 1983-
86,673), hexamethylphosphoric triamide and 4-alkylmorpholine (JP 62-217,5
75), bicyclic tertiary amine (JP-A-62-217,5
78), oil (JP-A-62-287,580), quaternary phosphonium salt (JP-A-63-121,268), tertiary sulfonium salt (JP-A-63-121,269). Further, in order to make the electrolytic solution non-flammable, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluorochloride can be included in the electrolytic solution. (Unexamined Japanese Patent Publication No. 48-36,
632) Furthermore, carbon dioxide gas can be included in the electrolytic solution in order to make it suitable for high-temperature storage. (Unexamined Japanese Patent Publication No. 59-134,567)

[0014] Furthermore, the positive electrode active material can contain an electrolytic solution or an electrolyte. For example, the ion conductive polymer, nitromethane (Japanese Patent Application Laid-Open No. 48-36,633),
Addition of an electrolyte (Japanese Patent Laid-Open No. 57-124,870) is known. Moreover, the surface of the positive electrode active material can be improved. For example, the surface of a metal oxide is treated with an esterifying agent (JP-A-55-163,779), a chelating agent (JP-A-55-163,780), and a conductive polymer (JP-A-58-1989).
163,188, 59-14,274), and polyethylene oxide (Japanese Unexamined Patent Publication No. 60-97,561). Moreover, the surface of the negative electrode active material can also be modified. For example, a method of providing an ion-conductive polymer or polyacetylene layer (Japanese Patent Application Laid-Open No. 58-111,276
), LiCl (JP-A-58-142,771), and ethylene carbonate (JP-A-59-31,573).

As a carrier for the electrode active material, for the positive electrode, in addition to the usual stainless steel, nickel, and aluminum, porous foam metal for conductive polymers (Japanese Unexamined Patent Publication No. 59-18,
578), titanium (JP 59-68, 169), expanded metal (JP 61-264, 686),
In addition to regular stainless steel, nickel, titanium, and aluminum, punched metal and negative electrodes include porous nickel (
JP-A-58-18,883), porous aluminum (JP-A-58-38,466), aluminum sintered body (JP-A-59-130,074), molded body of aluminum fiber group (JP-A-59-Sho 59) -148,277), silver plating on the surface of stainless steel (Japanese Patent Application Laid-Open No. 60-41,761), fired carbonaceous materials such as phenol resin fired bodies (Japanese Patent Application Laid-Open No. 60-11
2,264), Al-Cd alloy (JP-A-60-211,
779), porous metal foam (JP-A-61-74, 26
8) etc. are used.

The current collector may be any electron conductor that does not cause a chemical change in the constructed battery. For example, in addition to the commonly used stainless steel, titanium, and nickel, nickel-plated copper (Japanese Patent Laid-Open No. 48-36,627
), titanium-plated copper body, and sulfide positive electrode active material are coated with copper on stainless steel (Japanese Patent Laid-Open No. 175-37
3) etc. are used. The shape of the battery is coin, button,
It can be applied to both sheets and cylinders.

[0017]

[Examples] The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to the following Examples unless it goes beyond the gist of the present invention. Example 1 As positive electrode active materials, ■V6 O13, ■LiMn2O4, ■Li
Ni0.5 Co0.5 O2, ■88% by weight each of chemically oxidized polypyrrole, 6% by weight of acetylene black as a conductive agent, 6% by weight of ■diacetylcellulose, ■hydroxyethylcellulose, ■carboxymethylhydroxyethylcellulose as a binder. After drying the mixture mixed at a mixing ratio of
15 mmΦ, capacity of 20 mAH) was used. Lithium-aluminum alloy (alloy ratio 80-20
% by weight, 15 mmΦ, and a capacity of 40 mAh). When mixing cellulose, each was mixed at a mixing ratio of 3% by weight. 1 mol/1 LiBF4 (equal volume mixture of propylene carbonate and 1,2-dimethoxyethane) was used as the electrolyte, and a microporous polypropylene nonwoven fabric was used as the separator, and the nonwoven fabric was impregnated with the electrolytic solution. Then, a coin-type lithium battery as shown in FIG. 1 was manufactured. This lithium battery is 1mA/cm
A charge/discharge test was conducted at a current density of 2 and a charge/discharge depth of 5 mAH. The hardness of the pellets was measured using a constant pressure loading type hardness tester.

Comparative Example 1 As the binder used in Example 1, (1) Teflon and (2) carboxymethylcellulose were mixed in the same weight percent as in Example 1. Example 2 As positive electrode active materials, ■LiMn2O4, ■LiNi
0.5 Co0.5 O2 at a mixing ratio of 88% by weight, 6% by weight of acetylene black as a conductive agent, and 6% by weight of diacetylcellulose, ■hydroxyethylcellulose, and carboxymethylhydroxyethylcellulose as binders. After drying the mixture (using acetone, water, and water as solvents, respectively), compression-molded positive electrode pellets (15 mmΦ, 20 mAH capacity) were used. Needle coke was mixed at a mixing ratio of 90% by weight as a negative electrode active material, and diacetylcellulose, ■hydroxyethylcellulose, and carboxymethylhydroxyethylcellulose were mixed as binders at a mixing ratio of 10% by weight (
After drying the mixture (using acetone, water, and water as solvents, respectively), add and mix polymethylene polyphenyl polyisocyanate in an equal amount with the hydroxyl group of the binder in order to deactivate the hydroxyl group that reacts with lithium. , Negative electrode pellets (15 mmΦ, 60 mA
(capacity equivalent to H) was used. The same compound as the positive electrode mixture and the negative electrode mixture was used as the binder. When mixing cellulose,
Each was mixed at a mixing ratio of 5% by weight. 1 mo as electrolyte
l /1LiBF4 (propylene carbonate and 1,
using a mixture of equal volumes of 2-dimethoxyethane), and further,
A microporous polypropylene nonwoven fabric was used as a separator, and the electrolytic solution was impregnated into the nonwoven fabric. Then, a coin-type lithium battery as shown in FIG. 1 was manufactured. This lithium battery was subjected to a charge/discharge test at a current density of 1 mA/cm 2 and a charge/discharge depth of 5 mAH. The hardness of the pellets was measured using a constant pressure loading type hardness tester.

Comparative Example 2 As the binder used in Example 2, (1) Teflon and (2) carboxymethylcellulose were mixed in the same weight percent as in Example 2. The results of Example 1 and Comparative Example 1 and the results of Example 2 and Comparative Example 2 are summarized in the following Tables 1 and 2, respectively.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Effects of the Invention] Since a hardness of 2 kg is difficult to handle during production, the present invention provides at least one acetyl cellulose derivative, hydroxyethyl cellulose, substituted with at least two different functional groups. By including a cellulose derivative in the positive electrode mixture and/or the negative electrode mixture, good pellet hardness (and, by extension, the hardness of the rolled electrode in the case of cylinder-type batteries or the hardness of the rolled electrode in the case of sheet-shaped batteries) can be improved. (This means that the hardness of the sheet electrode is increased.) This means that it can provide good charge/discharge cycle characteristics.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of a coin-shaped battery used in Example 1 and Example 2.

[Explanation of symbols]

1 Negative electrode sealing plate 2 Negative electrode mixture pellets 3 Separator 4 Positive electrode mixture pellets 5 Current collector 6 Positive electrode case 7 Gasket

Claims (1)

[Scope of Claims] [Claim 1] A secondary battery comprising a chargeable and dischargeable positive electrode active material, a negative electrode active material, and an electrolytic solution having ion conductivity, comprising at least one acetyl cellulose derivative, hydroxyethyl cellulose, or , a cellulose derivative substituted with two or more different functional groups is contained in a positive electrode mixture and/or a negative electrode mixture.Claim 2: A secondary battery characterized in that the acetylcellulose derivative is diacetylcellulose, diacetylcellulose, 3. The secondary battery according to claim 1, wherein the cellulose derivative substituted with at least two or more different functional groups is carboxymethylhydroxyethylcellulose or hydroxypropylcarboxymethylcellulose. 4. The secondary battery according to claim 1, wherein one of the positive electrode active materials is Co oxide,
The secondary according to claims 1 to 3, characterized in that it is Li-Co oxide, Li-Ni-Co oxide, V oxide, Li-V oxide, Mn oxide, Li-Mn oxide. battery【
5. The secondary battery according to claim 1, wherein one of the positive electrode active materials is an organic polymer.
6. The organic polymer is a polyaniline derivative,
The secondary battery according to claims 1 and 5, characterized in that it is a polypyrrole derivative or a polyacene derivative [Claim 7]
Claim 1, wherein one of the negative electrode active materials is a fired carbonaceous compound capable of intercalating and deintercalating lithium.
8. The secondary battery according to claim 1, wherein the positive electrode active material is a Ni compound, and the negative electrode active material is a hydrogen storage alloy.