JP2000311710A - Solid electrolyte battery and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a charge / discharge rate characteristic and a storage property of a battery, and to improve a cycle characteristic as a secondary battery containing no electrolytic solution at all, particularly a solid electrolyte having a high energy density. It is intended to provide a battery. SOLUTION: In a solid electrolyte battery in which a solid electrolyte is interposed between a pair of electrodes composed of a positive electrode active material and a negative electrode active material, an inorganic oxide made of the same material as the solid electrolyte is used as the positive electrode active material or the negative electrode active material. Were interposed between the particles of the positive electrode active material or the negative electrode active material so as to form a three-dimensional network structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solid electrolyte battery using a solid electrolyte made of an inorganic oxide.

[0002]

2. Description of the Related Art Conventionally, aqueous or non-aqueous liquid electrolytes have been used for various types of batteries. Recently, however, portable batteries such as video photographing devices, notebook computers, and mobile phones have been used. 2. Description of the Related Art Along with a demand for thin, lightweight, and miniaturized electronic application devices represented by information terminal devices, a solid electrolyte battery using a solid electrolyte made of a polymer material instead of a liquid electrolyte has attracted attention.

[0003] In such a solid electrolyte battery, since the electrolyte is not liquid, there is no need to worry about leakage of liquid which may cause ignition of the battery.
It has the characteristic of low corrosiveness. However, when a solid electrolyte made of such a polymer material is used as, for example, an electrolyte for a secondary battery, a large current cannot be taken out due to the low ionic conductivity of the polymer material, and the rate characteristics in charge / discharge. There is a problem that battery performance such as battery characteristics, cycle characteristics, and storage characteristics is poor.

In order to solve such a problem, an attempt is made to improve the utilization rate of an active material by forming a solid electrolyte in which a metal oxide or electron-conductive fine particles are added and dispersed in a polymer material (for example, a solid electrolyte). JP-A-5-314995, JP-A-5-314995
JP-A-315008, JP-A-5-07466, and those using a polymer network structure as an ion conduction path (JP-A-5-325990) have been proposed.

However, even in these batteries, unless the organic electrolyte is taken in, good ionic conductivity cannot be ensured, and the solid electrolyte cannot sufficiently play a role as a good ionic conductor in a target electrode reaction. Was something.

Therefore, even if each of these techniques is applied to a solid electrolyte battery, the ionic conductivity is several steps lower than that of a conventional liquid electrolyte, and the effectiveness as a solid electrolyte battery is insufficient. In addition, the charge / discharge cycle history causes ions to be trapped at the interface between the solid electrolyte and the active material and at the interface between the solid electrolyte particles. There was a problem.

In general, in an all solid state secondary battery, the performance of the battery can be improved by rapidly conducting ionic conduction in the solid electrolyte. Therefore, the solid electrolyte having a smaller number of defects that inhibit ionic conduction therein is better. It serves as an ion conductor to improve charge / discharge performance. However, in the above proposal, the ionic conduction path is interrupted by the porous structure of the solid electrolyte itself, or the ionic conduction path is interrupted by an additive or the like, and the ionic conduction is not performed promptly.
The resulting current density is low, and without any intervening electrolytic solution, a secondary battery having a high energy density cannot be obtained, and there is a problem that practicality is lacking.

[0008]

The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems. As a result, the reason why a large current cannot be taken out is that the contact resistance at the interface between the solid electrolyte particles is high and the ionic conductivity is high. It has been found that it is possible to reduce the resistance in the solid electrolyte by promptly conducting the ionic conduction at this interface which affects the resistance.

The present invention has been made based on such knowledge, and an object of the present invention is to provide a solid electrolyte battery having improved characteristics such as charge / discharge rate characteristics and storage stability as a battery. In particular, it is an object of the present invention to provide a solid electrolyte battery which is excellent in cycle characteristics and contains no high-energy-density electrolytic solution at all.

[0010]

According to a first aspect of the present invention, there is provided a solid electrolyte battery having a solid electrolyte interposed between a pair of electrodes comprising a positive electrode active material and a negative electrode active material. In the battery, an inorganic oxide made of the same material as the solid electrolyte is interposed between particles of the positive electrode active material or the negative electrode active material so as to form a three-dimensional network.

In the above solid electrolyte battery, it is preferable that the inorganic oxide interposed between the particles of the positive electrode active material or the negative electrode active material is continuously present in the solid electrolyte.

According to a third aspect of the present invention, in the method for manufacturing a solid electrolyte battery, a mixture of a positive electrode active material and an inorganic oxide, an inorganic oxide, and a mixture of a negative electrode active material and an inorganic oxide are each formed into a sheet. After lamination, the relative density is 80
% To form a positive electrode, a solid electrolyte, and a negative electrode.

[0013]

According to the solid electrolyte battery of the present invention, the inorganic oxide made of the same material as the solid electrolyte forms a three-dimensional network in the electrode. A network structure can be formed even on the electrode surface.

In addition, an integral structure connected to the solid electrolyte made of the same inorganic oxide interposed between the electrodes can be formed, and a three-dimensional network structure can be constructed over the entire pair of electrodes. It is.

By employing a structure in which ionic conduction is rapidly performed inside the electrode as described above, a large current can be extracted from the battery. In addition, since there is no reaction at the interface between the solid electrolyte particles that hinders ion transfer, irreversible reaction is reduced, and the charge / discharge cycle performance is further improved.

Further, densification can be performed by heat and pressure molding,
By increasing the amount of energy per volume that can be taken out, high energy density can be achieved.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a sectional view showing an example in which the solid electrolyte battery of the present invention is applied to a coin-type battery. In FIG. 1, 1 is a positive electrode, 2 is a negative electrode, 3 is a solid electrolyte, 4 is a positive electrode current collector layer, 5 is a negative electrode current collector layer, 6 is a spring, 7 is a positive electrode can, 8 is a negative electrode can, 9 is Insulation packing. Current collector layers 4 and 5 made of a vapor-deposited film are provided on the outer surfaces of a pair of electrodes 1 and 2 sandwiching the solid electrolyte 3 to constitute a main part, and are pressed by spring spacers 6 to form battery case cans 7 and 8. Contact is ensured, and the outer periphery is sealed with a resin-filled packing 9 to form a coin-type battery.

As the electrodes 1 and 2 of the present invention, manganese (Mn), cobalt (Co), which can occlude and release lithium ions by an electrochemical oxidation-reduction reaction,
Nickel (Ni), vanadium (V), niobium (Nb)
Metal oxides containing at least one of the following are used. Particularly, for example, Fe ₂ O ₃ , TiO ₂ , Nb ₂ O ₃ , V ₂ O ₅ , which can supply and move lithium ions,
Metal oxides such as WO ₃ , preferably manganese (M
n), titanium (Ti), vanadium (V), niobium (N
b) metal oxide or LiMn ₂ O containing at least one of
_{4 and the} like are preferable. This metal oxide is, for example, 0.1 to
It has a particle size of about 20 μm.

The active materials forming the electrode materials of the positive electrode 1 and the negative electrode 2 are determined by where the battery operating voltage determined by the charge / discharge potential difference of the selected materials is obtained. Is not fixed, and the operating voltage of the solid electrolyte battery changes depending on which combination of active materials is selected.

Therefore, it is possible to construct a battery even if the materials listed as materials for the positive electrode 1 are selected as the material for the negative electrode 2 depending on the combination.

The solid electrolyte 3 is not particularly limited as long as it has ion conductivity of lithium ions. For example, LiAlTi (PO) or LiGeVO
Crystalline solid electrolyte such as, 30LiI-41Li ₂ O-
29P ₂ O ₅ and _{40Li 2 O-35B 2 O 5} -25Li
An oxide amorphous solid electrolyte such as NbO ₃ can be used. In the solid electrolyte battery of the present invention, the type of ions to be transferred is not particularly limited, but is particularly effective for lithium ions, and the ionic conduction in the solid electrolyte 3 containing lithium (Li) is not limited to the electrode active material 1, This can be performed promptly because the ion supply from 2 is balanced.

FIG. 2 schematically shows a cross section of the electrodes 1 and 2.
Inorganic oxide 1 consisting of the same material as the target solid electrolyte
0 intervenes between the active material particles 11 while forming a three-dimensional network through the pores 12. In this case, since sufficient densification cannot be promoted, the three-dimensional network of the inorganic oxide forms the interface 13 therein, and thus the network configuration becomes insufficient.
It becomes a factor inhibiting ion conduction. Therefore, by forming a denser body, the ion conductivity can be improved, and the rate characteristics and the cycle charge / discharge characteristics can be further improved. That is, in order not to cause traps at the interface between the solid electrolyte and the active material and the interface between the solid electrolyte particles, which are the main causes of the ion conduction inhibition factor and the cycle performance deterioration mode, the density is 82% in relative density. Above, preferably 93%
The above is preferred. In other words, this three-dimensional network
It is not necessary to constitute between all the particles of the active material, and a part of the particles of the active material in which the metal oxide does not exist may be present.

[0023]

EXAMPLES (Example 1) First, Li as a positive electrode active material was used.
85% by weight of Mn ₂ O ₄ and 30 as an inorganic solid electrolyte
_{LiI-41Li 2 O-29P 2} O 5 to 15 wt% and mixed well. To this mixture, 5% by weight of polyvinyl alcohol was externally added as a binder for molding, and an appropriate amount of toluene was added as a solvent to prepare a slurry for molding. This slurry was formed into a sheet having a thickness of about 50 μm using a doctor blade, and the solvent was evaporated to cut into a sheet having a predetermined size. After firing the sheet electrode thus manufactured at 450 ° C. for 20 hours, the sheet electrode was heated at 600 ° C. for 100 k.
Firing was performed for 1 hour under a pressure of gf / cm ² . The thickness of the fired body was about 30 μm.

Using Li ₄ Mn ₅ O ₁₂ as the negative electrode active material, a fired body was prepared in the same manner as the positive electrode.
The thickness was also 30 μm. Also, after preparing a molding slurry using only 30LiI-41Li ₂ O-29P ₂ O ₅ as a solid electrolyte using a binder in the same manner as the positive and negative electrodes, the slurry was molded to a thickness of 30 μm with a doctor blade. Thus, a sheet was prepared. After cutting out the prepared sheet, it is baked at 450 ° C. for 20 hours in the same manner as the electrode, and 100 kgf / c
Press molding was performed at a pressure of m ² . The finished thickness was about 15 μm. In the analysis after firing all of these fired bodies, it was confirmed that the components of the binder used did not remain. The relative density of each fired body was 93% for the positive electrode, 95% for the negative electrode, and 98% for the solid electrolyte.

Next, a contact electrode was formed on one of the positive and negative electrodes by sputtering with Au argon plasma. These three fired bodies are put in 150
After drying at 2 ° C. for 2 hours, a coin-type battery was assembled in a glove box. After laminating the Au electrode on the outside to form a battery, a spring washer was inserted to make contact between the electrode and the battery can to assemble the coin battery.

The battery performance was measured with a secondary battery charging / discharging device. As a charging condition, the coin cell battery for evaluation was charged to 2.8 V with a current of 100 μA, and the voltage was 2.8 V.
After reaching, the charge was stopped and held for 5 minutes, then discharged to a voltage of 1.0 V with a discharge current of 100 μA, and then recharged to 2.8 V and held for 5 minutes. Then, the amount of discharge electricity was obtained for each fixed cycle, and the battery performance as a secondary battery was evaluated.

(Comparative Example 1) Each electrode and the solid electrolyte molded sheet produced by the method shown in Example 1 were fired in the air at 600 ° C without pressurization to produce a fired body. The relative density of the fired body obtained by this firing was a positive electrode 80%, a negative electrode 79%, and a solid electrolyte 90%.

The fired body was prepared in the same manner as in Example 1.
A comparative example was set up in a coin-type battery. The measurement of the comparative example was also performed under the same conditions as in Example 1.

Table 1 shows the charging / discharging measurement results of both samples of Example 1 and Comparative Example 1 described above.

[0030]

[Table 1]

In the example, the charge / discharge characteristics were confirmed. In contrast, in the comparative example 1, the voltage reached the upper limit voltage at the same time as the measurement, and immediately reached the lower limit voltage even in the switched discharge. Could not.

Further, when the cross section of the fired body of the electrode manufactured in Example 1 and Comparative Example 1 was observed, in the cross section of the fired body manufactured in Example 1, the three-dimensional metal oxide was formed between the particles inside the electrode. It was confirmed that a network had been formed and that sufficient densification had progressed. On the other hand, in the comparative example, many defects such as the pores 12 shown in the schematic diagram of FIG. 2 were confirmed, and it was confirmed that the solid electrolyte network was not developed between the particles.

(Example 2) In Example 1, after each fired body electrode before forming the contact electrode made of Au produced by pressure firing in Example 1 was sandwiched between solid electrolyte sheets to form a battery. 10 at 650 ° C as in 1
Firing was performed at a pressure of 0 kgf / cm ² for 15 minutes to obtain an integrated body. When the relative density of the manufactured battery having an integral structure was measured, it was confirmed to be 95%.

(Comparative Example 2) Each fired body produced by pressure firing in Example 1 and a solid electrolyte were laminated in the same manner as in Example 2 to form a battery. Firing was performed at 650 ° C. for 15 minutes. The relative density of this fired body was 78%.

Contact electrodes made of Au were formed on both sides of each of the laminated fired bodies of Example 2 and Comparative Example 2 by a sputtering method, and assembled into a coin-type battery in the same manner as in Example 1 to perform charge / discharge measurement. Table 2 shows the results of the charge / discharge characteristics of the manufactured batteries.

[0036]

[Table 2]

In the second embodiment, the initial capacity is 85 μA.
h and more than double the comparative example, and 80% of the initial capacity ratio
Maintenance was possible over 60 cycles. However, in the comparative example, the capacity was low and the deterioration of the cycle characteristics was remarkable, and the capacity was 80% or less in 18 cycles, and the difference in the performance of the battery was obvious.

The junction interface between the electrode of each battery and the solid electrolyte was observed. In Example 2, at the junction between the solid electrolyte having a network inside the electrode and the solid electrolyte sandwiched between the electrodes, no particular interface of the junction was observed, and it was confirmed that a good junction was formed. On the other hand, in Comparative Example 2, it was confirmed that good bonding was partially formed as in Example 2 at the joint between the solid electrolyte inside the electrode and the solid electrolyte sandwiched between the electrodes. The formation of a joint interface was clearly observed at the joint of Example 1, and it was confirmed that a continuous network at the joint was broken.

As shown in Examples 1 and 2 and Comparative Examples 1 and 2, the inorganic oxide forms a sufficient three-dimensional network inside the electrode, and furthermore, the inorganic oxide forms a connection between the positive electrode and the negative electrode. The object of the present invention is achieved by bonding to the solid electrolyte in between to obtain a sufficient network, and as shown in Examples 1 and 2, and Comparative Examples 1 and 2, the solid electrolyte structure is a solid A solid electrolyte battery is obtained by pressurizing, heating and firing a laminated molded body having a configuration in which a solid electrolyte similarly molded into a sheet is sandwiched between a pair of electrodes molded into a sheet composed of a mixture of an electrolyte and an active material. Can be manufactured.

Example 3 Example 1 was prepared by preparing a slurry.
Similarly to the above, the positive electrode and the negative electrode were formed into a sheet shape using a doctor blade, and the solvent was evaporated to prepare an electrode. A sheet was formed in the same manner as in Example 1 to produce a solid electrolyte. All 4
After firing at 50 ° C. for 20 hours, the layers were laminated as in Example 1, and then densification was promoted by heating under pressure at 650 ° C. The relative density of each sample is shown relative to the molding pressure. The Archimedes method was used to measure the density, and the relative density was calculated by assigning the true specific gravity of each raw material to the mixture ratio.

Electrodes were produced in the same manner as in Example 1 to form a coin-type battery, and charge / discharge measurement was performed. Table 3 shows the results.
Shown in

[0042]

[Table 3]

When the relative density was less than 80%, the discharge capacity per unit weight could be obtained to some extent, but the energy density itself could not be improved, and particularly good results could not be obtained in the cycle characteristics. However, it was confirmed that when the relative density was 80% or more, both the absolute value of the discharge capacity and the cycle performance were rapidly improved.

It should be noted that the temperature, pressure, and pressurizing time by pressurizing, heating and firing can be variously changed without departing from the spirit of the invention.

Further, the present invention is not limited to the above embodiment, and even when applied to a rectangular or thin battery,
Various changes can be made without departing from the scope.

[0046]

As described above, according to the solid electrolyte battery of the present invention, the particles of the positive electrode active material or the negative electrode active material are formed so that the inorganic oxide composed of the same material as the solid electrolyte forms a three-dimensional network. Since the solid electrolyte has an integrated structure of a fired body having a three-dimensional network structure between the electrode active materials and between the electrodes,
The purpose is to balance the contact interface between particles in the electrolyte and to speed up ionic conduction between the solid electrolytes. In addition, by increasing the density of the three-dimensional network structure as the ion conduction path, it becomes possible to act as an ion-conductive solid electrolyte having better conductivity,
This reduces polarization as a factor inhibiting ion conduction inside the battery, lowering the internal resistance of the battery itself,
By rapidly conducting ion conduction inside the solid, a large current can be obtained from the battery, and it is possible to prevent trapping of ion conduction, which is a cause of cycle deterioration due to repeated charging and discharging,
Its industrial utility value is extremely high.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one embodiment in which a solid electrolyte battery of the present invention is applied to a coin-type battery.

FIG. 2 is a cross-sectional view showing contact between active material particles and a solid electrolyte in the solid electrolyte battery of the present invention.

[Explanation of symbols]

1 ‥‥‥ cathode, 2 ‥‥‥ anode, 3 ‥‥‥ solid electrolyte, 4
{Positive electrode current collector layer, 5} Negative electrode current collector layer, 6}
Spring spring, 7 mm positive can, 8 mm negative can, 9
{Insulating packing, 10} three-dimensional solid electrolyte structure, 11 {active material particles, 12} pore, 13}
‥‥ Solid electrolyte interface

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinji Magome 3-5 Koikadai, Seika-cho, Soraku-gun, Kyoto Prefecture Inside the Central Research Laboratory, Kyocera Corporation (72) Inventor Makoto Osaki 3-chome Koikadai, Soraku-gun, Kyoto Prefecture 5 Kyocera Corporation Central Research Laboratory (72) Inventor Tohru Hara 3-chome, Seika-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 AA01 AA02 AA03 AA04 BA01 BA03 BB12 BC05 BC06 BD05 5H029 AJ02 AJ03 AJ04 AJ05 AK02 AK03 AL02 AL03 AM12 BJ03 BJ12 CJ02 CJ06 CJ08 HJ08

Claims (3)

[Claims] 1. A solid electrolyte battery in which a solid electrolyte is interposed between a pair of electrodes composed of a positive electrode active material and a negative electrode active material, wherein an inorganic oxide composed of the same material as the solid electrolyte forms a three-dimensional network. Wherein a solid electrolyte battery is interposed between particles of the positive electrode active material or the negative electrode active material. 2. The solid electrolyte battery according to claim 1, wherein the inorganic oxide interposed between the particles of the positive electrode active material or the negative electrode active material is continuously present in the solid electrolyte. 3. A sheet obtained by forming a mixture of the positive electrode active material and the inorganic oxide, the inorganic oxide, and the mixture of the negative electrode active material and the inorganic oxide into a sheet shape and laminating the same, and then having a relative density of 8%.
A method for producing a solid electrolyte battery in which a positive electrode, a solid electrolyte, and a negative electrode are formed by firing to 0% or more.