JP2001068116A - Lithium battery and method of manufacturing therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high energy density, high safety and high reliability by including a conductive oxide or a carbon material as a conductive material in at least one of a positive electrode prepared by bonding an active material with oxide glass and a negative electrode arranged through an oxide-based inorganic solid electrolyte. SOLUTION: The positive electrode 1 is made of a porous body prepared by pressure-molding a mixture of a positive electrode active material, oxide glass, and a molding assistant, and heat-treating the molded body, and the negative electrode 3 is made of a porous body using a transition metal oxide having a charging/discharging potential lower than that of the positive electrode active material in the positive electrode 1 as an active material. An oxide conductive material of conductive materials to be after-impregnated into the positive electrode 1 and/or the negative electrode 3 is preferable to be SnO2, In2O3, SnO2 doped with Sb2O3, In2O3 doped with SnO2, or a carbon material, preferably carbon black. By binding the active material with the oxide glass, the electrode is made string, and by after-impregnating the conductive material, conductivity is imparted without decreasing battery capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lithium battery and a method for manufacturing the same, and more particularly, to a lithium battery having improved electrodes and a method for manufacturing the same.

[0002]

2. Description of the Related Art With the recent remarkable development of portable devices typified by portable telephones and personal computers, demand for batteries as power sources has been rapidly increasing. In particular, lithium batteries are batteries that use lithium, which has a small atomic weight and a large ionization energy, and are therefore being actively studied as batteries capable of obtaining high energy densities. Has been reached.

In general, a lithium battery has a sheet-like positive electrode in which a positive electrode active material and a carbon-based conductive agent are bound with an organic binder, and a sheet-like negative electrode in which a negative electrode active material is bound with an organic binder. The electrode group wound through the container is inserted into a battery case, and an organic electrolyte is injected into the electrode group and sealed.

In a lithium battery, lithium cobalt oxide (LiCoO ₂ ) or lithium manganate (LiMn ₂ O ₄ ) is generally used as a positive electrode active material, and the negative electrode active material is carbon dioxide such as coke or carbon fiber. Materials are used. As a result, by combining these positive electrode active materials and negative electrode active materials, the lithium battery has a nominal voltage of 3.5V.
The above high voltage is achieved.

However, since the organic electrolyte is used as the electrolyte, there are problems such as leakage due to the organic electrolyte and a narrow operating temperature range.

Further, in a lithium battery using a carbon material such as coke or carbon fiber as a negative electrode active material, since the charge and discharge voltage of the carbon material is around 0 V, lithium metal precipitates on the surface of the negative electrode during the charging process of the battery. It may cause an internal short circuit and cannot be said to have sufficient reliability.

As a method for solving such a problem, for example, Japanese Patent Application Laid-Open No. Hei 7-296850 discloses that Nb ₂
A battery using O ₅ and using Li ₂ MnO ₃ as a positive electrode active material has been proposed.
In Japanese Patent Laid-Open Publication No. H11-157, a battery using a spinel-based lithium-containing metal oxide as a positive electrode and a negative electrode active material is proposed.

[0008] As described above, when an oxide is used for the positive and negative electrode active materials, the cycle life and the overdischarge resistance are improved.
Although a lithium battery having high reliability is obtained, problems caused by the electrolyte such as leakage and a narrow operating temperature range cannot be solved because the organic electrolyte is used as the electrolyte.

Therefore, in order to solve these safety problems, development of an all-solid lithium battery excellent in heat resistance and reliability using an inorganic solid electrolyte composed of a nonflammable inorganic solid material has been promoted. I have. An example of a lithium battery using an inorganic solid electrolyte as an electrolyte is disclosed in, for example, JP-A-11-7.
As disclosed in Japanese Unexamined Patent Publication No. 942, there is one using sulfide glass as a solid electrolyte. However, sulfide glass has a problem in that it has poor stability against moisture and oxygen, which leads to an increase in battery manufacturing cost.

On the other hand, demands for lithium batteries are not limited to safety and reliability, and further higher energy density and higher output are required as portable devices become smaller and lighter.

In order to solve such problems, various attempts have been made to improve the conductive agent contained in the positive electrode. For example, a mixture of graphite and carbon black is used (see JP-A-8-22).
No. 2206), flaky graphite and fibrous carbon having different shapes are mixed (Japanese Patent Application Laid-Open No. 9-27344), and a transition metal carbide is used other than the carbon material (Japanese Patent Application Laid-Open No. 5-2).
17582), the use of aluminum powder or tantalum powder has been proposed (JP-A-8-78054).
No.). However, since none of these conductive agents directly contributes to an increase in battery capacity, attempts have been made to increase the capacity of the battery and thereby increase the energy density by not using a conductive agent.

Japanese Patent Application Laid-Open No. 8-148141 discloses a lithium battery having excellent charge / discharge characteristics by using a fired body of only an active material as an electrode without using a material such as a conductive agent or a binder which causes a decrease in battery capacity. is suggesting.

However, in the above proposal, since the binder is not contained in the active material layer, there is a problem that the electrode is brittle and handling is difficult. Furthermore, since the electrode is not provided with conductivity, when the thickness of the active material layer exceeds 20 μm, the charge / discharge capacity is extremely reduced, and there is a problem that a sufficient energy density cannot be obtained as a practical battery. Became clear.

The present invention has been made in view of such conventional problems, and has as its object to provide a lithium battery having a high energy density and excellent safety and reliability.

[0015]

According to a first aspect of the present invention, there is provided a lithium battery according to the first aspect, wherein an oxide-based inorganic material is provided between a positive electrode and a negative electrode each formed by binding an active material with an oxide glass. In a lithium battery with a solid electrolyte interposed,
In the above lithium battery, at least one of the positive electrode and the negative electrode contains a conductive oxide as a conductive agent, wherein the conductive oxide is SnO ₂ and / or I
Desirably, n ₂ O ₃ .

In the above lithium battery, the SnO 2
It is desirable to Sb ₂ O ₃ is doped in the conductive oxide consisting of _2.

In the above lithium battery, the In ₂
It is desirable that SnO ₂ be doped in the conductive oxide made of O ₃ .

According to a fifth aspect of the present invention, there is provided a method of manufacturing a lithium battery comprising an oxide-based inorganic solid electrolyte interposed between a positive electrode and a negative electrode each having an active material bound by oxide glass. In the manufacturing method, at least one of the positive electrode and the negative electrode is impregnated with a conductive oxide as a conductive agent after the active material is bound with oxide glass.

Further, in the lithium battery according to claim 6,
In a lithium battery in which an oxide-based inorganic solid electrolyte is interposed between a positive electrode and a negative electrode obtained by binding an active material with oxide glass, at least one of the positive electrode and the negative electrode contains a carbon material as a conductive agent. It is characterized by having.

In the above lithium battery, it is desirable that the carbon material is carbon black.

In the above-mentioned lithium battery, the carbon material is preferably a mixture of carbon black and graphite.

In the above lithium battery, the active material of the positive electrode and the negative electrode is Li _{1 + X} Mn _2-X O ₄ (0 ≦ X ≦ 0.
2), LiMn _2-Y MeYO ₄ (Me = Ni, Cr, C
u, Zn, 0 <Y ≦ 0.6), desirably at least one selected from the group consisting of Li ₄ Ti ₅ O ₁₂ and Li ₄ Mn ₅ O ₁₂ .

According to a tenth aspect of the present invention, there is provided a method for manufacturing a lithium battery comprising an oxide-based inorganic solid electrolyte interposed between a positive electrode and a negative electrode each having an active material bound by oxide glass. In the manufacturing method, after binding the active material with oxide glass, at least one of the positive electrode and the negative electrode is impregnated with a carbon material as a conductive agent.

[0024]

[Function] By binding the active material with oxide glass, the electrodes are strengthened, and the handling of the electrodes in the manufacturing process is facilitated, and the gap between the electrodes is impregnated with a conductive agent later.
Conductivity can be imparted to the electrode without lowering the battery capacity, and excellent charge / discharge characteristics can be obtained even with an electrode having a thickness of more than 20 μm, so that the energy density of the lithium battery can be improved.

In general, the charge / discharge voltage of an oxide shows a more noble potential than the charge / discharge voltage of a carbon material. No lithium precipitation reaction occurs, and the reliability and safety of the battery are improved.

Further, when SnO ₂ doped with Sb ₂ O ₃ and / or In ₂ O ₃ doped with SnO ₂ are used as the conductive oxide, good charge / discharge can be achieved due to its high conductivity. Characteristics will be obtained.

Further, when carbon black or a mixture of carbon black and graphite is used as the carbon material,
Good chargeability and conductivity, and excellent charge / discharge characteristics can be obtained.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the lithium battery of the present invention will be described. FIG. 1 is a sectional view showing a configuration example of the lithium battery according to the present invention. In FIG. 1, 1
Is a positive electrode, 2 is an electrolyte layer, 3 is a negative electrode, 4 is a positive electrode container, 5 is a negative electrode container, and 6 is a sealing resin.

The positive electrode 1 and the negative electrode 3 are mainly composed of an active material and an oxide glass. Examples of the active material used for the positive electrode 1 and the negative electrode 3 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 are given.

Among the above transition metal oxides, in particular, Li
_{1 + X} Mn _2-X O ₄ (0 ≦ X ≦ 0.2), LiMn _2-Y M
eYO ₄ (Me = Ni, Cr, Cu, Zn; 0 <Y ≦
0.6), the group consisting of Li ₄ Ti ₅ O ₁₂ and Li ₄ Mn ₅ O ₁₂ is a spinel-based active material in which the crystal of the active material having a small volume change during charge and discharge is formed by an oxide glass. It shows good cycle characteristics when worn.

Here, there is no clear distinction between the positive electrode active material and the negative electrode active material, and the charge and discharge potentials of two types of transition metal oxides are compared, and the one showing a more noble potential is used as the positive electrode, A battery having an arbitrary voltage can be formed by using a material having a potential as a negative electrode. When a transition metal oxide is used for the positive electrode active material and the negative electrode active material, deposition of metallic lithium does not occur even when the battery is overcharged, and the reliability of the battery is improved.

Examples of the oxide glass according to the present invention include phosphate glass, borate glass, silicate glass, and multi-component oxide glass mainly composed of borosilicate glass. Further, the addition of an alkali metal element is preferable because the volume resistance can be reduced, and particularly when lithium is added, lithium ion conductivity is expected.

Although the composition of the oxide glass is not particularly limited,
Since heat treatment for binding the active material particles is performed at a temperature equal to or higher than the glass transition point of the oxide glass and equal to or lower than the synthesis temperature of the active material, it is preferable to select an oxide glass exhibiting fluidity in this temperature range.

The amount of the oxide glass to be added is considered to have various optimum values depending on the combination of the active material and the oxide glass, but is generally preferably 30% by weight or less. If the content exceeds 30% by weight, the volume of the oxide glass occupying the electrode volume becomes large, and the filling rate of the active material is rather lowered.

The positive electrode 1 is made of a porous material obtained by adding a molding aid to a positive electrode active material and an oxide glass, press-molding and heat-treating the negative electrode, and the negative electrode 3 has a charge-discharge potential of the positive electrode active material in the positive electrode 1. And a porous body using a transition metal oxide having a low charge / discharge potential as an active material.

To produce the positive electrode 1 and the negative electrode 3,
(1) A slurry is prepared by dispersing an active material and an oxide glass in water or a solvent in which a molding aid is dissolved, and this slurry is applied on a substrate film, dried, and then molded under pressure and cut. (2) a method in which a mixture of the active material and the oxide glass is granulated directly or with the addition of a molding aid, and then granulated and injected into a mold, followed by pressure molding with a press machine, followed by heat treatment. And (3) a method in which the granulated mixture is pressure-formed by a roll press machine, processed into a sheet shape, and then cut and heat-treated.
The granulation of (2) and (3) may be wet granulation that granulates from the slurry described in the method of (1) or dry granulation without using a solvent.

Next, the positive electrode 1 and / or the negative electrode 3
For example, SnO ₂ and In
₂ O ₃ , TiO _{2 -X} , ZnO, Fe ₃ O ₄ , ReO ₃ ,
MoO ₂ , RuO ₂ , VO, WO ₂ etc. at room temperature, about 1 ×
A conductive oxide having a resistivity of 10 ⁻⁴ Ω · m or less can be used. More preferably, in order to obtain a stable low resistivity, SnO ₂ doped with Sb ₂ O ₃ and S
In ₂ O ₃ doped with nO ₂ is mass-produced for antistatic purposes and for transparent electrodes, and the use of these is advantageous in terms of quality and cost.

Examples of the carbon material post-impregnated into the positive electrode 1 and / or the negative electrode 3 include carbon black such as furnace black, acetylene black, and thermal black, and scaly or fibrous natural graphite or artificial graphite. Can be. In particular, the average primary particle size is 0.0
Furnace black and acetylene black of 25 to 0.07 μm have good filling properties and are suitable as carbon black. Further, graphite obtained by finely pulverizing flaky graphite to sub-μm is suitable for its excellent filling property and conductivity. Note that these carbon materials that have been subjected to a surface modification treatment with a silane coupling agent or the like in advance can also be used.

As a method of post-impregnation, for example, a suspension in which fine particles of an oxide conductive agent or a carbon material having an average particle diameter of one-tenth or less of the average particle diameter of the active material are dispersed in water or an organic solvent. There is a method in which the porous body of the positive electrode 1 and / or the negative electrode 3 obtained by heat treatment is immersed and impregnated, or a method in which the power generating element integrated by heat treatment in a lump through the electrolyte 2 is immersed and impregnated. Further, in order to accelerate the impregnation, it is also possible to perform the impregnation under reduced pressure or under reduced pressure. When the power generating element is impregnated, it is necessary to grind or cut the peripheral part in order to remove the oxide conductive agent attached to the peripheral part of the power generating element.

The oxide-based inorganic solid electrolyte used for the electrolyte layer 2 includes, for example, Li _1.3 Al _0.3 Ti _1.7 (P
Crystalline solid electrolytes such as O ₄ ) ₃ and Li _3.6 Ge _0.6 V _0.4 O ₄ , 30LiI-41Li ₂ O-29P ₂ O ₅ and 40Li ₂ O-35B ₂ O ₃ -25LiNbO ₃ , 10
_{Li 2 O-25B 2 O 3} -15SiO 2 amorphous solid electrolytes such as -50ZnO, or can be given mixture or fired crystalline solid electrolyte and an amorphous solid electrolyte.

The electrolyte layer 2 is formed, for example, by the above-mentioned production methods (1) to (4).
In the same manner as in (3), a compact can be prepared by adding a molding aid to a mixture of a crystalline solid electrolyte and an amorphous solid electrolyte, which are oxide-based inorganic solid electrolytes, and then heat-treated. .

The method for producing a power generating element by laminating the above-described positive electrode 1, negative electrode 3, and electrolyte layer 2 is as follows.
A method of laminating the positive electrode 1 and the negative electrode 3 which are individually heat-treated into a porous body through the electrolyte layer 2 or (b) laminating the positive electrode 1 and the negative electrode 3 after the heat treatment via the electrolyte layer 2 before the heat treatment. And (c) laminating the layers before the heat treatment and heat-treating them collectively. However, in consideration of the contact state of each layer, the method (b) or (c), in which adhesion between layers is possible, is preferable.

In any case, examples of the molding aid usable here include polytetrafluoroethylene, polyacrylic acid, carboxymethyl cellulose, polyvinylidene fluoride, polyvinyl alcohol, diacetyl cellulose, hydroxypropyl cellulose, polybutyral, polyvinyl One or a mixture of two or more of chloride, polyvinylpyrrolidone and the like can be mentioned.

As the base 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 metal thin plate used for the positive electrode case 4 and the negative electrode case 5 may be a metal material such as stainless steel, aluminum, nickel, copper, Kovar, 42 alloy, titanium or an aluminum alloy. The sealing resin 6 may be any adhesive resin having an adhesive property to the metal material, and a heat sealer or a hot plate can be used for the sealing.
The thickness of the positive electrode container 4 and the negative electrode container 5 is desirably thin from the viewpoint of the energy density of the battery, but an appropriate thickness is selected in view of the presence or absence of pinholes and the strength as an exterior material. Should. For example, for aluminum 30
It is desirable that the thickness be not less than μm. On the other hand, when the thickness is large, the thickness is preferably 500 μm or less from the viewpoint of the restriction by the sealing method and the adhesive strength and energy density of the sealing portion.

The electrode group accommodating portions of the positive electrode container 4 and / or the negative electrode container 5 may be formed in a concave shape in advance, and an existing conventional technique can be used for the concave forming method. For example, press working with a molding die is common. The shape is not particularly limited as long as it is concave as viewed from the electrode group storage portion, and the depth and the size are not particularly limited. , Should be shaped. Also, depending on the molding method, it may be more convenient to form a concave pole group storage portion in a trapezoidal shape during molding, or to provide a curved surface at the bent portion, and any design suitable for the molding method may be used. No problem.

As the sealing resin 6, an adhesive resin having an adhesive property to the above-mentioned metal container can be used. For example, a heat-fusible adhesive resin such as a modified polyethylene or a modified polypropylene is easy to handle and suitable.

The shape of the lithium battery of the present invention is not particularly limited, such as a square, triangular or circular shape such as a card type, a film type, a coin type, a cylindrical type and a flat type.

[0049]

The present invention will be described below in more detail with reference to examples.

[Example 1] Lithium hydroxide and manganese dioxide were mixed at a molar ratio of Li: Mn of 1: 2, and this mixture was heated and fired at 700 ° C. for 15 hours in the air to obtain lithium manganese. Complex oxide (LiMn
₂ O ₄ ) was prepared and used as a positive electrode active material.

Next, lithium hydroxide and titanium dioxide are
The mixture was mixed so that the molar ratio of i and Ti was 4: 5, and the mixture was heated and calcined at 750 ° C. for 15 hours in the air to prepare a lithium titanium composite oxide (Li ₄ Ti ₅ O ₁₂ ). This was used as a negative electrode active material.

Each of the LiMn ₂ O ₄ and Li ₄ Ti ₅ O ₁₂ and an oxide glass, here 50P ₂ O ₅ -30
PbO-20ZnO was dry mixed at a weight ratio of 90:10 to obtain a mixed powder. With respect to this mixed powder 100, polyvinyl butyral as a molding aid was added so as to be 10 in weight ratio,
Further, toluene was added to prepare a slurry. The slurry was applied on a polyethylene terephthalate (PET) film, dried, and formed into a sheet. The resulting sheet was press-compressed by a roll press to obtain a sheet having a thickness of 0.25 mm for both the positive electrode and the negative electrode. Each sheet was punched out with a mold to obtain a sheet-shaped positive electrode and negative electrode molded body of 20 mm square.

An oxide-based inorganic solid electrolyte, here 10 L
_{i 2 O-25B 2 O 3} -15SiO 2 -50ZnO a molding aid polyvinyl butyral weight ratio of 100 were mixed with 10, a slurry was prepared further by adding toluene, P
20m by molding and cutting on ET film
A sheet-like electrolyte molded body having an m square and a thickness of 0.1 mm was produced.

The above-mentioned positive electrode molded body and negative electrode molded body were laminated via an electrolyte molded body, and this was heat-treated at 550 ° C. in air at a time, and 18 m between the positive electrode 1 and the negative electrode 3 with the electrolyte layer 2 interposed therebetween.
A power generating element having an m square and a thickness of 0.55 mm was produced.

The post-impregnation of the conductive oxide was performed as follows. Sb manufactured by Kojundo Chemical Co., Ltd.
With ₂ O ₃ doped SnO _2, and this is first to prepare a SnO ₂ suspension is dispersed so that the concentration in pure water is 5 wt%. Next, the power generating element produced by batch heat treatment was immersed in this suspension, left for 5 minutes, taken out, and the surface liquid was wiped off, followed by drying at 120 ° C. for 10 minutes. These immersion and drying operations were repeated five times, and the periphery of the power generating element was lightly polished to remove unnecessary portions of SnO ₂ to obtain a power generating element.

The positive electrode case 4 and the negative electrode case 5 have a thickness of 0.1 m.
m was cut into a 25 mm square metal sheet. However, the positive electrode case 4 used was one in which the electrode group housing portion was formed in a concave shape by press molding in advance. As the negative electrode case 5, a case in which a sealing case 6 having an adhesive property and a case previously cut into a window frame having a width of 5 mm were heat-sealed was used.

Finally, assembling the battery, the above-mentioned power generating element is placed in the center of the negative electrode container 5, and then the positive electrode container 4 is covered, and the positive electrode container 4 and the negative electrode container 5 are heat-sealed and adhered. Was prepared.

Example 2 A lithium battery was assembled in the same manner as in Example 1 except that SnO ₂ -doped In ₂ O ₃ manufactured by Kojundo Chemical Co., Ltd. was used as the conductive oxide.

Example 3 A lithium battery was assembled in the same manner as in Example 1 except that a carbon material was used instead of the conductive oxide of Example 1. The post-impregnation of the carbon material was performed as follows. A conductive ink (JEF-505) manufactured by Acheson Japan Co., Ltd. is used as the carbon material. First, this is diluted with a dedicated solvent so that the concentration of the carbon material becomes about 5% by weight to prepare a suspension of the carbon material. Prepared. Next, the power generation element produced by batch heat treatment was immersed in this suspension, left for 5 minutes, taken out, and the surface liquid was wiped off.
Dry at 20 ° C. for 10 minutes. This dipping and drying operation is performed in 5
This was repeated several times, and the periphery of the power generating element was lightly polished to remove unnecessary carbon material, thereby obtaining a power generating element.

Example 4 Finely ground flaky natural graphite was added to the suspension of carbon material prepared in Example 3 so that the weight ratio of carbon black to graphite was 4: 1 and mixed well. A lithium battery was assembled in the same manner as in Example 1 except that the mixture was dispersed to form a mixed suspension of carbon black and graphite.

Comparative Example 1 A lithium battery was manufactured in the same manner as in Example 1, except that the step of post-impregnation with an oxide conductor was omitted.

Comparative Example 2 A positive electrode was prepared in the same manner as in Example 1.
As the negative electrode, a sheet-shaped positive electrode and a negative electrode molded body having a thickness of 0.25 mm and a size of 20 mm square were obtained. 550 ° C in air
Then, Sb ₂ O ₃ -doped SnO ₂ was post-impregnated in the same manner as in Example 1 to obtain a positive electrode and a negative electrode, respectively.

Next, the concentration of lithium perchlorate (LiClO ₄ ) as an electrolyte in a non-aqueous solvent in which propylene carbonate and 1,2-dimethoxyethane were mixed at a ratio of 1: 1 by volume was used as the electrolyte. It was prepared by dissolving to 1 mol / l.

The positive electrode was placed in a positive electrode case, a separator made of a 100-μm-thick polypropylene nonwoven fabric impregnated with the electrolytic solution was placed on the positive electrode, and the negative electrode and the negative electrode case were laminated. The negative electrode case was heat-sealed and bonded to produce a lithium battery.

[Comparative Example 3] LiMn ₂ O ₄ prepared in the same manner as in Example 1, acetylene black as a conductive agent, and polytetrafluoroethylene as a binder were used in a weight ratio of an active material, a conductive agent, and a binder. 8
After mixing and kneading in a ratio of 4: 10: 6, toluene as a solvent was added, and the mixture was sufficiently kneaded and formed into a 0.25 mm-thick strip-shaped sheet by a roll press. This sheet was punched out with a die to obtain a sheet-shaped positive electrode having a size of 18 mm square.

Next, the Li fabricated in the same manner as in Example 1 was used.
₄ Ti ₅ O ₁₂ , acetylene black as a conductive agent, and polytetrafluoroethylene as a binder were mixed with an active material, a conductive agent, and a binder in a weight ratio of 80: 1.
After mixing and kneading at a ratio of 2: 8, toluene as a solvent was added and kneaded sufficiently, and formed into a strip-shaped sheet having a thickness of 0.25 mm by a roll press. This sheet was punched out with a mold to obtain a sheet-shaped negative electrode of 18 mm square. A lithium battery was produced in the same manner as in Comparative Example 2 except that the post-impregnation of the conductive oxide was omitted using the above positive electrode and negative electrode.

Comparative Example 4 A positive electrode was prepared in the same manner as in Example 3.
As the negative electrode, a sheet-shaped positive electrode and a negative electrode molded body having a thickness of 0.25 mm and a size of 20 mm square were obtained. 550 of this in the atmosphere
Then, the carbon material was post-impregnated in the same manner as in Example 3 to obtain a positive electrode and a negative electrode, respectively.

Next, the concentration of lithium perchlorate (LiClO ₄ ) as an electrolyte in a non-aqueous solvent in which propylene carbonate and 1,2-dimethoxyethane were mixed at a volume ratio of 1: 1 was used. It was prepared by dissolving to 1 mol / l.

The positive electrode was placed in a positive electrode case, a separator made of a 100 μm-thick polypropylene nonwoven fabric impregnated with the electrolytic solution was placed on the positive electrode, and the negative electrode and the negative electrode case were laminated. The negative electrode case was heat-sealed and bonded to produce a lithium battery.

(Evaluation) Examples 1 to 4 and Comparative Example 1
The discharge capacity of the batteries prepared in Nos. 1 to 4 was measured, and the discharge capacity and the average discharge voltage were determined. The discharge capacity of the battery was constant current charging at a charge end voltage of 2.8 V and a current value of 0.2 mA. After that, the battery was left for 1 hour and discharged at a constant current of 0.2 mA to 2.0 V at a constant current. I asked. The discharge average voltage is
The voltage was an intermediate value of the discharge capacity.

The volume energy density was calculated from the obtained discharge capacity and average discharge voltage, and the results are also shown in Table 1. In calculating the volume energy density, the positive electrode 1 and the negative electrode 3 integrated via the electrolyte 2 containing no battery case or the separator impregnated with the electrolytic solution were used.
The product of the discharge capacity and the discharge average voltage was used as the numerator with the volume of only the power generation element consisting of

[0072]

[Table 1]

As is clear from Table 1, the batteries of Examples 1 to 4 have a higher weight energy density than the batteries of Comparative Examples.

Specifically, when the discharge capacities and the discharge average voltages of Examples 1 to 4 and Comparative Example 1 were compared, Examples 1 and 2 were impregnated with an oxide conductive agent, and Examples 3 and 4 were impregnated with a carbon material. Therefore, the battery of Comparative Example 1, which was not impregnated with the oxide conductive agent or the carbon material, could not be discharged at all, and the discharge capacity was 0 mAh. In addition, the batteries of the examples were able to charge and discharge despite the electrode thickness being as thick as 200 μm or more. This indicates that the post-impregnation of the oxide conductive agent and the carbon material greatly improved the charge / discharge characteristics of the battery.

When Examples 1 to 4 are compared with Comparative Examples 2, 3 and 4, Comparative Example 3 contains acetylene black and polytetrafluoroethylene in the electrode, so that the volume occupied by the active material is reduced. Battery capacity decreased despite high utilization of active material. On the other hand, since the battery of the example contains only 5% by weight of the oxide glass having a higher density than polytetrafluoroethylene, the volume occupied by the active material in the electrode increases, and as a result, the battery has a high capacity. It is considered that

Since the battery of Comparative Example 2 uses the same electrode as that of Example 1, the result was the same as that of Example 1.

Since the battery of Comparative Example 4 uses the same electrodes as in Example 3, the same results as in Example 3 were obtained.

Next, Examples 1-4 and Comparative Examples 2, 3,
A high temperature (60 ° C.) cycle test was performed using the battery No. 4. The cycle test was performed up to 50 cycles in the same charge / discharge current value and voltage range as the discharge capacity measurement. Table 2 shows the discharge capacity obtained by the discharge capacity measurement as the initial discharge capacity together with the discharge capacity at the 50th cycle.

[0079]

[Table 2]

From the results in Table 2, it can be seen that the lithium battery of the embodiment using the oxide-based inorganic solid electrolyte as the electrolyte is stable with almost no capacity reduction, whereas the battery using the organic electrolyte has a discharge capacity of It decreased to about half.

When the external appearance of the battery after the cycle test was visually confirmed, the battery of the comparative example using the organic electrolytic solution was found to have swollen. In contrast, there was no change in the appearance of the batteries of the examples.

From these facts, it is considered that the battery of the comparative example swelled due to the internal pressure of the battery increasing due to some reaction between the active material and the electrolytic solution accompanied by gas generation.

From the above, it was found that the battery of the present invention using an oxide-based inorganic solid electrolyte as the electrolyte had a high energy density and was excellent in safety and reliability.

Although only one type of positive electrode active material and one type of negative electrode active material are disclosed in this embodiment, an oxide-based inorganic solid electrolyte is used as an electrolyte, and an oxide conductive agent or a carbon material is used as an electrode. It is clear that the impregnation can provide the same effect on energy density, safety and reliability even if other active materials are used.

[0085]

As described above, according to the lithium battery of the present invention, since at least one of the positive electrode and the negative electrode contains a conductive oxide or a carbon material as a conductive agent, the energy density is high and the safety is high. Thus, a highly reliable lithium battery can be provided.

In general, the charge and discharge voltage of an oxide shows a more noble potential than the charge and discharge voltage of a carbon material. No lithium precipitation reaction occurs, and the reliability and safety of the battery are improved.

According to the method of manufacturing a lithium battery according to the present invention, at least one of the positive electrode and the negative electrode is impregnated with a conductive oxide or a carbon material as a conductive agent after binding the active material with the oxide glass. Therefore, a lithium battery having high energy density, excellent safety and reliability can be provided.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a lithium battery according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Positive electrode, 2 ... Electrolyte layer, 3 ... Negative electrode, 4 ... Positive electrode container, 5
Negative battery case…, 6… Sealing resin

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Nobuyuki Kitahara 3-5 Koikadai, Seika-cho, Soraku-gun, Kyoto Prefecture Inside the Central Research Laboratory, Kyocera Corporation (72) Inventor Toru Hara 3-chome Koikadai, Soraku-cho, Kyoto Prefecture 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-chome 5-term Kyocera Corporation Central Research Laboratory F-term (reference) BJ02 BJ03 BJ04 CJ06 CJ15 CJ23 DJ08 EJ04 EJ05 EJ06 HJ02

Claims (10)

[Claims] 1. A lithium battery in which an oxide-based inorganic solid electrolyte is interposed between a positive electrode formed by binding an active material with an oxide glass and a negative electrode, wherein at least one of the positive electrode and the negative electrode is used as a conductive agent. A lithium battery containing a conductive oxide. 2. The lithium battery according to claim 1, wherein the conductive oxide is SnO ₂ and / or In ₂ O ₃ . 3. The conductive oxide comprising SnO ₂ contains S
_{3. The method according} to claim 2, wherein b ₂ O ₃ is doped.
The lithium battery according to 1. 4. The method of claim 2, characterized in that the SnO ₂ is doped in the conductive oxide made of the In ₂ O ₃
The lithium battery according to 1. 5. A method for producing a lithium battery, comprising an oxide-based inorganic solid electrolyte interposed between a positive electrode and a negative electrode, wherein the active material is bound with oxide glass, wherein the active material is made of oxide glass. A method for manufacturing a lithium battery, comprising: impregnating at least one of the positive electrode and the negative electrode with a conductive oxide as a conductive agent after binding. 6. A lithium battery in which an oxide-based inorganic solid electrolyte is interposed between a positive electrode and a negative electrode obtained by binding an active material with an oxide glass, wherein at least one of the positive electrode and the negative electrode serves as a conductive agent. A lithium battery containing a carbon material. 7. The lithium battery according to claim 6, wherein the carbon material is carbon black. 8. The lithium battery according to claim 7, wherein the carbon material is a mixture of carbon black and graphite. 9. The active material of the positive electrode and the negative electrode is Li _{1 + X} Mn.
_2-X O ₄ (0 ≦ X ≦ 0.2), LiMn _2-Y MeYO ₄
(Me = Ni, Cr, Cu, Zn, 0 <Y ≦ 0.6),
Li ₄ Ti ₅ O ₁₂ and Li ₄ Mn ₅ lithium battery according to claim 1 or claim 6, characterized in that it consists of at least one of the O ₁₂ group consisting of is selected. 10. A method for manufacturing a lithium battery in which an oxide-based inorganic solid electrolyte is interposed between a positive electrode and a negative electrode obtained by binding an active material with oxide glass, wherein the active material is formed of oxide glass. A method for manufacturing a lithium battery, comprising: impregnating at least one of the positive electrode and the negative electrode with a carbon material as a conductive agent after binding.