JP2000311692A - Manufacture of electrochemical element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the filling factor of an active material and to prevent the reduction of a capacity by pinching an electrolyte between electrodes made of the active material, sealing them in a can, covering the surface of active material powder with an amorphous material, then baking it. SOLUTION: A positive electrode current collecting layer 2 and a negative electrode current collecting layer 7 of a coin type lithium ion battery are arranged to be stuck to a positive electrode can 1 or a negative electrode can 8 and for current collection, and they are made of a polyimide adhesive including a carbon material, for example. A transition metal oxide such as a lithium manganese composite oxide, manganese dioxide, vanadium oxide, and tungsten oxide and their derivatives are available as the active materials used for an oxide positive electrode sintered body 3 and an oxide negative electrode sintered body 6. An organic electrolyte dissolved with required electrolyte salt in an organic solvent, a polymer solid electrolyte dissolved with electrolyte salt in an ionic conductive polymer material, or an inorganic solid electrolyte made of a gel electrolyte combined with them and an inorganic material is used for a separator 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing an electrochemical device, and more particularly to a method of manufacturing an electrochemical device in which an electrolyte is sandwiched between electrodes made of an active material and sealed in a can.

[0002]

2. Description of the Related Art There is a lithium ion secondary battery as a device using an electrochemical element capable of inserting and removing lithium ions accompanying an electrochemical redox reaction. In this lithium ion secondary battery, molding the active material powder at a high density leads to an improvement in electrochemical capacity.

Conventionally, a polymer adhesive has been used as a bonding material in order to ensure the shape retention of an electrode made of an active material powder. However, there have been the following two problems. First, at least 3 wt% or more of the electrode is occupied by the polymer adhesive, and there is a problem that the density of the active material is reduced. In addition, in the portion of the active material powder covered with the adhesive, there is a problem in that the lithium ion deinsertion site is blocked and the capacity is reduced.

There is also a method of sintering active material powder in order to improve the filling rate of the active material. That is, a material having the same component as the main material or at least one component is coated with a small amount of coating material powder composed of an amorphous or ultra-fine crystal composed of the same material, and then sintered to form a porous or dense body. (JP-A-8-59351). However, in this method, after sintering, the coating material is also crystallized epitaxially and cannot be distinguished from the main material, and is not suitable for an active material having lithium ion conductivity in which thermal decomposition occurs prior to epitaxial growth.

Accordingly, the present invention is to provide a method of manufacturing an electrochemical device comprising an active material, in which the filling factor of the active material is improved while maintaining the shape retention of the active material and the capacity is not reduced. Is what you do.

[0006]

According to a method of manufacturing an electrochemical device according to the present invention, an electrolyte is sandwiched between electrodes made of an active material and sealed in a can. The method for manufacturing a device is characterized in that the surface of the active material powder is coated with an amorphous material and then fired.

In the method of manufacturing an electrochemical device, it is desirable to coat the surface of the active material powder by sol-gel synthesis of an amorphous material.

[0008] In the method for manufacturing an electrochemical device,
It is desirable to irradiate the active material powder with UV light and coat it with an amorphous material.

[0009]

[Function] By chemically bonding the active material powder and the amorphous material, a stronger bonding can be achieved with a smaller amount of the coating material than in the case of using a polymer adhesive, and therefore, the filling of the active material powder is performed. The rate is improved.

[0010] Further, by chemically bonding the active material powder and the amorphous material, the lithium ion deinsertion site is directly bonded at the interface like heteroepitaxial, so that the desorption of lithium ion is not hindered. , Does not cause a decrease in capacity.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing an electrochemical device according to the present invention will be described. FIG. 1 is a cross-sectional view showing a configuration example of an electrochemical device manufactured by the manufacturing method of the present invention, taking a coin-type lithium ion battery as an example. In FIG. 1, 1
Is a positive electrode can, 2 is a positive electrode current collecting layer, 3 is a positive electrode, 4 is an insulating packing, 5 is a solid electrolyte or a separator containing an electrolyte, 6 is a negative electrode, 7 is a negative electrode current collecting layer, and 8 is a negative electrode can.

The positive electrode current collecting layer 2 and the negative electrode current collecting layer 7 are disposed for adhesion and current collection between the positive electrode can 1 or the negative electrode can 8 and the positive electrode 3 or the negative electrode 6. For example, a polyimide-based adhesive containing a carbon material is used. Consisting of agents.

The active materials used for the positive electrode 3 and the negative electrode 6 include the following transition metal oxides. For example, lithium manganese composite oxide, manganese dioxide, lithium nickel composite oxide, lithium cobalt composite oxide, lithium nickel cobalt composite oxide, lithium vanadium composite oxide, lithium titanium composite oxide, titanium oxide, niobium oxide, vanadium oxide, Tungsten oxide and derivatives thereof. Here, the active materials used for the positive electrode 3 and the negative electrode 6 are not clearly distinguished, and those showing a more noble potential by comparing the charge and discharge potentials of the two types of transition metal oxides are given to the positive electrode 3 and the more negative ones. A battery having an arbitrary voltage can be formed by using each of the negative electrodes 6 having a high potential. A transition metal oxide may be used only for the positive electrode 3, and a carbon material or metallic lithium may be used for the negative electrode 6. These can remove and insert lithium ions accompanying the electrochemical redox reaction.

Examples of the amorphous material used in the present invention include phosphate glass, borate glass, silicate glass, silicate glass, and oxide glass mainly composed of borosilicate glass. The addition of lithium is preferable because not only the lithium ion conductivity is increased, but also the sintering temperature is lowered by lowering the glass transition point. Further, addition of a transition metal such as vanadium, iron, titanium, cobalt, nickel, or manganese is preferable because it can impart electron conductivity to the glass.

The composition of the amorphous material is not particularly limited, but the heat treatment for bonding the active material particles is performed at a temperature equal to or higher than the glass transition point of the amorphous material so as to secure the shape retention of the electrochemical element. And it is performed below the synthesis temperature of an active material. for that reason,
It is preferable to select a composition that exhibits fluidity in this temperature range. However, when a coating material such as silicate glass that does not show fluidity is coated within the heat treatment temperature range for joining the active material particles, the bonding property with the coating material is good, and the fluidity is maintained within the heat treatment temperature range. After mixing the oxide glass powder having good properties, sintering may be performed. In this case,
Since the oxide glass mixed later does not need to cover the active material particles, it is sufficient to mix a minimum amount necessary for imparting shape retention.

Although the optimum value of the amount of the amorphous material varies depending on the combination of the active material and the amorphous material, it is generally preferably 5% by weight or less. If the content exceeds 5% by weight, the volume of the amorphous material in the electrode volume becomes large, and the filling rate of the active material is rather lowered.

When an electron-conductivity imparting agent is added for the purpose of enabling a large current discharge, a metal powder such as gold or silver, tin-doped indium oxide, It is preferable to add at least one kind selected from electron conductive oxides such as antimony-doped tin oxide.

The battery manufactured according to the method of manufacturing an electrochemical device according to the present invention is characterized in that the positive electrode 3 and / or the negative electrode 6 perform sol-gel synthesis of an amorphous material in the presence of the active material powder. And a coating in which the amorphous material and the amorphous material are chemically bonded, and then the powder is fired to obtain a porous body or a dense body.

To manufacture the positive electrode 3 and the negative electrode 6,
(1) A slurry is prepared by dispersing an active material coated with an amorphous material, an electron conductivity-imparting agent, and a molding aid in water or an organic solvent in which the slurry is prepared. After coating and drying, the cut pieces are 500-800
Or (2) an active material coated with an amorphous material and an electron-conductivity-imparting agent are granulated directly or with the addition of a molding aid, and then granulated and put into a mold. A method of performing heat treatment at 500 to 800 ° C. after pressure molding, (3)
The granulated mixture is pressed into a sheet by a roll press and processed into a sheet.
For example, a method of performing a heat treatment at a temperature of ° C.

Examples of the molding aid usable here include polytetrafluoroethylene, polyacrylic acid, carboxymethylcellulose, polyvinylidene fluoride, polyvinyl alcohol, diacetylcellulose, hydroxypropylcellulose, polybutyral, polyvinyl chloride, polyvinylpyrrolidone and the like. Or a mixture of two or more.

As the substrate film, for example, resin films such as polyethylene terephthalate, polypropylene, polyethylene and polytetrafluoroethylene, and metal foils such as aluminum, stainless steel and copper can be used.

The electrolyte 5 may be an organic electrolyte in which a required electrolyte salt is dissolved in an organic solvent, a solid polymer electrolyte in which an electrolyte salt is dissolved in an ion-conductive polymer material, or a gel electrolyte in which these are combined. An inorganic solid electrolyte made of an inorganic material can be used. When an organic electrolyte is used as an electrolyte, a separator for separating the positive electrode 3 and the negative electrode 6 is required.

The organic solvent used for the organic electrolyte includes, for example, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, sulfolane,
There is one or a mixture of two or more solvents selected from 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran, 2-methyltetrahydrofuran, and methylethyl carbonate.

As the ion conductive polymer material, for example, a polymer having an ethylene oxide skeleton represented by polyethylene oxide, a polymer having an acrylonitrile skeleton represented by polyacrylonitrile, or a mixture or copolymer thereof is used. is there.

Examples of the electrolyte salt include LiClO ₄ ,
LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ , Li (C
And a lithium salt such as F ₃ SO ₂ ) ₂ .

As the inorganic solid electrolyte, for example, Li _1.3
Al _0.3 Ti _1.7 (PO ₄ ) ₃ , Li _3.6 Ge _0.6 V
Oxide crystalline solid electrolyte such as _0.4 O ₄ , 40 Li _{2
O-35B 2 O 3 -25LiNbO 3} , 30LiI-4
1Li ₂ O-29P ₂ O ₅ oxide-based amorphous solid electrolytes such as, mention may be made of sulfide-based amorphous solid electrolytes such as _{1Li 3 PO 4 -63Li 2 S-} 36SiS 2.

As the separator, for example, a nonwoven fabric made of polyolefin fiber or a microporous film made of polyolefin can be used. Here, examples of the polyolefin include polyethylene and polypropylene.

[0028]

[Example 1] Li [Li as active material powder
_1/3 Ti _5/3 ] O ₄ as an amorphous material, Li ₂ O: Si
O ₂ : Al ₂ O ₃ : B ₂ O ₃ = 15: 70: 7.5:
A porous electrochemical device was produced using 7.5 mol% glass by the method shown in FIG. That is, Li [Li _1/3
Ti _5/3 ] O ₄ with 2-methoxyethanol,
A mixture of Si (OEt) ₄ and 2-methoxyethanol was mixed, irradiated with UV light, and stirred.
2-methoxyethanol and acetylacetone were added to a mixture of iOMe, Al (OBu) ₃ , and B (OEt) ₃ , refluxed, stirred, dried, and dried to reduce Au to 1%.
The mixture is molded by adding wt% and calcined at 650 ° C. under normal pressure.

In the porous body thus manufactured, the ratio of the amorphous material was 0.98 wt%. That is, the filling amount of the active material powder was about 98% by weight. The volume filling rate of the active material powder measured by the He gas replacement method was 65 vol%.

Example 2 Li [Li
_1/3 Ti _5/3 ] O ₄ as an amorphous material, Li ₂ O: Si
O ₂ : Al ₂ O ₃ : B ₂ O ₃ = 15: 70: 7.5:
A dense electrochemical element was produced using 7.5 mol% glass by the method shown in FIG. Li [Li _1/3 Ti _5/3 ]
The O _{4/2-methoxyethanol,} Si (OEt) ₄ /
Add 2-methoxyethanol, irradiate with UV and stir to obtain LiOMe, Al (OBu) ₃ , B (OEt)
_After adding ₃ / 2-methoxyethanol and acetylacetone, refluxing, stirring and drying, adding 1 wt% of Au and molding, 0.5 × 10 5 at 650 ° C.
Sinter while pressing at ³ kgf / cm ² .

In the dense body thus manufactured, the ratio of the amorphous material was 1.96 wt%. That is, the filling amount of the active material powder was about 97% by weight. The volume filling rate of the active material powder measured by the He gas replacement method was 85 vol%.

Comparative Example 1 Active Material Powder Li [Li _1/3 T]
A porous electrochemical element was produced without coating [i _5/3 ] O ₄ with an amorphous material. That is, the filling amount of the active material powder is about 99.
wt%. The volume filling rate of the active material powder measured by the He gas replacement method was 45 vol%.

Comparative Example 2 A porous electrochemical device was manufactured in the same manner as in Example 1 except that UV irradiation was not performed.

The proportion of the amorphous material in the porous body thus produced was 0.98% by weight. That is, the filling amount of the active material powder was about 98% by weight. In addition, the volume filling rate of the active material powder measured by the He gas replacement method was 58 vol%.

Comparative Example 3 Li [Li _1/3 Ti _5/3 ] O
₄ 96wt%, Teflon-based polymer adhesive 3wt%,
Au was mixed with 1 wt% of N-methylpyrrolidinone and formed into a tape. The volume filling rate of the active material powder measured by the He gas replacement method was 55 vol%.

[Electrochemical Evaluation] Example 1, Example 2,
The electrochemical devices shown in Comparative Example 1, Comparative Example 2, and Comparative Example 3 were used for the positive electrode, and graphite and Teflon-based polymer adhesive were mixed in the negative electrode at a ratio of 97: 3 wt% using N-methylpyrrolidinone. After drying, LiCl is used as the electrolyte.
Propylene carbonate in which O ₄ is dissolved at 1 mol / l:
A 1: 1 solution of diethyl carbonate, a microporous polypropylene membrane for the separator, an Al foil for the positive electrode current collector, a Cu foil for the negative electrode current collector, and a coin cell for electrochemical capacity evaluation I crossed.

Using this coin cell, 1.2 to 2.0
Between V, the charge / discharge capacity was measured at a current value of 10 mA / g. Table 1 shows the results.

[0038]

[Table 1]

The active material filling rate and the initial charge capacity of the porous electrochemical device of Example 1 and the dense electrochemical device of Example 2 are higher than those of the conventional electrochemical device of Comparative Example 3. It is confirmed that. That is, the effect of the present invention is confirmed. Further, the capacity retention after 500 cycles is remarkably improved because the active material powders are strongly bonded to each other by chemical bonding via the amorphous material.

The initial charging capacity of Example 1 was higher than that of Comparative Example 1 because Comparative Example 1 had no amorphous material and was fired at a high temperature in order to obtain shape retention of the active material powder. It is presumed that thermal decomposition occurred due to the bonding.

The capacity retention after 500 cycles was higher in Example 1 than in Comparative Example 2.
Comparative Example 2 did not perform UV irradiation, and thus did not form a chemical bond between the active material powder and the amorphous material. Therefore, the bonding between the active material powders via the amorphous material was weak. It is speculated that

[0042]

As described above, according to the method of manufacturing an electrochemical device according to the present invention, the active material powder is coated with an amorphous material and then baked. Strong bonding can be achieved with a smaller amount of coating material than when used, and therefore the filling rate of the active material powder is improved.

Further, since the active material powder is chemically bonded to the amorphous material, the lithium ion deinsertion site is directly bonded to the heteroepitaxial like at the interface, so that the desorption of lithium ions is inhibited. And does not cause a decrease in capacity.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration example of a coin-type lithium-ion battery using an electrochemical device according to the present invention.

FIG. 2 is a view showing the steps in one embodiment of the method for manufacturing a porous electrochemical device of the present invention.

FIG. 3 is a diagram showing steps in one embodiment of the method for producing a dense electrochemical device of the present invention.

[Explanation of symbols]

1 ‥‥‥ positive electrode can, 2 ‥‥‥ positive electrode current collector layer, 3 ‥‥‥ positive electrode,
4 Insulation packing, 5 Solid electrolyte or separator containing electrolyte, 6 Negative electrode, 7 Negative current collecting layer, 8 Negative electrode can

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yoko Mishima 3-5-chome, Seika-cho, Soraku-gun, Kyoto Prefecture Inside the Central Research Laboratory, Kyocera Corporation (72) Inventor Shinji Magome 3-chome, Seika-cho, Soraku-gun, Kyoto 5 Kyocera Corporation Central Research Laboratory (72) Inventor Makoto Osaki 3-chome, Soka-cho, Soraku-gun, Kyoto Prefecture 5-5-2 Kyocera Corporation Central Research Laboratory (72) Inventor Ei Higuchi Seika-cho, Soraku-gun, Kyoto Prefecture 3-5-5 Kyocera Corporation Central Research Laboratory F-term (reference) 5H003 AA02 AA04 BA00 BA01 BB01 BB11 BC01 BC05 5H029 AJ03 AJ05 AK03 AL07 AM03 AM04 AM05 AM07 AM12 BJ03 BJ16 CJ02 CJ21 CJ28 DJ08 DJ16 EJ11 HJ12

Claims (3)

[Claims] 1. A method of manufacturing an electrochemical element in which an electrolyte is sandwiched between electrodes made of an active material and sealed in a can, and the surface of the active material powder is coated with an amorphous material and then fired. A method for producing an electrochemical device, comprising: 2. The method according to claim 1, wherein the surface of the active material powder is coated by sol-gel synthesis of an amorphous material. 3. The method according to claim 1, wherein the active material powder is irradiated with UV light and coated with an amorphous material.