JPH0426073A - Fully solid secondary battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an all-solid-state secondary battery that uses the same silver vanadium oxide as the electrode active material for both the positive and negative electrodes and uses a silver ion conductive solid electrolyte as the solid electrolyte. The purpose of this invention is to provide an all-solid-state secondary battery with particularly excellent high-rate characteristics.

BACKGROUND OF THE INVENTION In recent years, the use of microelectronic devices in electronic devices has rapidly progressed, and there has been a strong demand for batteries used in these devices to have high reliability, an expanded operating temperature range, and the like. However, with conventional batteries that use liquid electrolytes such as acids and alkalis, there is a risk of expansion and rupture due to electrolyte leakage and gas generation, so it is important to ensure the absolute reliability of the equipment used. is not possible.

On the other hand, since solid electrolyte batteries do not use any liquid electrolyte, they do not have the above problems and have the potential to be highly reliable. In addition, solid electrolytes do not cause freezing or evaporation that occurs with liquid electrolytes, and can be expected to be used over a wide temperature range. For this reason, all-solid-state batteries that use solid electrolytes instead of liquid electrolytes are being actively developed. Examples include a copper-based all-solid-state secondary battery using a copper ion conductive solid electrolyte, and a lithium-based all-solid-state battery using a lithium ion conductive solid electrolyte. However, R
A solid electrolyte of the bC;l -CjuOl -Our system is used, and a transition metal disulfide with a layered structure such as titanium disulfide or niobium disulfide or Gu x is used as the positive electrode active material.
In a copper-based all-solid-state secondary battery using a copper Chevrel phase compound represented by M O68B and using metallic copper or a copper Chevrel phase compound for the negative electrode, RbC1-CuC] -Cu
Since the I-based copper ion conductive solid electrolyte decomposes in the presence of moisture and oxygen, a battery with stable characteristics cannot be obtained, and the electronic conductivity at high temperatures is relatively high.
If the self-discharge of the battery becomes large and the usable temperature range is 6.
The limit was 0°C.

In addition, in lithium-based all-solid-state batteries that use LiI or the like as a solid electrolyte, the current that can be extracted as a battery is extremely low because the solid electrolyte has low lithium ion conductivity. It was not possible to obtain a stable battery because of the susceptibility to Due to the above-mentioned problems, no all-solid-state battery has been put into practical use to date.

As a method to solve these problems, 4AgN/Ag2W04, etc., which are stable against moisture, oxygen, and heat, are used as a silver ion conductive solid electrolyte, and silver vanadium oxide is used as an electrode active material for the positive and negative electrodes. Solid state secondary batteries have been proposed. However, although this battery also had stable battery characteristics and excellent high-temperature characteristics, the capacity decreased significantly when used at a current of 0.1 mA or more, and it had problems in high-rate characteristics.

Problems to be Solved by the Invention Using silver vanadium oxide as an electrode active material, 4Ag
All-solid-state batteries that use a solid electrolyte with a composition such as I.Ag2W04 are stable against moisture, oxygen, and heat, and have almost no electronic conductivity even at high temperatures, so they can be heated from low temperatures to 100°C. This is a secondary battery that operates stably over a wide temperature range, up to high temperatures exceeding . However, since the electron conductivity of the electrode active material is only 1, which is not excellent, a battery that only has electrodes made of a mixture of the electrode active material and the solid electrolyte placed on both ends of the solid electrolyte layer is not suitable. The internal resistance of the battery was high, and when used at a large current, the capacity decreased significantly, resulting in problems with the erase characteristics.

The present invention solves the above problems while maintaining stable characteristics, and provides an all-solid-state secondary battery with excellent high-rate characteristics.

Means for Solving the Problems The present invention provides an electrode using a silver ion conductive solid electrolyte represented by 4AgI/Ag2No, etc. and Agxv205-7 (0
, 6≦x≦0.8, y is oxygen vacancy). , the electrode contains spherical graphite having excellent electron conductivity.

In particular, when the content of the spherical graphite in the electrode is 1 to 6 by weight, the high rate characteristics can be significantly improved.

Action Agx V205-y (0-6≦x≦0.8, y is oxygen deficiency) A composite oxide consisting of silver and vanadium oxide can electrochemically intercalate silver,
Deintercalation can be performed.

Therefore, an all-solid-state secondary battery can be constructed by using it in combination with a silver ion conductive solid electrolyte.

The all-solid-state secondary battery is constructed by disposing electrodes made of a mixture of a silver ion-conductive solid electrolyte powder and a silver vanadium oxide powder at both ends of the silver ion-conductive solid electrolyte. The electrochemical reaction during charging and discharging of the battery takes place at the interface between the solid electrolyte and the electrode active material, and in the case of a charging reaction, deintercalation of silver ions and electrons from the silver vanadium oxide of the electrode active material takes place at the positive electrode. At the negative electrode, silver ions and electrons are intercalated into the electrode active material. However, in the discharging reaction, a reaction opposite to the charging reaction proceeds.

Therefore, the charge/discharge characteristics are greatly influenced by the electron conductivity inside the electrode. Conventionally, since silver vanadium oxide, which is an electrode active material constituting an electrode, has a volume resistivity of about 10Ω, electron conduction in the electrode has been carried out by the silver vanadium oxide itself, which is an electrode active material. However, in no-ylate charging and discharging, optical characteristics could not be obtained because the internal resistance of the battery was high.

In the present invention, spherical graphite with volume resistivity on the order of 10 Ω・cm and excellent electron conductivity is contained in the electrode to improve electron conduction during charging and discharging, thereby improving erase characteristics. It is. Furthermore, the authors examined the amount of spherical graphite added to the electrode and clarified the most effective range, thereby completing an all-solid-state secondary battery with excellent no-ylate characteristics.

This will be explained in detail below using examples.

Examples First, AgI, Ag20. WO3 in molar ratio 4:1:1
and mixed in an alumina mortar. This mixture was molded under pressure to form a pellet, sealed in a Pyrepukunu tube under reduced pressure, and melted at a temperature of 400 °C for 17 hours.
Made it react. The reaction product was crushed in a mortar and classified to 200
A silver ion conductive solid electrolyte powder represented by 4Agx·Ag2wo4 having a mesh size or less was obtained.

Next, vanadium oxide represented by v205 and metallic silver powder were weighed so that the molar ratio was 1:0.7, and mixed in a mortar. The mixture was pressure-molded into a pellet shape, and then placed in a quartz tube sealed under vacuum 2 and allowed to react at a temperature of 600°C for 48 hours. An electrode active material powder of silver vanadium oxide represented by 17v205 was obtained.

Using the solid electrolyte and electrode active material obtained in this way,
An all-solid-state secondary battery was fabricated using the following method. At first,
Solid electrolyte powder and electrode active material were mixed at a weight ratio of 1:1, and to this were added spheroidal graphite (13) with an average particle size of 1 μm, spheroidal graphite (13) with an average particle size of 7 μm, and is 30μ
m of spheroidal graphite (C) was mixed uniformly with varying contents as shown in the table below to obtain an electrode material containing spheroidal graphite.

100 μm of this electrode material was weighed and pressure molded at a pressure of 4 tons/c4 to produce a positive electrode plate having a diameter of 1 om+n. On the other hand, weigh 250 μ of the same electrode material as the upper layer,
Pressure molding was performed at a pressure of 4 ton/c2 to produce a negative electrode pellet with a diameter of 10 mm. The positive electrode and negative electrode bezels 7) obtained as described above were placed through a 300 mq solid electrolyte, and the whole was welded under pressure at a pressure of 4 ton/c4 to form a belenium-shaped all-solid diode with a diameter of 10. The next battery was fabricated. In order to confirm the photodischarge characteristics of this all-solid-state secondary battery, we added conductive carbon beanets (1o9B manufactured by Nippon Acheson Co., Ltd.) to the positive and negative electrodes of the pellets.
The entire body was coated with an epoxy resin powder coating (Nitron C-7200M manufactured by Nitto Denko Co., Ltd.) to a 150”
It was painted at a temperature of C. Furthermore, in addition to the examples of the present invention, a conventional example in which no spheroidal graphite was contained in the electrode was prepared for comparison.

The results of evaluating the spheroidal graphite content of the prototype all-solid-state secondary battery and the discharge capacity at the 5th cycle of constant current charging and discharging in a temperature atmosphere of 20'C are shown on the robe. In addition, constant current charging and discharging of the all-solid-state secondary battery produced as an example was performed at a charging voltage of 500 m
The current value was set to 500μ in order to confirm high rate characteristics. In addition, the conventional solid electrolyte secondary battery for comparison was first charged and discharged at a constant current of 50 μm to confirm the capacity in the same charging/discharging voltage range as the example, and then the fifth cycle was performed at a current value of 500 μm. The discharge capacity was evaluated.

In addition, the evaluation results of discharge capacity each showed the average value of two batteries.

(Left below) As shown in this table, when conventional example 17, which does not contain graphite in the electrode, is charged and discharged with a current of 6 μm,
A discharge capacity of 1960 μm h was obtained in the cycle, but when conventional example 18 with the same configuration was charged and discharged with a current of 600 μm, the obtained capacity was only 845 μm h, which was 60 μm.
In the conventional example, when charging and discharging with a large current, the capacity decreases significantly, indicating that there is a problem in high rate characteristics. On the other hand, Examples 1 to 16 of the present invention, in which spheroidal graphite (M), (B), and (C) having different average particle sizes were contained in the electrode, were all 500 μm in diameter.
It can be seen that the capacity during constant current charging and discharging of the battery is larger than that of the conventional example, and that the improvement of the electron conductivity of the electrode by the spherical graphite is effective in improving the high rate characteristics.

In Examples 5 to 12, the average particle size of spheroidal graphite is 7 μm.
The high-rate characteristics of the battery were evaluated when the content in the electrode active material was varied from 0.6% by weight to 7% by weight, and when the content was 2% by weight, 8, The most effective case is that when graphite is not contained, a discharge capacity 1.99 times higher than that of No. 17 can be obtained. When the content is decreased from 2% by weight, the discharge capacity of 5 to 7, or when it is increased to 9 to 12, the discharge capacity slightly decreases from 8 to 0.
．． When containing 5% by weight, 5 has almost no effect.

This is because when spheroidal graphite is contained in an electrode composed of a solid electrolyte and an electrode active material, a content of 1% by weight or more is required to significantly improve the electronic conductivity of the electrode active material. However, if the graphite content is too high, electronic conductivity improves, but this is thought to interfere with the ionic conductivity of the solid electrolyte, and high-rate discharge capacity is significantly improved by containing spherical graphite with an average particle size of 7 μm. It can be seen that the preferred content is in the range of 1% to 6% by weight.

Spheroidal graphite (mu) with an average particle size of 1 μm and an average particle size of 3
The same procedure as above applies to 0 μm spheroidal graphite (C), and when using graphite (body), the content is 1 to 4.
In the case of weight percent, 2 is the most effective, and when graphite (C) is used, 13 to 16 are most effective in the case of 3 weight percent. This indicates that the improvement of the electronic conductivity of the electrode is also affected by the particle size of spheroidal graphite, and the most effective content varies depending on the particle size, but for each size confirmed. Both types of spherical graphite were effective in improving high rate characteristics.

In addition, in order to confirm the characteristics of batteries 1 to 16 of Examples of the present invention as secondary batteries, the above charge/discharge cycle test was continued and the discharge capacity at the 300th cycle was confirmed, but in all cases, the discharge capacity was confirmed at the 5th cycle. was almost the same. moreover,
For 2, 8, and 15, which have even better high-rate characteristics, batteries with the same configuration were fabricated, and constant current charging and discharging was performed at a temperature of 110'C with a current value of 500 μm, and the discharge capacity at the 100th cycle was determined. After checking, it was confirmed that there was almost no change in the initial capacity and that it had stable characteristics as a secondary battery.

As described above, the present invention includes spherical graphite with excellent electronic conductivity in the electrode, and by examining the graphite content that is significantly effective in improving high-rate characteristics, the present invention achieves excellent practical performance. This is the realization of an all-solid-state secondary battery.

In the Examples, Mu[I, Ag20, WO! , the solid electrolyte represented by 4AgI・Ag2w○4 was prepared by synthesizing S-02., which has no hygroscopicity. Mo
Compounds selected from O2゜V2O5 and AgI, Ag20
Whether using a solid electrolyte synthesized from a compound selected from CrO2, P2O5, B2O5, which does not have hygroscopicity, a solid electrolyte synthesized from Ag, or Ag20, the results are almost the same as above. Similarly, it has been confirmed that the high rate characteristics are improved.
Ag where the deintercalation reaction occurs almost the same way
It has been confirmed that similar effects can be obtained even when composite oxides of silver and silver vanadium such as f16 V2O5 and Agl18v205 are used as electrode active materials.

Effects of the Invention As described above, according to the present invention, a silver ion conductive solid electrolyte and Ag x V2Os-y (0-6≦x≦0.8
By incorporating spherical graphite as an electron conductive material into an electrode mixed with an electrode active material represented by .

Claims (4)

[Claims] (1) Silver ion conductive solid electrolyte and Ag_xV_2O_5_-_y (0.6≦x≦0.8,
An all-solid-state secondary battery characterized by containing spherical graphite as an electron conductive material in an electrode made of a mixed oxide of silver and vanadium oxide, represented by y (oxygen vacancies). (2) The all-solid-state secondary battery according to claim 1, wherein the electrodes are arranged at both ends of the electrode with a silver ion conductive solid electrolyte layer interposed therebetween. (3) The silver ion conductive solid electrolyte is 4AgI・A
The all-solid-state secondary battery according to claim 1 or 2, characterized in that it has a composition represented by g_2WO_4. (4) The all-solid-state secondary battery according to any one of claims 1 to 3, wherein the content of the spherical graphite in the electrode is 1 to 5% by weight.