JPH0456077A - Whole 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 is to provide an all-solid-state secondary battery that is particularly suitable for high-rate customization.

Conventional technology In 2007, the use of microelectronics in child devices rapidly gained momentum, and there was a strong demand for batteries used in these devices to have high reliability and an expanded operating temperature range. . 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 absolute reliability of the equipment used must be ensured. That is impossible. 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 six-cell batteries using solid electrolytes instead of liquid electrolytes are being actively developed. For example, an all-solid-state secondary battery uses AgI, Mug2wo4, etc., which are stable against moisture, oxygen, and heat, as a silver ion conductive solid electrolyte, and uses silver vanadium oxide as an electrode active material for the positive and negative electrodes. Proposed (Patent Application Hei 1-67063)
.

However, these six batteries also have stable battery characteristics and excellent high temperature characteristics, but Q, 11! When used at a current of more than IA, the capacity decreases significantly, and there is a problem in the retention of the current.

Problems to be Solved by the Invention Using silver vanadium oxide as a Muroran active material, 4A
All-solid-state batteries using solid electrolytes with compositions such as gI・mug2wo4 are stable against moisture, oxygen, and heat, and have almost no electronic conductivity even at high temperatures. This is a custom-made secondary battery that operates stably over a wide temperature range, even up to extremely high temperatures.

However, since the electron conductivity of the electrode active material is not very good, 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 has a poor battery performance. The internal resistance is high, and when used with a large current, the capacity decreases significantly, resulting in problems with the durability of the battery.

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

Means for Solving the Problems The present invention provides an electrode using a silver ion conductive solid electrolyte represented by 4mgI/mg2WO4, etc., and AgxV2O5-y(
0.6≦X≦0.8, y is acid layer deficiency) Improving the high rate performance of an all-solid-state secondary battery that is a mixture of electrode active materials made of a composite oxide of silver and vanadium oxides Therefore, two types of graphite, fibrous graphite and spherical graphite, which have excellent electron conductivity, are included in the polarization.

In particular, when the total content of the above two types of graphite in the electrode is 1 to 2% by weight, the no-ylate properties can be significantly improved.

A composite oxide consisting of silver and vanadium oxide expressed as AffxV20s -y (o-e≦X≦0.8, y is oxygen deficiency) can electrochemically inhibit silver intercalation and 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 a silver ion-conductive curved solid electrolyte layer. The electrochemical reaction during charging and discharging of the pond (as described above) takes place at the interface between the solid electrolyte and the electrode active material, and in the case of a charging reaction,
At the positive electrode, deintercalation of silver ions and electrons from the silver vanadium oxide of the electrode active material is performed, and at the negative electrode, intercalation of silver ions and electrons into the electrode active material is performed. Further, 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. The silver vanadium oxide of the electrode active material constituting the conventional electrode is 100.
Because the electrode has a volume resistivity of approximately 500 yen, electron conduction in the electrode was performed by the silver vanadium oxide itself, which is the active material of the electrode. However, in high-rate charging and discharging, sufficient characteristics could not be obtained because the internal resistance of the six cells was high.

Fibrous graphite has an extremely low volume resistivity value, and a battery containing fibrous graphite in the electrode layer has an electron conductivity in the electrode of 8:
It is possible to increase the high rate characteristics slightly. However, when fibrous graphite is mixed with a straight bar material, the fibers tend to become entangled with each other and are not dispersed uniformly during polarization, but tend to localize, causing some problems in improving electronic conductivity. Spheroidal graphite has a slightly higher volume resistivity value than fibrous graphite, so it cannot significantly improve electron conductivity for polarization, but it is very well dispersed in the electrode constituent materials, making it possible to improve the electron conductivity to some extent. .

In the present invention, fibrous graphite with low volume resistivity and excellent electron conductivity is contained in the electrode, and spherical graphite, which creates a very uniform dispersion state, is mixed in to improve electron conduction during charging and discharging. , which has improved high-rate characteristics. Further, the mixing ratio of fibrous graphite and spherical graphite to be contained in the electrode, and the I#3. of the two types of graphite.
By examining the added acid and clarifying the range in which it is particularly effective, we have completed an all-solid-state secondary battery with excellent high-rate characteristics.

Hereinafter, a detailed explanation will be given with reference to the implementation row.

Example First, Mu gI, Mu g2o, and wo5 were weighed so that the molar ratio was 4:1, and mixed in an alumina mortar. This mixture was pressure-molded into pellets, sealed in a Pyrex tube under reduced pressure, and heated to 400℃ for 17 hours.
Allow time to melt and react. The reaction product was pulverized in a mortar and classified to obtain a silver ion conductive solid electrolyte powder having a mesh size of 200 mesh or less and expressed by 4 mgI.mug2Woa.

Next, powders of vanadium oxide represented by V2O5 and metallic silver were weighed so that the molar ratio was 7.7, and mixed in a mortar. After pressure-molding the mixture and making it into pellets,
The reaction product was sealed in a quartz tube under reduced pressure and reacted at a temperature of 600° C. for 48 hours, and the reaction product was crushed in a mortar and classified to obtain a silver vanadium oxide electrode active material powder having a kEa7V205 of 200 mesosites or less.

An all-solid-state secondary battery was fabricated using the solid electrolyte and tuntan active material thus obtained by the following method. First, solid electrolyte powder and electrode active material are mixed at a weight ratio of 1:1, and then fibrous graphite with an average fiber diameter of 0.1 μm and an average fiber length of 10 μm and fibrous graphite with an average particle size of 7 μm are added. Electrode materials containing two types of graphite were obtained by varying the mixing ratio of spheroidal graphite and the amount of gold in the electrode as shown in the table below.

Weighed 100119 of this electrode material, 4ton/, 1A
Pressure molding was carried out at a pressure of 1.5 mm to produce a Seian pellet with a diameter of 1 omm.

On the other hand, weigh 250cm of the same electrode material as the positive electrode, and
Pressure molding was performed at a pressure of n/j to produce a negative electrode pellet with a diameter of 10111 m. The positive electrode and negative electrode pellets obtained in the above manner were placed through 300 μm of solid electrolyte,
The entire body was welded under pressure at a pressure of 41 on/pJ, and the diameter was 1 o.
A pellet-like all-solid-state secondary battery of mm size was produced. In order to confirm the charging and discharging characteristics of this all-solid-state secondary battery, plated copper wires were further bonded to the positive and negative electrodes of the pellets using conductive carbon paste (109B manufactured by Acheson Japan Co., Ltd.).
The entire surface was coated at a temperature of 160° C. using an epoxy resin powder coating (Nitron C-7200, manufactured by Nitto Denko Corporation). Furthermore, in addition to the practical examples of the present invention, batteries containing no graphite in the electrodes, batteries containing only fibrous graphite in the electrodes, and conventional examples containing only spheroidal graphite in the electrodes were prepared for comparison.

The following table shows the results of evaluating the discharge capacity of the prototype all-solid-state secondary battery at the 6th cycle of constant current charging and discharging in a temperature atmosphere of 20'C. Note that constant current charging and discharging of the all-solid-state secondary battery produced as an example row was performed between a charging voltage soomv and a lower discharge limit voltage of 25 QmV, and the current value was 1 mA in order to confirm high-rate characteristics. In addition, a conventional solid electrolyte secondary battery for comparison was used in the same charging/discharging voltage range as the example, and the battery did not contain graphite in the electrode. First, constant current charging and discharging of 60 μA was performed to confirm the capacity, and then 1111A
For batteries containing only fibrous graphite or spherical graphite in the electrode, only the discharge capacity at the 6th cycle at a current value of 1 mA 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 16, which does not contain graphite in the electrode, is charged and discharged with a current of 0.0511 people, the discharge capacity at the 6th cycle is 1960 μm h. However, when conventional example 16 with the same configuration was charged and discharged with a current of 1 mA, the obtained capacity was only 420 μm h, and 0.
In the case of 06IIIA (7), it decreased to 21.4%, and in the conventional example that did not contain graphite, the capacity decreased significantly when charged and discharged with a large current, indicating that there is a breakthrough in no-erate characteristics. Further, the battery 13 in which 1.6% of fibrous graphite alone is contained in the electrode has a capacity of 680 μm h when charged and discharged with a current of 1 mA, and furthermore, 1.6% of fibrous graphite is contained in the electrode. Battery 14 containing 6% graphite had a capacity of 610 μm h, and although it was possible to increase the discharge capacity slightly in high-rate charging and discharging by including graphite, a significant improvement could not be achieved. In contrast, Examples 1 to 1 of the present invention in which fibrous graphite and spherical graphite were contained in the electrode
No. 12 has the same capacity as the conventional one when charging and discharging at a constant current of 1 mA! It can be seen that the high rate characteristics are larger than AI and are significantly improved compared to the case of using fibrous graphite or spheroidal graphite alone.

In Examples 7 to 9, the total amount of graphite in the electrode active material was changed from 1% by weight to 2% by weight for those in which the mixing ratio of fibrous graphite and spherical graphite was 3:2. This is an evaluation of the erase characteristics of the battery. When the total content was 1.6% by weight, No. 8 was most effective, and when no graphite was added, three times the discharge capacity was obtained compared to No. 16. When the total amount is reduced from 1.6% by weight7,
Or if it is increased, 91 discharges, both of which have a discharge capacity of 8
It decreased slightly. This is thought to be because when the graphite content is too low, the electronic conductivity does not improve much, and when the graphite content is too high, the electronic conductivity improves, but on the other hand, it interferes with the ionic conductivity in the solid electrolyte.

If fibrous graphite with an average fiber diameter of o, i μm and average fiber length of 10 μm and spherical graphite with an average particle size of 7 μm are simultaneously contained in the range of 1% to 2% by weight,... It can be seen that the capacity of is significantly improved. Batteries with electrodes with a total graphite content of less than 1% or more than 2% are also constructed.
We confirmed that the effect of improving high-rate characteristics was further reduced. There is a similar tendency as above for Nos. 4 to 6, which have a mixing ratio of fibrous graphite and spheroidal graphite of 2:3. When the total content is 1.6% by weight, No. 6 is most effective, but when the mixing ratio is When a large amount of spheroidal graphite is added to the ratio of 1:6, 1 to 3 are most effective when the amount is 2% by weight.

On the other hand, those with a high mixing ratio of fibrous graphite 10 to 1
When 2 is 1% by weight, 10 is most effective. This I indicates that the electron conductivity of the electrode is also influenced by the mixing ratio of fibrous graphite and spherical graphite, and the amount of parent metal.

The most effective mother metal content varies depending on the difference in the mixing ratio, but each size of graphite was effective in improving high-rate characteristics at any graphite mixing ratio and total content.

In addition, in order to confirm the characteristics of batteries 1 to 12 of Examples of the present invention as secondary batteries, the above charge/discharge cycle test was continued to confirm the discharge capacity at the 300th cycle, but in all cases, the discharge capacity at the 300th cycle was It was almost identical to the eye. Furthermore, for batteries 2, 6.8, and 11, which have even better no-yrate characteristics, batteries with the same configuration were fabricated, and constant current charging and discharging was performed at a current value of 1XIIm at a temperature of 110'C.
The discharge capacity at the 100th cycle was checked, and there was almost no change from the initial capacity, confirming that the battery had stable characteristics as a secondary battery.

As described above, the present invention simultaneously contains fibrous graphite and spheroidal graphite with excellent electronic conductivity in an electrode, and also confirms the mixing ratio and total amount of graphite that is significantly effective in improving high-rate characteristics. As a result, an all-solid-state secondary battery with excellent practical performance was realized.

In Example 1, the solid electrolyte represented by 4mgI/muK2No4 was prepared by synthesizing MugI, Mug20, and WOs as a silver ion conductive solid electrolyte. Genderless 5i02,
A compound selected from MoO3, V2O5 and MugI,
The solid electrolyte synthesized from Mu10, and the one further synthesized has hygroscopicity (ros, P2O5, B2O
It has been confirmed that, in almost the same way as above, the IE of ).

Furthermore, in Examples (AgnzV2 is used as an electrode active material)
Although the explanation was given using the composition expressed by 0s, silver intercalation, deintercalation force, laser reaction, vch 6'/20s O and Agna'
It has been confirmed that the same effect as Habo can be obtained even when a composite oxide of /20s silver and silver vanadium is used as a reprint active material.

Effects of the Invention As described above, according to the present invention, a silver ion conductive solid electrolyte and AgxV2O5-y (0,8≦X≦0,8, y
By incorporating fibrous graphite and spheroidal graphite as electron conductive materials into an electrode containing a mixture of cardiac activity and proboscis expressed by oxygen deficiency (oxygen deficiency), an all-solid-state secondary battery with excellent oxide properties is obtained. be able to.

Claims (4)

[Claims] (1) Silver ion conductive solid electrolyte and Ag_xV_2O_5_-_y (0.6≦x≦0.8,
An all-solid material characterized by containing two types of graphite, fibrous graphite and spheroidal graphite, as electron conductive materials in an electrode made of a mixture of a composite oxide consisting of silver and vanadium oxide, represented by y (oxygen vacancies). Secondary battery. (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 4AgIAg
The all-solid-state secondary battery according to claim 1 or 2, having a composition represented by _2WO_4. (4) The total solid carbon dioxide according to any one of claims 1 to 3, wherein the total content of the fibrous graphite and spherical graphite in the electrode is 1 to 2% by weight. Next battery.